Disinfection By-products In Water Research Articles

Cocamidopropyl betaine - a potential source of nitrogen-containing disinfection by-products in pool water.

Water treatment for most public pools involves disinfection with active chlorine leading to the formation of disinfection by-products (DBPs). Among them, nitrogen-containing compounds (N-DBPs) having increased toxicity and adverse effects on human health are of the greatest concern. Being the major component of various body washers for swimmers, cocamidopropyl betaine (CAPB) represents a potential and still underestimated anthropogenic precursor of N-DBPs in pool water. The purpose of this study was to investigate CAPB transformation pathways and mechanisms under the aqueous chlorination conditions. High-performance liquid and two-dimensional gas chromatography hyphenated with high-resolution mass spectrometry were used for the search and tentative identification of the primary and final CAPB transformation products. A wide range of DBPs containing up to five chlorine atoms including these in combination with hydroxyl and additional carbonyl groups has been revealed in model chlorination experiments for the first time. The proposed mechanism of their formation involves nucleophilic substitution of the secondary amide hydrogen atom at the first stage with subsequent free radical and electrophilic addition reactions resulting in non-selective introduction of halogen atoms and hydroxyl groups in the alkyl chain. The deep transformation products include short-chain chlorinated hydrocarbons and their oxidation products as well as dimethylcarbamoyl chloride possessing high toxicity and carcinogenic properties. Targeted analysis of real swimming pool water samples confirmed the results of model experiments enabling semi-quantitative determination of CAPB (0.8µg L-1) and 18 primary DBPs, including 10 chlorine-containing compounds with the total concentration of 0.1µg L-1. Among them, monochloro (50%) and hydroxydichloro (25%) derivatives predominate. The toxicity and health of the main DBPs has been estimated using QSAR/QSTR approach. Thus, the possibility of formation of new classes of potentially toxic chlorine-containing DBPs associated with the widespread use of detergents and cosmetics was shown.

Measurement of haloacetic acids in human urine samples from six megacities of China using a refined detection method

Haloacetic acids (HAAs) are common disinfection by-products in chlorine disinfected water. Humans are extensively exposed to them. However, nationwide biomonitoring data were not available for any country. This study developed a labor-efficient and sensitive method for the detection of urinary HAAs, including trichloroacetic acid (TCAA) and dichloroacetic acid (DCAA), and conducted an exposure assessment in a Chinese population. A total of 850 first-morning-void urine samples were collected from adults in six megacities in China: Wuhan (central), Lanzhou (northwest), Chengdu (southwest), Taiyuan (north), Shanghai (east), and Dalian (northeast). Each participant (n = 425) provided a pair of urine samples during the warm (September to October 2018) and cold (December 2018 to January 2019) seasons. The detection method achieved good retention of the target analytes using a Fluoro-Phenyl column and excellent selectivity using in-source fragmentation ions as precursor ions in multiple reaction monitoring. The detection rate of urinary TCAA in Chinese populations was high (78.5%) but varied among different regions (54.0% to 98.0%). DCAA was rarely detected (<10%). The overall median value of specific gravity adjusted TCAA concentrations was 5.70 μg/L in the warm season and 3.87 μg/L in the cold season, respectively. Higher urinary TCAA concentrations were more likely to occur in Wuhan (Yangtze River Basin), urban areas, and during the warm season. The upstream region of the Yangtze River Basin (Chengdu) typically has lower TCAA concentrations. TCAA formation in coastal cities such as Shanghai and Dalian may be impacted by seawater intrusion. Estimated daily intakes of TCAA were lower than its chronic reference dose of 20 μg/kg-bw/day. This detection method can be applied to future biomonitoring of urinary HAAs. More attention should be paid to the highly exposed subgroups when exploring the health effects of long-term TCAA exposure.

