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Subject: Re: fighting dioxin (The Orange Resource Book)
From: B.Hamilton@irl.cri.nz (Bruce Hamilton)
Date: Jul 07 1995
Newsgroups: sci.environment
In article <804977892snx@dale.cam.org>
dale@dale.cam.org (Dale Wharton) writes:
>Thanks to Jeff Sutter <jsutter@igc.apc.org> for posting this review to
>alt.politics.greens.
I'm not certain why you didn't just leave it in alt.politics.greens,
- there is nothing relevent to sci.environment.
As anyone with any interest in Dioxins is aware, the relevent
technical assessment is the EPA's peer-reviewed one. The
EPA review is still progressing through the review process,
and it now seems very likely that some of the fundamental
assertions ( such as there is no threshold below which dioxin
poses no health risk ) will be removed, as they do not
match the available evidence.
The value of peer-review of such an emotive topic is
demonstrated in the latest review of the EPA assessment
of Dioxin by the expert panel appointed by the EPA Science
Advisory Board. They noted that EPA ignored data that
did not support the conclusion that dioxin is harmful, and
one panel member also noted " It's hard to determine which
conclusions are based on data and which represent
policy-driven interpretations of data". It now seems likely
that EPA may have to remove all assertions that dioxin is
likely to cause health effects at near-background levels.
While dioxin is highly toxic, the risks of exposure need to
be quantified, and readers should be reminded that Dioxin
can be created in forest fires, so there is an extremely
low ( compared to manmade pollution ) background level.
The emotion of this issue has resulted in the EPA assessment
blurring the boundary between science and policy, and
they have rightly been chastised for that error.
The current situation is briefly discussed in
"Panel Slams EPA's Dioxin Analysis" by Richard Stone
Science v.268 p.1124 ( 26 May 1995 )
Bruce Hamilton
Subject: Re: fighting dioxin (The Orange Resource Book)
From: B.Hamilton@irl.cri.nz (Bruce Hamilton)
Date: Jul 11 1995
Newsgroups: sci.environment
In article <1995Jul10.144008.5807@vexcel.com>
dean@vexcel.com (Dean Myerson) writes:
>In article <...> B.Hamilton@irl.cri.nz (Bruce Hamilton) writes:
...
>>As anyone with any interest in Dioxins is aware, the relevent
>>technical assessment is the EPA's peer-reviewed one.
...
>The EPA dioxin draft was peer reviewed.
>The current process is an external review based on public
>comments.
But using EPA-selected reviewers, there were at least
three reviews, and this is not the first or last criticism :-)
"Dioxin Report faces Scientific Gauntlet" R.Stone.
Science v.265 p1650 16 Sept 1994
" One outside scientist who has risk-characterization chapter
written by EPA scientists cpomplains that it contains "sky-is-falling
statements that don't belong in a scientific document." Adds
Nancy Kerkvliet, "I just don't think people have been exposed
to enough dioxin to see effects, especially on the immune system."
Kerkvliet authored the review chapter on dioxin's immunotoxic
efects, which focussed on animal studies and found "no clear
pattern of immunotoxicity" in humans."
"EPA rebuffs challenge to its assessment of dioxin data"
T.Reichhardt Nature v.371 p.272 22 Sept 1994
" EPA's models assume there is no such threshold, and therefore
no 'safe' level of dioxin. Most European countries, as well as
Canada, think this model is unrealistic, and have set their dioxin
exposure limits much higher"
>>demonstrated in the latest review of the EPA assessment
>>of Dioxin by the expert panel appointed by the EPA Science
>>Advisory Board.
The panel is chaired by Morton Lippmann and the brief article
just notes three or four of the 39 panel members.
>>While dioxin is highly toxic, the risks of exposure need to
>>be quantified, and readers should be reminded that Dioxin
>>can be created in forest fires, so there is an extremely
>>low ( compared to manmade pollution ) background level.
>Do you know what the natural sources of chlorine are in forests?
>Do forest fires create dioxin or release it?
Create and release it.
From Dioxins in Food. Food Surveillance Paper 31.
ISBN 0112429262 ( 1992 ) p9
" The possible formation of dioxins and furans in natural forest
fires has been tested in simulated forest fires in Ontario (27).
No firm conclusions could be drawn as to whether natural forest
fires were a source of dioxins and furans, although there appeared
to be a small increase in levels of higher chlorinated homologues in
the soil in the test areas. It is therefore likely that, because of their
chemical stability and ease of formation, there may always have
been low levels of dioxins in the environment"
(27) = Chemosphere v20 p.1533-1536 (1990)
From "Natural Organohalogens - Many more than you think!."
G.W.Gribble J.Chem.Ed v.71 p.907-911
"The relatively poor efficiency and imcomplete oxidation when damp
vegetation and wood are burned in the presence of high chloride
concentrations (70-2100 ppm in wood pulp ) are conditions conducive
to PCDD formation, and two research groups have concluded that
forest and brush fires are the major source of PCDD's and PCDF's
in the environment (55,56). It is estimated that some 130 pounds of
PCDD's are produced in Canadian forest fires annually (56)."
(55) = Anal. Chem v.54 p.2292 (1982)
(56) = Chemosphere v.14 p.811 (1985)
For comparison 118 grams of dioxin and related compounds are
released by US paper mills ( Science v.266 p.1162 18 Nov 1994).
Here's a free quote, as some people like to refer to this
authority on sci.environment :-).
Naturally Occuring Organohalogen Compounds - a Survey
G.W.Gribble. J. Natural Products v.55 p.1353-1395 ( Oct. 1992 )
" The Science Advisory Board to the International Joint Commission
on the Great Lakes stated recently: " There is something
nonbiological about halogenated organics ( excluding iodinated
compounds). ...Chemicals [ that ] do not occur naturally...are often
persistent, since there are often no natural biological processes
to metabolise or deactivate them" (1). Not only are these statements
incorrect, but, coming from a "Science Advisory Board," they reflect
a disturbing ignorance of the chemical composition of our environment
and of biochemical processes therein"
...
>If significant modifications occur, I hope tracability is provided
>so that someone can see what evidence was provided to lead to
>the change. I would have expected the original peer review
>panels to find more errors than public comment reviews.
This appears to be a very eminent panel, and the onus is on the
EPA to rework the draft and represent it to the panel early in
1996. The panel is providing the EPA with written summaries of
their comments.
Bruce Hamilton
Subject: Re: fighting dioxin (The Orange Resource Book)
From: B.Hamilton@irl.cri.nz (Bruce Hamilton)
Date: Jul 12 1995
Newsgroups: sci.environment
In article <1995Jul11.151237.22626@vexcel.com>
dean@vexcel.com (Dean Myerson) writes:
>In article <...> B.Hamilton@irl.cri.nz (Bruce Hamilton) writes:
>>In article <...> dean@vexcel.com (Dean Myerson) writes:
...
>I am aware of many of the criticisms of the EPA statements but we must
>remember that these statements were made as indicating some proof
>existied for these impacts, not that they were proven. Public
>health measures are not always based on solid proof, but an
>indication of danger.
That is not disputed. The SAB panel criticised the selectiveness
of the information the EPA used to establish their conclusions.
>>"EPA rebuffs challenge to its assessment of dioxin data"
>>T.Reichhardt Nature v.371 p.272 22 Sept 1994
>>" EPA's models assume there is no such threshold, and therefore
>>no 'safe' level of dioxin. Most European countries, as well as
>>Canada, think this model is unrealistic, and have set their dioxin
>>exposure limits much higher"
>I believe the European levels are 2 to 3 times higer, but still in
>the ppt range. Is that true? Not such a huge difference. .....
> Without knowledge of how dioxin works, any threshhold would
> be arbitrary.
I assume the current US limits use the threshold assumption,
and it would be new limits (based on this assessment ) that
would reflect the 'no threshold' concept.
"Crump and others contend EPA erred in putting all its eggs in one
basket in constructing a single dose-response model to explain
dioxin's impact after it binds to a protein called the aryl hydrocarbon
receptor. " It's a little arrogant of the agency to exclude the possibility
of other mechanisms" of action that might explain how dioxin exerts
its toxic effects, says toxicologist John Doull of the University of
Kansas, an SAB member" Science v.268 p.1124 26 May 1995.
From the other comments in the same article I get the impression
that the EPA is departing from standard toxicological procedures
in trying to establish a 'no threshold' limit, and certainly their
selective use of information is being hammered.
>>The panel is chaired by Morton Lippmann and the brief article
>>just notes three or four of the 39 panel members.
>So the EPA chose this review panel also?
I'm not familiar with US govt. systems. As far as I can tell the
panel of 39 outside scientists " organised by EPA's Science
Advisory Board " means that if the SAB itself consists of
outside scientists, and they select the panel, then the EPA
may not choose the review panel. If the SAB is EPA staff,
then yes - the EPA does choose this review panel.
....
>We still have sediment records indicating major increases in
>dioxin sediments in recent decades.
Of course. I never meant to imply that naturally-occuring
sources were currently significant - I thought I had noted
earlier that they are not. What I was trying to convey was
that the baseline may not be zero.
...
>While there are numerous naturally-occurring oc's, the actual load
>has not been measured. But more important is the fact that manmade
>oc's are more highly halogenated than those that occur naturally
>and I think this is what the GLC SAB was referring to.
??
The number of halogen atoms in each oc molecule is constant, regardless
of being manmade or neutral. If you are suggesting that manmade ocs
include more of the highly halogenated molecules I suspect that would
be correct. It is important to remember that of all the dioxins and furans
only those containing 4 to 8 chlorine atoms _and_ with chlorine atoms in
the 2,3,7,8 positions are currently considered toxic.
>Furthermore, there is no record that humans had any body burden
>of these naturally occurring oc's while we obviously do have such
>burdens for manmade ones.
As far as I'm aware my body isn't so picky, it has a burden based
solely on the molecules it encounters - it doesn't ask whether they
had natural or manmade on their birth certificates :-). We obviously
have a body burden of all dioxins we recently encounter, but it is
only the 2,3,7,8-substituted compounds that accumulate, with levels
of the higher chlorinated homologues predominating. There is
evidence that suggests concentrations of dioxins and furans in
human adipose tissue are falling ( "Polychlorinated dibenzo-p-dioxin
and dibenzofuran concentration levels in human adipose tissue
samples from the continental US collected from 1971 through 1987"
J.S.Stanley et al. Chemosphere v.20 p.895-901 (1990).
>While much has been made of Greenpeace's error
>in stating that there is only 1 naturally-occurring oc,
How remiss of them. I should refrain from pointing that Gribble
notes there were approximately 1500 in 1992. :-)
>there are still reasons to believe in qualitative differences in risk
>between the manmade and natural oc's. Have you seen anything
> discussing metabolization of natural oc's?
I think I am misunderstanding your use of the term ocs. In the
case of dioxin we measure very specific molecules ( including the
infamous "dioxin" ( 2,3,7,8-dibenzo-p-dioxin ) ) and there would
be no difference in the metabolization of each depending on its
origins. There are differences depending on molecular structure,
but as dioxins are produced by fires (forest = natural, engines and
incinerators = manmade ) the structure distribution will be complex.
Obviously the application of manmade dioxins in chlorinated products
such as 2,4,5-T will seriously skew the profile of manmade pollution.
It is that skew that puts elevated levels of compounds into the
environment, many of which are highly toxic. As the environment
has not had such levels available, then there is unlikely to be a
mechanism for biologically munching them up, as when they were
present in trace amounts it wasn't worthwhile for the bugs to
metabolise them. As the levels get higher, then maybe some bugs
will utilize them ( but I'm not suggesting that we should keep on
throwing chemicals around the planet in the vain hope a bug will
appear to biodegrade them :-) ).
>The same issue exists wrt phyto- vs xeno-estrogens.
>The literature commonly deems the natural ones as being
>metabolized and not being persistant.
Dioxins are characterised, we know which congeners ( individual
dioxin or furan molecule ) accumulate and are toxic, whereas what
you are describing is a poorly-characterised family, where we don't
chemically analyse each molecule. If we did, we could say which
individual molecule causes the toxicity, and it would not matter
whether its birth certificate showed it was natural or manmade.
Remember that the detection levels for dioxin ( parts per quadrillion
= picograms/kilogram = 1 in 10^15 ) are well below many other individual
pollutant molecules we routinely analyse for ( parts per million =
milligrams/kilogram = 1 in 10^6 ). If we could detect such low levels of
other individual compounds we still may not be able to identify whether
they are natural or manmade ( usually carbon isotope ratios can be
used if the manmade ones are derived from fossil fuel chemicals, but
if they are derived from biological sources that can be of little use )
>The quote above is from 1992 so the GLC SAB
>statement must be a couple of years earlier. It may also be out of date.
>Since the SAB statement is refed, maybe you could provide that.
Science Advisory Board of the International Joint Commission on the
Great Lakes, "1989 Report," International Joint Commission, Hamilton,
Ontario, October 1989.
>I have ordered some of these documents so I may be lucky and
>have it. If not, I could order it so that we can determine whether their
>credibility is indeed compromised.
