Evaluation of Health Effects of Pesticides Among Rural Populations
The Agricultural Health Study is a large, prospective cohort study of men and women in agriculture involving the states of Iowa and North Carolina. It is designed to explore potential causes of cancer and other diseases among farmers and their families and among commercial pesticide applicators. The University of Iowa Environmental Health Sciences Research Center has cooperated with NIEHS and NCI to enroll the cohort and then to carry out nested studies within the cohort. Iowa was selected for this important study because of its strong agricultural sector with diverse production methods, commodities, and products and the availability of strong environmental health investigators and necessary facilities to manage a cohort study of this magnitude. Current medical research suggests that while agricultural workers are generally healthier than the general US population, they may have higher rates of some cancers, including leukemia, myeloma, non-Hodgkin's lymphoma, and cancers of the lip, stomach, skin, brain, and prostate. Other conditions, like asthma, neurologic disease, and adverse reproductive outcomes may also be related to agricultural exposures. The Agricultural Health Study is designed to identify occupational, lifestyle, and genetic factors that may affect the rate of diseases in farming populations.
Working with NIEHS and NCI, EHSRC investigators began enrolling Agricultural Health Study cohort members in 1993. Eligible cohort members were identified through pesticide applicator certification programs. Enrollment ended in 1997, at which time 89,658 men and women (68,564 from Iowa and 31,094 from North Carolina) had enrolled by completing questionnaires that collected information about agricultural exposures. The overall enrollment response rate was 75%. Currently, 4,916 commercial applicators, 52,395 farmer applicators, and 32,347 spouses of farmer applicators are enrolled. Mean ages (in years) of these groups at enrollment were 39.2, 46.7, and 48.4, respectively. When spouses were enrolled, they were also requested to register their children under 18 years of age. Follow-up outcome information is being obtained through electronic linkages of the cohort to statewide cancer incidence registries, mortality databases, and other data sources. These data will allow for cohort analyses evaluating the relationship between reported agricultural exposures and chronic disease. Where these analyses support a relationship, nested case-control studies can be conducted. Currently, exposure histories of cohort members are being updated, dietary information is being collected, buccal cell samples are being collected and stored, and pesticide exposure assessments are being conducted and analyzed.
The Agricultural Health Study Registry has served as the base for a number of research projects. One study (Blair et al. 2002) reported that repeat interviews from 4,088 Iowa pesticide applicators participating in the Agricultural Health Study provided the opportunity to evaluate the reliability of self-reported information on pesticide use and various demographic and life-style factors. Percentage agreement for ever-/never-use of specific pesticides and application practices was quite high, generally ranging from 70% to more than 90%, and did not vary by age, educational level, or farm size. Agreement was lower (typically 50-60%) for duration, frequency, or decade of first use of specific pesticides. Level of agreement regarding pesticide use in this population is similar to that generally found for factors typically used in epidemiologic studies such as tobacco use and higher than typically reported for diet, physical activity, and medical conditions.
Another study (Hoppin et al. 2002) evaluated the role of pesticide exposure and a common respiratory symptom, wheeze, among 20,000 farmers who are licensed pesticide applicators. They found that individuals who used particular pesticides (paraquat, EPTC, parathion, malathion, and chlorpyrifos) were more likely to wheeze than those who did not use these chemicals. In addition, all pesticide application methods had an increased chance of wheeze and pesticide application to animals was also associated with wheeze. It was also found that the herbicides, atrazine and alachlor were associated with wheeze. The associations with these pesticides were small, but since farmers are generally healthier than the general population and may avoid exposures and activities that contribute to respiratory and other symptoms, these results suggest that further investigation of these chemicals is warranted.
A third study (Alavanja et al. 2001) examined the effects of a high pesticide exposure event in 1997 as reported by farmers enrolled in the cohort study. Six out of 1,000 farmers reported an event that resulted in an unusually high pesticide exposure in 1997. When comparing applicators who reported such an event in 1997 to those who did not, it was found that applicators who reported they could not afford certain protective equipment were four-times more likely to have a high pesticide exposure event than those who could afford such equipment. Those who voiced opinions such as "accidents are just one of the occupational hazards of farming that you must accept if you are going to be in the business" were almost four times as likely to experience an event resulting in usually high pesticide exposure. These results suggest that multiple factors influence who experiences an unusual pesticide exposure. A follow-up study found that inexperienced applicators had more accidental exposures than expected, based on the data from those who reported more lifetime days of pesticide use. For all other applicators, the chances of having an accidental high exposure each time pesticides are applied does not change with time, but the lifetime risk is increased. In other words, the more days pesticides are applied, the more chances there are of experiencing a spill. Important factors that may contribute to high pesticide exposure events are inexperience, and random events such as breaking a hose. The results suggest that special precautions may be needed to protect infrequent users.
