Estimating occupational exposure to the pyrethroid termiticide bifenthrin by measuring metabolites in urine

The control of subterranean termites in Australia is predominantly through the application of chemical barriers in the soil beneath and surrounding buildings. The chemicals used to repel or kill termites are the organophosphorus insecticide, chlorpyrifos, and the synthetic pyrethroid, bifenthrin. These are applied through surface sprays and subfloor injection by licensed pest control operators. To determine the exposure of these personnel to these pesticides it is most usual to measure airborne concentrations or dermal deposition rates. However, to support information obtained from these methods it is often appropriate to determine the amount of the chemicals absorbed, using biological monitoring techniques including measurement of the chemicals or their metabolites in urine. While there are effective techniques for the monitoring of chlorpyrifos exposure by measuring either the alkyl phosphate or trichloropyridinol metabolites, there have been no published reports of suitable methods to measure bifenthrin metabolites in urine. This paper describes an extraction and HPLC-UV method used to simultaneously measure the urinary excretion of 2-methyl-3-phenylbenzoic acid (MPA), a metabolite of bifenthrin, and 3-phenoxybenzoic acid (PBA), a metabolite of several other common pyrethroid insecticides, with a detection limit for each of 2.5 ng/ml. The paper also describes the pilot application of this method to a study of South Australian pest control operators handling bifenthrin. MPA ranged from 1.8 to 31.9 microg/g creatinine and PBA from 1.3 to 30.0 microg/g in the urine of pest control workers. MPA was detected in urine of control workers without bifenthrin exposure only at low levels (1.0-1.4 microg/g creatinine), but PBA was found in both at higher levels (1.2-61.1 microg/g creatinine).