Modeling source water disinfection byproducts formation potential using environmental variables

AbstractPredictive models of disinfection byproducts (DBPs) formation in treated drinking water have been widely used to guide operational decisions. However, very few studies have addressed the issue of managing DBPs through watershed protection programs and proactive management of water supply systems through predictive modeling of DBP formation potential in source waters. Here, we propose a two‐component, simple statistical approach to predict the formation potentials of the sum of five haloacetic acids (HAA5fp) and total trihalomethanes (TTHMfp) in source water streams using environmental variables and ultraviolet absorbance at 254 nm wavelength (UV254) as a surrogate for DBP precursors. In the first component of the model, using three feature selection regression models and cross‐validation of subsets of the selected predictors, we identified three commonly monitored variables—streamflow, soil temperature, and total phosphorus for predicting UV254. In the second component, HAA5fp and TTHMfp are predicted from UV254. The approach is successfully demonstrated for two source water streams of the New York City water supply system (R2 was 0.8, and 0.7–0.8 for the two model components). Long‐term predictions of HAA5fp and TTHMfp showed distinct seasonal patterns that are linked to differences in land uses of the two watersheds. Moreover, sensitivity analysis showed that transport processes were important in one watershed whereas production processes were more important in the other.

Wrangling Whole Mixtures Risk Assessment: Recent Advances in Determining Sufficient Similarity.

Human health risk assessments for complex mixtures can address real-world exposures and protect public health. While risk assessors typically prefer whole mixture approaches over component-based approaches, data from the precise exposure of interest are often unavailable and surrogate data from a sufficiently similar mixture(s) are required. This review describes recent advances in determining sufficient similarity of whole, complex mixtures spanning the comparison of chemical features, bioactivity profiles, and statistical evaluation to determine "thresholds of similarity". Case studies, including water disinfection byproducts, botanical ingredients, and wildfire emissions, are used to highlight tools and methods. Limitations to application of sufficient similarity in risk-based decision making are reviewed and recommendations presented for developing best practice guidelines.

Disinfection by-products in drinking water and risk of colorectal cancer: a population-based cohort study.

Colorectal cancer is the third most common malignancy worldwide and is strongly linked to lifestyle and environmental risk factors. Although several drinking-water disinfection by-products are confirmed rodent carcinogens, the evidence in humans for carcinogenicity associated with these by-products, including colorectal cancer, is still inconclusive. We assessed the association of long-term exposure to trihalomethanes (THMs), the most prevalent disinfection by-products in chlorinated drinking water, with incidence of colorectal cancer in 58 672 men and women in 2 population-based cohorts. Exposure was assessed by combining long-term information of residential history with drinking water-monitoring data. Participants were categorized according to no exposure, low exposure (<15µg/L), and high exposure (≥15µg/L). Incident cases of colorectal cancer were ascertained by use of the Swedish National Cancer Register. During an average follow-up of 16.8years (988 144 person-years), 1913 cases of colorectal cancer were ascertained (1176 cases in men and 746 in women, respectively). High THM concentrations in drinking water (≥15 µg/L) were associated with increased risk of colorectal cancer in men (hazard ratio = 1.26, 95% confidence interval = 1.05-1.51) compared with no exposure. When subsites were assessed, the association was statistically significant for proximal colon cancer (hazard ratio = 1.59, 95% confidence interval = 1.11 to 2.27) but not for distal colon cancer or rectal cancer. In women, we observed overall no association of THMs with colorectal cancer. These results add further evidence that disinfection by-products in drinking water may be a possible risk factor for proximal colon cancer in men. This observation was made at THM concentrations lower than those in most previous studies.

