Carbazole in source water is a potential precursor for toxic chlorocarbazoles in drinking water when chlorine is used as a disinfection agent in drinking water treatment plants. However, the reactivity of carbazole and the specific structures and predominant analogues of chlorocarbazoles produced during aqueous chlorination remain unknown. In this study, the aqueous chlorination of carbazole was performed to characterize its reactivity and the chlorinated products. Chlorocarbazoles generated from carbazole were identified by a comprehensive two-dimensional gas chromatography-mass spectrometry method, and their molecular structures were predicted by the Fukui index of electrophilic attack, f−1(r). As a result, the comprehensive chlorination pathway of carbazole was extrapolated with a total of nine chlorocarbazoles identified, including two monochlorocarbazoles (3-chlorocarbazole and 1-chlorocarbazole), four dichlorocarbazoles (3,6-dichlorocarbazole, 1,6-dichlorocarbazole, 1,3-dichlorocarbazole and 1,8-dichlorocarbazole), two trichlorocarbazoles (1,3,6-trichlorocarbazole and 1,3,8-trichlorocarbazole) and one tetrachlorocarbazole (1,3,6,8-tetrachlorocarbazole). The f−1(r) value indicates that the C1, C3, C6 and C8 atoms of carbazole were the favored positions for electrophilic attack, with the C3 and C6 atoms being the predominant sites for chlorine substitution. 3-Chlorocarbazole, 3,6-dichlorocarbazole, 1,3,6-trichlorocarbazole and 1,3,6,8-tetrachlorocarbazole were the major analogues of each chlorocarbazole group; however, the production of minor analogues such as 1-chlorocarbazole and 1,6-dichlorocarbazole should not be overlooked. The chlorination of carbazole was a pseudo first order reaction with a reaction rate of 0.1836 nmol/(L· h) and half-life of 3.77 h (pH = 6.4, Cl2 = 4.7 mg/L), and the chlorination rate of carbazole was approximately 5 times faster than that of an known chlorination precursor pyrene. These results showed that Fukui index was efficacious to predict the chlorination sites of aromatic compounds, and that carbazole is readily transformed into toxic chlorocarbazoles in drinking water treatment plants that use chlorine as a disinfection agent.

The study of the DNA damage response in erythrocytes after γ-irradiation may provide evidence for its effectiveness as a biomarkers for genotoxic environmental stress. We previously reported various malformations in erythrocytes of medaka irradiated with10 Gy, but not in their micronuclei. In this study, we optimized an assay method for γ-H2AX and double strand breaks in erythrocytes of adult medaka fish after 15 Gy of γ-irradiation. The highest level of apoptosis and nuclear abnormalities, including in micronuclei, were recorded 4 h after γ-irradiation, as was the highest level of γ-H2AX foci in erythrocytes. These results suggest that recognition and repair processes occur as a response to DNA damage in erythrocytes in medaka.

Atmospheric deposition of mercury (Hg) to surface water is one of the dominant sources of Hg in aquatic environments and ultimately drives methylmercury (MeHg) toxin accumulation in fish. It is known that freshly deposited Hg is more readily methylated by microorganisms than aged or preexisting Hg; however the underlying mechanism of this process is unclear. We report that Hg bioavailability is decreased by photochemical reactions between Hg and dissolved organic matter (DOM) in water. Photo-irradiation of Hg-DOM complexes results in loss of Sn(II)-reducible (i.e. reactive) Hg and up to an 80% decrease in MeHg production by the methylating bacterium Geobacter sulfurreducens PCA. Loss of reactive Hg proceeded at a faster rate with a decrease in the Hg to DOM ratio and is attributed to the possible formation of mercury sulfide (HgS). These results suggest a new pathway of abiotic photochemical formation of HgS in surface water and provide a mechanism whereby freshly deposited Hg is readily methylated but, over time, progressively becomes less available for microbial uptake and methylation.

