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#648 - Pesticides and Aggression, 28-Apr-1999

For the past 25 years, tens of millions of Americans in hundreds of
cities and towns have been drinking tap water that is contaminated with
low levels of insecticides, weed killers, and artificial fertilizer.
They not only drink it, they also bathe and shower in it, thus inhaling
small quantities of farm chemicals and absorbing them through the skin.
Naturally, the problem is at its worst in agricultural areas of the

The most common contaminants are carbamate insecticides (aldicarb and
others), the triazine herbicides (atrazine and others) and nitrate
nitrogen.[1] For years government scientists have tested each of these
chemicals individually at low levels in laboratory animals -- searching
mainly for signs of cancer -- and have declared each of them
an "acceptable risk" at the levels typically found in groundwater.

Now a group of biologists and medical researchers at the University of
Wisconsin in Madison, led by Warren P. Porter, has completed a 5-year
experiment putting mixtures of low levels of these chemicals into the
drinking water of male mice and carefully measuring the results. They
reported recently that combinations of these chemicals -- at levels
similar to those found in the groundwater of agricultural areas of the
U.S. -- have measurable detrimental effects on the nervous, immune and
endocrine (hormone) systems.[2] Furthermore, they say their research
has direct implications for humans.

Dr. Porter and his colleagues point out that the nervous system, the
immune system, and the endocrine (hormone) system are all closely
related and in constant communication with each other. If any one of
the three systems is damaged or degraded the other two may be adversely
affected. The Wisconsin researchers therefore designed their
experiments to examine the effects of agricultural chemicals on each of
the three systems simultaneously. To assess immune system function,
they measured the ability of mice to make antibodies in response to
foreign proteins. To assess endocrine system function, they measured
thyroid hormone levels in the blood. And to assess nervous system
function they measured aggressive behavior in the presence of intruder
mice introduced into the cages. They also looked for effects on growth
by measuring total body weight and the weight of each animal's spleen.

The experiments were replicated many times, to make sure the results
were reproducible. They found effects on the endocrine system (thyroid
hormone levels) and the immune system, and reduced body weight, from
mixtures of low levels of aldicarb & nitrate, atrazine & nitrate, and
atrazine, aldicarb & nitrate together. They observed increased
aggression from exposure to atrazine & nitrate, and from atrazine,
aldicarb & nitrate together.

The Wisconsin research team wrote, "Of particular signficance in the
collective work of Boyd and others,[3] Porter and others,[4] and our
consistently a response due to mixtures, but NOT usually to individual
chemicals." [Emphasis in the original].

In the five-year experiment, thyroid hormone levels rose or fell
depending upon the mixture of farm chemicals put into the drinking
water. Dr. Porter and his colleagues present evidence from other
studies showing that numerous farm chemicals can affect the thyroid
hormone levels of wildlife and humans. PCBs and dioxins can have
similar effects, they note. Proper levels of thyroid hormone are
essential for brain development of humans prior to birth. Some, though
not all, studies have shown that attention deficit and/or hyperactivity
disorders in children are linked to changes in the levels of thyroid
hormone in the blood. Children with multiple chemical sensitivity (MCS)
have abnormal thyroid levels. Furthermore, irritability and aggressive
behavior are linked to thyroid hormone levels.

Interviewed recently by Keith Hamm of the SANTA BARBARA [CAL.]
INDEPENDENT,[5] Dr. Porter explained, "Earlier work had shown that
thyroid hormone typically changed when exposure to these pesticides
occurred. Thyroid hormone not only affects and controls your metabolic
rate, that is, how fast you burn food, it also controls your
irritability level. For example, Type A personalities are more
assertive, more aggressive, more hyper. These people tend to have
higher levels of thyroid hormone. Type B personalities--people that are
really laid back, really take things very easily--have lower levels of
thyroid hormone. We expected that changes in thyroid [would] change
irritability levels. This was a concern because there was information
that kids are getting more hyper and [that their] learning abilities
are going down," Dr. Porter said.