Don't take it so literally, I tossed the quote in just because the IJCGL
has often been cited here. I wasn't suggesting their credibility is
compromised - just that not every they write is gospel. :-)
Bruce Hamilton
Subject: Re: fighting dioxin (The Orange Resource Book)
From: B.Hamilton@irl.cri.nz (Bruce Hamilton)
Date: Jul 14 1995
Newsgroups: sci.environment
In article <1995Jul12.193347.15354@vexcel.com>
dean@vexcel.com (Dean Myerson) writes:
>In article <...> B.Hamilton@irl.cri.nz (Bruce Hamilton) writes:
>>In article <...>dean@vexcel.com (Dean Myerson) writes:
>>The number of halogen atoms in each oc molecule is constant, regardless
>>of being manmade or neutral. If you are suggesting that manmade ocs
>>include more of the highly halogenated molecules I suspect that would
>>be correct.
>By context, this is how I understood the use of the term "highly
>halogenated" (length of the chain).
Picky I know, but dioxins are two aromatic ring joined by two ether links,
and dibenzofurans are two aromatic rings joined by one ether link and
one carbon-carbon link. The halogens add to the benzene rings and
adding more can reduce the toxicity ( refer below )..
>I wasn't suggesting that our bodies can differentiate for the same
>compound, just that prior to production of dioxin, there was no
>body burden.
I'm still not certain this is correct. Our bodies process all molecules
we encounter, we react to them differently, some we metabolise,
some we don't affect, some we store. As there is significant evidence
that there are natural sources of dioxins from combustion it is highly
probable that we have always encountered dioxins and thus do have
a background level. It's important to realise that even at part per
quadrillion levels, that is still a huge number of molecules. I don't
know the average molecular weight of humans but as we are 70%
water (MW 18) and have a reasonable amount of fat ( eg tristearin
at MW 891 ) lets assume fat = MW 850, 5% fat and a mass of 75kg,
and the oc ( usually reported as ppq in mass/mass ) has a MW=320.
1 ppq mass/mass oc in fat = 2.66 ppq moles oc in fat
That is 75 x 0.05 = 3,750/850 = 4.41 moles of fat molecules.
As ( from memory ) one mole = 6.02 x 10^23 molecules
Then the person contains 2.65 x 10^24 fat molecules and
thus one part per quadrillion mass/mass
2.66 x 10^-15 times 2.65 x 10^24 =
7,000,000,000 oc molecules in the fat ( and there will be others
in other tissues and fluids ).
Now as we currently only measure down to ppq levels, I believe
we probably all have some ocs from natural sources, just that
the levels are below our current level of detection, and we know
they do have a body half-life and thus there will always be an
equilibrium, and that the extra burden of higher exposures
pushes the burden up, perhaps overwhelming whatever
normal body processes control the toxin. Just because current
analytical technology can not detect low levels ( even ppq levels
are difficult - inadvertent contamination during analysis becomes
more and more a problem ), that does not mean we have none.
A far more difficult issue is what level can we cope with - this is
difficult because we don't know enough about near-background
levels of potential toxins to establish what is toxic ( overwhelms
the body's defence mechanisms). We don't even know many of
the mechanisms, so we have to be careful to ensure any testing
of toxins does include the defence mechanisms - that is why for
decades the measurements have been based on detectable
effects in humans. As we are a diverse molecular soup, we have
difficulty ascertaining that the 9 billion oc molecules would cause
adverse effects, not any of the other molecules, and ensuring
that the bodies defence systems are not coping.
This is why some toxicological test results are disputed ( eg cell
culture tests for some carcinogens ), they do not seem to reflect
the way the whole body processes chemicals. Based on the
test results we should all be a festering mass of fatal ailments.
Life is a cancer, and we know some humans in some environments
have longer lifespans than others, but we don't know if that is the
environment ( exposed to less toxin, thus defences last longer ) or
the individuals ( exposed to the same toxin, but better defences ).
Sometimes we know less about defence mechanisms than we
know about toxicity.
>>I think I am misunderstanding your use of the term ocs. In the
>>case of dioxin we measure very specific molecules ( including the
>>infamous "dioxin" ( 2,3,7,8-dibenzo-p-dioxin ) ) and there would
>>be no difference in the metabolization of each depending on its
>>origins. There are differences depending on molecular structure,
>>but as dioxins are produced by fires (forest = natural, engines and
>>incinerators = manmade ) the structure distribution will be complex.
>I switched to the more general case. I believe that most of the
>natural oc's identified by Gribble have shorter chains and may be
>more easily metabolized.
No, it's far more complex than that. Remember that for dioxins, four
chlorines in specific positions (2,3,7,8) are required before the
molecules are regarded as toxic, and additional chlorine molecules
to such toxins actually decrease the toxicity. ( There is one exception
2,3,4,7,8 pentachlorodibenzofuran is more toxic than 2,3,7,8 tetra
chlorodibenzofuran). I've not bothered following the rationale, but
I believe the toxicity is due in part to the very neat shape/symmetry
of the 2,3,7,8-substituted molecules. There are some very small
molecules that are highly toxic ( HCN ), and we presumably have
some defences/redundancy for background levels of the vast
majority of molecules we encounter. There is nothing particularly
malicious about the chlorine atom, we appreciate it in inorganic
compounds like salts. The problem is that we are sometimes
subjected to levels of chemicals that overwhelm our normal
defence processes, and it's not really associated with molecular
size usually, more with solubility, stability and reactivity. We
metabolise large molecules ( fats have 54 carbons ), and we can
even convert harmless molecules into toxins.
...
>And that is why it is important to determine whether they oignored
>available evidence. 1989 is 6 years ago, a long time for these issues.
Gribble noted " An exhaustive review published in 1973 documented
200 organohalogen compounds from all natural sources"
The rate of discovery has continued rapidly ( possibly because of the
development of the Electron Capture Detector and Mass Specs in the
1970s and early 1980s ) until over 1500 are known now.
There is no excuse for the IJCGL Science Advisory Board to write
in1989 that
" There is something non-biological about halogenated organics
( excluding iodinated compounds )... Chemicals [that] do not occur
naturally....."
Bruce Hamilton
Subject: Re: fighting dioxin (The Orange Resource Book)
From: B.Hamilton@irl.cri.nz (Bruce Hamilton)
Date: Jul 21 1995
Newsgroups: sci.environment
In article <3uj8kb$iv3@news.uni-c.dk>
iaotb@inet.uni-c.dk (Torsten Brinch) writes:
>Bruce Hamilton (B.Hamilton@irl.cri.nz) wrote:
...
>>I'm still not certain this is correct. Our bodies process all molecules
>>we encounter, we react to them differently, some we metabolise,
>>some we don't affect, some we store. As there is significant evidence
>>that there are natural sources of dioxins from combustion it is highly
>>probable that we have always encountered dioxins and thus do have
>>a background level.
>The messy combustion processes in volcanoes and forest fires can lead
>to almost any molecule. Alas - maybe in very low numbers.
>-this leaves us with the conclusion that we have a background level for
>almost any chemical compound. And you may be right that this constitutes
>a body burden. I am not sure of the value of this observation.
There are several aspects. Obviously a body burden exists only if
our body accepts or stores the chemical. So although we encounter
all the various chemicals, only specific configurations accumulate.
In the cause of dioxin, it is only the 2,3,7,8-substituted compounds
that accumulate, thus the toxicity of other substituions are not
really relevant, as they don't accumulate - obviously their toxicity
would be important if we still encountered a toxic dose. But there
are always the metabolism and excretion mechanisms to consider
as well. If we ingest more than we excrete, and don't metabolise it,
we have a problem of accumulation.
>The question is, whether processes, caused by man, have led to
>a significant increase of this body burden. And whether this increase
>has taken us from levels insignificant to biological processes, to
>harmful levels.
It is a continuous biological process, it is when the defences are
overwhelmed, or the equilibrium position changed, that causes
problems. To suggest that only processes caused by man are
responsible ignores the detail that man has learnt to avoid
many of the toxins. Remember the most toxic substances
known are various marine toxins, and more people still die
of a huge range of diseases than from chemical poisoning
- the bugs hate us as well :-).
Organochlorines may be nasty to us, probably because we have
significantly added to the background levels, but if it takes 100
OC molecules to kill me, it doesn't really matter what their birth
certificates say. It does matter if "natural" OCs only ever reached
99, but then a manmade one appears, or if natural background
levels were 5 and then 95 manmade ones appear.....
>>A far more difficult issue is what level can we cope with - this is
>>difficult because we don't know enough about near-background
>>levels of potential toxins to establish what is toxic ( overwhelms
>>the body's defence mechanisms).
>I am not sure, that I understand this. Are you saying, that near-background
>levels could not be toxic, because we must have developed a sufficient
>defence mechanism in order to survive?
I'm saying that as we have survived in our environment till now,
various natural selection processes may have provided some
defence mechanisms, but when we accidentally overload them
then we encounter toxic effects. If I assume we are the product
of our environment then we do respond to what we encounter,
both non-toxic and toxic - we avoid the latter..
>>We don't even know many of
>>the mechanisms, so we have to be careful to ensure any testing
>>of toxins does include the defence mechanisms - that is why for
>>decades the measurements have been based on detectable
>>effects in humans.
>Don't close your eyes for effects in non-humans. They are important too.
Not when we are considering humans. It is the toxic effect on humans
that is important, animals are only acceptable surrogates because
using humans as deliberate experimental subjects is unacceptable.
>But which defence mechanisms, measurements, detectable effects in humans
>are you actually referring to? You seem to have something specific
>in mind, yet are so vague.
>Evaluations of toxins are not usually made with measurements based on
>detectable effects in humans. Such evidence is only obtainable
>'by accident'.
Exactly. The toxicological basis for determining "safe" exposure limits
for chemicals has been "no observed effect" when compared to a
control group. This group has had several major threads on the
history of the ACGIH TLVs over the last few years. A good assessment
is the six-part series " The Toxicological Basis of TLVs" in the Industrial
Hygiene Journal in 1959. The information was not obtained "by accident"
but by carefully designed experiments involving human subjects. The
series is interesting because it looks forwards and backwards. They
predicted we would move towards various mechanism models and
an ability to assess toxicity by structure, what they failed to see was
the complexity of our molecular soup would still confound our ability
to clearly establish "safe" limits.
>Is it really a fact, that humans demonstrably take in chemicals in levels
>shown by these tests to be mutagenic to cell cultures
>('festering mass of fatal ailments').
How many mutagenic studies have 100% hit rate?. Most toxicity
studies try hard to control various parameters. In real life we
may well take in both the toxin and the antidote at the same
time, often in crude "natural" products - eg antioxidants with
toxic lipids. Certainly several experimentally-toxic levels of
chemicals are below typical exposure levels for some
populations - fluoride springs to mind. I suppose I could search
out specific mutagens if you really wish identified examples, I
suspect Vinyl Chloride monomer would be a candidate, given
the prediction of huge increases in poisoning that did not occur.
Certainly there are several models that use no threshold ( no defence
mechanisms ) when specifying safe limits, but equally there are
models that do.
>Those people, who have longer lifespans than others, would be those
>with the combined benefit of better defences and less toxin,
>wouldn't they?
Possibly, but if the population never encounters the toxin, the
superiour defences are irrelevant. It's dangerous to add various
factors without identifying the relevance, that's why many toxicity
tests can not be universally applied - we don't know what other
factors are significant.
>And the people with weak defences, in environments subjecting them to more
>toxin should then have shorter lifespans?
Possibly, but it will not always be that exposure will be below some defences,
and above others - it could be above or below both, meaning the additional
defences confer no advantage, and if having them is a liability against
another toxin......
>And we cannot abandon the latter
>(sorry, you are to weak for our environment). Rather we should attempt
>protection by attempting less toxin, shouldn't we?
The problem is that we don't know enough about the toxins to establish
what is an acceptable level. Should we chop down forests to remove
pollen and other toxins for allergic and sensitised people?. Better to
move the people?.
>>No, it's far more complex than that. Remember that for dioxins, four
>>chlorines in specific positions (2,3,7,8) are required before the
>>molecules are regarded as toxic, and additional chlorine molecules
>>to such toxins actually decrease the toxicity. ( There is one exception
>>2,3,4,7,8 pentachlorodibenzofuran is more toxic than 2,3,7,8 tetra
>>chlorodibenzofuran).
...
>As stable molecules, dioxines must exercise toxicity by having a
>shape, that fits into biological structures, disturbing some function
>- and as substitution pattern affects shape, it also must affect toxicity.
>So it may well be, that some measured toxic effect (which, by the way?)
>is tied to/augmented by the 2,3,(4),7,8 substitution in dibenzodioxines
>and dibenzofuranes. I'd then suspect other substitution patterns to
>be effective too, but less potent. Some substitution patterns might not have
>the effect at all.
Only the 2,3,7,8-substituted ones accumulate, thus the toxicity of
the others is irrelevant.
...
>>There is nothing particularly
>>malicious about the chlorine atom, we appreciate it in inorganic
>>compounds like salts.
