ASSOCIATION BETWEEN INDOOR RESIDENTIAL CONTAMINATION WITH METHYL PARATHION AND URINARY PARA-NITROPHENOL

Methyl parathion, a pesticide listed by the U.S. Environmental Protect ion Agency in Toxicity Category I(i.e., most toxic), is not licensed f or indoor use, and human exposure has resulted in the deaths of infant s and children. From January 1991 through November 1994, an unlicensed pesticide applicator sprayed the interior of more than 200 homes in L orain County Ohio, with methylparathion. To measure the environmental contamination this spraying caused, we measured methyl parathion in re sidential samples (air filtration and surface wipe) collected from a s ubset of 64 homes. To measure human exposure, we collected urine sampl es from 142 people living in these homes and measured urinary levels o f para-nitrophenol, a methylparathion metabolite. We then used a gener alized estimating equation to evaluate the association between residen tial contamination and human exposure. The model included the age of t he resident, the number of days between pesticide application and samp le collection, and air and surface-wipe methyl parathion concentration s. As expected, the air and surface-wipe concentrations each had a sig nificant inverse relationship with the number of days between applicat ion and sample collection. The model explained 65.7% of the variation in urinary para-nitrophenol concentrations. The form of this model cou ld be used to estimate urine p-nitrophenol in residents exposed to met hyl parathion in situations where urine specimens are not available. W e recommend site-specific validation of this model.