The Agricultural Health Study is unique among studies of occupational groups in that the wives of farmers who apply pesticides and their children are included in the study. Since farmers generally "live where they work", their families have many opportunities to come into contact with pesticides and other farm hazards. By studying these family members whose exposures are often more like those in the general non-farm population, we have the potential to learn things about the health effects of pesticides that are applicable to the population at large. In this paper we document that farm families do in fact have many opportunities for exposure - both directly and indirectly - to pesticides. We found, for example, that 21% of homes are within 50 yards of the pesticide mixing area, that 27% of applicators store pesticides in their homes (including attached garage or basements), and that most pesticide-contaminated clothing is washed in the same machine as other laundry. Furthermore, at least half of the wives reported working the fields, 40% reported mixing or applying pesticides, and more than half of the children over age 11 did farm chores that potentially put them into contact with pesticides. Thus, it will be important to study the health consequences of such exposures and to identify methods for minimizing the exposures of family members.
Implications and Public Health Impact
Findings from this study have indicated important exposure hazards and elevated health risks faced by farmers and farm family members. These findings are relevant to farmers throughout the United States and other countries who use modern agricultural technologies. The study has shown the high prevalence of injuries among rural dwellers and that attitudes about pesticide risks are an important determinant of exposure. A number of future studies are planned to address other aspects of rural exposures and disease patterns that differ from urban exposures and diseases.
Center Contribution
The EHSRC has provided support to the Agricultural Health Study primarily by supporting the Health Registry Facility. This facility performs linkage analysis for research on cancer, birth defects, and other chronic disease outcomes and provides programming support for nested studies. Dr. Charles Lynch who heads up the Iowa component of the Agricultural Health Study is director of the Environmental Epidemiology Research Core of the EHSRC.
EHSRC Investigators
Charles F. Lynch, The University of Iowa, College of Public Health, P30ES005605, N01CP081119-00098, N01CP033048-00093;
Nancy L. Sprince, The University of Iowa, College of Public Health, P30ES005605;
Leon F. Burmeister, The University of Iowa, College of Public Health, P30ES005605, 5P50HL037121-109001
Craig Zwerling, The University of Iowa, College of Public Health, P30ES005605
Wayne Sanderson, The University of Iowa, College of Public Health, P30ES005605, 5U50OH007548-03
Burton C. Kross, formerly The University of Iowa, College of Medicine, P30ES005605, 5N01CP095602-00289
Steve Reynolds, formerly The University of Iowa, College of Public Health, P30ES005605
Publications
Alavanja MCR, Samanic C, Dosimeci M, Lubin J, Tarone R, Lynch CF, Knott C, Thomas K, Hoppin JA, Barker J, Coble J, Sandler DP, Blair A. (2003). Use of agricultural pesticides and prostate cancer risk in the Agricultural Health Study cohort. American Journal of Epidemiology, 157(9), 800-814.
Alavanja, M. C., Akland, G., Baird, D., Blair, A., Bond, A., Dosemeci, M., Kamel, F., Lewis, R., Lubin, J., Lynch, C., et al. (1994). Cancer and noncancer risk to women in agriculture and pest control: the Agricultural Health Study. J Occup Med, 36(11), 1247-1250.
Alavanja, M. C., Sandler, D. P., McDonnell, C. J., Lynch, C. F., Pennybacker, M., Zahm, S. H., Mage, D. T., Steen, W. C., Wintersteen, W., Blair, A. (1999). Characteristics of pesticide use in a pesticide applicator cohort: the Agricultural Health Study. Environ Res, 80(2 Pt 1), 172-179.
Alavanja, M. C., Sandler, D. P., McDonnell, C. J., Lynch, C. F., Pennybacker, M., Zahm, S. H., Lubin, J., Mage, D., Steen, W. C., Wintersteen, W., Blair, A. (1998). Factors associated with self-reported, pesticide-related visits to health care providers in the Agricultural Health Study. Environ Health Perspect, 106(7), 415-420.
Alavanja, M. C., Sandler, D. P., McDonnell, C. J., Mage, D. T., Kross, B. C., Rowland, A. S., Blair, A. (1999). Characteristics of persons who self-reported a high pesticide exposure event in the Agricultural Health Study. Environ Res, 80(2 Pt 1), 180-186.
