HEALTH HAZARDS OF PESTICIDES
"Late in the afternoon of April 1, 1990, a
three-year-old girl playing in front of her trailer home in
California’s San Joaquin Valley suddenly lost control of her
body and began foaming at the mouth. By the time the girl
arrived at the local emergency room, she was near death. She
recovered eventually. A report filed with the California
Department of Pesticide Regulation concluded the child had
been poisoned by aldicarb, a highly toxic insecticide that
works the same way on people as it does on bugs -- like
nerve gas. ‘Somebody had parked a tractor with pesticide
material on it right in front of the play area,’ said
Michael O’Malley, the author of the report and a physician
at the University of California, Davis."
-- Matt Crenson, Associated Press, December 9, 1997
Pesticides are specifically formulated to be toxic to
living organisms, and as such, are usually hazardous to
humans. Most pesticides used today are acutely toxic to
humans. Pesticides cause poisonings and deaths every year and
are responsible for about one out of every sixteen calls to
poison control centers.
Chronic health effects have also been reported from
pesticides, including neurological effects, reproductive
problems, interference with infant development, and cancer.
Acute pesticide poisonings frequently involve
organophosphate pesticides, or sometimes their close
relatives, the n-methyl carbamates. These pesticides were
originally derived from chemical warfare agents developed
during World War II. Some common organophosphates in use today
include chlorpyrifos (Dursban®), diazinon, azinphos-methyl
(Guthion®), malathion, and methyl-parathion. Aldicarb (Temik®)
and carbaryl (Sevin®) are common n-methyl carbamates. They
kill by blocking the enzyme that breaks down a critical
nerve-impulse-transmitting chemical known as acetylcholine.
The result is that certain nerve impulses are over-expressed,
resulting in an array of acute toxic symptoms. Symptoms of
organophosphate or carbamate poisoning include blurred vision,
salivation, diarrhea, nausea, vomiting, wheezing, and
sometimes seizures, coma, and death. Mild to moderate
pesticide poisoning mimics gastroenteritis, bronchitis, or
intrinsic asthma, and even astute clinicians may not link
these symptoms to pesticides.
The American Association of Poison Control Centers reported
97,278 calls about pesticide poisonings in 1996. Half of the
reported poisonings involved children under six years of age.
Occupational pesticide poisonings are required to be reported
in California, and there are approximately 1,500 reported
cases per year.,
 Efforts to
extrapolate to national occupational pesticide poisonings
result in estimates of anywhere between 10,000 and 40,000
physician-diagnosed pesticide illnesses and injuries annually
among agricultural workers.
These estimates do not include children of agricultural
Research has shown that current estimates based on
occupational surveillance or poison control centers may
greatly underestimate the problem of pesticide poisonings. A
study in California that involved active surveillance, with
extensive physician education and recruitment, revealed that
this intervention significantly increases the number of
reports of pesticide illness. A follow-up evaluation of
poisoned workers discovered that 40 percent of the exposure
incidents also involved co-workers who did not seek medical
treatment for various reasons, suggesting that the total
burden of illness is grossly underreported.
Poison control centers are commonly called after accidental
ingestions or spills of pesticides in the home, but are less
frequently called when illnesses occur after routine
agricultural pesticide exposures.
Mild signs of acute pesticide poisoning, such as nausea,
vomiting, diarrhea, or wheezing are often not recognized as
being potentially linked to pesticide toxicity. Rashes and
other skin reactions are another major manifestation of
pesticide toxicity that is often misdiagnosed.
Even Dr. Lynn Goldman, Assistant Administrator of the Office
of Prevention, Pesticides and Toxic Substances of the U.S.
EPA, has publicly admitted, "Medical problems caused by
pesticide exposure are often overlooked or misdiagnosed by
health care providers."
Even severe pesticide poisoning is frequently misdiagnosed.
