Short-chain chlorinated paraffins in fish from two developed regions of China: Occurrence, influencing factors and implication for human exposure via consumption

Tracking and optimizing toxic chemical exposure pathways through food trade: A case study in SCCPs contaminated seafood in China

Food safety is related to human health and sustainable development. International food trade poses food safety risks through the collateral transport of toxic chemicals that are detrimental to human health. Domestic interprovincial trade has similar effects within countries but has not been comprehensively investigated previously. Here, we assessed the effects of interprovincial trade on food safety and human dietary exposure to short-chain chlorinated paraffins (SCCPs), a group of emerging persistent toxic chemicals, in seafood across China by synthesizing data from field observation and various models. Our findings indicate that there is a higher level of SCCPs exposure risk in coastal provinces compared to inland provinces. Approximately, 70.3% of human exposure to SCCPs through seafood consumption in China was embodied in the interprovincial seafood trade in 2021. Specifically, the domestic trade led to a remarkable increase in SCCPs exposure in the coastal provinces in South China, attributable to low SCCPs pollution in these provinces and imported seafood from those provinces with high SCCPs pollution. In contrast, human exposure to SCCPs decreased in those coastal provinces in East China due to importing seafood from those provinces with low SCCPs concentrations. The interprovincial seafood trade routes were optimized by linear programming to minimize human exposure to SCCPs considering both shipping cost and health risk constraints. The optimized trade routes reduced the national per capita SCCPs exposure through seafood consumption by over 12%. This study highlights the importance of interprovincial food trade in the risk assessment of toxic chemicals.

Investigating the levels, spatial distribution, and trophic transfer patterns of short-chain chlorinated paraffins in the Southern Bohai Sea, China

The marine environment of the southern Bohai Sea is severely polluted by short-chain chlorinated paraffins (SCCPs). To improve understanding of how SCCPs occur and of how they migrate, are transformed, and transferred in this area, we collected seawater, sediment, and organism samples, and determined the SCCP contents using a new approach based on high-resolution mass spectrometry. The ΣSCCP concentrations in the seawater, sediment, and organism samples ranged from 57.5 to 1150.4 ng/L, 167.7-1105.9 ng/g (dry weight), and 11.4-583.0 ng/g (wet weight), respectively. Simulation of the spatial distribution of SCCPs using Kriging interpolation showed that SCCPs were markedly influenced by land-based pollution. Substantial quantities of SCCPs were transported to the marine environment via surface runoff from rivers that passed through areas of major SCCP production. Once discharged from such rivers into the Bohai Sea, these SCCPs were further dispersed under the influence of ocean currents. Furthermore, the logarithmic bioaccumulation factor that varied from 2.12 to 3.20 and the trophic magnification factor that reached 5.60 (r2 = 0.750, p < 0.01) suggest that organisms have the ability to accumulate and biomagnify SCCPs through the food chain, which could potentially present risks to both marine ecosystems and human health.

Biomonitoring, exposure routes and risk assessment of chlorinated paraffins in humans: a mini-review

Chlorinated paraffins (CPs), which were conventionally classified into short- (SCCPs), medium- (MCCPs) and long- (LCCPs) chain CPs, have received growing attention due to their wide usage and extensive detection in environmental samples and biota. The number of studies regarding the biomonitoring of CPs in human beings increased rapidly and their health risk gained great concern. This review summarized their occurrence and homologue patterns in human matrices including blood/serum, placenta, cord serum and breast milk. As the production and usage of SCCPs was progressively banned after being listed in Annex A of the Stockholm Convention, the production of MCCPs and LCCPs was stimulated. Accordingly, the ratio of MCCPs/SCCPs in human samples has increased rapidly in the last 5 years. The current understanding of exposure routes and risk assessments of CPs was also reviewed. Oral dietary intake is the most predominant source of daily CP intake, but dust ingestion, inhalation and dermal exposure is also nonnegligible, especially for MCCPs and LCCPs. Furthermore, the reported upper bound of the estimated daily intakes (EDIs) in various risk assessment studies was close to or exceeded the tolerable daily intakes (TDIs). Considering the bioaccumulation and long-lasting exposure of CPs, their health impacts on humans and the ecosystem required continuous monitoring and evaluation.