A recent study of 4 and 5 year-old children in Mexico specifically
noted a decrease in mental ability and an increase in aggressive
behavior among children exposed to pesticides.[6] Elizabeth A.
Guillette and colleagues studied two groups of Yaqui Indian children
living in the Yaqui Valley in northern Sonora, Mexico. One group of
children lives in the lowlands dominated by pesticide-intensive
agriculture (45 or more sprayings each year) and the other group lives
in the nearby upland foothills where their parents make a living by
ranching without the use of pesticides. The pesticide-exposed children
had far less physical endurance in a test to see how long they could
keep jumping up and down; they had inferior hand-eye coordination; and
they could not draw a simple stick figure of a human being, which the
upland children could readily do.

Notably, in the Guillette study we find this description of the
behavior of pesticide-exposed children: "Some valley children were
observed hitting their siblings when they passed by, and they became
easily upset or angry with a minor corrective comment by a parent.
These aggressive behaviors were not noted in the [pesticide-free]
foothills [children]."

The human body can defend itself against poisons to some degree, but
Dr. Porter and his colleagues describe ways in which low-level mixtures
of pesticides and fertilizer might get past the body's defenses:

The body is prepared to protect itself against poisons taken by mouth.
The liver begins to produce enzymes that try to break down fat-soluble
chemicals. However, if a poison enters through the lungs or the skin,
the body does not offer the same kind of defenses. Furthermore, the
body's ability to put up defenses may be compromised by taking certain
medications (e.g., antibiotics), or by receiving "pulses" of toxins
rather than a steady dose.

Receiving "pulses" of poisons would be normal in the case of
agricultural poisons which are sprayed onto crops only at certain times
of the year. During those periods, people living near sprayed fields
might get a sudden dose of poison via their lungs, their skin and their
drinking water. Dr. Porter describes such a situation this way:

"Imagine [that] you're standing in a boxing ring and a boxer jumps in
with you, and he walks toward you smiling with his hand outstretched.
And you reach out to shake his hand and he smacks you in the stomach as
hard as he can. And when you bring your arms up to defend yourself, he
backs away. Finally you get tired of holding your defenses up and you
drop them and he rushes in and smacks you again. That's the physical
equivalent to a 'pulse dose,' which is normally what we tend to get
exposed to.

"The defenses we have take a while to induce, just like it takes a
while to bring your arms up. It takes anywhere from a half a day to
five days to induce those [defenses] to appropriate levels. If you're
in a particular stage of your hormone cycle or you're taking some
antibiotics, it can compromise your ability to defend yourself even if
you did have enough time to induce your defenses. If you've got pulse
doses coming in under your defenses or coming in faster than you can
bring your defenses up then you've got a situation where you're totally

"If you've got a pregnant mom, for example, in day 20 when the fetus's
neural tube is closing and she gets an exposure, she hasn't had enough
time to induce her defenses. Her thyroid level goes up or goes down,
the hormone crosses the placenta and can permanently alter the
developmental pattern of the fetus's brain. And then the pulse dose is
gone, you have no detection, mom doesn't even know she's pregnant, and
you may have an offspring that is neurologically compromised and
wonder, 'How did this happen?'"

In the interview with Keith Hamm, Dr. Porter expressed concern for the
overall effect of pesticides on the nation's children:

Hamm: "Are pesticides, herbicides, and fertilizer used more or less
these days than fifty years ago and have the toxicities changed?"

Porter: "The usage has continued to climb. There's an enormous amount
of these [chemicals being used] right now. There was a recent study
that examined the urine of people across the country, [asking] if
people are being exposed. On average, anywhere from five to seven
compounds were being excreted. There's a great deal of expo- sure to
the general populace.

