Last, he concludes on the basis of his rather narrow -- and as shown
below inadequate -- literature search that risks of injury to farmers, and
respiratory problems are much more serious than pesticide-based risks.
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 risks. 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 urge Dale to think a little more deeply about this topic, after
becoming more familiar with the literature. Dale missed several thousand
citations in his searches, which together constitute overwhelming evidence
and 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; the issues/debates involve
specific cause-effect relationships and how significantly pesticide
exposures (and which ones, and when) contribute to elevated cancer risks.
Obviously there are huge gaps in information and no practical way to
affirmatively coax out some of the linkages. And people disagree about how
society should balance the benefits of pesticides with the risks they pose.
These issues will never be easy to work through, but having a working
understanding of the science at least helps lessen the chance of making a
really bad decision.
The Blair abstract below states as directly as possible the Nat.
Cancer Institute's "official" view on pesticide and cancers. It is a little
dated (1995), more recent studies simply strengthen the associations. I
have included a few other abstracts from Medline to give a feel for the
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
Search on "pesticide* and immune*" you get 50 citations in last 5
years. The World Resources Institute overview of pesticides-immunotoxicity
found several hundred citations worldwide. The literature is exploding in
this area and the new evidence is indeed worrisome for some classes of
Last, Dale is willing to make a leap from his, and the scientific
community's current understanding of pesticide health effects to the
conclusion that known, easily recorded accidental risks faced by farmers are
far greater than the often hard to detect impacts of pesticide exposures.
Others are not willing to make this leap. I hope Dale is right but fear he
may not be.
Assessing relative risks is tricky since there are differing levels
of scientific certainty in risk assessments, very different populations at
risk, and the impacts on people's lives of different risks vary greatly.
Some 2-3 million folks are at risk to farm accidents; the people exposed to
onfarm risks have control/power over steps taken to avoid risks, and bear
the responsibility, and harm, if they are not careful.
The whole population is exposed to pesticides in food, and a
significant portion is also exposed through water, air and occupationally.
The general public has little control over most dietary/water based
exposures, and enjoys none of the "direct" economic benefits of pesticides.
Sorting out what is "right" and defensible scientifically is very complex in
this arena -- we do no favors by asserting this is easy or obvious.
Many in the agricultural community discount risks in the absence of
definitive, simple, direct cause-effect proof. This judgement/attitude
basically writes off serious inquiry of the role of pesticide exposures in
the majority of adverse health effects suffered by humans, from cancer to
birth defects, to immune system, reproductive and neurological problems.
This is perhaps comforting to farmers and those who are convinced pesticides
are always safe, but that does not make it right. I personally believe
farmers, their families, farm workers, and rural neighbors are innocent
victims of the need for the "system" to discount pesticide risks.
The NCI "Agricultural Health Study" is starting to produce results,
which I am told are going to rather dramatically expand the range of health
effects correlated to pesticide exposures and also strengthen past
associations in the literature. I will update the list as I learn of the
Environ Health Perspect 1995 Nov;103 Suppl 8:205-8
Agricultural exposures and cancer.
Blair A, Zahm SH
Occupational Studies Section, National Cancer Institute, Bethesda, Maryland,
The purpose of this report is to review the literature on cancer among
persons employed in agriculture, to characterize the value of this line of
research, and to recommend future directions. Farmers, despite a generally
favorable mortality, appear to experience elevated rates for several
cancers, including leukemia, non-Hodgkin's lymphoma, multiple myeloma,
soft-tissue sarcoma, and cancers of the skin, lip, stomach, brain, and
prostate. The rates for several of these tumors (i.e., non-Hodgkin's
lymphoma, multiple myeloma, skin, brain, and prostate) appear to be
the general population. No set of established etiologic factors explains all
the cancer excesses observed among farmers, although several are associated
with naturally occurring or medically induced immunodeficiencies. This
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. Studies to further characterize the cancer risk among
farmers, their dependents, and farm laborers, and to identify the exposures
that may be involved would not only be useful in providing a safe work
environment in agriculture but may furnish considerable insight into the
causes for a number of tumors that are rising in incidence in the general
Occup Med 1997 Apr-Jun;12(2):269-89
Pesticides and cancer.
