All Americans are exposed to pesticides. Among approximately 1,900 subjects selected in 1999 and 2000 from the National Health and Nutrition Examination Survey (NHANES) to represent the United States population six to 59 years of age, at least 90 percent of these persons had detectable serum levels of dichlorodiphenyltrichloroethane (DDT) metabolites.¹ In addition, detectable levels of five of the six measured urinary organophosphate insecticide metabolites were found in at least 50 percent of the subjects, with those six to 11 years of age having the highest metabolite concentrations.¹

The sources of these pesticide exposures include diet,² indoor pesticide exposures (indoor pesticide applications to control pests³ and tracking-in of pesticides used outdoors),⁴ other environmental exposures (drift of pesticides from their intended target),⁵ and occupational exposures (exposures on farms and in pest-control occupations).⁶

There are approximately 16,000 different pesticide products currently used in the United States, and each of them contains one or more of approximately 600 approved pesticide active ingredients. According to the U.S. Environmental Protection Agency, 1.23 billion lb of conventional pesticides (excluding disinfectants and wood preservatives) are used annually in this country, a figure that accounts for more than one fifth of global pesticide use.⁷

Despite the pervasiveness of pesticides, relatively few acute poisonings are identified annually. The Toxic Exposure Surveillance System (TESS), which collects poisoning reports submitted by poison control centers in the United States, identified 20,110 acute pesticide poisoning cases in 2001.⁸ However, this number should be considered a minimal estimate of the true magnitude of the problem because reporting to poison control centers is voluntary, and poison control centers appear to capture only a minority of acute pesticide poisoning cases.⁹ Unfortunately, no better national estimate of acute pesticide poisoning exists.

Another reason for the low detection of acute pesticide poisonings is that physicians may fail to make the correct diagnosis. This failure may result because the clinical findings of pesticide poisoning are rarely pathognomonic but instead can resemble an acute upper respiratory illness, acute conjunctivitis, or acute gastrointestinal illness, among other conditions.

Making the correct diagnosis requires the physician to obtain an occupational and environmental history that solicits information on pesticide exposures. Physicians whose patients reside or work in agricultural areas, or are employed in the pest-control industry should be particularly vigilant about the role that pesticides may play in a patient's illness. Advice on acute pesticide poisoning management is available from published sources,¹⁰ and from poison control centers (the local poison control center can be contacted by dialing 1-800-222-1222). The accompanying table on page 1616 lists additional pesticide information resources.

Little is known about the health effects associated with chronic, low-level pesticide exposure. Although studies have identified associations between low-level pesticide exposures and chronic illness, for almost none of these associations has a causal link been established.¹¹ Studying the human health effects associated with chronic, low-level pesticide exposure is fraught with difficulty, often because accurate data are not available on relevant pesticide exposures or on nonpesticide exposures that may confound or modify the effects of pesticide exposure. In addition, there may be a genetic component to a pesticide-related chronic illness, but associating pesticide exposure with such an illness is troublesome in the absence of biologic markers to identify genetically susceptible patients.

Apart from better recognition of acute pesticide poisoning, what measures can physicians take to reduce acute and chronic pesticide-related illnesses? First, physicians can encourage patients to minimize pesticide exposures. Patients can be reminded about exposure sources and be advised about ways to reduce those exposures. Patients who use pesticides should be counseled to comply with all pesticide label instructions and to take measures to prevent tracking pesticides into unintended locations (such as homes or cars).

Second, recognizing that most diseases are multifactorial and that pesticides or other chemicals may contribute to the etiology of some diseases (e.g., arsenic exposure is associated with lung cancer),¹¹ the physician should consider whether chemical exposures may be playing a role in a patient's illness. When a physician suspects that chemicals are responsible for an illness, referral to an occupational and environmental health specialist may be prudent.

Fortunately, efforts are under way to assist physicians in the recognition and prevention of occupational and environmental illnesses. For example, the National Environmental Education & Training Foundation, in collaboration with several federal government agency and academic partners, is identifying effective approaches that clinicians can adopt in practice settings that will lead to improved recognition, management, and prevention of pesticide-related illnesses.¹²

Finally, by reporting pesticide-related illnesses to a poison control center or state department of health, physicians can help prevent and improve our understanding of pesticide toxicity. These reports are useful for identifying the most problematic pesticides and can draw attention to gaps in epidemiologic and toxicologic data. Ultimately, these reports can aid in the adoption of healthier pest-control approaches.