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ENVIRONMENTAL EXPOSURES TO CHLOROPHENOXY HERBICIDES AND ASSOCIATION WITH ADVERSE HUMAN HEALTH EFFECTS: EXAMPLE OF THE NEED FOR BETTER METHODS
Citation:
SCHREINEMACHERS, D. M. ENVIRONMENTAL EXPOSURES TO CHLOROPHENOXY HERBICIDES AND ASSOCIATION WITH ADVERSE HUMAN HEALTH EFFECTS: EXAMPLE OF THE NEED FOR BETTER METHODS. Presented at Ethical Consdierations and Future Challenges in Occupational and Environmental Health: International Conference in Memory of Olav Axelson, Borgholm, SWEDEN, May 19 - 20, 2005.
Description:
Previous studies have made the following observations: newly emerging global patterns of disease have been observed, and environmental exposures have been implicated. Ecologic studies are fundamental for the identification of public health problems. Some level of exposure in a given geographic region may be common throughout the study population, but the difficulty caused by lack of a null referent can be overcome by comparing regions with different levels of exposure. Subsequent multidisciplinary studies ranging from the molecular to the ecologic domain, are needed to confirm the links observed between environmental exposures and health effects in ecologic studies. For example, residents of rural, agricultural counties of Minnesota, Montana, North Dakota, and South Dakota are most likely exposed to environmental levels of chlorophenoxy herbicides, such as 2,4-D and MCPA due to treatment of spring- and durum wheat crops. 2,4-D and MCPA are applied during the spring, and can be transported over short and long distances attached to air particles, with concentrations highest in regions where they are applied at the time of application. Exposures to these herbicides are involuntary, potentially widespread and low dose. Residents may not know they are exposed. Ecologic studies are a first step towards identifying adverse health effects associated with these environmental exposures. Information on herbicide use by county is not available. Because chlorophenoxy herbicides are the predominant herbicides applied to wheat, and other major field crops in these four states such as corn and soybeans, are mostly treated with other herbicides, wheat acreage per county is used as a surrogate exposure measure. Information on adverse health effects by county such as birth malformations and cancer mortality, is obtained from existing databases. Associations between level of wheat farming and rate of adverse health effects are investigated for single or grouped counties. Resulting associations serve as hypotheses for more definitive studies. In this role, ecological studies contribute to Public Health by identifying potential hazards for more intensive study.