While the exposure through breast milk is absolutely greater than during development in the womb, in utero exposure is relatively more significant due to the greater vulnerability of the fetal brain and CNS.

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.

Symptoms of low-level pesticide exposure are non-specific and can easily be missed because they mimic those of common conditions such as influenza.

Studies have shown that many commonly used pesticides can be measured in lawns and in house dust long after application.

The use of insecticides should be avoided, especially indoors where residues may linger in carpets, upholstery, stuffed toys and other surfaces.

Pesticides

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.

Symptoms of low-level pesticide exposure are non-specific and can easily be missed because they mimic those of common conditions such as influenza.65

• An important reference is the US EPA's pesticide poisoning handbook (5th Ed), Recognition and Management of Pesticide Poisonings. By Drs. Routt Reigart & James Roberts.
• See also the University of Nebraska Cooperative Extension resource, Signs and Symptoms of Pesticide Poisoning.

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:

The Community

• 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.

The Home

• 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.

Occupational Exposure

• 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.

Personal Habits

• 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 vegetable.
  
  
• 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 and effects.

Personal Prevention

• 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 uses include:

• The Canadian Mortgage and Housing Corporation (CMHC-SCHL), "FAREWELL To Cockroaches: Getting Rid of Cockroaches the Least Toxic Way"
• The World Wildlife Fund Canada Guide, Reducing Your Risk From Pesticides

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 Environmental Standard 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.

Protecting 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.

The 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.

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