Chlorinated Paraffin Pollution in the Marine Environment

Chlorinated paraffins (CPs) are ubiquitous in the environment due to their large-scale usage, persistence, and long-range atmospheric transport. The oceans are a critical environment where CPs transformation occurs. However, the broad impacts of CPs on the marine environment remain unclear. This review describes the sources, occurrence and transport pathways, environmental processes, and ecological effects of CPs in the marine environment. CPs are distributed in the global marine environment by riverine input, ocean currents, and long-range atmospheric transport from industrial areas. Environmental processes, such as the deposition of particle-bound compounds, leaching of plastics, and microbial degradation of CPs, are the critical drivers for regulating CPs' fate in water columns or sediment. Bioaccumulation and trophic transfer of CPs in marine food webs may threaten marine ecosystem functions. To elucidate the biogeochemical processes and environmental impacts of CPs in marine environments, future work should clarify the burden and transformation process of CPs and reveal their ecological effects. The results would help readers clarify the current research status and future research directions of CPs in the marine environment and provide the scientific basis and theoretical foundations for the government to assess marine ecological risks of CPs and to make policies for pollution prevention and control.

Short- and medium-chain chlorinated paraffins in fish from an anthropized south-western Atlantic estuary, Bahía Blanca, Argentina

Chlorinated paraffins (CPs) are synthetic organic compounds of growing environmental and social concern. Short-chain chlorinated paraffins (SCCPs) were listed under the Stockholm Convention on Persistent Organic Pollutants (POPs) in 2017. Further, in 2021, medium-chain chlorinated paraffins (MCCPs) were proposed to be listed as POPs. We investigated SCCP and MCCP amounts and homolog profiles in four wild fish species from Bahía Blanca Estuary, a South Atlantic Ocean coastal habitat in Argentina. SCCPs and MCCPs were detected in 41% and 36% of the samples, respectively. SCCP amounts ranged from <12 to 29 ng g^-1 wet weight and <750-5887 ng g^-1 lipid weight, whereas MCCP amounts ranged from <7 to 19 ng g^-1 wet weight and <440-2848 ng g^-1 lipid weight. Amounts were equivalent to those found in fish from the Arctic and Antarctic Oceans and from some North American and Tibetan Plateau lakes. We performed a human health risk assessment and found no direct risks to human health for SCCP or MCCP ingestion, according to present knowledge. Regarding their environmental behavior, no significant differences were observed among SCCP amounts, sampling locations, species, sizes, lipid content, and age of the specimens. However, there were significant differences in MCCP amounts across species, which could be attributed to fish size and feeding habits. Homolog profiles in all fish were dominated by the medium-chlorinated (Cl₆ and Cl₇) CPs and shorter chain length CPs were the most abundant, with C₁₀Cl₆ (12.8%) and C₁₁Cl₆ (10.1%) being the predominant SCCPs and C₁₄Cl₆ (19.2%) and C₁₄Cl₇ (12.4%) the predominant MCCPs. To the best of our knowledge, this is the first study on the presence of CPs in the environment in Argentina and the South Atlantic Ocean. CP occurrence in the environment, particularly in the food chain, promotes the need for further research on their occurrence and behavior, and the impact of CPs in marine ecosystems in Argentina.

The potential health risks of short-chain chlorinated paraffin: A mini-review from a toxicological perspective

