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Using GIS To Investigate Possible Associations Between Select Herbicide Concentrations And The Incidence Of Cancer In Iowa

Seventy-five percent of all Iowans rely on groundwater as their drinking water source. At the same time, Iowa is intensely agricultural, with an emphasis on industrial agriculture and the associated chemicals involved. During recent years, concern about environmental estrogens has raised questions about the link between agricultural chemicals and cancer incidence. We looked specifically at atrazine and metolachlor, suspected endocrine disrupters and environmental estrogens. Atrazine, belonging to the triazines group, has been detected in 78% of the water samples monitored by the U.S. Geological Survey nationwide and has been found to cause cancer in rats and have an estrogenic effect. Recently, we found that the combined effects of atrazine and metolachlor, another commonly used herbicide, significantly decreased survival in guppies and changed gender ratios, favoring females. As US standards for herbicide use are generally set through controlled experiments with a single pesticide, the reality of farmers using mixtures of pesticides has serious implications of the run-off generated from agricultural land. Using atrazine and metolachlor data measured in surface and ground water from the U.S. Geological Survey over the measurement record (1988-2004), we mapped their concentrations temporally and spatially. From the SEER Cancer registry website, the spatial occurrence and temporal incidence of varying types of cancer were mapped within a GIS for the period 1973-2002 as ten year aggregates. These data were combined and analyzed spatially to determine links of herbicide contamination in water to cancer incidence in Iowa, specifically cancers possibly linked to environmental estrogens.