Pyrethroid exposure of the general population—is this due to diet

Abstract

Inhabitants (1177) of a residential area in Frankfurt/Main have been investigated with respect to internal exposure to pyrethroids. Biological monitoring revealed a body burden of pyrethroids. The 95th‰ for the urinary metabolites of pyrethroids, such as permethrin and cypermethrin, cis and trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid (cis-DCCA and trans-DCCA), was determined to be 0.5 and 1.4 μg/l, respectively. 95th‰ for cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid (DBCA), a specific metabolite of deltamethrin, and 4-fluoro-3-phenoxybenzoic acid (F-PBA), a metabolite of cyfluthrin, were 0.3 and 0.27 μg/l, respectively. The metabolic pattern found for these samples points out that pyrethroids are probably ingested orally with daily diet.

Introduction

Pyrethroids are a group of very important insecticides with neurotoxic properties. They are used in agriculture as well as for indoor pest control on a great scale. In formulations, they are usually present as a mixture of several stereo- and optical isomers. Pyrethroids exert their neurotoxic effects especially on insects. Their toxicity to humans is at least three orders of magnitude lower than for insects. Consequently, the toxicity of pyrethroids for mammals is classed as low and the WHO has set acceptable daily intakes for pyrethroids such as permethrin and cypermethrin of 0.05 mg/kg per body weight (Lu, 1995). In mammals, these substances are readily cleaved at the central ester bond to relatively non-toxic metabolites (Dorman and Beasley, 1991).

Pyrethroids, because of their widespread use and their potential health effects, have been the subject of a great public debate in Germany. Carpets and other textiles containing pyrethroids for insect protection have been suspected of causing neurological disorders.

Recent papers show that the general population in Germany obviously is exposed to these insecticides rather homogeneously (Heudorf and Angerer, 2001, Hardt and Angerer, 1999, Butte et al., 1998). In many of these studies, a lack of any relationship between external exposure, ascertained by dust analysis, and the results of biological monitoring has been reported. Therefore, we suppose, that this is due to an uptake of pyrethroid residues with normal diet. To clarify this question, we examined the relationship between two pyrethroid metabolites, trans-DCCA and cis-DCCA, determined in urine samples of 1177 persons who were investigated with respect to their internal exposure to pyrethroids in another study (Heudorf and Angerer, 2001). There are experimental studies which show that the relationship between these two metabolites is influenced by the route of uptake and therefore, may be suitable for a confirmation of our hypothesis (Woollen et al., 1992).