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To investigate human exposure to short-chain chlorinated paraffins (SCCPs) and medium-chain chlorinated paraffins (MCCPs) through dermal and oral intake via hand-to-mouth contact, wipes from the face, forearm, hand, and foot of 30 volunteers were sampled. The concentration of ∑SCCPs and ∑MCCPs ranged from 0.66 to 119 and 0.71 to 565 µg/m2, respectively. Hands exhibited significantly higher ∑CPs concentrations than other skin areas, indicating that direct contact with indoor surfaces contributed considerable CP levels on this bare skin area. Gender differences in CP levels were observed in wipes from all locations, except for the hands, possibly because of the significant variability in residuals on the hands. A significant positive relationship was found between CP levels on the hands and faces, and the CP ratios of the hands/faces were related to log KOA. Bare skin showed more significant variations in CP partitioning among related congeners and between genders than skin covered by clothing, as elucidated by the linear analysis of RSD and log KOA. Although concentrations on clothing-covered areas were relatively lower than on bare skin, the median estimated dermal absorption doses of ∑SCCPs and ∑MCCPs (152 and 737 ng/kg bw/day, respectively) for the entire body were approximately 1–2 orders of magnitude higher than those for oral ingestion (1.62 and 7.94 ng/kg bw/day, respectively), emphasizing indirect dermal uptake as a significant exposure pathway for humans.

Rhizoremediation is a promising remediation technology for the removal of soil persistent organic pollutants (POPs), especially benzo[a]pyrene (BaP). However, our understanding of the associations among rhizospheric soil metabolites, functional microorganisms, and POPs degradation in different plant growth stages is limited. We combined stable-isotope probing (SIP), high-throughput sequencing, and metabolomics to analyze changes in rhizospheric soil metabolites, functional microbes, and BaP biodegradation in the early growth stages (tillering, jointing) and later stage (booting) of ryegrass. Microbial community structures differed significantly among growth stages. Metabolisms such as benzenoids and carboxylic acids tended to be enriched in the early growth stage, while lipids and organic heterocyclic compounds dominated in the later stage. From SIP, eight BaP-degrading microbes were identified, and most of which such as Ilumatobacter and Singulisphaera were first linked with BaP biodegradation. Notably, the relationship between the differential metabolites and BaP degradation efficiency further suggested that BaP-degrading microbes might metabolize BaP directly to produce benzenoid metabolites (3-hydroxybenzo[a]pyrene), or utilize benzenoids (phyllodulcin) to stimulate the co-metabolism of BaP in early growth stage; some lipids and organic acids, e.g. 1-aminocyclopropane-1-carboxylic acid, might provide nutrients for the degraders to promote BaP metabolism in later stage. Accordingly, we determined that certain rhizospheric metabolites might regulate the rhizospheric microbial communities at different growth stages, and shift the composition and diversity of BaP-degrading bacteria, thereby enhancing in situ BaP degradation. Our study sheds light on POPs rhizoremediation mechanisms in petroleum-contaminated soils.

Organophosphate esters (OPEs) are normally used as flame retardants, plasticizers and lubricants, but have become environmental pollutants. Because OPEs are normally present alongside heavy metals in soils, the effects of interactions between OPEs and heavy metals on plant uptake of OPEs need to be determined. In this study, we investigated the effects of OPEs chemical structure, plant cultivar and copper (Cu) on the uptake and translocation of OPEs by plants. The bioaccumulation of OPEs varied among plant cultivars. They were preferentially enriched in carrot, with the lowest concentrations observed in maize. OPEs with electron-ring substituents (ER-OPEs) exhibited a higher potential for root uptake than did OPEs with open-chain substituents (OC-OPEs), which could be attributed to the higher sorption of ER-OPEs onto root charged surfaces. This was explained by the stronger noncovalent interactions with the electron-rich structure of ER-OPEs. The presence of Cu slightly reduced the distinct difference in the ability of roots to take up OC-OPEs and ER-OPEs. This was explained by the interactions of Cu ions with the electron-rich structure of ER-OPEs, which suppressed the sorption of ER-OPEs on the root surface. A negative relationship between the logarithms of the translocation factor and octanol-water partition coefficient (Kow) was observed in treatments with either OPEs only or OPEs + Cu, implying the significant role of hydrophobicity in the OPEs acropetal translocation. The results will improve our understanding of the uptake and translocation of OPEs by plant cultivars as well as how the process is affected by the chemical structure of OPEs and Cu, leading to improvements in the ecological risk assessment of OPEs in the food chain.