>Chlorine atoms as well as chlorine molecules are strong oxidants and
>are malicious to life. Chlorine ions in salts are comparably safe.
No. Their oxidizing ability isn't malicious - it is harmful, but that
doesn't imply maliciousness. I wa trying to demonstrate that
occupying position 17 in the periodic table doesn't confer
willing membership of the "hate humanity" gang. If this chlorine
bikie puts on his chloride jacket, he is friendly. The same applies
to other members of the periodic table - eg oxygen/ozone
>But this tells us absolutely *nothing* about the necessarily diverse
>effects of the diverse group of molecules called organochlorines.
Nor was I implying that it did.
....
>We know that most 'non-biological' molecules are
>useless as food, and they can be harmful to life,
>if they interfere with the processes going on with
>the 'biological' molecules.
?. Some minerals are essential for life, and many
animals actually get the minerals direct, eg at salt
licks. The minerals around here haven't yet become
paid up members of the "life" club...yet :-).
>>" There is something non-biological about halogenated organics
>>( excluding iodinated compounds )... Chemicals [that] do not occur
>>naturally....."
>Well, there could be excuses..
>First of all:
>This is a quotation first snipped by
>Gribble, then by you. What is the context?
Pass. Regardless, the sentences are incorrect statements of faith.
>And yet more: If it is wrong (in your and Gribble's opinion) to write,
>that there is something non-biological about halogenated organics,
>then you must think, that it would be correct to write,
>that there is *nothing* non-biological about halogenated organics.
>or more simply: that halogenated organics are biological.
:-). If I say it wrong to say the sky is white, that does not imply
that I think the sky is black. The basic fact is that many organisms
use halogens, and some use organohalogens, just like some organisms
use many other elements. Because humanity found organochlorines
useful does not confer "non-biological" attributes on OCs
>If I think of the fundamental chemical structures in living organisms
>and the processes that carry life as we know it (replication, photosynthesis,
>respiration etc.) ... it leaves me with an opinion rather close
>to the quotation from the IJCGL Science Advisory Board.
Your choice.
>By snipping the last part of the quotation, you make the impression, that
>the Board postulates that halogenated organics do not occur naturally.
>This is not fair
"...Chemicals [that] do not occur naturally..." is a direct extract from
Gribble's article, seems pretty unambiguous to me. I'd be hard pushed
to get "chemicals that occur naturally " from it - regardless of what
followed it.
>The part you use:
>"Chemicals [that] do not occur naturally ...."
>continues even in the version given by Gribble with
>" ..are often persistent, since there are often no natural biological
>processes to metabolize or deactivate them"
>- a statement, which is not *terribly* wrong.
You must also be aware that the same Gribble article (p.1378-9)
has a whole section devoted to "Metabolism and Biodegradation"
" Thus, contrary to common perception, organohalogen compounds,
both natural and unnatural, are readily metabolised and biodegraded
to halide ion by a myriad of microorganisms"
That statement isn't *terribly* right either, and, after all, this is
supposed to be a Science Advisory Board.
>Mind you, Gribble has done an excellent job. I am sure, that he has
>counted the known naturally occurring halogenated organics quite
>efficiently, and that very few has been forgotten. He found more
>than 1500 naturally occurring halogenated organics.
Gribble clearly attributes that number to Professor J.F.Siuda of the
University of Pittsburgh.
>Does anyone know the number of naturally occurring oxygenated organics?
Oxygen is just another element in the period table, and we do have
problems with it as well, but I suppose volume two of the Orange
Resource Book might deal with them :-).
>Gribble does not make the comparison for perspective. He does not mention
>the number of known man-made halogenated organics either....
The title was " Naturally Occurring Organohalogen Compounds - A
Survey " - how very remiss of him to ignore the ( approx 90 )
remaining elements, I suppose Vol 2 of his Survey will select another
two elements :-).
>Oh I keep forgetting. All kinds of halogenated organics can be found in
>the smoke from forest fires or in the plume from a volcano.
>They're all natural.
Yup, and they don't behave any differently to their man-made brothers
and sisters. The problem is the numbers, not the birth certificates :-).
Bruce Hamilton
Newsgroups: sci.agriculture,sci.environment
From: B.Hamilton@irl.cri.nz (Bruce Hamilton)
Subject: Re: Pesticides and Reproduction
Date: Sat, 13 Jul 1996 21:30:35 GMT
af329@james.freenet.hamilton.on.ca (Scott Nudds) wrote:
>: Thomas T. Aquilla, Ph.D. wrote
>: You still don't seem to get the point. The abundance of naturally-occuring
>: chlorinated hydrocarbons exceeds the total of all synthetics (including
>: chlordane) by orders of magnitude. Relative to the naturally-occurring
>: halogenated hydrocarbons (with potential estrogen-like activities), the
>: levels of synthetic compounds are insignificant.
....
> I'm sorry, your conclusion does not logically follow at all.
I understood that he was reporting Gordon Gribble's conclusion.
For the curious, one of the best sources of detailed information is
"Naturally Occuring Organohalogen Compounds - A Survey"
G.W.Gribble
Journal of Natural Products. v.55 p.1353-1395 ( October 1992 )
Yes, that is 42 pages long, with 556 references, in a peer-reviewed
highly-repected *Science* journal - not the media release promo
stuff Mr Nudds produces so prolifically when challenged to produce
verifiable sources, especially if from the Science Advisory Board of
the International Joint Commission on the Great Lakes. One of
their more infamous statements in their 1989 report included:-
" There is something non-biological about halogenated organics
( excluding iodinated compounds )... Chemicals [ that ] do not occur
naturally... oare often persistent, since there are often no natural
biological processes to to metabolise or deactivate them "
As G.W.Gribble notes, " not only are these statements incorrect, but,
coming from a " Science Advisory Board", they reflect a disturbing
ignorance of the chemical composition of our environment and the
biochemical processes therein." ( from J.Nat.Prod. article above ).
> What you are doing however is comparing chemicals,
>natural and synthetic that are in many cases dissimilar, and you are
>ignoring the fact that it is most probable that we have evolved to
>tolerate exposure to naturally occuring chlorinated hydrocarbons.
The only difference between a naturally-occuring
and a man-made molecule is likely be the isotopic ratios of the
elements if the synthetic is petroleum derived - by definition,
dioxin is 2,3,7,8-tetrachlorodibenzo-p-dioxin, whether made by
man ( municipal incinerators or leaded petrol powered automobile
exhausts etc ) or nature ( forest fires ). Some early peer-reviewed
studies indicated that natural production of dioxin was larger.
" Indeed at least two groups conclude that forest and brush fires
are the major source of dioxins in the environment ( 397,408 ).
in the words of one author, "based on available information, forest
fires are estimated to be the largest source of PCDD release to the
environment "( 408 )." ( J.Nat.Prod. article above ). These days, it
is accepted that at least for industrial nations like the UK, the major
sources now are manmade, but that there is a low "natural"
background.
In fact, if you had read the supplied references you would
have discovered information like " The total pool of adsorbable
halogen species in peat in sweden is 300,000-400,000 tons, whereas
the largest industrial emissions are from paper pulp industries and
are 10,000 tons year (474). Since in this area of Sweden the
topography excludes leaching fron surrounding areas into the
bog under study, these organic halogen compounds must be of
natural origin" ( from J.Nat.Prod. article above ).
> Meaningless. It is a good bet that any stable chemical you can design
>will be found somewhere in nature. Unless concentrations and exposures
>are provided meaningful comparisons can not be made.
No. it is not meaningless, and I suggest you would be hard pushed
to find an awful lot of stable chemicals - many of the natural catalytic
and enzymatic reactions *only* favour one isomer, even in the case of
the fatty acids that make up our fats, the biochemical naming system
( omega ) assumes all double bonds are cis, whereas chemically
trans bonds are often favoured, and synthetic mixtures contain both.
> From what I have seen of "National Review", its reason for existence
>is to distribute political propaganda. I therefore doubt if it
>provided comparisons based on the relative concentration and exposure to
>the naturally occurring and synthetic chemicals of the same type.
What about the Journal of Natural Products, or even the Journal of
Chemical Education - which you obviously don't read. ( " Natural
Organohalogens - Many More Than You Think". G.W.Gribble
J.Chem.Ed. v.71 p.907-911 ( November 1994 ) - with 98 references ).
Perhaps you have developed another distasteful obsession against
G.W.Gribble, like you have against John McCarthy. In which case,
the article "Organohalogens: the natural alternatives" E.J.Hoekstra
and Ed W.B. De Leer. Chemistry in Britain. February 1995 p.127-131
with 23 references, is a good introductory alternative.
You have this very unfortunate habit of deciding that all who don't
agree completely with you must oppose you. As Paul Savage,
Thomas Aquilla, and others have noted - some of your claims
are not relevant, are still being researched and are ambiguous,
or are incorrect. That does not mean they support washing the
planet with man-made pesticides, or are claiming that pesticides
are harmless - they * have * provided the peer-reviewed
references for their position, and in the sci.* hierarchy, you
should attempt the same.
I support replacing environmentally harmful chemicals with less
harmful chemicals when it is responsible to do so - but I don't
support jumping from the frying pan into the fire just because
of a panic attack that is not grounded in good science, and often
solely from media-fuelled public misperceptions about chemicals.
Bruce Hamilton
Newsgroups: sci.agriculture,sci.environment
From: B.Hamilton@irl.cri.nz (Bruce Hamilton)
Subject: Re: Pesticides and Reproduction
Date: Wed, 17 Jul 1996 17:14:35 GMT
[....]
From the Gribble article in the Journal of Natural Products,
Manmade emissions of methyl chloride ( from burning PVC etc ), 26,000 t/yr,
Natural emissions of methyl chloride = 5 million t/yr.
" It is estimated that some 130 pounds of PCDDs are produced from
Canadian forest fires annually ( 56).... Another milestone observation is
the enzymatic conversion of chlorophenols into both PCDD's and PCDF's
in the ppm range by horseradish peroxidase enzyme (HRP)(58). This
extraordinary revelation opens the door to the possibility that a source
of environmental PCDD's and PCDFs' may be their completely natural
formation from (natural) chlorophenols by soil and water molecules "
" Natural Organohalogens - Many more than you think " G.W.Gribble
J.Chem.Ed v.71 p.907-911 ( November 1994 ).
You might like to compare the 0.26kg TCDD found in the soil around
the Seveso factory and the estimated release of up to 3 kg total
mentioned in " Dioxins released from chemical accidents " A.H.Meharg,
D.Osborn. Nature v.375 p.353-354 ( 1 June 1995 ).
The same article notes that previous reviews of dioxin sources
in Sweden and the UK have identified only enough sources to account
for around 10% of the total depositions, and that the EPA reached
similar conclusions for the USA. The article notes that those
results are based on relatively few observations, and the underlying
science requires strenghtening.
Another article notes that the EPA dioxin report ( has it been released
yet? ), estimated that 2.9 - 22.7 Kg/yr of TEQs may come from manmade
sources, but as much as 50kg/yr may be raining downing on the US
( "Incinerators Targeted by EPA" J.Johnson. ES&T p33A-35A v29 (1995).
Note that in the discussion about dixoin emissions, people should be
careful with their units. For example the EPA reported that the USA
emitted 30 lb of dioxins as 2,3,7,8-TCDD toxic equivalents, which is
actually eqivalent to around 1800 pounds of the typical congener
profile ( EPA reassesses Dioxin, p6 Sept 19, 1994 C&EN ).
>: Some early peer-reviewed
>: studies indicated that natural production of dioxin was larger.
>: " Indeed at least two groups conclude that forest and brush fires
>: are the major source of dioxins in the environment ( 397,408 ).
> This is very doubtful. The study of lake sediment cores show
>increasing dioxin levels corresponding to the increase in
>industrializaion. If Dioxin was primarily produced naturally by the
>environment, one would expect the core studies to show that dioxin
>levels would not change substantially in the cores.
Not necessarily so, the dioxin could degrade over time, and
thus the older part of cores would show reduced levels. Much of the
evidence for background levels comes from sealed soil samples,
not lake sediment core samples. The archived soil and herbage
samples from the UK covering the period 1846-1986 were analysed
for total levels of dioxins and furans. The concentration in soil
samples increased from 31ng/kg dry weight in 1893 to 92 ng/kg in
1986, whilst the concentrations in unwashed herbage increased
from 12 ng/kg in the 1880s to 96 ng/kg in the 1970s. As noted above
only about 105 of the sources had been identified in three national
studies...
>: These days, it
>: is accepted that at least for industrial nations like the UK, the major
>: sources now are manmade, but that there is a low "natural"
>: background.
> This would seem to be most compatible with the evidence.
As noted above, the UK evidence is from sealed samples, not from
core samples - which may be consistent with the archived samples.
However, the conclusion is still open, as source/deposition mass
balances are still extremely poor.