Toxic effects of disinfection by-products on Pseudokirchneriella subcapitata and co-cultured algae community

The widespread use of disinfectants in response to the COVID-19 pandemic may increase the concentration of disinfection by-products (DBPs) in surface water, posing ecological risks. This study assessed the acute toxicity of haloacetic acids and halophenols DBPs to Pseudokirchneriella subcapitata, and evaluated the impact of environmental concentrations of DBPs on co-cultured algae communities. The results showed that after exposure to disinfection by-products, the photosynthetic pigments of Pseudokirchneriella subcapitata were significantly reduced, and the MDA content and antioxidant enzyme activity were increased. The results of the ecological risk assessment showed that the RQ values of TBAA, 2,4-DBP, and 2,6-DBP were >0.1, with medium and high ecological risks. Despite this, the three DBPs with the highest risk values had little effect on the community structure of co-cultured algae. In contrast, the disinfection by-products with low ecological risk had a greater impact on the community structure and greatly promote the growth of cyanobacteria, which may cause new ecological risks. Therefore, not only high-risk disinfection by-products need to be paid attention to, but the impact of low-risk disinfection by-products cannot be ignored.

Occurrence of bromide and bromate in chlorinated indoor swimming pools, and associated health risks

Swimming is a physical activity that is accessible to people of all ages in all seasons. However, continuous organic and inorganic precursor load and disinfectant dosing make pool water chemistry much more complex than other disinfected waters. Carcinogenic bromate compound is one of the hundreds of disinfection by-products in pool water. The occurrence of bromate in pool waters depends on the precursor content of filling water, the disinfection process, operating parameters, and the purity of disinfectants. While the average filling water bromide concentrations of University Campus indoor swimming pool in Gülbahçe –Urla (SP1) and Buca public indoor swimming pool (SP2) were determined to be 182 μg/L and 11.0 μg/L, respectively, the average bromate concentrations of SP1 and SP2 were 59.4 μg/L and 68.3 μg/L. Estimated chronic-toxic health risks of accidental ingestion of pool water during swimming (between 10-3 and 10-1) were lower than the threshold level (‘1’). Although the carcinogenic risks in central tendency scenario (

Genotoxicity Induced by Low Dose and Mixed Exposure to Haloacetaldehydes, an Emerging Class of Drinking Water Disinfection By-products

Genotoxicity Induced by Low Dose and Mixed Exposure to Haloacetaldehydes, an Emerging Class of Drinking Water Disinfection By-products

Effect of spray aeration on unregulated drinking water disinfection byproducts

AbstractSpray aeration is a comparatively low‐cost option to reduce trihalomethane (THM) concentrations in distribution system storage. The effect of spray aeration on unregulated, toxic disinfection by‐products was investigated in a bench‐scale apparatus in closed‐tank and open‐tank experiments. In the closed‐tank experiments, initially over 90% of THMs, trichloroacetonitrile, and chloropicrin were removed, while 36% of dihaloacetonitriles were removed. However, due to the buildup of concentrations in the tank headspace, removal rates for all compounds decreased significantly with time, falling to 44% removal of THMs, 76% removal of trichloroacetonitrile, and 58% removal of chloropicrin. Removal of dihaloacetonitriles decreased to zero. In the open‐tank experiments, THM removal rates were high and did not decrease with time. Considering the results with open and closed tanks as approximate bounds for performance expected under real‐world conditions in storage tanks, the findings suggest that spray aeration may not significantly reduce haloacetonitrile‐related toxicity while halonitromethane‐related toxicity may be reduced.

Drinking water disinfection byproduct iodoacetic acid affects thyroid hormone synthesis in Nthy-ori 3–1 cells

Iodoacetic acid (IAA) is an emerging and the most genotoxic iodinated disinfection byproduct to date. IAA can disrupt the thyroid endocrine function in vivo and in vitro, but the underlying mechanisms remain unclear. In this work, transcriptome sequencing was used to investigate the effect of IAA on the cellular pathways of human thyroid follicular epithelial cell line Nthy-ori 3–1 and determine the mechanism of IAA on the synthesis and secretion of thyroid hormone (TH) in Nthy-ori 3–1 cells. Results of transcriptome sequencing indicated that IAA affected the TH synthesis pathway in Nthy-ori 3–1 cells. IAA reduced the mRNA expression of thyroid stimulating hormone receptor, sodium iodide symporter, thyroid peroxidase, thyroglobulin, paired box 8 and thyroid transcription factor-2, inhibited the cAMP/PKA pathway and Na+-K+-ATPase, and decreased the iodine intake. The results were confirmed by our previous findings in vivo. Additionally, IAA downregulated glutathione and the mRNA expression of glutathione peroxidase 1, leading to increased reactive oxygen species production. This study is the first to elucidate the mechanisms of IAA on TH synthesis in vitro. The mechanisms are associated with down-regulating the expression of genes related to TH synthesis, inhibiting iodine uptake, and inducing oxidative stress. These findings may improve future health risk assessment of IAA on thyroid in human.

