Transformation pathways of chlorinated paraffins relevant for remediation: a mini-review

Chlorinated Paraffin Pollution in the Marine Environment

“…Environmental degradation is crucial for determining the persistence and assessing the risk of organic pollutants in the environment. Previous studies have indicated that environmental degradation is an efficient way to remove SCCPs from the atmosphere due to the presence of hydroxyl radicals (·OH). ,, However, the atmospheric half-lives of SCCPs ranged from 1.9 to 10 days based on their ·OH oxidation rates, explaining their occurrence in the oceanic atmosphere and LRAT potential. ,, …”

“…Direct photochemical degradation is not viable for removing SCCPs from the environment, as CPs cannot absorb light in relevant wavelengths of the Earth’s surface . However, indirect photodegradation is an efficient pathway to remove SCCPs by involving reactions with photochemically produced reactive intermediates of ·OH and hydrated electrons (e – (aq) ), with more effective degradation of ·OH than e – (aq) . , The laboratory study has indicated SCCPs photodegradation occurs in the aqueous solution by producing more stable and persistent dechlorinated products. ,, Likewise, in UV-based degradation experiments, high elimination rates of CPs were reported in the presence of acetone and H 2 O 2 . The chloride ion and long-chain n -alkanes (>C25) were identified as photoproducts of SCCPs, and the latter were significantly less toxic to biotas. ,, However, it is still unclear how in situ photodegradation of CPs is in aqueous solution.…”

“…They only make up a small proportion (<16.5%) of CPs . By contrast, MCCPs and LCCPs, as the SCCPs candidate, contribute a significant share of global CP production. , At the same time, results of field observations have also verified more release of MCCPs than SCCPs in the environment. − However, no international regulations currently address the increasing emissions of MCCPs and LCCPs, especially their persistence, bioaccumulation, and potential toxicity in the marine environment.…”

Bioaccumulation and Biotransformation of Chlorinated Paraffins

“…LCCPs were first detected in human blood samples in China with median concentrations of 150 ng/g lw, which were lower than those of SCCP (3500 ng/g dw) and MCCPs (740 ng/g dw) [61]. Since then, LCCPs were detected in marine organisms from the Baltic Sea (nd: 130 ng/g dw) [34], Greenland and Iceland (<0.41-930 ng/g dw) [1], aquatic and terrestrial organisms from Germany (nd: 2400 ng/g dw) [44], plants from Beijing, China (27-561 ng/d dw) [54], and cereal and legume samples from China (48.1-664 ng/g dw) [59]. Compared with SCCPs and MCCPs, the concentrations of LCCPs in the abovementioned samples were on the same order of magnitude as those of SCCPs and MCCPs.…”

“…They are divided into short-chain (SCCPs, C 10-13 ), medium-chain (MCCPs, C 14-17 ), and long-chain CPs (LCCPs, C ≥ 18) according to the lengths of their carbon chain. Recently, very-shortchain CPs (vSCCPs, chain lengths below 10) have been reported in wildlife and human samples [1,2]. CPs have the advantages of low volatility, flame retardancy, good electrical insulation, and low cost.…”