Simplified urinary immunoassay for 2,4-D: Validation and exposure assessment

Urinary monitoring of exposed workers by either analytic chemical methods o r radioimmunoassay suggests that urinary levels of 2,4-dichlorophenoxyaceti c acid (2,4-D) exceeding 30 ppb are indicative of occupational exposure. Ho wever, the current methods do not lend themselves to clinical laboratory us e in the rural medical setting. The major goal of this project was to provi de medical practitioners who care for members of the agricultural community with a cost-efficient way to conduct exposure assessment. This project use d a direct 2,4-D enzyme immunoassay (EIA) and measurement of the ratio betw een 2,4-D-spiked and non-spiked samples of the same urine to quantify 2,4-D levels. This simplified approach minimizes the effects of non-specific int erfering substances in urine and eliminates the need for sample extraction and clean-up. Possible urine co-contaminants (2,4-dichlorophenol and 2,5-di chlorophenol) do not significantly interfere with this immunoassay. Twenty- two forest pesticide applicators who apply and use chlorophenoxy herbicides in their work and 14 comparable control subjects were studied to validate the assay in the occupational setting. Coded urine specimens were examined for levels of 2,4-D by high-performance liquid chromatography-tandem mass s pectrometry (HPLC-MS/MS) and compared with immunoassay results from the sam e specimens. A correlation coefficient of r = 0.982 with a P value of .0001 for a plot of HPLC-MS/MS versus immunoassay demonstrated that the results from these methods were comparable over urinary dose levels ranging from no t detectable (<19 ppb) to 1700 ppb 2,4-D, as determined by immunoassay.