Newsgroups: sci.agriculture,sci.environment
From: B.Hamilton@irl.cri.nz (Bruce Hamilton)
Subject: Re: Pesticides and Reproduction
Date: Fri, 26 Jul 1996 20:19:19 GMT
iaotb@inet.uni-c.dk (Torsten Brinch) wrote:
>Bruce Hamilton wrote:
>>So it would be interesting to obtain some data for degradation rates
>>during transportation and storage in air, water, plants and soil, and
>>ascertain what the actual background quantities are. An 1893
>>UK soil sample gave 31,000pg/kg dry weight, whereas a 1986 sample
>>gave 92,000pg/kg dry weight of total dioxins. That is still an awful
>>lot of dioxin for 1893, especially when the organochlorine industries
>>hadn't started.
>1893 is certainly pre-chloro-organic, but it is not pre-industrial.
>I would be very cautious to interpret the 31 pg/g total dioxin
>in the 1893 UK soil sample as some kind of natural background level.
>Great Britain was not exactly pristine in 1893!
I never said it was. I said it was an awful lot of dioxin for 1893
especially when the organochlorine industries hadn't started.
Of course the combustion of wood and coal will have contributed
to the elevated levels, but I was pointing out that such levels
aren't attributable to the organochlorine industry.
>Combustion of wood (whether by forest fires or by man)
>or combustion of coal could be the main sources contributing
>to this figure.
>It should be possible to distinguish between the wood-combustion
>source and the coal-combustion source in this sample by examining
>the dioxin congener profile. Wood combustion would be expected to
>yield preferentially TCDD, whereas coal combustion
>would yield almost equal amounts of TCDD, PnCDD, HxCDD, HpCDD,
>and OCDD.
This is nowhere near as clearcut as you imply. The congenor
profiles are not unique to combustion source, and depend a lot
on the combustion conditions, you also need to consider the
isomer profiles, homologue profiles, and the 2,3,7,8 substituted
PCDD/PCDF congenor profiles as well. I've already referenced
Hagenmaier's paper discussing this topic in this thread,
( "Correlation of Environmental Occurance of PCDDs and PCDFs
with possible sources". H.Hagenmaier, C.Lindig, J.She.
Chemosphere v.29 p.2163-2174 1994 )
>A mapping of the congener profile would also be helpful to
>exclude the possibility that the 1893 sample was contaminated
>post-sampling from sources (PCP to name one) in the chloro-organic
>society of the 1970ties and onward, which gave not only
>a dramatic increase in the dioxin flux, but also an obvious
>change in congener profile.
This was not one sample, but a systematic analysis of archived
herbage and soil samples from 1840 onwards. This UK data is
often cited as representing historical trends because the samples
were sealed in containers.
Stuff from sediment cores deleted - I've covered the
failings of those previously. Whilst the authors might
calculate the half life in the sediment as 45 years, compare
that to the weathering half life of dioxin on plants of 10-14
days ( ie the dioxins are removed from the plant surfaces
- not nessarily that they are completely degraded ), and
the known fact that atmospheric processes tend to favour
deposition of the higher chlorinated dioxins (' Wet and dry
deposition of chlorinated dioxins" C.J.Koester and R.A.Hites
ES&T v26 p1375-1382 (1992) ). The sediment core data is
not as robust as the archived herbage and soil data as a
means of determining historical trends of dioxins.
Bruce Hamilton
Newsgroups: sci.agriculture,sci.environment
From: B.Hamilton@irl.cri.nz (Bruce Hamilton)
Subject: Re: Pesticides and Reproduction
Date: Fri, 26 Jul 1996 20:19:25 GMT
[....]
Once again,
for the USA:-
" { discussing medical and municipal waste incinerators }
These two incinerator types contribute 20-50% of all dioxins
that drift to Earth through air deposition, according to EPA's
exposure estimate. Some 8100 grams of dioxin per year come
from these incinerators out of a total of 9300 grams emitted to
the atmosphere by all incinerator sources, EPA says. These
figures are midpoint averages with huge variances, however.
The Agency believes 2900-22,700 grams per year may come
from all known anthropogenic air sources. But when unknown
sources and recirculating dioxin are counted, EPA says as much
as 50,000 g may be raining down each year on the United States.
These figures are in " Toxic equivalents " (TEQ) for all dioxins
and furans, based on the toxicity of 2,3,7,8- TCDD "
" Incinerators targetted by EPA " J.Johnson. ES&T v29 p33A-35A
( 1995 )
" In previous reviews in the UK, and Sweden, the 'known' sources
of dioxins ( manufacture of chlorinated organic compounds,
chlorinated waste incineration, wood and coal burning, metal
recycling and wood-pulp and paper bleaching ) account for only
10% of depositions. The EPA review draws similar conclusions for
the US. But these estimates are based on relatively few
observations and the underlying science requires strengthening."
" Dioxins released from chemical Accidents" A.A.Meharg, D.Osborn
Nature v375 p353-354 ( 1995 )
> The claim has been made that naturally occuring dioxins are more
>prevalent than man made dioxins. I have asked you to provide numbers to
>back up your claim, and you have refused. Is this because you don't
>have the numbers or because you simply refuse to provide them?
Scott is becoming disorientated again...you should reduce your
exposure to PTBs.. You have not asked me until this post, you have
asked Tracy to provide numbers. I've previously asked you to
provide those numbers, I've provided the methyl bromide numbers,
as they represent natural and synthetic molecules, the subject
under discussion. I've never, nor has Tracy, claimed that naturally
occuring dioxins are more prevalent than manmade dioxins, you
need to improve your comprehension skills. I had no problem with
Tracy's clearly defined assumption.
The major sources of manmade dioxins are from combustion processes,
and it can be quite difficult to quantify the amounts, some broad
estimates have been made, eg for Germany, and UK
in grammes of International toxic equivalents ( I-TEQs) per year
( "Sources and sinks of dioxins". H.Fieder and O.Hutzinger
Chemosphere v25 p1487-1491 ( 1992 ), "Dioxin Emissions to fall"
chemistry in Britain Nov 1995 p 862 )
Germany UK
Municipal waste incinerators 5.4 - 432 460 - 580
Hazardous waste incinerators 0.5 - 72 1.5 - 8.7
Hospital waste incinerators 5.4
Sewerage sludges incinerators 0.01 - 1.13
steel manufacturing 1.3 - 18.9 3 - 41
siner plants - 29-47
Non-ferrous manufacturing 38 -380
landfill gas incineration/burning 0.24 - 2.4
automotive - leaded fuel 7.2
automotive - unleaded, no cat 0.7
automotive - unleaded, catalyst 0.1
automotive - diesel fuel 4.6
traffic - 1- 45
crematoria - 1 -35
Home heating - oil 1.2
home heating - coal 1.1
Home heating - briquettes 1.76
Cigarettes 0.012
Total 67 - 928 560-1100
Note that the UK expects their new regulations to reduce the
emissions for incinerators to 15 g and the total to 110-350g by 1998.
There are still many chemical mechanisms available which can
be used to destroy organochlorines which do not involve
combustion, and it is highly likely that some of those will
be used for disposing of compounds that can produce
dioxins during incineration as permitted national emissions are
reduced. A brief review of some techniques that are
available for disposing of organochlorine contaminated
oils is available in "Comparative feasibilites of processes for the
destruction of organochlorines " W.A.Davies and R.G.H.Prince
Trans IChemE v72 p113-115 Part B (1994).
Our major exposure to dioxins is via food, with the average
dietary intake in the UK estimated at 125 pg TEQ/day. The
World Health Organisation regional office for Europe had
a tolerable daily intake of 600 pg / kg body weight / day
for 2,3,7,8-TCDD. This may have changed, with the new
indications of adverse effects at low levels as reported
in the EPA reassessment ( if that has finally passed all
the review stages, and is actually formally published)
The major daily sources ( in I-TEQ ) are;-
Meat, meat products, poultry and offals = 38 pg
Cow's milk = 23 pg
Mats and oils = 19 pg
Milk products = 12 pg
Fish = 7.7 pg
( Dioxins in Food. Food surveillance paper 31 UK MAFF ( 1992)
Germany and the Netherlands also came in the range of
70 -125 pg TEQ/day. A 1994 US survey ranged over 18 - 192
pg TEQs / day ( Dioxins in US Food and Estimated Daily Intake"
A. Schecter and 7 others. Chemosphere v29 p2261-2265 (1994).
It is worth noting that dioxin levels in US human adipose tissue
have been decreasing since about 1970 ( remember that only
the 2,3,7,8 substituted compounds accumlate, with the levels
of the higher chlorinated homologues predominating ) from
around 18 pg/g lipid in 1971 down to around 4 pg/g lipid in 1987.
(" PCDD and PCDFs concentration levels in human adipose
tissue samples from the continental US collected from 1971
through 1987" J.S.Stanley and 8 others. Chemosphere v20
p895-901 (1990).
There certainly is compelling evidence that during the period
from 1930-1970 the emissions of some manmade
organochlorines far exceeded natural production, and I've
never said otherwise. However, whether that was (or still is )
true for global dioxin remains to be seen, certainly some
industrialised countries were likely to have higher manmade
levels, but while we still can't detect 40,000 dioxin molecules
in each litre of air, and we don't understand the natural
production and destruction rates, it's a bit premature to suggest
there is no significant background. Even if there is no significant
background, that does not mean our ancestors didn't have
some small exposure from fires, and cooked food, ( nor does
that statement imply that they were exposed ). Nobody has
claimed that natural dioxin production exceeds manmade
production, but some people have trouble understanding that.
I wouldn't be surprised if it did, but also wouldn't be surprised
if it didn't..:-)
Well, that's all from me, there remains a lot of research to
be performed on sources, sinks, distribution, and toxicity of
Dioxin. Oh...., and Scott's poisoning by PTBs?
If you hadn't already guessed - Paul, Tracy, Bruce and Steinn :-).
Bruce Hamilton
From: paul.savage@chem.csiro.au (Paul Savage)
Newsgroups: sci.agriculture,sci.environment
Subject: Re: Pesticides and Reproduction
Date: Mon, 29 Jul 1996 14:32:49 +1000
In article <4t6120$r9d@news.uni-c.dk>, iaotb@inet.uni-c.dk (Torsten
Brinch) wrote:
> Paul Savage wrote:
> >By the way, if a scientist is funded by GreenPeace to do a study on, say,
> >the chlorine industry, would you consider his/her work to be tainted by
> >the funding source?
>
> I don't think I have ever read any Greenpeace funded study, Paul.
> If you give me the title, I'll tell you what I think of it.
It was a hypothetical question Torsten. But now that you raise the point I
wonder why Greenpeace don't fund scientific studies (if that's the case).
Surely not lack of funds.
> >OTOH, the GreenPeace position talks of toxicity of OC
> >compounds as a class -- this is clearly nonsense since while the the C-Cl
> >bond has an inherent *reactivity* it has no inherent *toxicity*.
>
> As I said, if you give me the title of the Greenpeace study, I'll read it.
> You say it claims inherent toxicity of the C-Cl bond?
> Interesting thought.
If you look at "Chlorine Crisis: Time for a global phase-out" by
Greenpeace you will see some of the following:
"Chlorine is the common link in many of the world's most notorious
environmental poisons.....If we wish to preserve the life-sustaining
capacity of the planet, the root of the problem -- the production
and use of chlorine -- must be phased out."
and
"Virtually all organochlorines that have been studied have
been found to cause at least one of a wide range of effects,
including ...[long list snipped]"
and
"It is prudnet, sensible and indeed necessary to treat these
[chlorinated organic] substances as a class rather than a series
of isolated individual chemicals."
and
"We need to focus on the entire class of organochlorines and the
chlorine-based industrial processes that give rise to these mixtures.
....organochlorines should be treated as a class and phased out,
with exceptions made only if industry can show that an individual
use is safe or essential"
I may be interpreting this incorrectly but if Greenpeace wants to treat
organochlorine compounds as a "class" and phase them out because of common
toxicity/environmental characteristics then they are ascribing some
special toxicity to the C-Cl unit. After all this is the only physical
thing that all organochlorine compounds have in common.
Paul Savage
--
* * p.savage@chem.csiro.au Australian Science
* . http://www.chem.csiro.au/savage/ Australia's Future
* these comments are personal opinions not official CSIRO policy
From: paul.savage@chem.csiro.au (Paul Savage)
Newsgroups: sci.agriculture,sci.environment
Subject: Re: Pesticides and Reproduction
Date: Tue, 30 Jul 1996 14:06:01 +1000
In article <4tdk36$jie@news.uni-c.dk>, iaotb@inet.uni-c.dk (Torsten
Brinch) wrote:
> quote Gribble:
> " METABOLISM AND BIODEGRADATION
> As it is with the other elements in our biosphere, the halogens,
> in the form of recyclable halide ions, must be recovered from plants and
> animals when they die, so that succeeding generations will
> have access to halide and others elements prerequisite for life.
> Thus contrary to common perception, organohalogen compounds,
> both natural and unnatural, are readily metabolized and biodegraded
^^^^^^^^^^^^^^^^^^^
> to halide ion by a myriad of microorganisms."
> unquote Gribble.