Thiol Reactome: A Nontargeted Strategy to Precisely Identify Thiol Reactive Drinking Water Disinfection Byproducts.

The precise identification of predominant toxic disinfection byproducts (DBPs) from disinfected water is a longstanding challenge. We propose a new acellular analytical strategy, the 'Thiol Reactome', to identify thiol-reactive DBPs by employing a thiol probe and nontargeted mass spectrometry (MS) analysis. Disinfected/oxidized water samples had reduced cellular oxidative stress responses of 46 ± 23% in Nrf2 reporter cells when preincubated with glutathione (GSH). This supports thiol-reactive DBPs as the predominant drivers of oxidative stress. This method was benchmarked using seven classes of DBPs including haloacetonitriles, which preferentially reacted with GSH via substitution or addition depending on the number of halogens present. The method was then applied to chemically disinfected/oxidized waters, and 181 tentative DBP-GSH reaction products were detected. The formulas of 24 high abundance DBP-GSH adducts were predicted, among which nitrogenous-DBPs (11) and unsaturated carbonyls (4) were the predominant compound classes. Two major unsaturated carbonyl-GSH adducts, GSH-acrolein and GSH-acrylic acid, were confirmed by their authentic standards. These two adducts were unexpectedly formed from larger native DBPs when reacting with GSH. This study demonstrated the "Thiol Reactome" as an effective acellular assay to precisely identify and broadly capture toxic DBPs from water mixtures.

Novel insights into impacts of the “7.20” extreme rainstorm event on water supply security of Henan Province, China: Levels and health risks of tap water disinfection by-products

Spatial distributions, levels, and comprehensive assessments of post-flood tap water disinfection by-products (DBPs) were first studied in Henan Province after the “7.20” Extreme Rainstorm Event in 2021. DBPs levels and health risks in tap water were higher in areas flooded (waterlogged) by storm or upstream flood discharge (WA) and rainstorm-affected areas (RA) compared with other areas (OA), suggesting that extreme rainstorm and flooding events may somehow exacerbate DBPs contamination of tap water through disinfection. WA sites were characterized as contamination hotspots. The results revealed high haloacetic acids (HAAs) levels in WA (Avg: 57.79 μg·L−1) and RA (Avg: 32.63 μg·L−1) sites. Compared with normal period, DBPs-caused cancer risk increased by 3 times, exceeding the negligible risk level. Cancer risk came primarily from the ingestion of trihalomethanes (THMs) (>80%), children were the sensitive group. Those between 30 and 69 showed approximately 1.7 times higher disability-adjusted life yearsper person-yearthan other age groups. Apart from regulated DBPs, bromochloracetic acid (BCAA) and dibromoacetonitrile (DBAN) appear to be the main toxicity contributors in these samples. Our results provide a scientific basis for preventing and controlling health risks from tap water DBPs and for assessing the social benefits and burdens of emergency disinfection.

Removal and transformation of disinfection by-products in water during boiling treatment

