The mechanisms of action of certain pesticides such as organochlorines
and organophosphates indicate that they do produce neurological
symptoms after acute exposure.51,52 Much
of what we know of pesticide effects in children comes mainly from
acute exposures in pesticide poisoning. At the Hospital for Sick
Children in Toronto, over 50% of the poisonings from pesticide in
one year (n=1026) were in children under age five.53
How are children exposed to pesticides?
There is a range of media and sources by which children may routinely
come into contact with pesticides, including applications in their
homes, yards, day-are facilities, schools, parks and on family pets.
They may also ingest minute amounts of pesticides via the residues
that remain in agricultural produce and, secondarily, via mother’s
milk.54,55,56 Organophosphate (OP) and
carbamate insecticides are identified as "high risk" pesticides
because several individual chemicals of these classes are relatively
very toxic to the nervous system, and they often leave residues
in foods that are consumed most by children.57
Other pesticides that can be neurotoxic in heavy doses include
pyrethroids,58 the insect repellant DEET59
and the chlorphenoxy pesticide, 2,4-D.60
Children, because of their smaller size and greater exploratory
and hand-to-mouth behaviour, are more likely to come into direct
contact with and take in pesticide residues present in the environment.
Lastly, physiologically speaking, children are generally more susceptible
to the toxic effects of pesticides because of their immature stage
of neurological development.61
Neurodevelopmental Effects of Exposure to Pesticides
Case-control and cross-sectional studies in humans have indicated
that those with prior pesticide exposure have problems with memory
loss and deficits in cognitive function and ability in spatial tasks
later in life.62,63
Subclinical neurological damage may also occur from lower level,
long-term exposure to OP pesticides, although these studies are
few in number and have inconsistent results, suggesting the need
for well-designed, longer follow-up research.49
Notably, few of these studies have specifically examined the potential
for neurotoxic effects in children.
A remarkable study
of preschool children in northwestern Mexico examined the
neurobehavioural impacts from relatively heavy exposure
to various pesticides.64 The Yaqui
Valley Indian community has adopted chemical-based agriculture
and, therefore, children are routinely exposed to aerial pesticide
spraying as well as daily household bug spraying. There have
been high levels of organochlorine pesticides measured in
newborn cord blood and breast milk in this community.
Compared to children from the Foothills
community, who are less exposed but otherwise similar for
genetic, economic and social features, the Yaqui Valley children
exhibited impaired stamina, gross and fine motor coordination,
memory and drawing ability, as well as other differences in
Guillette et.al. An anthropological approach to the evaluation
of preschool children exposed to pesticides in Mexico. Environmental
Health Perspectives. 106 (1998), pp. 347-353.
Symptoms of low-level pesticide exposure are non-specific and can
easily be missed because they mimic those of common conditions such
Questions to Ask
Given that there are a number of potential ways that a child may
be exposed to pesticides, questions must cover the fundamental areas
as outlined by the CH2OP framework.
To determine whether and in what way the child has been exposed
to pesticides, and to ensure that such exposure is eliminated, the
following questions are relevant to ask:
- Are there local sources of exposure to pesticides?
- Do people in the neighbourhood routinely apply pesticides
to their lawns?
- Have the neighbours nearby recently sprayed pesticides?
Children who play outdoors in summer may have direct exposure to
the drift from pesticide spraying, or they may be exposed from playing
on pesticide-treated lawns. Pesticide can also be tracked into the
home on shoes, feet and paws.
If the child lives in an agricultural community or on a
farm, there may be exposure to pesticides used in fields. There
may also be contamination of ground water from agricultural run-off.
Drift from pesticide spray may also contaminate household gardens.
If the neighbourhood is near a golf course there may also
be excess exposure to pesticides.
- Has there been use of pesticides (including bug or weed killers,
flea and tick sprays, collars, powder, or shampoos) within the
home or on the garden, lawn or pets?