Bacterial degradation is an important clearance pathway for organic contaminants from highly human-impacted environments. However, it is not fully understood how organic contaminants are selected for degradation by bacteria and genes in aquatic environments. In this study, PAH degrading bacterial genera and PAH-degradation-related genes (PAHDGs) in sediments collected from the Pearl River (PR), the Pearl River Estuary (PRE) and the South China Sea (SCS), among which there were distinct differences in anthropogenic impact, were analyzed using metagenomic approaches. The diversity and abundance of PAH degrading genera and PAHDGs in the PR were substantially higher than those in the PRE and the SCS and were significantly correlated with the total PAH concentration. PAHDGs involved with the three key processes of PAH degradation (ring cleavage, side chain and central aromatic processes) were significantly correlated with each other in the sediments. In particular, plasmid-related PAHDGs were abundant in the PR sediments, indicating plasmid-mediated horizontal transfer of these genes between bacteria or the overgrowth of the bacteria containing these plasmids under the stresses of PAHs. Our results suggest that PAH degrading bacteria and genes were rich in PAH-polluted aquatic environments, which could facilitate the removal of PAHs by bacteria.

Elemental mercury (Hg0) has different behavior in the environment compared to other pollutants due to its unique properties. It can remain in the atmosphere for long periods of time and so can travel long distances. Through air-surface (e.g., vegetation or ocean) exchange (dry deposition), Hg0 can enter terrestrial and aquatic systems where it can be converted into other Hg species. Despite being ubiquitous and playing a key role in Hg biogeochemical cycling, Hg0 behavior in the environment is not well understood. The objective of this review is to provide a better understanding of how the unique physicochemical properties of Hg0 affects its cycling and chemical transformations in different environmental compartments. The first part focuses on the fundamental chemistry of Hg0, addressing why Hg0 is liquid at room temperature and the formation of amalgam, Hg halide, and Hg chalcogenides. The following sections discuss the long-range transport of Hg0 as well as its redistribution in the atmosphere, aquatic and terrestrial systems, in particular, on the sorption/desorption processes that occur in each environmental compartment as well as the involvement of Hg0 in chemical transformation processes driven by photochemical, abiotic, and biotic reactions.

Studies have shown that residents living near rare earth mining areas have high concentrations of rare earth elements (REEs) in their hair. However, the adverse effects of REEs on human health have rarely been the focus of epidemiological studies. The goal of this study was to evaluate the relationship between REEs in hair and the risk of hypertension in housewives. We recruited 398 housewives in Shanxi Province, China, consisting of 163 women with hypertension (cases) and 235 healthy women without hypertension (controls). We analyzed 15 REEs (lanthanum (La), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), Yttrium (Y), cerium (Ce), praseodymium (Pr), and neodymium (Nd)) and calcium (Ca) accumulated in housewives hair over a period of two years. The results revealed that, with the exception of Eu, concentrations of the REEs in hair were higher in the cases than in the controls. The univariate odds ratios (ORs) of the 14 REEs were >1, and four of the REEs (Dy, Tm, Yb, and Y) also had adjusted ORs > 1. The increasing dose-response trends of the four REEs further indicated the potential for increased hypertension risk. Moreover, the REEs were negatively correlated with Ca content in hair. These results might suggest an antagonistic effect of REEs on Ca in the human body. It was concluded that high intake of REEs might increase the risk of hypertension among housewives.

Low-cost, light-scattering-based particulate matter (PM) sensors are becoming more widely available and are being increasingly deployed in ambient and indoor environments because of their low cost and ability to provide high spatial and temporal resolution PM information. Researchers have begun to evaluate some of these sensors under laboratory and environmental conditions. In this study, a low-cost, particulate matter sensor (Plantower PMS 1003/3003) used by a community air-quality network is evaluated in a controlled wind-tunnel environment and in the ambient environment during several winter-time, cold-pool events that are associated with high ambient levels of PM. In the wind-tunnel, the PMS sensor performance is compared to two research-grade, light-scattering instruments, and in the ambient tests, the sensor performance is compared to two federal equivalent (one tapered element oscillating microbalance and one beta attenuation monitor) and gravimetric federal reference methods (FEMs/FRMs) as well as one research-grade instrument (GRIMM). The PMS sensor response correlates well with research-grade instruments in the wind-tunnel tests, and its response is linear over the concentration range tested (200–850 μg/m³). In the ambient tests, this PM sensor correlates better with gravimetric methods than previous studies with correlation coefficients of 0.88. However additional measurements under a variety of ambient conditions are needed. Although the PMS sensor correlated as well as the research-grade instrument to the FRM/FEMs in ambient conditions, its response varies with particle properties to a much greater degree than the research-grade instrument. In addition, the PMS sensors overestimate ambient PM concentrations and begin to exhibit a non-linear response when PM2.5 concentrations exceed 40 μg/m³. These results have important implications for communicating results from low-cost sensor networks, and they highlight the importance of using an appropriate correction factor for the target environmental conditions if the user wants to compare the results to FEM/FRMs.

