Environmental pesticide illness and injury: the need for a national surveillance system.
Pesticides have been used since ancient times. The Egyptians had preparations for expelling fleas from homes in 1550 B.C., the Greeks and the Chinese were burning sulfur to fumigate dwellings before 1000 B.C., and arsenic was being used to control garden insects in China by 900 A.D. (1,2). The modern era of synthetically produced pesticides began in the 1930s, most notably with the development of dichlorodiphenyltrichloroethane (DDT). As alarm over the toxicity of DDT became widespread, the production and use of organophosphate and carbamate pesticides increased. The current generation of pesticides includes synthetic pyrethrins and chemicals that control pests by regulating plant and insect growth (1).
Pesticides are defined under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) as "any substance or mixture of substances intended to prevent, destroy, repel, or mitigate insects, rodents, nematodes, fungi, weeds, micro-organisms, or any other life form declared to be a pest by the Administrator [of the U.S. Environmental Protection Agency], and any substance or mixture of substances intended for use as a plant regulator, defoliant, or desiccant" (1). Pesticides include herbicides, insecticides, rodenticides, fungicides, disinfectants, wood treatment products, growth regulators, and insect repellents (2).
The knowledge that pesticides can harm human health is not new. The first federal Food and Drug Act was passed in 1906 to protect consumers from pesticide residues in foods. Pesticide use has been regulated under FIFRA since 1947 and, since 1954, under the Federal Food, Drug, and Cosmetic Act (FFDCA), which replaced the original 1906 law (2). Nevertheless, concern about the potential public health risks of pesticides did not become widespread until the 1960s, when the public became alarmed over the known and suspected toxicity associated with DDT. Public outcry concerning the adverse effects of DDT contributed to the creation of the U.S. Environmental Protection Agency (U.S. EPA) in 1970 (3). U.S. EPA's Office of Pesticide Programs was established specifically to protect public health and the environment from the risks posed by pesticides (4). The office was given the administrative authority to regulate the registration of pesticides under FIFRA, as well as to set tolerances (or legal residue limits) for pesticides in food under the FFDCA (3).
The public health benefits of pesticides cannot be denied. Pesticides have made valuable contributions to human health by increasing food and fiber production and by reducing the occurrence of vectorborne diseases. For example, following the introduction of pesticides into the United States, production of cotton, peanuts, and potatoes increased by as much as 119 percent (1). Hospitalization rates for malaria among army personnel during World War II decreased by more than half after the U.S. Army began using DDT for mosquito control (1). Pesticides have been largely responsible for controlling onchocerciasis (river blindness) in West Africa (2).
Pesticides, however, are also associated with a wide range of acute and chronic adverse health effects. Acute pesticide poisoning can result in neurotoxicity; peripheral neuropathy; lung, kidney, or liver damage; and death. Acute exposures also commonly cause skin disorders and ocular injuries and may result in chronic neurological effects (1,5,6). Evidence suggests that certain occupational pesticide exposures may lead to chronic health conditions such as cancer, aplastic anemia, and birth defects (7-9).
Recently, the public and scientific community have become concerned that chronic low-dose pesticide exposures might pose a serious health risk to the general population (10). The health conditions of concern include adult and childhood cancer, reproductive problems, birth defects and developmental abnormalities, chronic neurotoxic effects including Parkinson's disease, and, possibly, dysfunction of the immune and endocrine systems (3, 6, 10-16).
The risk of adverse health effects from environmental pesticide exposures may be higher for children than for adults for several reasons. Susceptibility and exposure to toxins are different for children than for adults. Children have "windows of opportunity" for toxic injury that are not present in adulthood: Developing organs both in fetuses and in young children may be at increased risk for damage from pesticides because the cells are dividing more rapidly than are cells in adult organs. Opportunities for exposure also are increased among infants and children because of crawling and mouthing behaviors. Furthermore, children are potentially at greater risk than adults from pesticide residues in the diet. Children absorb and metabolize food more efficiently, ingest more food and water per body mass, and ingest single food items in greater quantities than do adults (3, 17). In 1996, the federal government recognized the special risks pesticide exposures pose to children by enacting the Food Quality Protection Act, which authorized U.S. EPA to set tolerances for dietary pesticide residues at levels that would protect the health of the most sensitive or highly exposed populations, including children and infants (4).