This is probably wrong, at least by my definition of "readily". Certainly
there are organochlorine compounds that are readily metabolized and
biodegraded but there are some that I would think were quite stable. The
definitions of "readily metabolized" and "quite stable" or even
"refractory" :-) mean different things to different people. That said, if
we were to pick over word-for-word any scientific paper we could probably
find some statements that were not 100% cast in stone accurate. That is
why the language of science is usually equivocal (we believe that...., it
is thought that...., presumably, probably, etc.). One of the reasons
lawyers hate us :-)
> THEN Gribble goes on with some examples (referenced), showing
> that some bacteria and fungi are capable of degrading
> simple 1-2 carbon organochlorines and certain halobenzenes,
> halonaphtalenes, and chlorophenols and that a fungus-species
> has been shown to be capable of degrading not only some
> chlorophenols, but also DDT, PCP and PCBs.Finally Gribble mentions
> the degradation of PCBs by Pseudomonas as well as
> fungus mediated polymerization of halogenated phenols to humic-like
> products.
>
> In other words, Gribble shows examples, that even quite
> refractory :-) organohalogens CAN be degraded
> by microorganisms.
So? There's nothing wrong with this. Examples are useful in this debate.
Would you prefer the Greenpeace position (from "Chlorine Crisis: A time
for global phase-out")
"One reason that organochlorines are useful to industry is that
they tend to be very stable: they resist natural breakdown
processes. But this also means that they persist in the environment
for decades or even centuries."
I wonder if you could name an organochlorine likely to survive for
centuries in the environment? I couldn't.
> After this we are ready for the _conclusion_ :
>
> quote Gribble:
> "Thus, it can be seen that organohalogen compounds not only
> have a natural beginning, but, in the scheme of things, they have
> a natural ending as well. The commonly held belief that
> organohalogen compounds are impervious to biodegradation
> is erroneous."
> unquote Gribble.
So? It does seem to be a commonly held belief that organohalogen compounds
are impervious or at least highly resistant to biodegradation. And it *is*
true that this belief is erroneous. What's the problem here?
> Didn't Gribble make reference to some
> 'common perception' in the introduction?
> It has transmogrified into 'a commonly held belief',
This is a weak semantic quibble. A 'common perception' and a 'commonly
held belief' is pretty much the same thing. This criticism is without
substance.
> that organohalogen compounds are _impervious_ to
> biodegradation. A nice easy strawman, build exactly to
> fit the evidence which can rip it apart.
IMO, this is not a strawman. I talk to a lot of non-chemists and the
message that organohalogen compounds are stable and long-lived in the
environment has made its way into common acceptance. Take the quote above
from Greenpeace or the comment from Nudds (surely a non-chemist) about the
"unususal strength of the C-Cl bond" as evidence.
[unconvincing analogies clipped]
Your point being that a strawman argument is easy to set up and tear down.
I agree. However Gribble's "strawman" is real. There are people out there
saying that organochlorines are all (or mostly) man-made, and almost
impossible to bio-degrade. And not just underinformed environmental
fanatics like Scott Nudds -- big players like Greenpeace. As far as I can
tell, Gribble is just trying to counter-balance the public's perception
with some evidence.
Paul Savage
--
* * p.savage@chem.csiro.au Australian Science
* . http://www.chem.csiro.au/savage/ Australia's Future
* these comments are personal opinions not official CSIRO policy
Newsgroups: sci.agriculture,sci.environment
From: B.Hamilton@irl.cri.nz (Bruce Hamilton)
Subject: Re: Pesticides and Reproduction
Date: Tue, 30 Jul 1996 08:34:58 LOCAL
In article <31FBB19C.1EA0@ism.net>
"Cold Mountain, Cold Rivers" <cmcr@ism.net> writes:
I've answered most of Tony's points earlier, so I hope he finds
all the posts. This just clarifies a couple of points...
>> (Bruce Hamilton) wrote:
>> : The same article notes that previous reviews of dioxin sources
>> : in Sweden and the UK have identified only enough sources to account
>> : for around 10% of the total depositions, and that the EPA reached
>> : similar conclusions for the USA.
Sorry, this must be the 10% that Tony referred to. That's only
about 10% of the total depositions, and I had noted that both
studies used limited data. Tony has referenced a later study
that does seem to account for a much higher level of the
depositions, and has about 10% as all biomass combustion
including forest fires, which is well below some earlier
estimates that I referenced. I assume Tony's later reference
is more correct, but it's surprising the EPA haven't used it
as well in their assessment ( too late? ). It still doesn't
refute my suggestion that there may be a background level,
and that perhaps not all dioxins are manmade.
>> [ Response from Gordon Gribble.]
>> Hi. Thanks for your note. My monograph on the subject has just
>> appeared as Vol. 68 in Prog. Chem. Org. Nat. Prod., Springer Verlag, 1996,
>> in which I document all known examples (1452 as of press time) of
>> organochlorines, many of which are found in terrestrial (non saltwater)
>> environments (plants, fungi, bacteria, lichen, a frog, and now even humans
>> - chlorotyrosine). This comprehensive review should answer all of
>> Ms. Aquilla's questions.
>>
>> Gordon Gribble
>> [ End of response ]
> might be a good riposte from mr. gribble, but we will see how good
> this new data is. i was thoroughly unconvinced by his feature pieces
> on the matter in the front section of >_es&t_ (when he had cataloged 611).
>- how many of the 1452 are duplicate results?
>- what does he mean by "many" ("many were in terrestial environments")?
> the environments he mentions above might well all be more saline than the
> environment within mammal & vertebrates.
>- how many in mammals? in vertebrates? how do we know these aren't
> measurment artifacts?
Well, I don't have access to that review. "Zechmeister" as the Progress
in the Chemistry of Organic Natural Products series is commonly known
as, isn't taken by any local libraries. And volume 68 costs 330DM from
Springer Verlag. As far as I can tell, the whole volume of 498 pages
consists of Gribble's review - but I could be wrong. The ISBN
for curious, rich people is 3-211-82702-1. It is a well known scientific
publication series, so I'd expect a reasonable standard of science,
but also some errors in 1452 compounds and nearly 500 pages.
Knowledge marches on.
The J. Natural Products review tries to eliminate as many duplicates
as possible, and I'd worry about the state of science if a significant
number were artifacts. In some terrestial environments natural saline
environments are common ( eg coastal regions ), and I've no idea
if he separates those in his new review...
>> The issue of saltwater versus seawater is really a non-event,
>> due to various ionic mobility mechanisms, we should expect
>> almost every organism to utilise salts, so it's not surprising that
>> chloride is pervasive, and thus we should not be surprised if
>> some of the chloride is transformed into organochlorines for
>> various biological purposes. The profile of such enzymatically
> i'm sure i know even less than you on this subject, but this
> response is clearly wrong, as far as naturally produced o-cl's
> in saltwater non-mammals, anyway. even allowing for some
> correction in gribble's new survey results, the very high ratio of
> biologically produced o-cl's in high chloride environments to
> that in mammals, especially invertebrates, surely tells us
> something about the unaturalness of o-cl's to *our* environment
> (and about the unusual strngth of the C-Cl bond).
I think you are misreading what I wrote almost every
organism does use salts of some sort, in their cells.
What I meant is that if they have a specific use for an
organochlorine compound ( as a deterrent or predator
inhibitor perhaps ) for a biochemical role, they could
produce and use it. As Gribble and others point out,
( and I've posted some examples earlier ), complex
OCs can be produced by a range of organisms. I wasn't
suggesting we would routinely use them, as I've noted
that's not energetically very sensible, regardless of
any inherent toxicity.
I agree about the strength of the C-Cl bond, the energy
requirements make it unattractive for many purposes and,
as I've noted before, some researchers wonder if some
OCs are just byproducts of some other processes without
a major physiological/biochemical role.
>regardless, i believe this dicussion (and it's twins elswhere
> in this thread) began with a preposterous claim about the
> amount of natually produced o-cl's.
That's the problem - there *was* no such claim. I haven't
seen anyone *claim* the amount. The examples I have
posted have virtually all come from peer-reviewed
scientific literature, and I've just reported them, with any
qualifiers that were appropriate. There are large amounts
of natural OCs reported in soils, bogs etc. that can not
be explained by manmade deposition. Until you posted the
US dioxin data from Thomas and Spiro ( which directly
conflicts with the Canadian data, but is more recent and
sounds more rigorous ), nobody has yet provided references
to counter those examples. I'm not making those numbers
up, they are in the literature, and they need explaining or
refuting.
Methyl chloride ( the data I provided ) is an organochlorine
compound where the annual natural emissions *far* exceed
manmade emissions, so there is at least one example that
makes the claim less preposterous.
> there are too many separate lines of evidence (lake sediment
> time series samples, a d/r relationship between body burdens
> and living near sources of anthropogenic pcdd/f, and the
> agreement in the literature estimating sources of pcdd/f).
Now you are switching back to PCDD/PCDFs, and your
claim of agreement in the literature doesn't stand up. The
earlier data ( and cited by Gribble in his earlier surveys )
was ambiguous - at least two papers claimed large natural
sources from forest fires. Now it may be that later papers
show those claims to be wrong, but as I stated before, it is
necessary to look at the complete homologue and congener
profiles to try an unambiguously identify sources, as the
profiles from combustion are very similar. I suspect it will
become evident that the major source in industrialised
countries will be manmade, but that there will also be
some background from natural sources. If that is the
case, then we might find places on Earth where the natural
exposure is higher than the manmade exposure, depending
on the pervasiveness of the manmade emissions. Dioxin
levels in our tissues are dropping, but they may never have
been at zero. I've noted before the UK herbage and soil data
( ES&T v.25 p1619-127 ) that shows the huge increases that
correspond well with the growth of the OC industry, I've
never suggested otherwise.. my stance is that there may
still be a natural background of dioxins in our environment,
but I've seen no evidence that shows what level and what
source - certainly it was always going to be lower that the
huge amounts splattered around the environment
previously, but is it globally lower than current emissions?.
Nobody has provided a reference yet - has the necessary
profiling even be done?
I note that your signature is still quoting people from the future,
perhaps an earlier post of mine went unseen :-)?
> ||" 'Are the people being protected?'
>cmcr@ism.net || is too narrow a question."
>(Cold Mountain, Cold Rivers || -API lobbyists meeting, 12 Dec. '96
Bruce Hamilton
Newsgroups: sci.agriculture,sci.environment
From: B.Hamilton@irl.cri.nz (Bruce Hamilton)
Subject: Re: Pesticides and Reproduction
Date: Tue, 30 Jul 1996 16:41:18 GMT
It seems this thread has just about died, but as I've just obtained
a couple of new papers on dioxins, I thought I'd summarize them.
I'm crossposting it to sci.agriculture by Oz's request :-), so I
hope those readers who wanted sci.environment readers to stop
crossposting to avoid a Nudds infestation will understand....
I've included a brief background note on dioxins for those that
wonder what dioxins are, and why they cause justifable concerns.
Diligent readers with little else to do will remember that the
issue was whether natural sources of dioxin existed, and if they
did how significant were they?. I'd previously referenced a couple
of papers that claimed they were large, but Tony Tweedale recently
posted a reference to a more recent paper that indicated they were
not significant in the USA ( V.M.Thomas, T.M.Spiro.
Toxicol.Environ.Chem. v.50 p.1-37 (1995)).
Unfortunately, I don't have access to that journal, but I found an
even more recent article by the same authors comparing their results
to those of the large EPA dioxin survey, and specifically discussing
whether there are other sources. ( " The US Dioxin Inventory: Are there
missing sources?". V.M.Thomas T.M.Spiro. Environ.Sci.Technol. v.30
p.82A-85A (1996)). What that indicates is that both T&S and EPA
haven't used any actual data on forest fire emissions, and extrapolate
the numbers from data for residential wood burning. Obviously, there
are significantly different combustion conditions in both situations
- which may well cause significant deviations from such an assumption,
but until more actual field data arrives it seems the best we have.
As well as that, there have been several discussions on the guilt
of the organochlorine industry because the historical samples from
sediment cores show a curve that matches the industry growth. I've
previously pointed out that there are some known problems with
sediment cores, and the best source of such information ( which
provides the same link to the organochlorine industry ) is the
archived UK soil and herbage sample dataset. ( " Increases in the
PCDD and PCDF Content of Soils and Vegetation since the 1840s"
L-O.Kjeller, K.C.Jones, A.E.Johnston, and C.Rappe.
Environ.Sci.Technol. v.25 p.1619-1627 (1991) ). Those authors have
now extended that data in a recent publication ( " Evidence of a
Decline in Atmospheric Emissions of PCDD/Fs in the UK ". L-O.Kjeller,
K.C.Jones, A.E.Johnston, and C.Rappe. Environ.Sci.Technol. v.30
p.1398-1402 (1996)), so I'll include some of the new data.
Anyway....The background.
The only terms that need additional explanation are:-
Congener = an individual PCDD or PCDF. There are 75 possible PCDD
isomers and 135 possible PCDF isomers. Each isomer has one or more
congeners which differ by the substitution position of the chlorine
atoms. All the isomers of either dioxins or furans containing the
same number of chlorine atoms are known as homologues eg all the
Tetrachlorodibenzo-p-dioxins (TCDDs)
From the Sci.chem FAQ
31.12 What are Dioxins?
"Dioxins" are a group of closely-related compounds which are known as
polychlorinated dibenzo-p-dioxins (PCDDs). "dioxins" also commonly includes
polychlorinated dibenzofurans (PCDFs). All organic molecules that contain
chlorine are also members of the "organochlorine" family.
