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Deadly mix: agricultural chemicals
may affect aggression, development
The mixture of pesticides, herbicides, and fertilizers commonly found in America's
groundwater may be harming children's developing brains and increasing their
aggression, according to a report by researchers at the University of Wisconsin.
Warren P. Porter and colleagues spent five years testing the effects of mixtures of
agricultural chemicals, at levels commonly detected in groundwater, on the behavior,
immune system function, and endocrine hormone levels of mice. The study focused on
three of the most commonly used chemicals: the insecticide aldicarb, the herbicide
atrazine, and nitrate, a chemical fertilizer.
The researchers found that a mixture of these chemicals altered the thyroid hormone
levels and immune system functioning of young mice, and that exposure to either a
nitrate/atrazine mixture or a mixture of all three chemicals changed the mice's patterns
of aggression toward intruder mice. Results showed significant seasonal variation.
Porter et al. note that changes in thyroid hormone levels can cause increased
irritability, learning problems, altered sensitivity to stimuli, and even disrupted
development in utero. "Thyroid hormone levels also affect corticosteroid levels," they
note, "which implies altered aggression levels and immune properties."
Porter et al.'s findings in animals support the conclusions of an earlier study
(see related article, Crime Times, 1998, Vol. 4, No. 3, Page 1)
that revealed increased aggression, as well as
problems with motor control, memory, and eye-hand coordination, in Mexican children
regularly exposed to agricultural pesticides. Elizabeth Guillette, the lead author of that
study, told Crime Times, "Overall, disruptive behavior was the norm with exposed
children."
Porter and colleagues say their findings call the EPA's testing standards for
agricultural chemicals into question, because these chemicals are not studied in
combination. "The single most important finding of the study is that common mixtures,
not the standard one-chemical-at-a-time experiments, can show biological effects at
current concentrations in groundwater," Porter says.
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"Endocrine, immune, and behavioral effects of aldicarb (carbamate), atrazine (triazine)
and nitrate (fertilizer) mixtures at groundwater concentrations," W. P. Porter, J. W.
Jaeger, and I. H. Carlson, Toxicology and Industrial Health, Vol. 15, No. 1-2,
Jan.-March 1999, pp. 133-150. Address: W. P. Porter, National Center for Ecological
Analysis and Synthesis, Suite 300, 735 State St., Santa Barbara, CA 93101. (See also:
"Groundwater pesticides: interactive effects of low concentrations of carbamates aldicarb
and methomyl and the triazine metribuzin on thyroxine and somatotropin levels in white
rats," W. P. Porter et al., Journal of Toxicology and Environmental Health, Vol.
40, No. 1, Sept.1993, pp. 15-34.)
--and--
"Pesticides may harm brain, study says," Marla Cone, Los Angeles Times,
March 15, 1999.
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