Disinfection by-products (DBPs) remain an ongoing issue because of their widespread occurrence and toxicity. Boiling is the most popular household water treatment method and can effectively remove some DBPs. However, the transformation behavior of DBPs during boiling is still unclear, and the key contributors to toxicity have not been identified. In this study, the changes in the concentrations of DBPs in the single-DBP systems and the multi-DBP systems during boiling were monitored, and in-depth discussions on the removal and transformation of DBPs in both systems were carried out. The results showed that boiling was effective in removing volatile DBPs (over 90% for TCAL, TCAN, and DCAN, and over 60% for TCM), but ineffective for non-volatile DBPs (around 20% for TCAA and below 10% for DCAA and MCAA). By hydrolysis and decarboxylation, the transformation occurred among DBPs, i.e., 55% TCAL to TCM, followed by 23% DCAN to DCAA, 22% TCAN to TCAA, and 10% TCAA to TCM. The transformations were found to be significantly influenced by other co-existing DBPs. In multi-DBP systems, the transformations of DCAN to DCAA and TCAN to TCAA were both promoted, while the transformation of TCAN to TCAA was inhibited. Transformation and volatilization are the two processes responsible for DBP removal. Toxicity estimates indicated that boiling was effective in reducing the toxicity of DBPs and improving the safety of the water, despite the interconversion of DBPs in drinking water during boiling. This study emphasized the importance of studying the interconversion behaviors of DBPs in drinking water during boiling and provided practical information for end-use drinking water safety.

Polymorphisms of xenobiotic metabolism enzyme genes cyp2e1, gstm1, gstt1, ephx1 as biomarkers of sensitivity to exposure to water disinfection byproducts (using chloroform as an example)

Chloroform accumulation in the body and the increase in its steady-state concentrations in blood of exposed people have been established to be associated with polymorphisms of enzyme genes in a genotype involved in metabolism of water disinfection byproducts (A415G of EPHX1 gene, C1091T of CYP2E1 gene, zero mutations of GSTT1 and GSTM1 genes) (р &lt; 0.000001). These polymorphisms in a genotype correlate with higher chloroform levels in blood of people consuming chlorinated drinking water: by 43.8 % and higher for GSTM1 gene polymorphism; by 68.2 % and higher for GSTT1; by 80.4 % and higher for EPHX1 (р &lt; 0.01). EPHX1 genetic polymorphism makes chloroform accumulation much more probable (levels in blood ≥ Р75), which is the most pronounced when combined with GSTТ1 genetic polymorphism. The study results allow us to consider hetero- and homozygous polymorphic genotypes AG/GG for the EPHX1 gene, CT/TT for the CYP2E1 gene, and the null allele in the GSTT1 and GSTM1 genes as genetic predisposition factors for chloroform accumulation in the body. This increases the probability of health outcomes associated with chronic exposure to this disinfection byproduct. The A415G polymorphism of the EPHX1 gene and null alleles of GSTT1 gene, their combinations including the combination with the null allele of the GSTM1 gene and/or the C1091T polymorphism of the CYP2E1 gene can be used as the most informative biomarkers of sensitivity when assessing risks associated with exposure to trihalomethanes (chloroform) at levels not exceeding MPC in water.

Полиморфные варианты генов ферментов системы детоксикации ксенобиотиков CYP2E1, GSTM1, GSTT1, EPHX1 как биомаркеры чувствительности к экспозиции побочными продуктами водоподготовки (на примере хлороформа)

Chloroform accumulation in the body and the increase in its steady-state concentrations in blood of exposed people have been established to be associated with polymorphisms of enzyme genes in a genotype involved in metabolism of water disinfection byproducts (A415G of EPHX1 gene, C1091T of CYP2E1 gene, zero mutations of GSTT1 and GSTM1 genes) (р &lt; 0.000001). These polymorphisms in a genotype correlate with higher chloroform levels in blood of people consuming chlorinated drinking water: by 43.8 % and higher for GSTM1 gene polymorphism; by 68.2 % and higher for GSTT1; by 80.4 % and higher for EPHX1 (р &lt; 0.01). EPHX1 genetic polymorphism makes chloroform accumulation much more probable (levels in blood ≥ Р75), which is the most pronounced when combined with GSTТ1 genetic polymorphism. The study results allow us to consider hetero- and homozygous polymorphic genotypes AG/GG for the EPHX1 gene, CT/TT for the CYP2E1 gene, and the null allele in the GSTT1 and GSTM1 genes as genetic predisposition factors for chloroform accumulation in the body. This increases the probability of health outcomes associated with chronic exposure to this disinfection byproduct. The A415G polymorphism of the EPHX1 gene and null alleles of GSTT1 gene, their combinations including the combination with the null allele of the GSTM1 gene and/or the C1091T polymorphism of the CYP2E1 gene can be used as the most informative biomarkers of sensitivity when assessing risks associated with exposure to trihalomethanes (chloroform) at levels not exceeding MPC in water.