Short-chain chlorinated paraffins (SCCPs) are ubiquitously distributed in various environmental matrics due to their wide production and consumption globally in the past and ongoing production and use in some developing countries. SCCPs have been detected in various human samples including serum, milk, placenta, nail, and hair, and internal SCCP levels were found to be positively correlated with biomarkers of some diseases. While the environmental occurrence has been reported in a lot of studies, the toxicity and underlying molecular mechanisms of SCCPs remain largely unknown. The current tolerable daily intakes (TDIs) recommended by the world health organization/international programme on chemical safety (WHO/IPCS, 100 μg/kg bw/d) and the UK Committee on Toxicity (COT, 30 μg/kg bw/d) were obtained based on a no observed adverse effect level (NOAEL) of SCCP from the repeated-dose study (90 d exposure) in rodents performed nearly 40 years ago. Importantly, the health risks assessment of SCCPs in a variety of studies has shown that the estimated daily intakes (EDIs) may approach and even over the established TDI by UK COT. Furthermore, recent studies revealed that lower doses of SCCPs could also result in damage to multiple organs including the liver, kidney, and thyroid. Long-term effects of SCCPs at environmental-related doses are warranted.

Distinct biomagnification of chlorinated persistent organic pollutants in adjacent aquatic and terrestrial food webs

Biomagnification of persistent organic pollutants (POPs) in food webs has been studied for many years. However, the different processes and influencing factors in biomagnification of POPs in aquatic and terrestrial food webs still need clarification. Polychlorinated biphenyls (PCBs) and short-chain chlorinated paraffins (SCCPs) were measured in organisms from adjacent terrestrial and aquatic environment in this study. The median levels of PCBs in terrestrial and aquatic organisms were 21.7-138 ng/g lw and 37.1-149 ng/g lw, respectively. SCCP concentrations were 18.6-87.3 μg/g lw and 21.4-93.9 μg/g lw in terrestrial and aquatic organisms, respectively. Biomagnification factors (BMFs) of PCBs increased with higher log K_OW in all food chains. BMFs of SCCPs were negatively correlated with log K_OW in aquatic food chains, but positively correlated with log K_OW in terrestrial food chains. The terrestrial food web had similar trophic magnification factors (TMFs) of PCBs, and higher TMFs of SCCPs than the aquatic food web. Biomagnification of PCBs was consistent in aquatic and terrestrial food webs, while SCCPs had higher biomagnification potential in terrestrial than aquatic organisms. The distinct biomagnification of SCCPs was affected by the respiratory elimination for terrestrial organisms, the different metabolism rates in various species, and more homotherms in terrestrial food webs. Fugacity model can well predict levels of less hydrophobic chemicals, and warrants more precise toxicokinetic data of SCCPs.

Bioaccumulation and Biotransformation of Chlorinated Paraffins

Chlorinated paraffins (CPs), a class of persistent, toxic, and bioaccumulated compounds, have received increasing attention for their environmental occurrence and ecological and human health risks worldwide in the past decades. Understanding the environmental behavior and fate of CPs faces a huge challenge owing to the extremely complex CP congeners. Consequently, the aims of the present study are to summarize and integrate the bioaccumulation and biotransformation of CPs, including the occurrence of CPs in biota, tissue distribution, biomagnification, and trophic transfer, and biotransformation of CPs in plants, invertebrates, and vertebrates in detail. Biota samples collected in China showed higher CP concentrations than other regions, which is consistent with their huge production and usage. The lipid content is the major factor that determines the physical burden of CPs in tissues or organs. Regarding the bioaccumulation of CPs and their influence factors, inconsistent results were obtained. Biotransformation is an important reason for this variable. Some CP congeners are readily biodegradable in plants, animals, and microorganisms. Hydroxylation, dechlorination, chlorine rearrangement, and carbon chain decomposition are potential biotransformation pathways for the CP congeners. Knowledge of the influence of chain length, chlorination degree, constitution, and stereochemistry on the tissue distribution, bioaccumulation, and biotransformation is still scarce.

