Analysis of environmental and biologic methyl parathion data to improve future data collection

The Agency for Toxic Substances and Disease Registry analyzed concurrently collected data on environmental methyl parathion (MP) and urinary p-nitrophenol (PNP) at the request of the U.S. Environmental Protection Agency (U.S. EPA). The purpose of the analysis was to assess whether individuals' age or level of residential MP contamination might predict their urinary PNP level. Unlicensed pesticide applicators had sprayed residences in Mississippi with MP, which is approved as a pesticide only for outdoor agricultural use. Data were received from Mississippi for MP wipe sample levels for 409 homes and urinary PNP levels for 929 residents of the residences sampled. In addition to descriptive and bivariate analyses, ordinal logistic regression was performed after categorizing the data. Interpretation of results was limited by several identified data gaps and pre-existing data-quality issues. On the basis of the lessons learned from identified data gaps, specific recommendations were made to the U.S. EPA for improving future data collection methods for more meaningful exposure assessment in similar environmental contaminations. The recommended changes were successfully incorporated in subsequent data collected by other states that had experienced similar residential MP spraying.