Investigation of the nephrotoxicity of 2,6-dichloro-1,4-benzoquinone disinfection by-product in mice through a 28-day toxicity test

In recent years, 2,6-dichloro-1,4-benzoquinone (DCBQ) has become an emerging water disinfection by-product and widely distributed in disinfected water. Although kidney is a potential target of DCBQ, a systematic study of the in vivo nephrotoxicity of DCBQ is rare. In this study, a 28-day oral toxicity test was used to assess the nephrotoxic effects of DCBQ on mice. And the potential mechanisms of nephrotoxicity induced by DCBQ were explored through inflammation, oxidative stress, apoptosis and gut microbiota. The results showed that the kidney indexes of mice were not altered in DCBQ-exposed group in comparison with the control group. The histopathological investigation revealed that DCBQ caused swollen of renal tube, destruction of the renal structure, and infiltration of inflammatory cell in kidney. DCBQ has induced oxidative damage in kidney, as the observation of the increase of the renal superoxide dismutase (SOD) and catalase (CAT) activity. Also, DCBQ has triggered the inflammatory response in kidney through the increased expression of IL-1β, NF-κB and iNOS. Moreover, DCBQ has activated the apoptosis pathway, as indicated by the increased mRNA expression of Caspase-3 and Caspase-9. We eventually found an association between gut microbiota and nephrotoxic variables, demonstrating the importance of gut-kidney axis in DCBQ toxicity. Our results suggested that exposure to DCBQ in disinfected water might be a risk factor for kidney and provided novel insights into the underlying mechanisms of DCBQ–induced kidney injury, contributing to better interpretation of the health impact of the environmentally emerging contaminant DCBQ.

Swimming pool water disinfection by-products profiles and association patterns

The aim of this work was to determine and study the concentration of different groups of disinfection by-products (DBPs): trihalomethanes, haloacetic acids, haloacetonitriles, haloacetones and combined chlorine (as an indicator of chloramine levels), in the water of 175 public swimming pools in Gipuzkoa (Basque Country, Spain). The study included chlorinated and brominated pools, indoor and outdoor, used for recreational and sports purposes, and filled with water from calcareous and siliceous soils. The most abundant were haloacetic acids, followed by trihalomethanes, with chlorinated or brominated forms predominating depending on whether the pools were disinfected by chlorination or bromination, respectively. All the 75th percentiles of DBPs were below the limits established by the European Chemical Agency (ECHA), although the maximum values of trihalomethanes exceeded them. The same was true for dichloroacetonitrile in chlorinated pools and dibromoacetonitrile in brominated pools. All families of DBPs showed positive associations with each other, all being significant except for combined chlorine. Their mean levels were higher in outdoor pools than in indoor pools, significantly so in all except combined chlorine. Recreational pools showed higher levels of haloacetic acids and combined chlorine than sports pools. The concentrations of the different groups of DBPs were higher in the pools than in the mains water that fed them. This increase, especially that of the haloacetonitriles, as well as the high concentrations of brominated forms in the pools disinfected by bromination, make it necessary to focus on their toxicological implication. The differences in the DBP profiles of the filling network water were not transferred to the pool water.