Chronic organochlorine (OC) exposure has been shown to cause immune impairment in numerous vertebrate species. To determine if elasmobranchs exhibited compromised immunity due to high OC contamination along the coastal mainland of southern California, innate immune function was compared in round stingrays (Urobatis halleri) collected from the mainland and Santa Catalina Island. Proliferation and phagocytosis of peripheral blood, splenic, and epigonal leukocytes were assessed. Percent phagocytosis and mean fluorescence intensity (MFI) were evaluated by quantifying % leukocytes positive for, and relative amounts of ingested fluorescent E. coli BioParticles. Total cell proliferation differed between sites, with mainland rays having a higher cell concentration in whole blood. ∑PCB load explained significantly higher % phagocytosis in blood of mainland rays, while ∑PCB and ∑pesticide loads described increased splenic % phagocytosis and MFI in the mainland population. Data provides evidence of strong OC-correlated immunostimulation; however, other site-specific environmental variables may be contributing to the observed effects.

We investigated the carcinogenic and mutagenic respiratory health risks related to the exposure to atmospheric PAHs in an urban area. Our study focused in the association of these pollutants and their possible effect in human health, principally respiratory and circulatory diseases. Also, we determined a relationship between the inhalation risk of PAHs and meteorological conditions. We validated the hypothesis that in winter PAHs with high molecular weight associated to submicron particles (PM1) may increase exposure risk, especially for respiratory diseases, bronchitis and pneumonia diseases. Moreover, in our study we verified the relationship between diseases and several carcinogenic PAHs (Ind, BbkF, DahA, BaP, and BghiP). These individual PAHs contributed the most to the potential risk of exposure for inhalation of PM1.0. Even at lower ambient concentrations of BaP and DahA in comparison with individual concentrations of other PAHs associated to PM1.0. Mainly, research suggests to include carcinogenic and mutagenic PAHs in future studies of environmental health risk due to their capacity to associate to PM10. Such carcinogenic and mutagenic PAHs are likely to provide the majority of the human exposure, since they originate from dense traffic urban areas were humans congregate.

This study investigated the prevalence and abundance of halogenated flame retardants (HFRs) in sludge samples from 5 sewage treatment plants in Guangzhou, China. Detection of 18 polybrominated diphenyl ethers (PBDEs), 9 alternative HFRs including Dechlorane Plus (DP), brominated alkylbenzenes, and polybrominated biphenyls, and 2 related degradation products was conducted. Decabromodiphenyl ether (BDE 209) and decabromodiphenyl ethane (DBDPE) were the dominant HFRs, with concentrations ranging from 200 to 2150 ng/g and 680–27,400 ng/g, respectively. The DBDPE detected was the highest level reported so far, exceeding those previously reported by 10–100 times. PBDEs were surpassed as the dominant HFRs in sewage sludge, with mean DBDPE/BDE 209 ratio exceeding 2 in all samples. The review of earlier surveys reveals that DBDPE level was surging while BDE 209 was declining. Annual emissions of BDE 209, DP, and DBDPE were estimated to be 227.9, 10.5, and 979.3 kg/yr, respectively. Although ecological risks assessment suggested low risks for the examined sludge, the key environmental properties and transformation pathways of alternative HFRs remain largely unknown. These findings prompt for further investigations on alternative HFR and sustainable management practices for HFR-laden biosolids. The HFR emission pattern revealed in this study is likely representative of other similarly industrialized regions in the post-PBDE era.