Residential Exposure to Pyrethroid Pesticides in California Homes

Due to growing concerns about indoor pesticide exposure it is important characterize current indoor residential levels and resulting exposure to pyrethroid pesticides, a commonly used class of pesticides, as well as to investigate factors that may possibly influence these exposures. We investigate exposure as measured by biomarkers to these pesticides in homes from two different Californian populations, farm worker families and families from the general population in northern California. All data was collected in 2009. First, we investigate exposure of farm worker families to pyrethroids by looking at urinary pyrethroid biomarkers and levels of pyrethroids in the house dust in a study of mothers and children living in Mendota, CA within the population-based Mexican Immigration to California: Agricultural Safety and Acculturation (MICASA) Study. Exposure was quantified based on an ELISA analysis of urinary metabolite 3-phenoxybenzoic acid (3PBA) levels among 105 women and 103 children. The median urinary 3PBA levels were 2.56 ug/g creatinine in children and 1.46 ug/g creatinine in mothers. A positive association was evident between poor housing conditions and the urinary 3PBA metabolite levels, showing that poor housing conditions are a contributing factor to levels of 3PBA seen in the urine of these farm worker families. Next, we present pesticide use data and levels of pyrethroid pesticides in indoor dust measured by questionnaires and a GC/MS analysis of the pyrethroids cis- and trans-permethrin, cypermethrin, deltamethrin, esfenvalerate and resmethrin among 55 MICASA household dust samples. In these dust samples cis- and trans-permethrin had the highest detection frequencies at 67% with average concentrations of 349 and 202 ng/g dust respectively. Cypermethrin was detected in 52% of the homes and averaged 1258 ng/g dust. Esfenvalerate, resmethrin and deltamethrin were detected in less than half the samples. A positive association was seen with pyrethroid levels in house dust and the pesticide inventory, a potentially useful predictor of pesticide exposure in farm worker homes. Third, we investigate pyrethroid exposure in northern California homes by looking at a suite of urinary biomarkers in samples collected from 83 children and 90 adults as well as the indoor environmental concentrations of common pyrethroids and pyrethroid metabolites from floor wipe samples collected from 81 their households from those participating in the Study of Use of Products and Exposure Related Behavior (SUPERB). The median urinary 3PBA levels in the SUPERB population were 0.80 ug/g creatinine in children and 0.61 ug/g creatinine in mothers. In the SUPERB floor wipe samples permethrin (97.5%) and bifenthrin (59.3%) were frequently detected, while the rest of the parent compounds had relatively low detection frequencies. Of the pyrethroid metabolites, 3PBA (98.7%), 4F3PBA (34.2%), and DCCA (2.5%) were detected, while DBCA was not detected in any of the floor wipe samples. There were positive associations between urinary metabolite levels from children and indoor levels of pyrethroid pesticides. Comparing the populations, the median urinary 3PBA concentrations from the MICASA population were higher than those in the SUPERB population, showing that farm worker families are exposed to higher levels of pyrethroids. Both populations were higher than median urinary 3PBA concentrations reported in NHANES, a population based studies for the United States general population in the years 1999-2002. This is likely due to the increasing use of pyrethroids for residential applications over the same time period. These data combined show that indoor residential exposure to pyrethroid pesticides are an important route of exposure. Further research is warranted to fully investigate the contribution of indoor residential sources to pyrethroid exposure.