Definition of AOEL-based provisional BEIs for pesticide exposure monitoring : a proposed approach for the protection of farmer's health

Aims. Health-based limits of exposure for pesticides are defined in the frame of the pre-marketing risk assessment process as Acceptable Operator Exposure Levels (AOELs). Since they are expressed as a systemic dose, AOELs are not directly comparable with biological indicators, thus weakening their preventive value. Due to the limits of environmental monitoring in agriculture, identifying Biological Exposure Indices (BEI) for pesticides is a timely and needed activity. For this reason, we propose a new approach to calculate provisional BEIs to pesticides starting from AOELs. Methods. Data from biological monitoring (pesticide metabolite measurement in 24-hour urine) and from assessment of personal exposure (skin contamination levels measured through skin pads) of exposed individuals are elaborated. A log-log plot of urinary excretion of pesticide metabolite vs. personal exposure referred to the AOEL limit unveils a bimodal relationship, which accounts both for ubiquitous exposure of the general population and the relationship of the excreted biomarker to occupational exposure and from which a tentative value for a BEI can be calculated. Results. Two proof-of-principle results on a herbicide (propanil, BEI=1 mg 3,4-DCA/L 24-h urine) and on a fungicide (mancozeb, BEI=117 microg ETU/L 24-h urine) are discussed. Conclusions. This method can be adopted in order to define “Health-Based Biological Exposure Indices” for pesticides, to be used in the biological monitoring of pesticide workers, and, in perspective, to establish BEIs in the pre-marketing phase to become part of the information made available when a new active ingredient is marketed.