In one review of the medical records of 20 severely
pesticide-poisoned infants and children transferred to a major
medical center from other hospitals, 16 of the 20 children had
been wrongly diagnosed at the time of the transfer. Diagnoses
of the children’s symptoms included brain hemorrhage, head
trauma, diabetic acidosis, severe bacterial gastroenteritis,
pneumonia, and whooping cough, although all of the children
later turned out to have pesticide poisoning.
In this series, five of the children, all infants, were
poisoned after home application of a pesticide. Another child
was poisoned after mowing a lawn that had recently been
sprayed with an organophosphate. Although these cases did not
involve farm children, they demonstrate that all children can
be overexposed to pesticides in their home environment. Among
infants, only a small dose is required to have potentially
devastating health consequences. Furthermore, there is some
evidence from animal studies that undernourished individuals
are more vulnerable to poisoning by organophosphates, implying
that poor and undernourished children may be at greater risk.
"Twenty-two years that I have been working in the
fields, I’ve seen more illnesses, more children being born
ill, more families that miss work because every day they
have more problems, headaches. Sometimes their children are
sick and they have to miss work. . . . We live in a
depression. We don’t know if it’s because of the chemicals."
-- Laura Caballero, Lideres Campesinas (Salinas, CA Public
Meeting July 25, 1996)
Chronic effects of pesticide exposure may include adverse
effects on neurological function, cancer, reproductive harm,
reduced growth and development, and birth defects. Much of the
evidence of chronic effects is based on studies of adult
workers who are exposed to a mixture of chemicals every day,
making it difficult to pinpoint specific pesticides. The
effects of individual pesticides during specific periods of
fetal life, infancy, and early development have been studied
in laboratory animals. Little research on the chronic effects
of pesticides has been done directly on children, and even
less on farm children.
In adults, exposures to insecticides and herbicides have
been reported to confer an approximately fourfold increased
risk of early-onset Parkinson’s disease.,
 Other long-term
neurological problems, particularly shortened attention span
and reduced coordination, have been reported in adults
overexposed to organophosphate pesticides.
Although such studies have not been done in human children,
animal studies have revealed that some pesticides appear to
target the developing brain during the critical period of cell
division, thereby leading to lasting behavioral aberrations.,
 Not only do
organophosphate pesticides interfere with a critical
nerve-impulse transmitter, but they also can permanently
change the number of receptors in the brain for this
neurotransmitter. This mechanism may explain the subtle,
permanent effects observed in animals.
Subtle neurological effects may also occur in human
children. A recent study compared preschool children in two
farming communities in Mexico, one with heavy pesticide use
and one with little or no pesticide use. The children living
in the area with heavy pesticide use had strikingly impaired
hand-eye coordination, decreased physical stamina, short-term
memory impairment, and difficulty drawing, compared with the
less exposed children. Furthermore, observers of the exposed
children noticed increased aggressive and anti-social behavior
compared to their less exposed counterparts.
Studies have shown that lead, a known neurotoxicant, has
lasting effects on attention span, intelligence, and behavior.
Infants and children are more susceptible to the toxic effects
of lead than are adults, probably because their brains are
Similarly, it appears that infants and children are also more
susceptible to other neurotoxicants, including pesticides.
"There were three funerals in a row here in this
neighborhood for children that died of cancer. There was a
day when some of the children got together [across from] our
house. They were playing with the Barbies. They were picking
flowers . . . and they were burying the Barbie. I said ‘What
are you kids doing?’ Cause they were burying the Barbie and
they were crying and crying and crying . . . they said that
Barbie died of cancer. It had cancer in the leg and it died.