1 9 1 9
2/ \ _o_ / \8 2/ \ ___ / \8
| O |_o_| O | | O |_o_| O |
3\ / \ /7 3\ / \ /7
4 6 4 6
Dibenzo-p-dioxin Dibenzofuran
As dioxins are fat soluble, they will accumulate in fatty tissue. In general,
it is only the biologically active ( molecules containing the 2,3,7,8
substitution ) congeners that accumulate, with levels of the higher
homologues predominating [18]. It is important to remember that of all the
dioxins and furans, only those containing 4 to 8 chlorine atoms, _and_ with
chlorine atoms in the 2,3,7,8 positions are currently considered toxic.
The compounds only containing 0 to 3 chlorine atoms are currently not
considered toxic, however once all four of the 2,3,7,8 positions are filled,
the most toxic congener is created ( 2,3,7,8 TCDD = "dioxin" ). As additional
chlorines are added, the toxicity decreases, except that 2,3,4,7,8
pentachlorodibenzofuran is more toxic than 2,3,7,8 tetrachlorodibenzofuran.
There is evidence that suggests concentrations of dioxins and furans in
human adipose tissue are falling [19]. The analysis for dioxin can reliably
detect ppq ( parts per quadrillion = picograms/kilogram ) levels, but some
evidence suggests dioxins may still have toxic effects at such low levels.
The toxicity of dioxins is currently being carefully assessed by the US EPA
- who are due to present a comprehensive report in the next few months. The
draft of the report, and various reviews, have been available for public
comment and external peer review. A good discussion of current perceptions
is available in a special report published in the January 1995 Environmental
Science and Technology [20], where both sides of the debate are presented.
Dioxins can arise naturally from forest fires, but the major sources are
from incineration and the manufacture and use of organic chemicals. The most
well-known source is perhaps as an impurity in the the defoliant Agent Orange
which was widely used in Vietnam. Agent Orange was a 50:50 mixture of the
n-butyl esters of the herbicides 2,4-D ( 2,4-dichlorophenoxyacetic acid ) and
2,4,5-T ( 2,4,5-trichlorophenoxyacetic acid ), and dioxin was present as
an inpurity in the 2,4,5-T. Another well known incident was an industrial
accident at a 2,4,5-trichlorophenol manufacturing plant in Seveso, Italy
on 10 July 1976 which resulted in the release of 1-5 kg of dioxin.
Other dioxin sources involve combustion ( leaded gasoline, coal combustion,
metallurgical processes )[18].
As the various congeners have differing toxicity, dioxins are usually
reported using Toxic Equivalents systems. These assign to each congener a
toxicity factor relative to 2,3,7,8-TCDD, and these factors are used to
calculate the 2,3,7,8-TCDD Toxic Equivalent. The International Toxic
Equivalent Factor (I-TEF) system, proposed by the Challenges to Modern
Society Committee of the North Atlantic Treaty Organisation is widely used.
Food is the major source of dioxins for humans, and typical dietary intakes
in the US for a 65kg adult were estimated to be between 18-192 pgTEQ/day [21],
and UK intakes were estimated to be 125 pgTEQ/day [18]. The Regional Office
for Europe of the World Health Organisation suggests 10 pg/kg body weight/day
for 2,3,7,8-TCDD ( 600 pgTEQ/day for 60kg person ), as a Tolerable Daily
Intake, whereas the US-EPA suggests an intake of 0.006 pg/kg/day over a 70
year life will lead to one excess cancer in one million people.
Sources of Dioxins in the UK diet pgTEQ/day
Meat, meat products, poultry, and offals 38
Cow's milk 23
Fats and oils 19
Milk products 12
Fish 7.7
Eggs, cereal products, fruit, and vegetables 25.3
[18] Dioxins in Food
UK Ministry of Agriculture, Fisheries and Food
Food Surveillance Paper No. 31
HMSO (1992) ISBN 0-11-242926-2
[19] Polychlorinated dibenzo-p-dioxin and dibenzofuran concentration levels
in human adipose tissue samples from the continental US collected from
1971 through 1987
J.S.Stanley et al.
Chemosphere v.20 p.895-901 (1990).
[20] Dioxin Risk - Are We Sure Yet?. ( p.24A-25A )
EPA's Dioxin Reassessment. ( p.26A-28A )
EPA on the Right Track ( p.29A-30A )
EPA Assessment Not Justified ( p.31A-32A )
ES&T v.29 p.24A-32A. ( January 1995 )
[21] Dioxins in U.S.Food and Estimated Daily Intake
A.Schecter et al.
Chemosphere v.29 p.2261-2265 (1994)
OK, eyes glazed yet?.. Onwards..
The Forest Fire contribution...
from the T&M paper in February 1996 ES&T
" Wood burning is known to produce dioxins, and although the rates are
low, enough wood is burned for industrial and residential wood
combustion to produce significant total amounts of dioxin....
the average emission factors are about 2 ng TEQ/kg for both industrial
and residential wood burning. We used the values 0.7 and 7 ng TEQ/kg,
respectively, based on fewer data, and the EPA used 4 and 1 ng/kg,
respectively.
These numbers are important with respect to the contentious isssue of
forest fires, which on several occasions have been named as the
largest dioxin source. The amount of wood burned in US forest fires is
comparable to industrial and residential wood burning. Because there
are no dioxin emission data on forest fires per se, both we and the
EPA used the emission factors for residential wood burning to arrive
at the estimated forest fire contribution ( 0.4 and 0.08 kg,
respectively ) If a revised emission factor of 2 ngTEQ/kg were used,
then the estimate would fall in between, at 0.2 kg. This is a small
fraction of the total inventory "
Well, one could quibble at the use of "significant" to describe the
man-made quantity and "small fraction" for a similar quantity of
natural dioxins. The total inventory estimates are 9 kg TEQ/year (EPA)
and 6 kg TEQ/year (T&S), and the major contributors are ( taken mainly
from a small logscale figure, so expect significant errors ), in
g TEQ/yr
EPA T&S
Medical Waste Incineration 5,000 700
Municipal Waste Incineration 3,000 3,000
Cement Kilns and Boilers 500 200
Wood Burning ( Industrial ) 400 70
Secondary Copper Smelting 300 300
Forest Fires 80 400
Petroleum Combustion 80 60
Wood Burning ( Residential ) 40 200
Hazardous Waste Incineration 50 30
Sewage Sludge Incineration 30 70
Coal Combustion 10 10
From the above, you can see that T&S made forest fires the third
largest source of dioxins, whereas the EPA made them 6th equal.
However there still remains the problem that it may not be very
sensible to take source data from locations and average it over the
whole US, and if the equally scarce deposition data is used, the
total numbers would be 10-20kg TEQ/yr, which would suggest
some of the data needs refining.
Thus, if as Tony claims, the T&S study is more valid, then
forest fires are a significant source of dioxins. However, there
are other issues to consider, and T&S continue...
" However, it is possible that wood stoves have a dioxin emission
factor different from that of forest fires because of the differences
in combustion conditions (16). Also the wood used in residential
burning may have a lower average chlorine content because it lacks
the salt-containing sap that is present in the bark and foliage of
burning trees. But the relative importance of chloride ion versus
organaically bound chlorine in dioxin formation from combustion is
not understood. Tree bark mat absorb significant quantities of
anthropogenic chlorinated organics, which may increase dioxin
emissions from forest fires ".
So, until further information is forthcoming, I will use the
study offered by Tony as evidence that forest fires may be a
significant source of dioxins, and so our background exposure
may be above zero. Until further information is available, I'd
also assume that most US, UK and European exposure is from
man-made sources, but I'm still not certain of the overall
global burden and balance....
Anyway, now the good news from " Evidence of a Decline in Atmospheric
Emissions of PCDD/Fs in the UK ". L-O.Kjeller, K.C.Jones, A.E.Johnston,
and C.Rappe. Environ.Sci.Technol. v.30 p.1398-1402 (1996)
They found that almost all of the studied compoounds ( except for
the toxic 2,3,7,8-TCDD ) had declined over the last 30 years, and
they infer from the homologue and isomer profiles that combustion
sources provide the baseline, and the increase in chlorinated
aromatics production and use since the 1940s was responsible for
the peak levels, which are now declining...
Date 2,3,7,8 Total Total iTEF/89
TCDD PCDD PCDF
(fg/g) (fg/g) (fg/g)
1861-1865 <105 15681 14157 785
1871-1880 87 7608 16045 653
1881-1890 54 10345 18363 643
1891-1900 127 12330 13057 620
1901-1910 33 8739 12905 552
1911-1920 69 8912 12360 467
1921-1930 77 12168 12657 524
1931-1935 62 16551 16507 728
1936-1940 91 10751 13374 552
1941-1945 60 14052 15358 603
1946-1950 37 34180 13832 526
1951-1955 37 27617 11841 480
1956-1960 35 63658 15967 566
1961-1965 126 252171 60658 2174
1966-1970 53 61858 25753 772
1971-1975 37 86981 18090 1068
1976-1980 126 150654 33115 1890
1981-1985 156 101785 16671 1306
1986-1990 14 49013 10300 504
1991-1993 121 26973 11038 567
Now obviously, when working at such low levels, and summing a
large number on analyses of individual compounds, the cumulative
errors for each period can become significant, but the
definate trend of two peaks is apparent. The herbage samples
were from a rural site well away from point sources, and
were oven dried and sealed in containers. All the PCDDs and
PCDFs should have been from the atmosphere, and thus herbage
samples tend to reflect air concentrations, whereas soil samples
reflect cumulative exposure. The paper reports data for
17 other PCDD/PCDFs, as well as the sums for each homologous
series. It discusses the significance of the changes in the
profiles, and it's important to realise that the 2,3,7,8-TCDD
profile above was not typical of the others, which are better
represented in the total data. You can also see from the
calculated toxicity equivalent factor how the toxicity changed.
I've previously posted an estimate of how the UK plans to
reduce their emissions further, so further reductions may
well occur. Note that these downward trends have also been
seen in Germany, Sweden and the Netherlands as well as other
locations. If we continue down that road, we should find the
actual contribution from natural sources.
Well, on that relatively good news, that's it..
Bruce Hamilton
Newsgroups: sci.agriculture,sci.environment
From: B.Hamilton@irl.cri.nz (Bruce Hamilton)
Subject: Re: Pesticides and Reproduction
Date: Wed, 31 Jul 1996 16:22:35 GMT
paul.savage@chem.csiro.au (Paul Savage) wrote:
>In article <31FBB19C.1EA0@ism.net>, "Cold Mountain, Cold Rivers"
><cmcr@ism.net> wrote:
>> i'm sure i know even less than you on this subject, but
>> this response is clearly wrong, as far as naturally
>> produced o-cl's in saltwater non-mammals, anyway. even
>> allowing for some correction in gribble's new survey
>> results, the very high ratio of biologically produced
>> o-cl's in high chloride environments to that in mammals,
>> especially invertebrates, surely tells us something
>> about the unaturalness of o-cl's to *our* environment
>> (and about the unusual strngth of the C-Cl bond).
>There's an unusual strength to the C-Cl bond? Really? In what way unusual?
>I could name you a few C-Cl bonds that fall apart in the presence of water
>vapour. Are you sure you know what you're talking about?
As my earlier response contradicted Paul's, let me clarify my
position. when Tony was talking about "strength" I assumed
he was talking about it in the context of energy required for
biological production, ie - the amount of energy required to
produce organohalogens biologically, and in the case of
haloperoxidases, the reaction consumes significant quantities
of energy. That energy could have been better utilised in other
cycles, so unless there is a specific need for an organohalogen
molecule, production would seem to be better avoided - but
of course any other alternative production mechanisms may be
more energetically favoured.
Paul has provided the correct chemical perception of the actual
C-Cl bond in the context of other bonds and chemistry.
Only Tony knows what he intended....
" It is not yet clear why some organisms produce organohalogens.
Halometabolites may play a role in the formation of other metabolites;
the defence of an organism; or act as so-called "death hormones" or
endogenous herbicides that are secreted in the seeds, ultimately
killing the parent plant. These explanations are plausible because
chemists have discovered that halogens, particularly chlorine, are
very useful in organic synthesis, and that certain types of organic
chlorine compounds ( eg DDT and HCH ) are toxic to organisms.
However, the nonspecific halogenation of organic compounds by
haloperoxidases is unlikely because this reaction consumes a great
deal of energy. Natural organochlorines may therefore only be
byproducts from the synthesis of hypohalous acids that we need
in our immune systems. " ( "Organohalogens: the natural alternatives"
E.J.Hoekstra and E.W.B.De Leer. Chemistry in Britain February 1995
p.127-131 )
The same authors note that there may be several mechanisms
for the production of organohalogens, as well as the haloperoxidases
and the extracellular aryl alcohol oxidase mechanism proposed by
De Jong, there is also the possibility of chemical chlorination.