Public Health Impact
The potential impact of pesticides on public health is substantial. In 1996, U.S. EPA reported that 20,000 pesticide products containing 620 active ingredients were licensed for use in the United States. More than one billion pounds of conventional pesticide active ingredients are used annually in this country. If wood preservatives and disinfectants are included, more than four billion pounds of pesticides are used annually (4).
Virtually everyone is exposed to low levels of pesticides in the environment (18, 19). The general public is frequently exposed to pesticide residues in food, as a consequence of agricultural applications to crops, as well as in water (3, 17). In addition, routine pesticide applications in people's homes and yards and pesticide drift from agriculture and forestry activities can be important sources of exposure to the general population (2, 17, 20, 21). In the United States, approximately 75 percent of pesticide active ingredients are used in the agricultural industry; the remainder is used in people's gardens and homes, including for structural pest control. Seventy-five percent of all cropland and 70 percent of all livestock on more than 900,000 farms are reportedly treated with pesticides. U.S. EPA estimates that 69 million American households, or 85 percent of all families, store and use pesticides in and around the home (6).
The most intensive applications of pesticides may occur in urban areas where pesticides are used in structures to control cockroaches and termites and in yards and gardens to control weeds, insects, and fungi (5). In addition, pesticide residues may persist indoors because environmental factors such as sunlight, wind, and rain are not present to degrade and disperse the pesticide. For example, a study of the potential health risks to infants whose homes had undergone legal pesticide applications with chlorpyrifos showed that the estimated infant absorption of chlorpyrifos was potentially 1.2 to 5.2 times the no-observable-effect level (NOEL). The estimate was based on air and surface samples of pesticide residues taken during the 24-hour period after application of 0.5 percent chlorpyrifos for fleas (22).
In recent years, there have been a number of reports of outbreaks of pesticide poisoning in communities and other nonoccupational settings. Table 1 delineates a few of these outbreaks.
Poison control center (PCC) reports and hospital-based data suggest that the impact of acute pesticide poisoning is significant. The American Association of Poison Control Centers received reports of 45,000 pesticide-related calls from 64 PCCs in 1988; another study has showed that half of all pesticide-related calls to PCCs concerned young children (23, 24). According to hospital surveys, an estimated 20,000 people receive emergency care annually for known or suspected pesticide poisoning, and approximately 10 percent are admitted to the hospital (6). Half of all pesticide-related hospital admissions are reported to be caused by nonoccupational exposures, and half of those admitted because of nonoccupational exposures are young children (25). No data are available on the prevalence of pesticide-related chronic illness in the United States.
Reports such as these suggest that pesticide poisoning may pose a significant public health threat. In the absence of a national system for reporting and tracking pesticide-related illnesses, however, it is not possible to accurately estimate the public health impact of pesticide-related morbidity and mortality in the United States.
The Need for Surveillance
Despite the fact that pesticide use is pervasive and can lead to serious illness and injury, most states do not conduct case-based surveillance for pesticide-related health conditions (Table 2). In addition, there is currently no national-level reporting of nonoccupational pesticide-related health conditions. Only five states (Oregon, Texas, New York, California, and Florida) have received funding from the Centers for Disease Control and Prevention (CDC) to monitor and report cases of occupational [TABULAR DATA FOR TABLE 1 OMITTED] pesticide illness and injury to the National Institute for Occupational Safety and Health (NIOSH) Sentinel Event Notification System for Occupational Risks (SENSOR) program (26).
Surveillance is needed to provide the information essential for prevention and control of pesticide-related illness and injury. A well-designed national surveillance system could estimate the magnitude of the problem, monitor trends, detect emerging problems, identify high-risk populations and risk factors for pesticide poisoning, document the distribution and spread of pesticide-related illness in the population, and facilitate epidemiologic research. Pesticide-poisoning surveillance data also could assist in drafting and amending regulations, targeting enforcement, planning and directing prevention strategies, and evaluating the impact of intervention and prevention efforts (27-29).
A Proposal for National Surveillance
Surveillance for health conditions related to nonoccupational pesticide exposures requires consideration of several issues. Among these are the difficulty of diagnosing many pesticide-related illnesses, the underreporting of cases to state programs, the need for electronic linkages between databases to facilitate surveillance activities, and the importance of standardized data collection and reporting procedures so that comparability of data among states can be increased. Another important issue is the limited availability of funding.