Studies have shown that many commonly used pesticides can be measured
in lawns and in house dust long after application.66,67
A metabolite of chlorpyrifos, a common organophosphate insecticide
recently given restricted use status by the US EPA, has been measured
in the urine of 90% of American children.
- Have pesticides been used in the school or day-care facility?
Studies have shown that some pesticides can persist on household
surfaces and in dust in the home for substantial periods of time.
Children can readily inhale or absorb pesticides in their environment.
Young children are especially prone to pesticide exposure because
they crawl or ambulate closer to the ground and they frequently
put items, including their hands, in their mouths. Children may
also be accidentally poisoned from exposure to pesticides that
are improperly stored.
- Do parents’ occupations involve exposure to pesticides
either directly or indirectly?
People exposed to pesticides through their work (either in
lawn care, agriculture or handling of agricultural products) may
bring home pesticide residues.
- Do family members eat produce from home gardens?
Produce grown in home gardens may become contaminated with
pesticides that are used on lawns.
- Do parents always wash and/or peel fruits or vegetables given
to babies and young children?
Although the amounts are minute, we know that non-organically
grown fruits and vegetables can carry measurable residues of pesticides.
These are most often found in the peel of such produce; however,
systemic pesticides may be found in the flesh of the fruit or
- Does the child engage in pica? Does the child exhibit
a high degree of hand-to-mouth behaviour?
The above behaviours (i.e., eating dirt, thumb-sucking, putting
hands or objects in the mouth) put the infant and young child
at greater risk of exposure to pesticide residues that exist in
the immediate environment.
Assessing Exposure to Pesticides
Serum cholinesterase levels – a decline in serum cholinesterase
is typically indicative of poisoning by certain types of pesticides
(e.g., organophosphates and carbamates) that inhibit the action
of this enzyme. However, in practice it is difficult to assess what
a given measure of cholinesterase means, since the range for "normal"
cholinesterase levels is broad and there is a time lag between exposure/symptoms
- Parents should be aware of the special risks to children’s health
from the use of pesticides. In particular, insecticide use
should be avoided, especially indoors where residues may linger
in carpets, upholstery, stuffed toys and other surfaces. This
includes use of personal insect repellants, which should not be
used on infants at all and in only a limited way on children.
- Pesticides used outdoors may also be tracked in on the soles
of shoes and by animals. Children may become exposed by touching
sprayed surfaces or by inhalation of drift from pesticide spraying.
Suggested web resources with practical information on non-toxic
alternatives or non-spray versions of pesticides for various
Further Recommended Resources
The Ontario College of Family Physicians’ Environmental Health
Committee pamphlet entitled Pesticides
and Human Health (written by Dr. Kelly Martin).
US EPA’s Office
of Pesticide Programs has useful information especially for
the concerned citizen.
The Pesticide Action Network
is also a helpful web resource.
PSR’s document, Pesticides
and Children: What Primary
Care Physicians Should Know
Recommended Reference Material
The Ontario College of Family Physicians’ Environmental Health
Committee with the Canadian Environmental Law Association report
Setting and Children’s Health contains two detailed case
studies on lead and pesticides that can be separately downloaded
in PDF format.
Greater Boston Physicians for Social Responsibility publication,
In Harm’s Way: Toxic Threats to
Child Development (by Schettler T et al. May, 2000). Downloadable
in PDF format.
Your Child from Toxic Threats to Brain Development: Personal Guidelines
for Children, Parents, and Future Parents. Written as a
companion to the report, In Harm's Way: Toxic Threats to Child
Development, issued by Greater Boston Physicians for Social
Responsibility in May, 2000.
Developing Brain and the Environment. Edited by P.J. Landrigan
et al. Environmental Health Perspectives Volume 108, Supplement
3, June 2000. This monograph compiles recent conference papers by
researchers examining the effect of environmental toxicant exposure
on children's neurobehavioral development. A table of contents,
introduction (by Weiss and Landrigan) and abstracts are available.