A New Method Evaluates Human Exposure to a Harmful Pesticide

Many substances used in daily life could be potentially toxic for humans. One such substance is organophosphate pesticides. Widely used for industrial, agricultural, and public health applications, organophosphates (OPs) are known to be neurotoxic and have been associated with a wide range of developmental and behavioral impairments, as well as other diseases, like endocrine disorders and cancer. Therefore, measuring an individual’s exposure to these pesticides is important and necessary.

Monitoring exposure to OPs is done by analyzing urinary levels of their metabolites. While most OPs are metabolized to dialkyl phosphates, there are exceptions, like propetamphos (PPT). PPT, which is commonly used for pest control in residential, medical, commercial, industrial, and food service establishments, is metabolized to methylethylphosphoramidothioate (MEPT), which makes it difficult for the currently available biomonitoring methods to measure exposure to this OP.

Therefore, researchers from Japan have developed a method to biomonitor PPT exposure in humans using MEPT as a urinary marker. They collected urinary samples from PPT sprayers working in a pest control company the morning after they had last sprayed the pesticide, as well as from other workers of the same company (who sprayed other OPs but not PPT), and workers of a food distribution company as controls. They then performed acid hydrolysis of these samples for the deconjugation of MEPT (instead of the conventional alkaline hydrolysis process) and analyzed levels of MEPT in these samples, using gas chromatography–mass spectrometry. This is a more direct and sensitive method than that employed in a previous study conducted in the United Kingdom, and so the minimum detectable level of MEPT required in the samples in this study was less. Researchers were able to successfully detect MEPT levels as low as 10 μg/L.

This study has now established a biomonitoring method that can effectively measure exposure and metabolite levels in workers regularly exposed to PPT-containing pesticides, as well as in the general human population. This is very useful from a public, occupational, and environmental health perspective.

Link to the original journal article:
https://doi.org/10.1539/eohp.2020-0030-OA