Levels of Short- and Medium-Chain Chlorinated Paraffins in Edible Insects and Implications for Human Exposure

This study reports on the occurrence and distribution of short- and medium-chain chlorinated paraffins (SCCPs and MCCPs, respectively) in edible insects purchased from Asia and Europe. A total of 36 edible insect samples (n = 24 from Asia, n = 12 from Europe) authorized and prepared for human consumption were purchased and analyzed for SCCPs and MCCPs via gas chromatography and mass spectrometry. SCCPs were detected in 83% of all edible insect samples with an overall median ∑SCCP concentration of 8.7 ng/g dry weight (dw) and a range of <2.0 to 410 ng/g dw, while MCCPs were present in 92% of samples with a median ∑MCCP concentration of 51 ng/g dw and a range of <6.0 to 380 ng/g dw. Median ∑SCCP and ∑MCCP levels in edible insects purchased in Asia were approximately two- and four-times higher, respectively, than those from Europe, while the difference was statistically significant for ∑MCCPs (p < 0.001). Differences in homologue patterns were also observed between Asian and European samples to suggest diverse sources of CP contamination to insects which may include environmental accumulation, industrial processing equipment and food additives. Estimated daily intake of SCCPs and MCCPs via consumption of edible insects suggested that adverse health outcomes were very unlikely, but that continued monitoring of insect farming and processing practices are warranted.

Occurrence, Distribution and Health Risk of Short-Chain Chlorinated Paraffins (SCCPs) in China: A Critical Review

With being listed in the Stockholm Convention, the ban on short-chain chlorinated paraffins (SCCPs) has been put on the agenda in China. Based on the literature over the past decade, this study comprehensively analyzed the occurrence, distribution of and human exposure to SCCPs in China, aiming to provide a reference for the changes in SCCPs after the ban. SCCPs were ubiquitous in environmental matrices, and the levels were considerably higher than those in other countries. SCCPs from the emission region were 2–4 orders of magnitude higher than those in the background area. Environmental processes may play an important role in the SCCP profiles in the environment, and C10 and Cl6 were identified as potential factors distinguishing their spatial distribution. River input was the dominant source in the sea areas, and atmospheric transport was the main source in the remote inland areas. Ingestion and dermal absorption and food intake may pose potential risk to residents, especially for children and infants. More studies are needed on their temporal trend, source emission and environmental degradation. The enactment of the restriction order will have a great impact on China’s CP industry; nevertheless, it will play a positive role in the remediation of SCCP pollution in the environment.

Assessing Safety of Market-Sold Fresh Fish: Tracking Fish Origins and Toxic Chemical Origins

Increasing global and domestic food trade and required logistics create uncertainties in food safety inspection due to uncertainties in food origins and extensive trade activities. Modern blockchain techniques have been developed to inform consumers of food origins but do not provide food safety information in many cases. A novel food safety tracking and modeling framework for quantifying toxic chemical levels in the food and the food origins was developed. By integrating chemicals' multimedia environment exchange, food web, and source tracking systems, the framework was implemented to identify short-chain chlorinated paraffin (SCCP) contamination of fresh hairtail fish sold by a Walmart supermarket in Xi'an, northwestern China, and sourced in Eastern China Sea coastal waters. The framework was shown to successfully predict SCCP level with a mean of 17.8 ng g^-1 in Walmart-sold hairtails, which was comparable to lab-analyzed 21.9 ng g^-1 in Walmart-sold hairtails. The framework provides an alternative and cost-effective approach for safe food inspection compared to traditional food safety inspection techniques. These encouraging results suggest that the approach and rationale reported here could add additional information to the food origin tracking system to enhance transparency and consumers' confidence in the traded food they consumed.

Spatiotemporal distribution and risk assessment of short-chain chlorinated paraffins in 30 major rivers in Taiwan

Because of their highly persistent, bioaccumulative and toxic properties, short-chain chlorinated paraffins (SCCPs) have become emerging contaminants and have been included in Annex A (elimination) of the Stockholm Convention since 2017. The contamination of SCCPs has been observed in the environment and biota worldwide but has not been detected in Taiwanese river ecosystems. Thus, this study aimed to determine the occurrence of SCCPs in sediments and fish from 30 major rivers in Taiwan and to evaluate the risk of SCCPs to river ecosystems and human health. The concentrations of SCCPs in sediments and fish ranged from ND (not detected) to 12.6 mg/kg dw and ND to 2.07 mg/kg ww, respectively. The concentrations of SCCPs in sediments were significantly correlated with some indicators of the discharge sources and water quality variables, indicating that SCCPs were released via human activities and various discharges into rivers and accumulated in sediments. The bioaccumulation of SCCPs in fish exhibited species-specific profiles and was related to environmental contamination levels and the living pattern and trophic level of the fish. The SCCP levels in sediments from 20 major rivers in Taiwan might pose a potential ecological risk to river ecosystems according to the criteria of the Federal Environmental Quality Guidelines in Canada, the biota-sediment accumulation factor and the risk quotient. Consumption of SCCP-contaminated river fish by different gender and age groups showed no significant health risk to residents in Taiwan evaluated by the estimated daily intake and hazard quotient. However, there was a health concern for the 0- to 3-year-old group due to the consumption of contaminated river fish at a bioaccessibility of 100% for SCCPs by the margin of exposure. Routine monitoring of SCCPs in river ecosystems is needed to protect aquatic organisms and human health.

