> he concludes on the basis of his rather narrow -- and as
> shown below inadequate --
> Dale missed several thousand citations in his searches,
> which together constitute overwhelming evidence (snip)
> Search on "pesticides and cancer" in the last 5 years, you
> get 266 citations; thousands if you go back 20 years to when
> cancer testing got underway (snip).
I confined my searching to occupational risk for two reasons. First, since
higher doses probably occur among applicators than from food residues,
epidemiological evidence is more likely to accrue, and second, YOU
established the scope of this thread with your post "Cancer and Farmers."
> agreement that pesticide exposure increases cancer risk,
> and that pesticide impacts on the immune system are no doubt
> a major mechanism leading to elevated risk factors. There
> is essentially no debate anymore in the toxicology community
> over these facts;
Abstract from NCI you cited:
> suggests that there may be factors in the agricultural
> environment that introduce immune system deficiencies.
> Farmers are exposed to a variety of substances that could
> operate through this mechanism, including pesticides, engine
> exhausts, solvents, dusts, and zoonotic microbes.
This doesn't sound real definitive or well-understood.
I hear a lot of debate about these issues, and read about it within the
toxicology community. I don't think there is consensus on the relative
importance of immune system risk factors in agriculture. In perusing the
literature on non-hodgkins lymphoma (NHL), comparable elevated risk occurs
in many industries. Still, there does seem to be a consistent dioxin*
* ( Dioxin is an incidental byproduct of some chlorophenoxy herbicide
manufacture, and many other industrial products)
> the issues/debates involve specific cause-effect relationships
> and how significantly pesticide exposures (and which ones, and
> when) contribute to elevated cancer risks.
That was one of my main points. It is silly to condemn all pesticides when
cancer risk seems to be associated with only one or two classes of
pesticides and solvents.
> Obviously there are huge gaps in information and no practical way to
> affirmatively coax out some of the linkages.
Epidemiology is not a bad approach, at least in the context of high-dose
occupational risk, where increase in mortality is large enough to measure.
In an abstract of "Mortality from Hodgkin's disease and other lymphomas in
Europe, 1960-1990." (Oncology (Basel) 52(2): 93-96), I read that the risk of
NHL mortality has increased in Europe from 2.2 to 4.2 per thousand*. (I
can't find similar data from N. America, but I am sure it exists and is in
the ballpark). I don't have time to request all these papers and read them,
so I am sticking to the abstracts.
* (AIDS increases risk of NHL by immunosuppression, another potential
In "A meta-analysis of non-Hodgkin's lymphoma among farmers in the central
United States." (American Journal of Industrial Medicine 31(4): 442-444)
they found a relative risk of 1.34 for NHL mortality among ag workers. This
is comparable with other estimates I have seen.
So if you multiply 1.34 x 4.2 and subtract 4.2 you get a rough estimate of
1.4 additional deaths from NHL per 100,000. Remember, this estimated
increase is not necessarily caused by pesticides, but apparently caused by
being a farmer. Clearly, this is not something to ignore, but does not
constitute a crisis in the context of the 40 or so deaths per 100,000 due to
accidents among ag workers (National Safety Council, 1990).
> This kind of cursory dismissal of pesticide risks is fashionable
> and seductive. It is repeated so often in ag circles that many
> people have begun to assume it must true. Indeed, it has become
> "conventional wisdom" and is a part of the mythology of agriculture
> that frustrates efforts to bring good science and reason to managing
Really Chuck! Does what I am saying sound like a cursory dismissal? I'm
trying to put this in perspective with other more ordinary risk factors and
balance the fear-mongering I see on Sanet. I don't think we really disagree
much about the specifics and I am mystified by your strident tone.
> The ag community has got to get beyond denial and become
> more familiar with the enormous science base that leads many
> people with no axe to grind with farmers to conclude prudent
> steps should be taken to reduce use/exposure to high risk pesticides.
I couldn't agree with you more. This is the direction I see the EPA and
chemical industry heading. I see aggressive fast-tracking of safer classes
of pesticides and increased review of questionable classes. I see a very
high consciousness for prudent pesticide practices in the ag industries with
which I have come in contact, and measures taken to reduce occupational
P.S. let me know if you want any of the lit references I have dug up.
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