Distribution, behavior, and risk assessment of chlorinated paraffins in paddy plants throughout whole growth cycle

Distribution, uptake, and daily exposure of per- and polyfluoroalkyl substances in a paddy field: A growth cycle study

Rice, a crucial agricultural commodity, is potentially susceptible to contamination by persistent organic pollutants throughout its entire growth cycle in the field. Per- and polyfluoroalkyl substances (PFASs) have attracted great scientific attention due to their environmental persistence, bioaccumulation potentials, and toxicity. However, the occurrence and behavior of PFASs in the paddy ecosystem have not been confirmed. This study explored the uptake, accumulation, and potential risks of PFASs in the irrigation water, soils and paddy tissues from a typical paddy system at the main stages of rice growth. The total PFAS concentrations in irrigation water and soils were in the range of 62.9 -85.5 ng/L and 45.7 -75.4 ng/g dw. The concentrations of PFASs in paddy tissues followed the order of root>stem>leaf>grain. A minor decrease in PFAS concentrations in paddy tissues with growth time may be attributed to biotransformation and growth dilution. PFAS distribution in soils, irrigation water, and different paddy tissues also showed different patterns with the growing time of paddy. ΣPFCAs and ΣPFSAs were the most prevalent PFASs in all samples, which constituted 65.0 -96.3 % of the total PFASs. In addition, the transfer factor (TF) values from root to stem/leaf/grain decreased as Log KOW increased (Log KOW< 5). Significant correlations between the concentrations and protein contents in paddy grains were observed for most long-chain PFASs. Risk assessments have suggested that the current levels do not pose a health risk to humans, but PFAS alternatives cannot be neglected for food safety and environmental impacts.

Polychlorinated Alkanes in feed from the German market

Polychlorinated Alkanes (PCAs) were analysed in 47 feed samples, 13 and 34 respectively of animal and plant origin, collected from the southern German market in 2023. The overall median concentration of ∑PCAs- was determined as 10ngg-1 ww, with plant-based feeds being considerably lower than feed of animal origin, with respective median values of 8.8 and 44ngg-1 ww. Highest levels of PCAs with respect to fresh weight were found in plant-based fats and oils, including the highest sample at more than 9000ngg-1 ww, followed by feed of animal origin, particularly fish meal. Seeds, press cakes, meals and soy based products were usually lower. The ratio of ∑PCAs- to ∑PCAs- was below 1 for almost all samples, potentially resulting from the European enforcement of the Stockholm Convention. Homologue response pattern revealed a small difference in the abundances of chain lengths - between feed of animal origin and plant-based feeds.

Tibetan lake sediment records reveal historical emission and long-range atmospheric transport of chlorinated paraffins

The Tibetan Plateau, a recognized global sink for Persistent Organic Pollutants (POPs), lies adjacent to two major emitting regions, inland China and India. This unique geographical setting makes it a pivotal site for examining the presence and compositional evolution of POPs following their long-range atmospheric transport (LRAT). This study focuses on the current predominant POPs, chlorinated paraffins (CPs). We comprehensively screened 675 homologues of the very short- (vSCCPs), short- (SCCPs), medium- (MCCPs), and long-chain CPs (LCCPs) in six dated sediment cores across the extensive Tibetan area. The findings unveiled pronounced temporal disparities in CP concentrations and compositions between Tibet's southern and eastern sectors, reflecting divergent usage and emission chronicles of inland China and India. Notably, a market shift in China from regulated SCCPs to the in-use MCCPs and LCCPs was observed in the 21st century, contrasting with India's unregulated production of SCCPs. The Organization for Economic Cooperation and Development (OECD) Screening Tool, developed to assess the overall persistence (POV) and long-range transport potential (LRTP) of organic chemicals, elucidated the erosion of CP source signatures induced by fractionation, a process that intensifies with transport distance from the source regions. This study enhances our understanding of the emission inventories and LRAT behavior of these transitional regulatory contaminants, highlighting the Tibetan Plateau's crucial role as an environmental sentinel in global pollution dynamics.