Concentrations and distribution of chlorinated paraffins in Belgian foods

This study reports on concentrations of short- and medium-chain chlorinated paraffins (SCCPs and MCCPs, respectively) in a wide range of food samples (n = 211) purchased in Belgium during 2020. Samples were analysed by gas chromatography-mass spectrometry (GC-MS) and quantified using chlorine content calibration. ∑SCCPs were present above LOQ in 25% of samples with an overall range of <LOQ to 58 ng/g wet weight (ww), while ∑MCCPs were identified in 66% of samples ranging from <LOQ to 250 ng/g ww. ∑MCCP concentrations were greater than those of ∑SCCPs in all 48 samples in which both groups were detected with an average ∑MCCP/∑SCCP ratio of 5.8 (ranging from 1.3 to 81). In general, the greatest CP concentrations were observed in foods classified as animal and vegetable fats and oils and sugar and confectionary for both SCCPs and MCCPs. Significant correlations between lipid content in food samples and CP levels illustrated the role of lipids in accumulating CPs within foodstuffs, while industrial processing, food packaging and environmental conditions are each likely to contribute to overall CP loads. Selected samples (n = 20) were further analysed by liquid chromatography-high resolution MS (LC-HRMS) to investigate homologue profiles and the occurrence of long-chain CPs (LCCPs). LCCPs were detected in 35% of the 20 subset samples while the HRMS results for SCCPs and MCCPs matched closely with those obtained by GC-MS. This study reveals the widespread occurrence of SCCPs and MCCPs in Belgian food and indicates that LCCPs may represent a substantial contribution to overall CP levels in foodstuffs.

Status of short-chain chlorinated paraffins in matrices and research gap priorities in Africa: a review

Chlorinated paraffins (CPs) have been applied as additives in a wide range of consumer products, including polyvinyl chloride (PVC) products, mining conveyor belts, paints, sealants, adhesives and as flame retardants. Consequently, CPs have been found in many matrices. Of all the CP groups, short-chain chlorinated paraffins (SCCPs) have raised an alarming concern globally due to their toxicity, persistence and long-range transportation in the environment. As a result, SCCPs were listed in the Stockholm Convention on Persistent Organic Pollutants (POPs) in May 2017. Additionally, a limit for the presence of SCCPs in other CP mixtures was set at 1% by weight. CPs can be released into the environment throughout their life cycle; therefore, it becomes crucial to assess their effects in different matrices. Although about 199 studies on SCCP concentration in different matrices have been published in other continents; however, there are scarce/or limited studies on SCCP concentration in Africa, particularly on consumer products, landfill leachates and sediment samples. So far, published studies on SCCP concentration in the continent include SCCPs in egg samples, e-waste recycling area and indoor dust in Ghana and South Africa, despite absence of any production of SCCPs in Africa. However, there still remains a huge research gap in the continent of Africa on SCCPs. Consequently, there is a need to develop robust SCCP inventories in Africa since the Stockholm Convention has already developed guidance document in this respect. This review, therefore, examines the state of knowledge pertaining to the levels and trends of these contaminants in Africa and further provides research gaps that need to be considered in order to better understand the global scale of the contaminant.