The National Center for Environmental Health (NCEH) proposes to establish a national surveillance system to monitor pesticide-related health conditions resulting from residential, environmental, and other nonoccupational pesticide exposures. Initially, surveillance activities would be limited to tracking acute pesticide poisoning cases, because this is the information currently being collected by state-based surveillance programs and by the NIOSH SENSOR program. In the future, consideration would be given to adding known or suspected chronic pesticide-related health conditions to the national surveillance system if participants reached a consensus that such conditions should be tracked. Chronic conditions might include intermediate and delayed polyneuropathy, neurotoxicity that is not infectious in origin, and young-onset Parkinson's disease (1,2,5,6,15).
State surveillance programs would obtain case reports from a variety of data sources, including PCCs; health care providers; emergency departments; hospital discharges; and state health, environmental, and agricultural agencies. Data for the proposed national surveillance system would be collected according to a list of standardized core variables that is being developed cooperatively by CDC, state agencies, and other federal agencies. States would transfer this core data electronically to CDC without personal identifiers; however, unique identifiers would have to accompany the case reports so that CDC could obtain additional case information from state databases when necessary. NIOSH and NCEH would coordinate surveillance activities to ensure comparability between occupational and nonoccupational reports.
In the absence of acute overt pesticide poisoning, it is often difficult to determine whether an illness or death is linked to an environmental pesticide exposure (30). An additional complication is that it is generally not possible to obtain laboratory confirmation of the exposure; there are few biomarkers of pesticide exposure, and these few are not widely available to health care practitioners. Developing sensitive and affordable procedures for detecting low-level pesticide exposures is a priority for CDC (31). NCEH has developed methods for measuring urinary levels of 12 analytes that are biomarkers of 30 commonly used pesticides, and it has established reference ranges for these pesticide analytes in the general population (18). This effort is important in improving the ability to ascertain whether health conditions are pesticide related. Furthermore, to make these biomonitoring techniques more widely available, CDC supports capacity building in state and territorial laboratories.
TABLE 2 State Involvement in Surveillance of Pesticide-Related Illness, 1997(*) Level of Surveillance Number of States Collect data only 4 Collect and review data 4 Collect/review data, investigate cases 12 No surveillance at any level 30 * Based on information from Zeitz, P.A., S.C. Macdonald, and S.A. Yoon (1998), "1997 CSTE-CDC-ASPH Survey of Statewide Surveillance Systems of Sentinel Environmental Diseases: Status and Trends - Report to the Surveillance and Programs Branch, National Center for Environmental Health, Centers for Disease Control and Prevention," Unpublished report, Atlanta, Ga.: National Center for Environmental Health.
The proposed system would use software that is compatible with other state and federal surveillance software to facilitate electronic data transfer, which would be critical to the effectiveness of the surveillance system. Timely publication of provisional and final data would be emphasized at all levels of the surveillance system to ensure that appropriate public health action is taken and that the effects of such action are evaluated.
As an initial step toward establishing this national surveillance system, NCEH is developing a pilot surveillance project to be tested in 1999 in a state with an occupational pesticide-illness surveillance program. Choosing a state with the knowledge base and infrastructure already in place will reduce cost and startup time. Funding will be provided by NCEH and U.S. EPA.
Following evaluation of this pilot program by state and federal partners, NCEH proposes to incorporate any recommended changes and to expand the program to other states. Because of limited resources, the national program may not be able to provide funds to all states to conduct these surveillance activities.
NCEH and its state and federal partners have recognized the need for a national program for surveillance of nonoccupational pesticide-related health effects; however, funding will remain a challenge to establishing an effective and ongoing national surveillance system. To meet this challenge, NCEH will continue to actively seek partnerships with other federal agencies, including U.S. EPA, to share the cost of this important project.
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Corresponding Author: Kim M. Blindauer, D.V.M., M.PH., Environmental Epidemiologist, Health Studies Branch, Division of Environmental Hazards and Health Effects, National Center for Environmental Health, CDC, 4770 Buford Hwy., N.E., Atlanta, GA 30341-3724. E-mail: <email@example.com>.
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|Publication:||Journal of Environmental Health|
|Date:||Jun 1, 1999|
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