Organophosphate and organohalogen flame-retardant exposure and thyroid hormone disruption in a cohort of female firefighters and office workers from San Francisco

BackgroundOccupational exposures to flame retardants (FR), which are suspected endocrine disrupting compounds, may be of particular concern for firefighters as they are commonly found in consumer products and have been detected in fire station dust and firefighter gear. ObjectivesThe Women Workers Biomonitoring Collaborative is a community based participatory research study that sought to measure environmental chemicals relevant to firefighting and evaluate their effects on thyroid hormone levels. MethodsWe measured 10 FR or their metabolites in urine of female firefighters and office workers from San Francisco: bis(1,3-dichloro-2-propyl) phosphate (BDCPP), bis(2-chloroethyl) phosphate (BCEP), dibutyl phosphate (DBuP), dibenzyl phosphate (DBzP), di-p-cresyl phosphate (DpCP), di-o-cresyl phosphate (DoCP), 2,3,4,5-tetrabromobenzoic acid (TBBA), tetrabromobisphenol-A (TBBPA), 5-OH-BDE 47, and 5-OH-BDE 100. We assessed potential predictors of exposure levels and the association between FR exposures and thyroxine (T4) and thyroid stimulating hormone (TSH). ResultsBDCPP, BCEP, and DBuP were the most commonly detected FRs, among all study participants, with intermediate BMI and college educated women having the highest levels, and Black women having higher BDCPP levels than White women. Firefighters had higher detection frequencies (DF) and exposure levels compared to office workers; median BDCPP levels were five times higher in firefighters than in office workers. Among firefighters, occupational activities were not significantly associated with FR levels, although position (i.e. officer and firefighter versus driver), being on-duty (versus off-duty) and assigned to the airport suggested a positive association with FR levels. Among firefighters, a doubling of BDCPP was associated with a 2.88% decrease (95%CI -5.28,-0.42) in T4. We did not observe significant associations between FR and T4 among office workers. DiscussionFirefighters had significantly higher exposures to FR compared to office workers, and we observed a negative association between BDCPP and thyroxine in firefighters. Future research should elucidate occupational sources of FR exposure and opportunities for exposure reduction.