Alavanja, M. C., Sandler, D. P., McMaster, S. B., Zahm, S. H., McDonnell, C. J., Lynch, C. F., Pennybacker, M., Rothman, N., Dosemeci, M., Bond, A. E., Blair, A. (1996). The Agricultural Health Study. Environ Health Perspect, 104(4), 362-369.
Alavanja, M. C., Sprince N. L., Oliver E., Whitten P., Lynch C., Gillette P. P., Logsden-Sacket N., Zwerling C. (2001). A nested case-control analysis of high pesticide exposure events from the Agricultural Health Study. Am J Ind Med, 39(6):557-63.
Blair A, Tarone R., Sandler D., Lynch C. F., Roland A., Wintersteen W., Steen W. C., Samanic C., Dosemeci, M., Alavanja M. C. R. (2002). Reliability of reporting on lifestyle and agricultural factors by a sample of participants in the agricultural health study from Iowa. Epidemiology, 13:94-99.
Coble, J., Hoppin, J.A., Engel, L., Elci, C.E., Dosemeci, M., Lynch, C.F., Alavanja, M.C.R. (2002). Prevalence of exposure to solvents, metals, grain dust and other hazards among farmers in the Agricultural Health Study. Journal of Exposure Analysis and Environmental Epidemiology 12(6):418-426.
Curwin, B, Sanderson, W, Reynolds, S, Hein, M, Alvanja, MCR. Pesticide Use and Practices In An Iowa
Farm Family Pesticide Exposure Study. (2002). Journal of Agricultural Safety and Health 8(4): 423-433.
Engel LS, Rothman N, Knott C, Lynch CF, Logsden-Sackett N, Tarone
RE, Alavanja MC. (2002). Factors associated with refusal to provide a buccal cell sample in the Agricultural Health Study. Cancer Epidemiol Biomarkers Prev 11:493-496.
Flower KB, Hoppin JA, Lynch CF, Blair A, Knott C, Shore DL, Sandler DP. Cancer Risk and Parental Pesticide Application in Children of Agricultural Health Study Participants. Environmental Health Perspectives doi:10.1289/ehp6589.
Hoppin J. A., Umbach D. M., London S. J., Alavanja M. C. R., Sandler D. P. (2002). Chemical predictors of wheeze among farmer pesticide applicators in the Agricultural Health Study. Am J Resp Crit Care Med, 165(5), 683-9.
Hoppin, JA, Umbach, DM, London, SJ, Alavanja, MCR, Sandler, DP. (2003). Animal production and wheeze in the Agricultural Health Study: Interactions with atopy, asthma, and smoking. Occupational and Environmental Medicine, 60(8):e3.
Keim, S. A. Alavanja, M. C. (2001). Pesticide use by persons who reported a high pesticide exposure event in the Agricultural Health Study. Environ Res, 85(3), 256-259.
Mage, D. T., Alavanja, M. C., Sandler, D. P., McDonnell, C. J., Kross, B., Rowland, A., Blair, A. (2000). A model for predicting the frequency of high pesticide exposure events in the Agricultural Health Study. Environ Res, 83(1), 67-71.
Sprince NL, Park H, Zwerling C, Lynch CF, Whitten PA, Thu K, Gillette PP, Burmeister LF, Alavanja MCR. (2002). Risk factors for machinery-related injury among Iowa livestock farmers: a case-control study nested in the Agricultural Health Study. International Journal of Occupational and Environmental Health 8:332-338.
Sprince NL, Park H, Zwerling C, Lynch CF, Whitten PS, Thu K, Burmeister LF, Gillette PP, Alavanja MCR. (2003). Risk factors for animal-related injury among Iowa livestock farmers: a case-control study nested in the Agricultural Health Study. The Journal of Rural Health 19(2):165-173.
Sprince NL, Zwerling C, Lynch CF, Whitten PA, Thu K, Gillette PP, Burmeister LF, Alavanja MCR. (2003). Risk factors for falls among Iowa farmers: a case-control study nested in the Agricultural Health Study. American Journal of Industrial Medicine, 44:265-272.
Sprince NL, Zwerling C, Lynch CF, Whitten PS, Thu K, Logsden-Sackett N, Burmeister LF, Sandler DP, Alavanja MCR. (2003). Risk factors for agricultural injury: a case-control analysis of Iowa farmers in the Agricultural Health Study. Journal of Agricultural Safety and Health 9(1):5-18.