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Are environmental exposures to chlorophenoxy herbicides associated with adverse human health effects?
Citation:
Schreinemachers, D. M. Are environmental exposures to chlorophenoxy herbicides associated with adverse human health effects? Presented at U.S. Geological Survey, GIS Workshop, Denver, CO, May 12 - 16, 2008.
Impact/Purpose:
research results
Description:
Background: Exposures to environmental pollutants are suspected of playing a role in the observed increases of many diseases. However, it is difficult to establish a firm link between exposure and disease, because environmental exposures are usually widespread, low-dose in nature, and common throughout the study population. This is in contrast to occupational studies where exposures to a specific chemical are well defined and where job records provide information on level and duration of exposure. So how can we approach linking environmental exposures to disease? Several publications have suggested that a series of multilevel, multidisciplinary studies are required, starting with an inter-region comparison for the purpose of hazard identification, to be followed by more targeted studies. Existing databases routinely collected by Federal Agencies can be used for the hazard identification studies. An example of how to conduct this kind of research is presented. Methods: Minnesota, Montana, North Dakota, and South Dakota produce most of the spring- and durum wheat grown in the U.S. More than 85% of the spring wheat acreage is treated with predominantly chlorophenoxy herbicides. Information on herbicide use by county is not available. Therefore, in order to study the association of environmental exposure to chlorophenoxy herbicides with adverse human health effects, wheat acreage per county was used as a surrogate exposure measure. Information on birth defects and mortality from cancer, ischemic heart disease, and diabetes (underlying cause of death) was obtained from the National Center for Health Statistics. Agricultural information was obtained from the U.S. Department of Agriculture website. Rates of adverse health effects in rural, agricultural counties of the combined four states were analysed based on level of wheat agriculture per county. Results: Population (ecologic) studies showed that rates of birth defects and mortality rates for cancer, ischemic heart disease and type 2 diabetes in rural, agricultural counties of Minnesota, Montana, North Dakota, and South Dakota were associated with wheat acreage per county. Conclusions: Chlorophenoxy herbicides are among the most widely used herbicides in the U.S. Further investigations are needed to confirm the results from the ecologic studies. An ongoing more targeted study is investigating associations between biomarkers of effect (e.g. presence of herbicides or their metabolites in urine or blood) and changes in lipid profiles and glucose metabolism. Additional factors that merit attention are the effects from varying doses and routes of exposure, distance from cropland, and weather patterns. Disclaimer: This is an abstract of a proposed presentation and does not necessarily reflect EPA polic