"And yes, the toxicities have definitely changed. [Some toxicities are
now measured] in the parts-per-trillion range. I would point out that
fetuses are sensitive to chemicals in the parts per quadrillion range."

Hamm: "I would assume that most people in this country are eating
conventionally grown food. If that's the case, wouldn't the problems be
more apparent? Why are there not more hyperaggressive dim-witted people
with poor immune systems?"

Porter: "If we really looked carefully at what's been happening in this
county, you might find exactly that happening."

* * *

Because of recent violence in small cities and towns (such as
Littleton, Colorado, Laramie, Wyoming, and Jasper, Texas), this is a
time when Americans are searching for the causes of violence in their
society. Some are blaming a decline in religious upbringing. Others are
blaming households with the parents working and no one minding the
kids. Some say the cause is violent movies, violent TV and extremist
internet sites, combined with the ready availability of cheap guns.
Still others point to a government that has often sanctioned the
violence of "gunboat diplomacy" to open foreign markets for U.S.

No one seems to be asking whether pesticides, fertilizers and toxic
metals [see REHW #529, #551] are affecting our young people's mental
capacity, emotional balance, and social adjustment. From the work of
Warren Porter, Elizabeth Guillette and others, it is apparent that
these are valid questions.

--Peter Montague
(National Writers Union, UAW Local 1981/AFL-CIO)


[1] Jack E. Barbash and Elizabeth A. Resek, PESTICIDES IN GROUND WATER
(Chelsea, Michigan: Ann Arbor Press, 1996); Richard Wiles and others,
TAP WATER BLUES (Washington, D.C.: Environmental Working Group, 1994);
Brian A. Cohen and Richard Wiles, TOUGH TO SWALLOW (Washington, D.C.:
Environmental Working Group, 1997); Environmental Working Group,
D.C.: Environmental Working Group, 1996). See www.ewg.org. And: Gina M.
Defense Council, October, 1998).

[2] Warren P. Porter, James W. Jaeger and Ian H. Carlson, "Endocrine,
immune and behavioral effects of aldicarb (carbamate), atrazine
(triazine) and nitrate (fertilizer) mixtures at groundwater
concentrations," TOXICOLOGY AND INDUSTRIAL HEALTH Vol. 15, Nos. 1 and 2
(1999), pgs. 133-150.

[3] C.A. Boyd, M.H. Weiler and W.P. Porter, "Behavioral and
neurochemical changes associated with chronic exposure to low-level
concentration of pesticide mixtures," JOURNAL OF TOXICOLOGY AND
ENVIRONMENTAL HEALTH Vol. 30, No. 3 (July 1990), pgs. 209-221.

[4] W.P. Porter and others, "Groundwater pesticides: interactive
effects of low concentrations of carbamates aldicarb and methamyl and
the triazine metribuzin on thyroxine and somatotropin levels in white
(September 1993), pgs. 15-34. And see: W.P. Porter and
others, "Toxicant-disease-environment interactions associated with
suppression of immune system, growth, and reproduction," SCIENCE Vol.
224, No. 4652 (June 1, 1984), pgs. 1014-1017.

[5] Keith Hamm, "What's In the Mix?" SANTA BARBARA [CALIFORNIA]
INDEPENDENT April 15, 1999, pg. 21 and following pages. See
www.independent.com/007/001/002.html. Thanks to George Rauh for
alerting us to this interview.

[6] Elizabeth A. Guillette and others, "An Anthropological Approach to
the Evaluation of Preschool Children Exposed to Pesticides in Mexico,"
ENVIRONMENTAL HEALTH PERSPECTIVES Vol. 106, No. 6 (June 1998), pgs. 347-

Descriptor terms: violence; hormones; thyroid hormone; development;
aggression; chemicals and behavior; behavior and chemicals;
delinquency; studies; mexico; warren p. porter; elizabeth guillette;
adhd; attention disorders; hyperactivity; learning disabilities; brain
development; emotional stability;

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