GE - PANUPS: Inadequate Pesticide Testing
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Sent: 27 March 1999 03:28
Subject: PANUPS: Inadequate Pesticide Testing
P A N U P S
Pesticide Action Network Updates Service
New Study Points to Inadequate Testing of Pesticides
March 26, 1999
A new study in the journal Toxicology and Industrial Health identifies
significant shortcomings in toxicological testing protocols currently
used to register pesticides in the United States. The five year study
suggests that combinations of commonly used agricultural chemicals in
concentrations that mirror levels found in groundwater can significantly
influence immune and endocrine systems as well as neurological health.
"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," said Warren Porter,
lead author and University of Wisconsin professor of zoology and
environmental toxicology. "Although they frequently co-occur, tests for
these compounds in combination are very rare."
The experiments performed by Porter's group suggest that children and
the developing fetus are most at risk from pesticide-fertilizer
mixtures. Their influence on developing neurological, endocrine and
immune systems, said Porter, portend change in ability to learn and in
patterns of aggression.
The study focused on three commonly used farm chemicals:
aldicarb, an insecticide; atrazine, an herbicide; and nitrate, a
chemical fertilizer. All three are in wide use worldwide and are the
most ubiquitous contaminants of groundwater in the United States.
In the series of experiments, when mice were given drinking water laced
with combinations of pesticides and nitrate, they exhibited altered
immune, endocrine and nervous system functions. Those changes, according
to Porter, occurred at concentrations currently found in groundwater.
Effects were most noticeable when a single pesticide was combined with
The apparent influence of pesticide and fertilizer mixtures on the
endocrine system, the system of glands such as the thyroid that secrete
hormones into the bloodstream, may also result in changes in the immune
system and affect fetal brain development. "Thyroid disruption in humans
has multiple consequences," Porter said. Some of these include effects
on brain development, level of irritability, sensitivity to stimuli,
ability or motivation to learn and altered immune function.
A curious finding of the study is that animals may be more vulnerable to
the influence of such chemicals depending on the time of year:
"Our current working hypothesis is that animals are seasonally
vulnerable because of subtle modulation of natural seasonal variation in
hormone levels," according to Porter.
Need for new testing methods
The new study, Porter contends, adds to a growing body of evidence that
current testing methods required for the registration and use of
chemical pesticides in the U.S. are fundamentally flawed. The study
listed six important deficiencies in current testing protocols:
* Current tests do not require chemicals to be tested at low dose
pulse exposure. Pulse doses of low levels of pesticides at critical
times when developmental windows are open and body defenses are unable
to respond may lead to permanent changes in a fetus. It is important to
remember that the embryo has almost no defensive systems against
chemicals and no feedback systems to modulate chemical concentrations
early in its development.
* Toxicological tests have typically focused on cancer and
mutation endpoints and have not looked at other critical concerns such
as endocrine and immune system effects that can occur.
* Standard toxicological tests only evaluate one route of exposure
at a time, rather than all possible routes (oral, cutaneous and
* Most testing is done with pure forms of pesticidal active
ingredients rather than with commercial formulations. There are three
types of chemical additives that are missing from most testing:
contaminants of manufacturing processes, toxic waste deliberately added
from chemical reactor cleaning processes and "inert" ingredients.
* Current testing requirements do not evaluate exposure effects
from chemical mixtures. While it is impossible to examine all possible
mixtures, common combinations generated in specific areas due to crop
rotation and tillage practices could be examined.
* Laboratory animals generally live in an environment where
climate, nutrition and disease are carefully controlled. Researchers
know that when additional stresses are present, toxic responses to
registered chemicals occur that do not appear under current standard
Sources: Warren Porter, et al., "Endocrine, immune and behavioral
effects of aldicarb (carbamate), atrazine (triazine) and nitrate
(fertilizer) mixtures at groundwater concentrations," Toxicology and
Industrial Health (1999) 15, 133-150. University of Wisconsin-Madison
press release, March 15, 1999.
Pesticide Action Network North America (PANNA)
49 Powell St., Suite 500, San Francisco, CA 94102 USA
Phone: (415) 981-1771
Fax: (415) 981-1991
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