Definition and establishment of biological exposure limits of pesticides for the interpretation of biological monitoring data

Pesticides are among the most employed synthetic chemicals, and for which there, is the largest database of chemical and toxicological information that allows establishing health-based exposure limits. Protection of pesticide applicators and of the general population from over-exposure is both an ethical necessity and a contribution to planetary health. So far the exposure occupational and population exposure limits could not be efficiently used for health protection, due to the limitations of current techniques to be employed on a wide scale. Biological monitoring of exposure is a viable technique for occupational protection and for the assessment of chemical risk of the population when measurements can be compared with suitable limit values. This possibility is currently employed only for few metals and organics of industrial interest, but only insufficiently for pesticides. We propose a paradigm to assess exposure and exposure-related risk of pesticides based on the measurement of their metabolites excreted in urine and on the elaboration of results from field exposure studies. Regression models allow forecasting the pesticide excretion associated to a systemic dose of pesticide corresponding to its acceptable occupational exposure limit (AOEL) for agricultural pesticide applicators. For this indicator and its corresponding limit value, we propose the name of equivalent biological exposure limit (EBEL). To demonstrate the proposed procedure and to highlight its utility and current limitations, we report data and elaborations from a previously published study that allows establishing a provisional value for an herbicide. This procedure can be adapted to fill the identified sources of uncertainty and to derive a limit value that corresponds to the ADI-ARfD for the general population. The establishment of limit values according to this strategy allows performing risk assessment in the pesticide workers and in the general population by exploiting the capability of modern analytical approaches to the targeted measurement of trace chemicals in biological specimens.