"... Nevertheless, only a small number of natural halometabolites are
produced by the action of haloperoxidases..... The formation of brominated
and mixed chlorinated-brominated compounds in bromide-rich media
such as seawater, can be explained by the hypohalous acid intermediate,
because hypochlorous acid rapidly reacts with bromide:
HOCl + Br^- = HOBr + Cl^-
Accordingly, organic bromine compounds tend to occur predominantly
in marine environments, and organic chlorine compounds in terrestrial
environments."
That statement doesn't contradict Tony's, in that the comparism is with
bromine, rather than absolute numbers of organochlorines.
Bruce Hamilton
From: paul.savage@chem.csiro.au (Paul Savage)
Newsgroups: sci.agriculture,sci.environment
Subject: Re: Pesticides and Reproduction
Date: Fri, 02 Aug 1996 16:12:25 +1000
In article <3200E50D.4A63@ism.net>, "Cold Mountain, Cold Rivers"
<cmcr@ism.net> -- who still can't word-wrap to less than 80 characters --
wrote:
> Paul Savage wrote:
> > If you look at "Chlorine Crisis: Time for a global phase-out" by
> > Greenpeace you will see some of the following:
> >
> > "Chlorine is the common link in many of the world's most notorious
> > environmental poisons.....If we wish to preserve the life-sustaining
> > capacity of the planet, the root of the problem -- the production
> > and use of chlorine -- must be phased out."
> >
> > and
> >
> > "Virtually all organochlorines that have been studied have
> > been found to cause at least one of a wide range of effects,
> > including ...[long list snipped]"
> >
> > and
> >
> > "It is prudent, sensible and indeed necessary to treat these
> > [chlorinated organic] substances as a class rather than a series
> > of isolated individual chemicals."
> >
> > and
> >
> > "We need to focus on the entire class of organochlorines and the
> > chlorine-based industrial processes that give rise to these mixtures.
> > ....organochlorines should be treated as a class and phased out,
> > with exceptions made only if industry can show that an individual
> > use is safe or essential"
> >
> > I may be interpreting this incorrectly but if Greenpeace wants to treat
> > organochlorine compounds as a "class" and phase them out because of common
> > toxicity/environmental characteristics then they are ascribing some
> > special toxicity to the C-Cl unit. After all this is the only physical
> > thing that all arganochlorine compounds have in common.
>
> i have total agreement and no serious problems with any
> of the above, ditto for several serious and respected
> international organizations, and probably ditto for a
> good many chemists & other scientists. how many gp
> pub's on o-cl have you read?
A few. How can you rationally say that organochlorines should be treated
as a class? There are perhaps millions (certainly hundreds of thousands)
of reported organochlorine compounds and probably many more in company
databases around the world. These compounds have every possible range of
toxicity, flammability, carcinogenicity, stability, biodegradability, and
so on that you could imagine. It is as nonsensical to consider them as a
"class" as it would be to consider carbohydrates (CHO compounds) as a
"class".
> [the following is also in response to your separate
> querry to me about the strength of the c-halogen bond.
> i have yet to say any naysayers here or elsewhere post
> data on the distribution of env. half-lifes and
> bioconcentration & magnification of o-hl's. more to the
> point, do i hear any denials that on average o-hl's score
> much higher in those categories than the vast majority
> of other compounds? this is the heart of the basis for
> concerns over anthropogenic o-hl's as a class. it seems
> a no brainer to me, but i'm willing to be shown the
> light.
I doubt it, but I'll try (you can get this information from any standard
undergraduate chemistry text).
Bond Dissociation Energies, KCal/Mole ( A-B -> A. + B. )
--------------------------------------------------------
H-H 104 CH3-H 104
H-F 136 CH3-F 108 F-F 38
H-Cl 103 CH3-Cl 84 Cl-Cl 58
H-Br 88 CH3-Br 70 Br-Br 46
H-I 71 CH3-I 56 I-I 36
CH3-CH3 88
Ph-CH3 93 Ph-Cl 86 PhCH2-Cl 68
---------------------------------------------------------
It looks to me that the C-Cl bond is about where I would expect it --
stronger than the C-Br bond but weaker than C-F. Also weaker than the C-H
bond (perhaps we should treat hydrocarbons as a "refractory class" and ban
them?) and about on par with the H-Br bond. Nothing special there.
Now this is refering to homolysis of the bond and of course heterolysis is
generally favoured in solution (although more highly energetic in the gas
phase). In this case *it depends on the C-Cl bond in question*. Quick
class, which is the more "stable" organochlorine, benzoyl chloride or
chlorobenzene? Let me give you a hint, stiring benzoyl chloride in water
at room temperature for a few minutes will hydrolyse the C-Cl bond giving
benzoic acid and HCl. When it comes to solution phase chemistry the C-Cl
bond has no special properties -- it depends on the rest of the molecule.
This is why treating organochlorines as a "class" makes no sense.
> well, i cannot find my meager files on the physical
> nature of the o-hl bond (yes, i finally have my files in
> the same location as our computer, but they are not
> anywhere near organized yet!). as i recall, the c-fl
> bond is the strongest in the table of elements as
> measured by the energy required to tear it apart;
> followed by the c-cl bond.
True enough for what it's worth. As you can see from my figures the H-F
bond is stronger but when you dissolve H-F in water -- even at low
temperature -- the H-F bond completely dissociates, heterolytically.
Simple bond energies will not tell you a lot about stability in the
environment. Have you learn something Tony?
Paul Savage
--
* * p.savage@chem.csiro.au Australian Science
* . http://www.chem.csiro.au/savage/ Australia's Future
* these comments are personal opinions not official CSIRO policy
Newsgroups: sci.agriculture,sci.environment
From: B.Hamilton@irl.cri.nz (Bruce Hamilton)
Subject: Re: Pesticides and Reproduction
Date: Fri, 02 Aug 1996 17:53:05 GMT
iaotb@inet.uni-c.dk (Torsten Brinch) wrote:
>Bruce Hamilton wrote:
>> iaotb@inet.uni-c.dk (Torsten Brinch) wrote:
>>>quote Gribble:
>>>"Thus contrary to common perception, organohalogen compounds,
>>>both natural and unnatural, are readily metabolized and biodegraded
>>>to halide ion by a myriad of microorganisms.".....
>>Cheap shot. That was a summary sentence reviewing the previous
>>data he had supplied. Nowhere was he implying that they should
>>be treated as a single group, he *had* previously detailed specific
>>examples of different compounds and different organisms, and
>>he was providing his conclusions.
>No. I have quoted the conclusion in a previous post.
>It is re-quoted below.
>The sentence above is the _second_ sentence from the _introduction_
>to a short (1 page) section on METABOLISM AND BIODEGRADATION.
>Gribble treats this subject in this section only, nowhere else in his
>article.
Really?. Because earlier in the review, in the section "Halogenated organic
compounds in Nature " he lists a whole range of specific chemicals and
their sources, along with comments like " A selection of these compound
is shown in Figure 2, the major metabolite from B.Hamifera being a
tetrabromoketone, a compound possessing antimicrobial activity ".
Then he starts the Metabolism and Biodegradation with " As it is with
other elements in our biosphere, the halogens, in the form of recyclable
halide ions, must be recovered from plants and animals when they die,
so that succeeding generations will have access to halide and other elements
prerequisite for life." Then he starts the general statement at the top of
this article. So, I considered the statement refers to the immediate
sentence above it, which referred to the whole range of
metabolites he had previously listed, and that the subsequent
examples were detailing the process to support his summary.
However, if you want it to refer to the following, that's OK - it's still a
summary sentence for those examples, even in the introduction.
....
>After this we are ready for the _conclusion_ :
[ Complex semantic, irrelevant example all gone ]
>quote Gribble:
>"Thus, it can be seen that organohalogen compounds not only
>have a natural beginning, but, in the scheme of things, they have
>a natural ending as well. The commonly held belief that
>organohalogen compounds are impervious to biodegradation
>is erroneous."
>unquote Gribble.
>Bruce, maybe _you_ are able to perceive Gribble's
>approach to organochlorine metabolism and biogradation
>as unbiased.
>I can't.
Well, that's your choice. It seems to me that Gribble sets out to
address the "commonly held belief", and by documenting natural
organohalogens he has contributed to achieving that. It also seems
to me that many peop[le do believe we are the sole source of
organohalogens, and that man-made organohalogens are evil.
Showing that such molecules do also exist in nature is a reasonable
idea. From memory, no-one has cited a Gribble quote that says
" we can pump megatons ( or even megatonnes ), of our
organohalogens around the planet because they also exist
in nature". I've no idea what his stance is - but what he and other
writers on natural organohalogens have effectively done is make
readers realise that there are complex organohalogens in nature.
Biased?.. perhaps, but the message is still clear...
Bruce Hamilton
From: paul.savage@chem.csiro.au (Paul Savage)
Newsgroups: sci.environment
Subject: Re: Pesticides and Reproduction
Date: Tue, 06 Aug 1996 17:40:07 +1000
In article <32060AAD.4119@ism.net>, "Cold Mountain, Cold Rivers"
<cmcr@ism.net> wrote:
> well, a (u.s. epa) safe dose for a decade+, recently
> validated in epa's review, has been 10,000 times lower,
> 0.006 (!) pg/kg bw/day, for a 10 to the -6 cancer risk
> [schecter et al. ehp nov 94]. other effects have been
> observed in primates at body concentrations
> substantially lower than this, what is thought to cause
> cancer in humans (109-7000 ng/kg)--eg 10 ng/kg for
> endometriosis & immune disregulation. severe
> reproductive effects in rats (malby et al) at 10 ppt too
> (and these are only the lowest dose used, not the loel
> for the effect!). see de vito et al., _ehp_ 103/9 for
> this & more. (TEq basis, and not even counting other Ah
> acting nasties such as pcb's and other toxins in all of
I believe the labeling of PCBs as nasties is somewhat premature. Much of
the early literature on the toxicity of PCBs was flawed because of the
toxic effects due to polychlorinated dibenzofuranes and dioxin
contaminates. Perhaps you could read "Phantom Risk" edited by K. R.
Foster, D. E. Bernstein, and P. W. Huber (MIT Press, 1993, ISBN
0-262-06156-2) -- especially the chapter entitled "The Human Health
Effects of Polychlorinated Biphenyls" by R. D. Kimbrough. Be warned
though, there is science and reasoned logic therein :-)
> us). cancer alone is estimated to be 10-3 to 10-4 for
> pcdd/f/pcb TEq for an average joe. coincidentaly (?)
> overall cancer lifetime incidence is now approaching in 2
> in the u.s., not the old 1 in 3 or 4. tcdd is about the
Odd. I read the following:
Cancer death rates in the United States (after adjusting the
rates for age and smoking) are steady or decreasing. According
to an update from the National Cancer Institute "the age adjusted
mortality rate for all cancers combined except lung cancer has
been declining since 1950 for all individual age groups except
85 and above".
> most potent (non mutagenic) carcinogen ever tested, but
> cancer is not its scariest effect.
...or perhaps not even a real effect. There is no doubt that dioxin is one
of if not the most potent carcinogen tested in animals but the the volume
of information about epidemiologic studies related to dioxin make the
translation to human health effects much less clear. The carcinogenicity
to laboratory rodents (which are prone to tumors anyway) are nearly always
measured at near toxic doses mg/kg for humans. The only confirmed health
risk at non-toxic doses that I have seen for dioxins is chloracne.
Dioxin remains paramount in the group of chemicals that arouse public
fear. There are several reasons for this and the simplest is that dioxin
is clearly toxic to animals -- but so are many other chemicals. Politics
(such as the emotive Agent Orange use and the US public's confusion and
emotion over the Vietnam war) and publicity -- and lawyers -- have been
far more important than science in creating dioxin's image.
> schecter et al. (ehp nov 94) emphasize that an ave.
> american is ingesting at least 0.3 pg/kg bw/day--2
> orders of magnitude more than the safe dose for not the
> most sensitive endpoint. perinatals and others way more.
The acceptable daily intake (ADI) or virtually safe dose (VSD)
levels for 2,3,7,8-tetrachlorodibenzo-p-dioxin as set by the
World Health Org. is 10 pg/kg/day. [WHO, Regional Office for
Europe, 1991, Summary report: Consultation on tolerable daily
intake from food of PCDDs and PCDFs, Bilthover, Netherlands: WHO]
In Great Britian the ADI is also 10 pg/kg/day, as it is in Ontario. The US
EPA set their ADI at 0.006 pg/kg/day in 1985 and revised it to 0.1
pg/kg/day in 1987. Current US regulatory policy on dioxin specifically,
and on carcinogens generally, is a product of history. In the mid 1970s
scientists believed that most carcinogens were also mutagens. According to
this view a single molecule might cause a mutation, which might cause
cancer. As more chemicals were tested this postulate was found to be
mistaken; there is no close correlation between carcinogenicity were also
mutagenicity. Only about half the chemicals known to cause cancer in
animals also cause mutations [Tennant et. al. Science, 1987, 236, 933-942]
Paul Savage
--
* * p.savage@chem.csiro.au Australian Science
* . http://www.chem.csiro.au/savage/ Australia's Future
* these comments are personal opinions not official CSIRO policy
Newsgroups: sci.agriculture,sci.environment
From: B.Hamilton@irl.cri.nz (Bruce Hamilton)
Subject: Re: Pesticides and Reproduction
Date: Tue, 06 Aug 1996 16:45:30 GMT
"Cold Mountain, Cold Rivers" <cmcr@ism.net> wrote:
>Bruce Hamilton wrote:
>> > there are too many separate lines of evidence (lake sediment
>> > time series samples, a d/r relationship between body burdens
>> > and living near sources of anthropogenic pcdd/f, and the
>> > agreement in the literature estimating sources of pcdd/f).