Chlorinated paraffins in takeout food and its packaging in Beijing, China and dietary exposure risk

Chlorinated paraffins (CPs) are hazardous to humans, and dietary intake acts as the primary pathway for human exposure to CPs. Takeout food is popular worldwide, but the presence of CPs in takeout food and its packaging is unclear. In this study, the concentrations and distributions of short- and median-chain CPs (SCCPs and MCCPs, respectively) were measured in 97 samples of four categories of takeout food and 33 samples of three types of takeout packaging. The SCCP and MCCP median concentrations for the takeout food samples were 248 and 339, 77.2 and 98.2, 118 and 258, 42.9 and 64.4 ng/g wet weight in meat, starch, half meat/half starch, and vegetables, respectively. Takeout food contained higher concentrations of SCCPs than MCCPs. The dominant SCCP and MCCP congener groups in takeout food were C10Cl6-7 and C14Cl7-8, respectively. The CP concentrations in takeout food were lower than those in packaging. The SCCP and MCCP median concentrations, respectively, in packaging were 9750 and 245 ng/g in polypropylene, 2830 and 135 ng/g in paper, and 2060 and 119 ng/g in aluminum foil. The concentrations of SCCPs and MCCPs were comparable in aluminum foil, whereas the concentrations of SCCPs were higher than those of MCCPs in polypropylene and paper. Correlations between CP concentrations in the takeout food and packaging indicated that CPs in packaging were potentially an important source of CPs in the takeout food. A dietary exposure risk assessment showed the takeout food posed a low risk for human exposure to CPs; however, high-frequency consumption may pose a health risk. This study clarified the current contamination situation in takeout food in Beijing, China. The resulting data could be used to prevent human exposure to CPs through dietary intake and to facilitate the market's control over the quality of takeout food.

First comprehensive assessment of dietary chlorinated paraffins intake and exposure risk for the rural population of the Tibetan Plateau, China

Knowledge regarding the occurrence of short-chain and medium-chain chlorinated paraffins (SCCPs and MCCPs) in foodstuffs and their dietary exposure risks for rural Tibetan residents remains largely unknown. Herein, we collected main foodstuffs (including highland barley, vegetables, Tibetan butter, mutton, and yak beef) across the rural Tibetan Plateau and characterized the CP profiles and concentrations. The highest SCCPs concentrations were detected in Tibetan butter (geometric mean (GM): 240.6 ng/g wet weight (ww)), followed by vegetables (59.4 ng/g ww), mutton (51.4 ng/g ww), highland barley (46.3 ng/g ww), and yak beef (31.7 ng/g ww). For MCCPs, the highest concentrations were also detected in Tibetan butter (319.5 ng/g ww), followed by mutton (181.9 ng/g ww), vegetables (127.0 ng/g ww), yak beef (71.2 ng/g ww), and highland barley (30.3 ng/g ww). The predominant congener profiles of SCCPs were C13Cl7-8 in mutton and yak beef, C10Cl7-8 in Tibetan butter, and C10-11Cl6-7 in highland barley and vegetables. The predominant congener profiles of MCCPs were C14Cl7-9 in all sample types. Combined with our previous results of free-range chicken eggs, the median estimated daily intakes (EDIs) of SCCPs and MCCPs via diet for Tibetan rural adults and children was estimated to be 728.8 and 1853.9 ng/kg bw/day and 2565.6 and 5952.8 ng/kg bw/day, respectively. In the worst scenario, MCCPs might induce potential health risks for rural Tibetan population. To our knowledge, this is the first systematic dietary exposure research of SCCPs and MCCPs in the remote rural areas.

Uptake, accumulation and toxicity of short chain chlorinated paraffins to wheat (Triticum aestivum L.)