Zahm SH, Ward MH, Blair A
Occupational Epidemiology Branch, National Cancer Institute, Rockville,
The authors discuss pesticide exposure in both agricultural and
nonagricultural occupations, referring to a variety of studies on the cancer
risks of specific pesticides. Adult and childhood cancer are addressed, and
direction for future research efforts is offered.
Environ Health Perspect 1997 Oct;105(10):1068-77
Pesticides and childhood cancers.
Daniels JL, Olshan AF, Savitz DA
Department of Epidemiology, School of Public Health, University of North
Carolina-Chapel Hill, Chapel Hill, NC 27599, USA.
To evaluate the possible association between pesticides and the risk of
childhood cancers, epidemiologic studies published between 1970 and 1996
were critically reviewed. Thirty-one studies investigated whether
occupational or residential exposure to pesticides by either parents or
children was related to increased risk of childhood cancer. In general, the
reported relative risk estimates were modest. Risk estimates appeared to be
stronger when pesticide exposure was measured in more detail. Frequent
occupational exposure to pesticides or home pesticide use was more strongly
associated with both childhood leukemia and brain cancer than either
professional exterminations or the use of garden pesticides. Occupational
pesticide exposure was also associated with increased risk of Wilms' tumor,
Ewing's sarcoma, and germ cell tumors. Residence on a farm, a proxy for
pesticide exposure, was associated with increased risk of a number of
childhood cancers. Although increased risk of some childhood cancers in
association with pesticide exposure is suggested by multiple studies,
methodological limitations common to many studies restrict conclusions;
these include indirect exposure classification, small sample size, and
potential biases in control selection.
Opportunities for methodologic improvement in future studies of pesticides
and childhood cancers are described.
Arch Environ Health 1998 Sep-Oct;53(5):336-43
Cancer incidence and risks in selected agricultural
settlements in the Negev of Israel.
Avnon L, Oryan I, Kordysh E, Goldsmith J, Sobel R, Friger M
Department of Medicine, Faculty of Health Sciences, Ben Gurion University of
the Negev, Beer Sheva, Israel.
Medical staff of two Negev kibbutzim invited epidemiologists to help them
investigate cancer rates among their members. Our objectives were (a) to
determine whether the cancer rate in the kibbutzim was elevated or abnormal
and (b) to determine the role of agricultural and other relevant exposures
if cancer incidence was elevated. We validated cases of cancer by kibbutz
records and by surveying other information; we computed expected values on
the basis of the age-sex-calendar period and site-specific cancer incidence
rates reported by the Israel Cancer Registry for the entire population;
and we compared the data for the 2 kibbutzim with data derived for similar
age and sex groups in 2 other kibbutzim, which were assumed not to have
increased cancer rates. In addition, we planned and conducted a
case-referent study, including the design, pretest, and use of
questionnaires, including data about lifetime exposures (i.e., type of work
and its duration, agricultural and industrial chemicals, smoking and alcohol
use, demographic variables, health experiences, and family history). In only
one of the kibbutzim, for which high cancer rates were suspected, was there
excess for all sites in persons who were less than 40 y of age. In one of
the "comparison" kibbutzim, we found increased cancer rates overall. Much of
the excess in the high cancer kibbutzim was in hematological cancer (i.e.,
leukemia and lymphoma). Multiple years of work in fields, orchards, and
landscape, as well as orchard work that commenced before 1960, were
associated with increased risk of cancer (p < .08). We also found an
association between cancer rate and numbers of industrial chemicals used (p
< .08). Pipe and cigarette smoking were also associated with increased
cancer incidence. In the multivariate analysis, the association with
calendar year in which orchard
work was started and multiple exposures to industrial chemicals was stronger
than associations noted in the univariate analyses. Although duration of
agricultural work or multiple industrial exposures were clearly associated
with increase in cancer risk, we were unable to identify the causal role of
specific agent(s). Nonetheless, educational programs for cancer prevention
can be based, in part, on the results of such a study.
Charles Benbrook 208-263-5236 (voice)
Benbrook Consulting Services 208-263-7342 (fax)
5085 Upper Pack River Road firstname.lastname@example.org [e-mail]
Sandpoint, Idaho 83864 http://www.pmac.net
To Unsubscribe: Email email@example.com with the command
To Subscribe to Digest: Email firstname.lastname@example.org with the command
All messages to sanet-mg are archived at: