Reflection of serum PCB concentrations in silicone wristbands, hand wipes, indoor air, and dust and the associations between exposure and thyroid hormone homeostasis

Polychlorinated biphenyls (PCBs) are legacy contaminants that are enduring indoor environmental problems due to historical applications. Among residents living in PCB-contaminated and reference apartments, we compared the effectiveness of personal and environmental samples for determining exposure through associations with 14 serum PCBs and explored potential effects on thyroid biomarkers. Silicone wristband PCBs were strongly correlated with serum measurements, particularly for lower chlorinated PCBs (rs=0.59-0.82), and showed for the first time that wristbands are effective indicators of internal dose for PCBs. Similar correlations were observed for indoor air and dust, and hand wipes were significantly associated with serum for all congeners (rs=0.44-0.73). Stratified analyses, which accounted for some participant characteristics, demonstrated that significant relationships were specific to those living in contaminated apartments and most focused among lower chlorinated congeners. Here, residents had lived in their homes for many years (mean>10 years) and spent most of their time at home, due in part to being a majority aging population. As such, the four external exposure measures were strongly inter-correlated across the congeners. We also observed associations with free triiodothyronine (T3) and ratio between T3 and thyroxine (T4) in the exposed population. T3 and PCB-28 shared a significant, inverse dose-response relationship, with 13 and 17% decreases in T3 for the second and third serum PCB-28 tertiles, respectively. Our results suggest that any of the four sample types collected in this exposure scenario accurately pointed to elevated PCB exposure and that this exposure was associated with a change in thyroid hormone homeostasis.