Characterization of short-, medium-, and long-chain chlorinated paraffins in Tibetan butter and implications for local human exposure

Since short-chain chlorinated paraffins (SCCPs) were severely restricted under the Stockholm Convention in 2017, a shift to the production of other chlorinated paraffin (CP) groups has occurred, particularly medium-chain (MCCPs) and long-chain CPs (LCCPs), although data on the latter are sparser in the literature. This study described the occurrence of three types of CPs in butter samples from six livestock milk sources across 15 sites in Tibet. The median levels of SCCPs, MCCPs, and LCCPs were 132, 456, and 13.2 ng/g lipid, respectively. The detection rate of 97.6% suggests that LCCPs can be transmitted to humans. Thus, all CPs, regardless of their chain length and degree of chlorination, should be treated with caution. The differences in concentration were mainly caused by dynamic wet deposition and thermodynamic cold-trapping effects across the different districts. The homolog pattern of CPs varied widely across livestock species, which was attributed to the diverse impacts of the physicochemical properties of the homologs, especially the heterogeneity in the uptake and transfer of CPs across different organisms. Under three different criteria, the health risks associated with the daily intake of SCCPs should not be neglected, especially considering other intake exposure pathways and the degradation of longer-carbon-chain monomers.