Methods and Software to Analyze Gene-Environment Interactions under a Case-Mother-Control-Mother Design with Partially Missing Child Genotype

Introduction: The case-mother-control-mother design allows to study fetal and maternal genetic factors together with environmental exposures on early life outcomes. Mendelian constraints and conditional independence between child genotype and environmental factors enabled semiparametric likelihood methods to estimate logistic models with greater efficiency than standard logistic regression. Difficulties in child genotype collection require methods handling missing child genotype. Methods: We review a stratified retrospective likelihood and two semiparametric likelihood approaches: a prospective one and a modified retrospective one, the latter either modeling the maternal genotype as a function of covariates or leaving their joint distribution unspecified (robust version). We also review software implementing these modeling alternatives, compare their statistical properties in a simulation study, and illustrate their application, focusing on gene-environment interactions and partially missing child genotype. Results: The robust retrospective likelihood provides generally unbiased estimates, with standard errors only slightly larger than when modeling maternal genotype based on exposure. The prospective likelihood encounters maximization problems. In the application to the association of small-for-gestational-age babies with CYP2E1 and drinking water disinfection by-products, the retrospective likelihood allowed a full array of covariates, while the prospective likelihood was limited to few covariates. Conclusion: We recommend the robust version of the modified retrospective likelihood.

СОДЕРЖАНИЕ ХЛОРОФОРМА В КРОВИ НАСЕЛЕНИЯ КАК БИОМАРКЕР ЭКСПОЗИЦИИ ПОБОЧНЫМИ ПРОДУКТАМИ ДЕЗ-ИНФЕКЦИИ ПИТЬЕВОЙ ВОДЫ

The modern methodological approaches, such as biomonitoring, could be used to improve the evidence base reliability and reduce uncertainty under chemicals health risk assessments and hygienic rationing. The aim of the study was to substantiate using the results of chloroform determination in human blood as a biomarker of exposure to drinking water disinfection byproducts under republican conditions. A gas chromatography-mass spectrometry meth-od for determination of chloroform in whole blood based on the use of acetoni-trile as solvent and additional extraction of chloroform from acetonitrile su-pernatant by small amounts of hexane was developed. Chloroform concentra-tions in the blood of population at the territories supplied with chlorinated drinking water are significantly higher than that of population at the territories supplied with water without chlorination (0.03–0.54 ng/ml, P95 0.27 ng/ml versus 0.00–0.37 ng/ml, P95 0.13 ng/ml respectively). A proposed linear de-pendence model enables to predict the chloroform blood level in the exposed population based on water concentrations and vice versa. We recommend the determination of chloroform in the whole blood of the population as an in-formative biomarker of cumulative exposure, reflecting real exposure scenarios for the preceding period of time, based on identified trends.

Synthesis of magnetic metal-organic framework for efficient adsorption of disinfection by-products in water

The disinfection of drinking water is an important treatment process for protecting consumers from potential waterborne infectious and parasitic pathogens. However, the disinfection process may introduce disinfection by-products (DBPs), which are harmful to human health. It is necessary to control the contents of DBPs and their precursors. In this study, we synthesized Fe3O4@SiO2@PDA@NH2-MIL-53(Fe) magnetic composites via layer-by-layer self-assembly method. This green and eco-friendly materials were thoroughly characterized and used to adsorb the highly toxic DBPs, 2,6-dichloro-1,4-benzoquinone (2,6-DCBQ) and its precursors, bisphenol A and phenol. The maximum adsorption quantity of Fe3O4@SiO2@PDA@NH2-MIL-53(Fe) was up to 109.3 mg g-1 for 2,6-DCBQ, 82.4 mg g-1 for bisphenol A, and 64.8 mg g-1 for phenol. The saturation magnetization value of Fe3O4@SiO2@PDA@NH2-MIL-53(Fe) was 39 emu g-1, which could be fast magnetic separated. In addition, the adsorption process was fitted into the pseudo-first-order adsorption model and Freundlich equation, in which π-π interaction, hydrogen bond and pore-filling were the main adsorption mechanisms. After 5 cycles, the adsorption rate of the as-synthesized magnetic composites is still more than 80%. Due to its fast and strong adsorption capability, excellent stability, and easy separation ability from water, Fe3O4@SiO2@PDA@NH2-MIL-53(Fe) magnetic composites have the potential to be a promising adsorption material for removing the disinfection by-products in future.