A review on biological occurrence, bioaccumulation, transmission and metabolism of chlorinated paraffins

Chlorinated paraffins (CPs) are widely used persistent organic pollutants (POPs). Based on the carbon chain length, CPs can be classified as short-chain (C10-13) CPs (SCCPs), medium-chain (C14-17) CPs (MCCPs), and long-chain (C≥18) CPs (LCCPs). Since SCCPs have been listed as POPs of particular concern by the Stockholm Convention, the production of MCCPs and LCCPs is increased sharply. Therefore, the number of studies focusing on MCCPs and LCCPs has increased recently. Herein, we comprehensively reviewed recent studies on the biological occurrence, bioaccumulation, transmission, and transformation of CPs. CPs are pervasively distributed across biotas and exhibit diverse accumulation properties in different tissues. MCCPs and LCCPs are more abundant than SCCPs in some organisms. The absorption, translocation, and elimination behaviors of CPs directly influence their accumulation in organisms. The maternal transfer is an elimination pathway for CPs and could explain the discrepancy in CPs accumulation in opposite sexes of some organisms. With the establishment of novel screening methods, several transformation products of CPs have been identified in plants, microorganisms, and humans. By comparing the biotransformation pathways of CPs in different organisms, common and unique pathways have been identified in various species, although further studies on the transformation of CPs in humans and other animals are required. This review describes some noteworthy and prospective studies focused on the biological behavior of CPs. The review also derives novel conclusions based on recent studies in this field to provide a comprehensive understanding of the environmental fate of CPs.</p

Isotopic Composition and Distribution of Plutonium in Northern South China Sea Sediments Revealed Continuous Release and Transport of Pu from the Marshall Islands

The ^239+240Pu activities and ²⁴⁰Pu/²³⁹Pu atom ratios in sediments of the northern South China Sea and its adjacent Pearl River Estuary were determined to examine the spatial and temporal variations of Pu inputs. We clarified that Pu in the study area is sourced from a combination of global fallout and close-in fallout from the Pacific Proving Grounds in the Marshall Islands where above-ground nuclear weapons testing was carried out during the period of 1952–1958. The latter source dominated the Pu input in the 1950s, as evidenced by elevated ²⁴⁰Pu/²³⁹Pu atom ratios (>0.30) in a dated sediment core. Even after the 1950s, the Pacific Proving Grounds was still a dominant Pu source due to continuous transport of remobilized Pu from the Marshall Islands, about 4500 km away, along the North Equatorial Current followed by the transport of the Kuroshio current and its extension into the South China Sea through the Luzon Strait. Using a simple two end-member mixing model, we have quantified the contributions of Pu from the Pacific Proving Grounds to the northern South China Sea shelf and the Pearl River Estuary are 68% ± 1% and 30% ± 5%, respectively. This study also confirmed that there were no clear signals of Pu from the Fukushima Daiichi Nuclear Power Plant accident impacting the South China Sea

Remarkable Contamination of Short- and Medium-Chain Chlorinated Paraffins in Free-Range Chicken Eggs from Rural Tibetan Plateau

Rapid social-economic development introduces modern lifestyles into rural areas, not only bringing numerous modern products but also new pollutants, such as chlorinated paraffins (CPs). The rural Tibetan Plateau has limited industrial activities and is a unique place to investigate this issue. Herein we collected 90 free-range chicken egg pool samples across the rural Tibetan Plateau to evaluate the pollution status of CPs. Meanwhile, CPs in related soils, free-range chicken eggs from Jiangxi, and farmed eggs from markets were also analyzed. The median concentrations of SCCPs (159 ng g–1 wet weight (ww)) and MCCPs (1390 ng g–1 ww) in Tibetan free-range chicken eggs were comparable to those from Jiangxi (259 and 938 ng g–1 ww) and significantly higher than those in farmed eggs (22.0 and 81.7 ng g–1 ww). In the rural Tibetan Plateau, the median EDI of CPs via egg consumption by adults and children were estimated to be 81.6 and 220.2 ng kg–1 bw day–1 for SCCPs and 483.4 and 1291 ng kg–1 bw day–1 for MCCPs, respectively. MCCPs might pose potential health risks for both adults and children in the worst scenario. Our study demonstrates that new pollutants should not be ignored and need further attention in remote rural areas