. . . I was always wondering ‘Is my daughter going to be
next after having her so ill?’ . . . When I went to the
room, she was having another seizure and she kept saying,
‘My dollies are dying of cancer mom, please help me, please
-- Marta Salinas, McFarland, CA
According to Dr. Lynn Goldman of the U.S. EPA, at least 101
pesticides in current use are probable or possible human
Examples of pesticides which are known carcinogens in animals
and are still used around humans today include
pentachlorophenol, 1,3-dichloropropene (Telone II®), and
Studies of farm populations indicate that adults exposed to
pesticides may be at increased risk for cancers of the
lymphatics and blood, stomach, prostate, testes, brain, and
 Several human
studies and studies of household dogs have consistently
reported a particular association between exposure to the
common herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) and
There is evidence of associations between parental or
infant exposures to pesticides and childhood brain tumors,
leukemia, non-Hodgkin’s lymphoma, sarcoma, and Wilm’s tumor.–
In many of the reports, children’s increased cancer risks were
of greater magnitude than the risks reported in studies of
Five of the nine human studies that evaluated the risk of
childhood leukemia after parental exposures to pesticides
found an increased risk, while four out of five studies
looking at postnatal exposures to pesticides also found a link
with acute leukemia.
In one California study, children with leukemia were three to
nine times more likely to have a parent who reported using
pesticides in the home or garden during pregnancy or
Eight of the nine studies evaluating the link between
childhood brain tumors and pesticide use showed an
association, with three reaching statistical significance.
Reproductive and Developmental Toxicity
Numerous pesticides are known or suspected reproductive
toxicants. Examples include the fungicides benomyl (Benlate®)
and vinclozolin (Ronilan®), as well as the fumigants methyl
bromide and metam sodium.
People who live in agricultural regions or undergo
occupational exposure to pesticides are at increased risk of a
variety of adverse reproductive outcomes. An investigation of
stillbirths and neonatal deaths in California reported that
maternal occupational exposure to pesticides was associated
with more than a doubling of the risk of stillbirth due to
congenital anomalies, and a slightly increased overall risk of
all types of stillbirth.
Numerous types of birth defects, particularly limb-reduction
defects, have been associated with pesticide exposures in
A Minnesota study indicated an association between paternal
employment as a pesticide applicator and a variety of birth
defects in offspring, including abnormalities of the lungs,
heart, musculoskeletal system, and urogenital system.
Furthermore, the general population of agricultural regions of
the state had an increase of birth defects, with the peak
incidence among children conceived in the spring, when
spraying is most intense.
Many currently used pesticides are now known to interfere
with normal hormonal function in animals. For example,
vinclozolin and iprodione, popular fungicides, both break down
into a metabolite that interferes with testosterone and other
Several organochlorine pesticides, including DDT,
methoxychlor, endosulfan, and dicofol, mimic estrogen.,
 Lindane, which is
sometimes used to treat head lice in children, acts as an
anti-estrogen, and is also toxic to the nervous system.,
 Atrazine, a popular
herbicide, can disrupt ovarian function, cause mammary
(breast) tumors in animals, and interferes with the binding of
steroid hormones and the breakdown pathway of estrogen.–
Although no human studies have been done involving the
endocrine effects of these chemicals, the endocrine system in
animals is nearly identical with the human, making it likely
that effects observed may be relevant to human health. In
humans and animals, the endocrine system is critical to life.
Disruption of hormone function can permanently alter normal
development of the fetus and child.
Some pesticides have also been reported to be toxic to the
immune system in animals.
Nearly all of the epidemiological studies on children’s
health and pesticide exposures were done on the general,
non-farming population. These studies would likely
underestimate the health impacts that would be expected for
highly exposed subpopulations of children such as farm
children. Some studies did look at children of parents who
work in jobs that may involve pesticide exposure; however the
child’s exposure was almost never directly assessed, but was
indirectly estimated based only on the parent’s job title.
Such a technique is likely to lead to misclassification of
exposures and underestimation of the health impact. Thus
health impacts among farm children are likely much greater
than those described in most of the scientific research to
date. Because of the health impacts of pesticides, it is
important to identify the sources and levels of exposure to
these chemicals in order to protect the most highly exposed
children from these dangerous substances.