Short chain chlorinated paraffins (SCCPs) are ubiquitous persistent organic pollutants. They have been widely detected in plant-based foods and might cause adverse impacts on humans. Nevertheless, uptake and accumulation mechanisms of SCCPs in plants remain unclear. In this study, the soil culture data indicated that SCCPs were strongly absorbed by roots (root concentration factor, RCF>1) yet limited translocated to shoots (translocation factor<1). The uptake mechanism was explored by hydroponic exposure, showing that hydrophobicity and molecular size influenced the root uptake and translocation of SCCPs. RCFs were significantly correlated with logKow values and molecular weights in a parabolic curve relationship. Besides, it was extremely difficult for SCCPs to translocate from shoots back to roots via phloem. An active energy-dependent process was proposed to be involved in the root uptake of SCCPs, which was supported by the uptake inhibition by the low temperature and metabolic inhibitor. Though SCCPs at environmentally relevant concentrations had no negative impacts on root morphology and chlorophyll contents, it caused obvious changes in cellular ultrastructure of root tip cells and induced a significant increase in superoxide dismutase activity. This information may be beneficial to moderate crop contamination by SCCPs, and to remedy soils polluted by SCCPs with plants.

Methylation and Demethylation of Emerging Contaminants in Plants

Many contaminants of emerging concern (CECs) have reactive functional groups and may readily undergo biotransformations, such as methylation and demethylation. These transformations have been reported to occur during human metabolism and wastewater treatment, leading to the propagation of CECs. When treated wastewater and biosolids are used in agriculture, CECs and their transformation products (TPs) are introduced into soil-plant systems. However, little is known about whether transformation cycles, such as methylation and demethylation, take place in higher plants and hence affect the fate of CECs in terrestrial ecosystems. In this study, we explored the interconversion between four common CECs (acetaminophen, diazepam, methylparaben, and naproxen) and their methylated or demethylated TPs in Arabidopsis thaliana cells and whole wheat seedlings. The methylation-demethylation cycle occurred in both plant models with demethylation generally taking place at a greater degree than methylation. The transformation rate of demethylation or methylation was dependent on the bond strength of R-CH3, with demethylation of methylparaben or methylation of acetaminophen being more pronounced. Although not explored in this study, these interconversions may exert influences on the behavior and biological activity of CECs, particularly in terrestrial ecosystems. The study findings demonstrated the prevalence of transformation cycles between CECs and their methylated or demethylated TPs in higher plants, contributing to a more complete understanding of risks of CECs in the human-wastewater-soil-plant continuum.

Novel and legacy brominated flame retardants in snakes and frogs: Tissue distribution, biomagnification, and maternal transfer

Although many studies have examined polybrominated diphenyl ethers (PBDEs) and novel brominated flame retardants (NBFRs) in biota, information on the bioaccumulation characteristics of NBFRs from field works is limited. This study investigated the tissue-specific exposure to PBDEs and NBFRs in two reptilian (short-tailed mamushi and red-backed rat snake) and one amphibian species (black-spotted frog) prevalent in the Yangtze River Delta, China. The levels of ΣPBDEs and ΣNBFRs ranged from 4.4-250 and 2.9-22 ng/g lipid weight for snakes respectively and 2.9-120 and 7.1-97 ng/g lipid weight for frogs respectively. BDE-209, BDE-154, and BDE-47 were three major PBDE congeners while decabromodiphenylethane (DBDPE) dominated in NBFRs. Tissue burdens indicated that snake adipose was the major storage site of PBDEs and NBFRs. The biomagnification factors (BMFs) estimated from black-spotted frog to red-backed rat snake indicated the biomagnification of penta- to nona-BDE congeners (BMFs 1.1-4.0) but the lack of biomagnification of other BDE and all NBFR congeners (BMFs 0.16-0.78). Mother to egg transfer of PBDEs and NBFRs evaluated in frogs showed that maternal transfer efficiency was positively related to chemical lipophilicity. This is the first field study on the tissue distribution of NBFRs in reptiles and amphibians and the maternal transfer behavior of 5 major NBFRs. The results underline the bioaccumulation potential of alternative NBFRs.

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.

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.