A QUANTITATIVE RISK ASSESSMENT WITH ATTENDANT UNCERTAINTY ESTIMATIONS FOR IRRIGATED FARMLANDS IN OKLAHOMA
JON S. HANSON
WILLIAM F. MCTERNAN
AbstractAgricultural chemical use has increased dramatically in the post World War II era. Benefits to society include greater crop production and lower manpower requirements. Detriments include environmental and public health impacts. The subject research presents the results of a risk assessment which examined potential impacts of agricultural pesticide use. The two phase assessment focused in Phase 1 upon the projected risks associated with using six pesticides on four crop types within three hydrological soil groupings. Irrigation was compared with the dry land farming base case. The hypothetical target receptors were a "typical" farm family in Caddo County, Oklahoma; an area undergoing significant change from dry land farming to irrigated agriculture. Phase 2 addressed some of the uncertainties associated with the Phase 1 risk assessment. Both Phases utilized available transport and exposure codes to determine the probability of exceeding the U.S. Environmental Protection Agency's supported Reference Dose (RfD). Of the six pesticides evaluated only 2,4-D when used on peanuts presented potentially significant risk. Selection among the other variables such as other crops, the hydrologic soil groupings or the use of irrigation did not contribute consistently to this elevated risk. There was much uncertainty in these estimates. Phase 2 efforts showed that the exposure variables of receptor body weight and drinking water ingestion rate, together with the estimated pesticide concentration had the greatest impact on this uncertainty determination.
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