Biomonitoring Summary

Pyrethroid Pesticides Overview


CAS No. 68359-37-5

General Information

The chemical 4-fluoro-3-phenoxybenzoic acid is a specific metabolite of the pyrethroid insecticide cyfluthrin. Cyfluthrin accounted for one-third of pyrethroid-related worker illnesses reported in California from 1996-2002; most of which were dermal and respiratory irritations (Spencer and O’Malley, 2006). Cyfluthrin is rapidly metabolized and eliminated from the body. Following an indoor application exposure, the mean elimination half-life of cyfluthrin from the plasma was 16 hours (Williams et al., 2003).

Degradation of cyfluthrin to 4-fluoro-3-phenoxybenzoic acid occurs in the environment.Thus, the presence of 4-fluoro-3-phenoxybenzoic acid in urine not only reflects the metabolic transformation of cyfluthrin, but it can also reflect direct exposure to 4-fluoro-3-phenoxybenzoic acid formed in the environment.

Biomonitoring Information

Urinary levels of 4-fluoro-3-phenoxybenzoic acid reflect recent exposure to cyfluthrin or its environmental degradate. Urinary levels of 4-fluoro-3-phenoxybenzoic acid were generally below the limit of detection (0.2 μg/L) in the U.S. representative subsample in NHANES 2001-2002 (CDC, 2009). In an analysis of 217 urine specimens from a nonrandom sample of United States residents, Baker et al. (2004) reported a geometric mean concentration of 4-fluoro-3-phenoxybenzoic acid of 0.95 µg/L. Studies in Germany of 396 children and adolescents (Becker et al., 2006) and 1177 urban adults and children (Heudorf et al., 2001) showed that urinary levels of 4-fluoro-3-phenoxybenzoic acid at the 95th percentile ranged from either slightly higher or lower than the detection limit in the U.S. representative 2001-2002 NHANES subsample (CDC, 2009). Urinary levels for adults and children in these studies were similar (Heudorf et al., 2001,2006) and estimated daily intakes based on urinary levels in children were considered to be below acceptable daily intakes (Heudorf et al., 2004).

In 57 volunteers entering areas previously spot-sprayed with various pyrethroid pesticides (including cyfluthrin), median urinary levels of 4-fluoro-3-phenoxybenzoic acid were slightly less than the limit of detection in the NHANES 2001-2002 subsample (CDC, 2009; Leng et al., 2003). Seven individuals participating in floor exercises on cyfluthrin treated carpet demonstrated a rise in the urinary excretion of 4-fluoro-3-phenoxybenzoic acid in the 72 hours following the activity (Williams et al., 2003).

Finding a measurable amount of 4-fluoro-3-phenoxybenzoic acid in urine does not imply that the level will result in an adverse health effect. Biomonitoring studies of 4-fluoro-3-phenoxybenzoic acid in urine provide physicians and public health officials with reference values so that they can determine whether other people have been exposed to higher levels of cyfluthrin than levels found in the general population. Biomonitoring data can also help scientists plan and conduct research on exposure and health effects.


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Page last reviewed: April 7, 2017