Human bare and clothing-covered skin exposure to chlorinated paraffins for the general populations: Exposure pattern differential and significance of indirect dermal exposure via clothing-to-skin transport

To investigate human exposure to short-chain chlorinated paraffins (SCCPs) and medium-chain chlorinated paraffins (MCCPs) through dermal and oral intake via hand-to-mouth contact, wipes from the face, forearm, hand, and foot of 30 volunteers were sampled. The concentration of ∑SCCPs and ∑MCCPs ranged from 0.66 to 119 and 0.71 to 565 µg/m², respectively. Hands exhibited significantly higher ∑CPs concentrations than other skin areas, indicating that direct contact with indoor surfaces contributed considerable CP levels on this bare skin area. Gender differences in CP levels were observed in wipes from all locations, except for the hands, possibly because of the significant variability in residuals on the hands. A significant positive relationship was found between CP levels on the hands and faces, and the CP ratios of the hands/faces were related to log K_OA. Bare skin showed more significant variations in CP partitioning among related congeners and between genders than skin covered by clothing, as elucidated by the linear analysis of RSD and log K_OA. Although concentrations on clothing-covered areas were relatively lower than on bare skin, the median estimated dermal absorption doses of ∑SCCPs and ∑MCCPs (152 and 737 ng/kg bw/day, respectively) for the entire body were approximately 1-2 orders of magnitude higher than those for oral ingestion (1.62 and 7.94 ng/kg bw/day, respectively), emphasizing indirect dermal uptake as a significant exposure pathway for humans.