>>
>> Now you are switching back to PCDD/PCDFs, and your
>> claim of agreement in the literature doesn't stand up. The
>> earlier data ( and cited by Gribble in his earlier surveys )
>> was ambiguous - at least two papers claimed large natural
>> sources from forest fires. Now it may be that later papers
>what i've reviewed shows some agreement on the guess of natural biomass
>burn sources, eg the 300 g/yr TEq from man's & natures biomass burning
>in thomas & spiro's '95 estimate. ie, significant but not substantial.
Can you tell me whether their paper that you have uses the same
technique to estimate natural sources as their later ES&T article?.
If they assumed the same equivalence between human burning
emissions and forest fires, then the data is no more robust than
in the later papers.
Why am I concerned?. Well, contrary to popular belief, the structure
of dioxins mean that in certain natural environments ( such as on
the surface of plants ), they are not that stable, and subject to
photodegradation. For 2,3,7,8-TCDD, some researchers have exposed
grass to gas-phase tritium-labelled TCDD and varying levels of UV
radiation under controlled conditions. The photodegradation half-life
of 2,3,7,8-TCDD sorbed to grass and exposed to natural sunlight was
just 44 hours, whilst the half-life resulting from the volatilisation of
the pollutant was 128 hours ( J.K.McCrady, S.P.Maggard. ES&T v.27
p.343-350 (1993) ). The authors conclude that elimination of 2,3,7,8-TCDD
by photodegradation should be considered when estimating uptake.
How many papers have you seen on PCDDs that do?. I've only seen one
that has even discussed the variations and significance of trying to
incorporate that type of data. As Paul has been explaining there is
no unique strength in the carbon-halogen bond, and because it is
polarised the carbon is subjected to attack by nucleophiles, but the
dissociation energies and lengths of carbon-halogen bonds vary
considerably, depending on the particular halogen and hybridisation
state of the carbon atom that it is attached. [ Note for sci.agriculture
readers - " hybridisation " refers to states sp, sp2, sp3 - not to progeny
as played with by Mendel et al :-) ] Many organic molecules are only
"persistant" in the environment because they are hydrophobic and
lipophilic, thus they migrate to the lipid fractions and are protected
from destruction.
In another post you note that you were referring to the bond, not to
the energy-intensive biological synthesis, and so I'll have to move
over and stand by ( hide behind? :-)) Paul now. Chemical bonds
become messy in complex molecules, but the reality is that the
C-halogen bond does not have a unique strength when it is in
a molecule. Basically, for halomethanes, as the bond energy
decreases, the reactivity to nucleophiles ( such as OH- ) increases.
Bond dissociation energies in kJ/mole
Phenyl = Benzene ring.
Type Bond Energy
CH3-Hal C-F 448
C-Cl 335
C-Br 280
C-I 222
CH2=CH-Hal C-Cl 435
CH2=CH-CH2-Hal C-Cl 251
C-Br 193
Phenyl-Hal C-Cl 360
C-Br 297
Phenyl-CH2-Hal C-Cl 285
C-Br 213
for Carbon in different hybridisation states
Ethane C(sp3)-C(sp3) 353.8
C(sp3)-H 405.9
Ethylene C(sp2)-C(sp2) 545.8
C(sp2)-H 420.6
Acetylene C(sp)-C(sp) 713.6
C(sp)-H 458.0
Propylene C(sp3)-C(sp2) 374.8
Chloromethane C(sp3)-Cl 334.7
Vinyl Chloride C(sp2)-Cl 435.1
for sp3 bonds
C-H 406
N-H 431
O-H 494
From the above you can see that there is no unique strength
in the C-Cl bond, and that from the chemical viewpoint, many
other factors about the structure of a molecule would also
help define the stability of the molecule. Biologically, the
pathways for cleaving such bonds are not normally favoured
energetically, perhaps because organisms have evolved to
use molecules (such as O2, CO2, carbohydrates, proteins, lipids)
that can provide the major elements ( C,H,O,N) and are more
readily to hand, however there are some organisms that have
created specific molecules that do utilise the halogens. Why
should we be surprised?, survival is all about utilising what
ever resources you can use. Trying to present the halogens
as possessing evil bonds is futile and inaccurate, it is the
structure and properties of individual molecules that should
be considered. Organochlorines, unlike organometallics -
such as organolead ( alkyl lead additives to gasolines ), and
organonickel ( nickel carbonyl ) compounds, don't have an
element at the other end of the bond that is highly toxic when
cleaved as an ion. They should be treated like other organics
with elements such as oxygen ( ethanol has much lower toxicity
than methanol ) and nitrogen ( nitroglycerine is both an explosive
and a medicine ) attached. That is, consider each molecule, or
group of molecules with similar properties and functionality,
on their own merits.
I could stupidly suggest that nitrogen and its oxygen-containing
organic compounds have killed more humans than chlorine,
should we ban nitrogen? :-)
Bruce Hamilton
Newsgroups: sci.environment,sci.agriculture
From: B.Hamilton@irl.cri.nz (Bruce Hamilton)
Subject: Re: Pesticides and Reproduction
Date: Thu, 08 Aug 1996 08:43:01 GMT
"Cold Mountain, Cold Rivers" <cmcr@ism.net> wrote:
>Bruce Hamilton wrote:
>> Our major exposure to dioxins is via food, with the average
>> dietary intake in the UK estimated at 125 pg TEQ/day. The
>> World Health Organisation regional office for Europe had
>> a tolerable daily intake of 600 pg / kg body weight / day
>> for 2,3,7,8-TCDD. This may have changed, with the new
>well, a (u.s. epa) safe dose for a decade+, recently validated in epa's
>review, has been 10,000 times lower, 0.006 (!) pg/kg bw/day, for a 10 to
>the -6 cancer risk [schecter et al. ehp nov 94].
Minor detail, but as far as I'm aware that's the "EPA *estimated* dose which
would lead to one excess cancer per one million people " ( " Dioxins in US Food
and estimated daily intake " A.Schecter and 7 others. Chemosphere v.29
p.9-11 9 1994 ). Yes, same author, and I suspect the data is still subject to
review and debate - has the EPA report appeared?....
>the old 1 in 3 or 4. tcdd is about the most potent (non mutagenic) carcinogen
> ever tested, but cancer is not its scariest effect.
Please provide some evidence that TCDD is " about the most potent ( non
mutagenic ) carcinogenic ever tested "... as your old friend :-) Gribble once
said in October 1992 " There is no evidence that dioxin causes any serious
health effects in humans apart from chloracne and some reversible liver
dysfunctions. ( M.Gough. Sci.Total Environ.. v.104 p.129 (1991 ) "
The lowering of body burdens of TCDDs is certainly welcome, but the actual
consequences for humans still have to be unravelled - witness the problems
the EPA report has encountered - not all from groups with strong vested
interests....
>schecter et al. (ehp nov 94) emphasize that an ave. american is ingesting
>at least 0.3 pg/kg bw/day--2 orders of magnitude more than the safe dose
>for not the most sensitive endpoint. perinatals and others way more.
" * estimated * dose which would lead to one excess cancer in one
million people ". I belive this estimate may have been disputed
>> It is worth noting that dioxin levels in US human adipose tissue
>> have been decreasing since about 1970 ( remember that only
>> the 2,3,7,8 substituted compounds accumlate, with the levels
>> of the higher chlorinated homologues predominating ) from
>> around 18 pg/g lipid in 1971 down to around 4 pg/g lipid in 1987.
>this is disputed because the database is so poor. what is this
>recurring reference to only the planar congeners bioaccumulating?
Whilst the US database may be poor, other nations have some
monitoring schemes. I've previously provided the reference for the
quote Tony, last time you implied because it wasn't from the US it was
probably less credible - I believe the US EPA also uses much of the
same European data ( and also got decried by parocial ( sp?) yanks ).
Either front up with an actual reference that indicates the studies
are wrong, or be prepared for me to push them in your face each time :-)
" ... Everyone carries a certain body burden of dioxins and furans; it
has been found that only the 2,3,7,8-substituted compounds accumulate,
with levels of the higher chlorinated homologues predominating...'
( " Dioxins in Food " UK Ministry of Agriculture, Fisheries and Food.
Food Surveillance Paper No. 31. p.9 ( 1992 ) ISBN 0 11 242926 2 )
>> Well, that's all from me, there remains a lot of research to
>> be performed on sources, sinks, distribution, and toxicity of
>yes, incl. the possibility that it's an unknown sink that accounts for
>the excess of sources claimed, rather than natural sources. i believe
>this has been the cae with other classes of pollutants. again, the
>independent _and_ corroborating evidence strongly points to minimal env.
>levels until the 1940's. epa's science advisory board went out of their
>way to pooh pooh arguments for serious natural sources in their
>pre-release review of epa's reasesment.
Refer my subsequent post on T&S, this is by no means as clearcut as you would
imply - the T&S report assigns Forest Fires a bronze medal, and really has
confirmed the natural contribution because of their assumption :-)
>- ||" 'Are the people being protected?'
>cmcr@ism.net || is too narrow a question."
>(Cold Mountain, Cold Rivers || -API lobbyists meeting, 12 Dec. '9researching it!
I must say Tony, your posts have greatly improved - excellent cites from
relevant articles and journals - one of these days we'll agree on something,
( or else I'll be humilated ) , how boring....
Bruce Hamilton
From: paul.savage@chem.csiro.au (Paul Savage)
Newsgroups: sci.environment
Subject: Re: Pesticides and Reproduction
Date: Mon, 26 Aug 1996 15:55:41 +1000
In article <321F254F.73E9@ism.net>, "Cold Mountain, Cold Rivers"
<cmcr@ism.net> wrote:
> looks like all the time and effort we spent on this subthread boils down
> to me not mentioning o-cl's with reactive elements, and you not admiting
> that C/Cl/H o-cl's are persistant as a class (you still haven't cited any
> exceptions, only molecules with radicals and polar components). so if
Oh come on, what are you talking about? I will not "admit" that "C/Cl/H
o-cl's are persistant as a class" simply because it isn't true. I don't
know what you mean when you talk about "molecules with radicals" (because
it's nonsense) but I have given you examples of non-persistant "C/Cl/H
o-cl's" without "polar components" (by which I interpret you mean carbonyl
groups, amines, alcohols etc.). The truth is that the C-Cl bond itself is
polar so the only way to get a truely non-polar o-cl is to have something
like carbon tetrachloride.
Okay, for the record. Benzyl chloride (C7H7Cl), and allyl chloride
(C3H5Cl) are both readily hydrolysed in water and contain only carbon,
hydrogen and chlorine. They also contain no extra polar groups. Satisfied?
> you look at greenpeace publications, _all_ (to my recollection) the
> o-cl's they list in tables of compounds they'd like to see phased-out
> contain only C/Cl/H.
Great. So why attack the whole chlorine industry and make broad-brush
statements about organochlorine compounds? BTW, I suppose the above means
that Greenpeace and others don't mind Dieldrin (contains oxygen) or
Endosulfan (contains sulfur and oxygen).
> we enviros for years have been focusing debate on
> the persistent & haz's o-cl's, and i believe you deliberatly distract
> attention from this real problem onto a point you know to be correct but
> more importantly for your purposes, irrelevant to the debate you want to
> draw attention from.
Absolutely untrue. As a research chemist, if anything, I have a vested
interest in having older pesticides deregistered! This provides
opportunities for new chemical entities with superior
environmental/biological/physical profiles to replace those that are no
longer allowed -- and hence research for me to do. All I want is for the
debate on persistent and hazardous organochlorines to be scientifically
sensible. Greenpeach attacks the whole chlorine industry with a "some
organochlorines are bad so let's get rid of the source" attitude which I
find to be lazy and lacking scientific rigor.
> have your damn insistance on obviously reactive
> molecules not being persistant; i'm spending my time addressing the real
> problem: massive industrial use of thousands of persistant and hazardous
> o-cl's.
Massive industrial use of thousands of persistant and hazardous
organochlorines? Are you sure? Where did you hear that number? The truth
of the matter is that environmental groups have projected the
toxicological and physicochemical properties of a few dangerous
organochlorine compounds onto the entire organochlorine group. This
obviously flawed approach is now being parroted by those that cannot
understand the science or choose not to. If you repeat a lie often
enough....
Paul Savage
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