Concentrations and sources of short- and medium-chain chlorinated paraffins in farmed Chinese mitten crabs in China

Aquatic foods are important sources of chlorinated paraffins (CPs) to humans. Farmed crabs are bottom-dwelling aquatic animals, and can accumulate CPs through food and aquatic environment. However, limited information is available on CPs concentrations in and sources to farmed crabs. In this study, short-chain CPs (SCCPs) and medium-chain CPs (MCCPs) concentrations in 59 samples from the farmed crab food web (crab, crab feed, and aquaculture environment) were determined. The samples were from 17 crab farms in Anhui Province, Jiangxi Province, and Shanghai, in China. The SCCPs and MCCPs concentrations in the crab samples were 82-1760 and not detected-680 ng/g lipid weight, respectively. The dominant SCCPs and MCCPs in the crab samples were C₁₀Cl_6-7 and C₁₄Cl_7-8, respectively. The SCCPs concentrations in the crab food web samples were higher than the MCCPs concentrations. SCCPs contamination of the crab food web samples was not directly related to CPs product use. The main factors affecting SCCPs concentrations in the crab samples were different for different crab farms. Crab feed and the aquaculture environment could be sources of SCCPs to farmed crabs. No marked health risks are posed to humans through consuming CPs in Chinese mitten crabs farmed in China.

Temporal trends of "old" and "new" persistent halogenated organic pollutants in fish from the third largest freshwater lake in China during 2011-2018 and the associated health risks

The study aimed to investigate temporal trends of "old" and "new" persistent halogenated organic pollutants (HOPs) in Taihu Lake, the third largest freshwater lake in China, and the associated health risks. Five fish species were consecutively collected from the lake every year during 2011-2018. HOPs including 37 polychlorinated biphenyls (PCBs), 10 organochlorine pesticides (OCPs), short- and medium-chain chlorinated paraffins (SCCPs and MCCPs), 19 polybrominated diphenyl ethers (PBDEs), and 10 new brominated flame retardants (NBFRs), were measured. The results showed that all the HOPs were detected, with MCCPs and NBFRs showing the highest and lowest concentrations, respectively. The levels of SCCPs and MCCPs were several orders of magnitude higher than those of the other HOPs. There were obvious increasing trends for SCCPs, MCCPs, and hexachlorobenzene, but a decreasing trend for PBDEs. No obvious increasing or decreasing trends were observed for the other HOPs. The present study indicated that the use of NBFRs to replace PBDEs was not yet clearly observed. Fish consumption did not result in non-carcinogenic risks, but posed low carcinogenic risks, with PCBs and DDTs being the highest-risk contaminants because of historical residues. This is the first study for the temporal variations of the HOPs in the lake.

Occurrence, trophic magnification and potential risk of short-chain chlorinated paraffins in coral reef fish from the Nansha Islands, South China Sea

As emerging persistent organic pollutants in marine environment, short-chain chlorinated paraffins (SCCPs) have attracted increasing attentions recently. Coral reefs are important ocean ecosystems. However, data on SCCP pollution in the coral reef regions is still unavailable. In the present work, bioaccumulation of SCCPs in the coral reef ecosystems was reported for the first time. SCCP concentrations in coral reef fish from the Nansha Islands of the South China Sea were in the range of 37.9-25,400 ng/g lipid weight (lw) (average: 4400 ± 6590 ng/g lw; median: 1020 ng/g lw). C₁₀ SCCPs were the dominating SCCP homologues, accounting for 59% to 80% of the total SCCPs (average: 70 ± 5.0%), followed by C₁₁ SCCPs (average: 23 ± 4.5%). Regarding chlorine substitution, SCCPs were dominated by Cl₇ SCCPs (average: 45 ± 2.5%) and Cl₈ SCCPs (average: 30 ± 5.4%). Trophic magnification factor (TMF) of total SCCPs was 8.5, indicating trophic magnification potential of SCCPs in the coral reef ecosystems. In addition, a parabolic relationship was established between TMFs and log K_ow of specific SCCP homologues. SCCP residues in the coral reef fish from the Nansha Islands of the South China Sea did not pose significant risk to human health.