Bromodichloromethane Research Articles

Urinary brominated trihalomethanes among pregnant women: Correlation with lifestyle factors

According to the epidemiological evidences, long-term exposure to trihalomethanes containing bromine (Br-THMs) is associated with a variety of unpleasant consequences such as congenital malformations, preterm delivery, changing in gestational age, fetal growth and death, etc. The objective of current work was to monitor Br-THMs concentration in the pregnant women’s urine samples, to understand relationship between Br-THMs concentration and sociodemographic and water-use behavior as lifestyle factors. In this study, 118 third-trimester pregnant women, who cooperated in the Persian Birth Cohort, were studied. The concentration distribution of urine samples that were measured by a gas chromatography-mass spectrometer (GC-MC) had a positive deviation that was exposed to logarithmic transformation. By utilization of independent samples of t test, one-way ANOVA, Spearman ranks correlation coefficient, and multivariable linear regression, relationship between Br-THMs concentrations of urine with demographic and lifestyle factors was evaluated. According to the results, mean concentrations (standard deviation) of Br-THMs including bromodichloromethane (BDCM), dibromochloromethane (DBCM), and total bromoform (TBM) were recorded as 30.17 (40.80), 10.25 (11.37), 14.76 (27.17), and 4.96 (3.21) ng/L, respectively. The regression model predicted significant increase in relationship between time of washing clothes by hand and the concentration of Br-THMs. In the analysis of the relationship between using storage tanks as a source of drinking water and the contaminants, according to different statistical methods, inverse meaningful correlation relationship was found.

Mechanistic insight into co-metabolic dechlorination of hexachloro-1,3-butadiene in Dehalococcoides

Hexachloro-1,3-butadiene (HCBD) as one of emerging persistent organic pollutants (POPs) poses potential risk to human health and ecosystems. Organohalide-respiring bacteria (OHRB)-mediated reductive dehalogenation represents a promising strategy to remediate HCBD-contaminated sites. Nonetheless, information on the HCBD-dechlorinating OHRB and their dechlorination pathways remain unknown. In this study, both in vivo and in vitro experiments, as well as quantum chemical calculation, were employed to successfully identify and characterize the reductive dechlorination of HCBD by Dehalococcoides. Results showed that some Dehalococcoides extensively dechlorinated HCBD to (E)-1,2,3-tri-CBD via (E)-1,1,2,3,4-penta-CBD and (Z,E)-1,2,3,4-tetra-CBD in a co-metabolic way. Both qPCR and 16S rRNA gene amplicon sequencing analyses suggested that the HCBD-dechlorinating Dehalococcoides coupled their cell growth with dechlorination of perchloroethene (PCE), rather than HCBD. The in vivo and in vitro ATPase assays indicated ≥78.89% decrease in ATPase activity upon HCBD addition, which suggested HCBD inhibition on ATPase-mediated energy harvest and provided rationality on the Dehalococcoides-mediated co-metabolic dechlorination of HCBD. Interestingly, dehalogenation screening of organohalides with the HCBD-dechlorinating enrichment cultures showed that debromination of bromodichloromethane (BDCM) was active in the in vitro RDase assays but non-active in the in vivo experiments. Further in vitro assays of hydrogenase activity suggested that significant inhibition of BDCM on the hydrogenase activity could block electron derivation from H2 for consequent reduction of organohalides in the in vivo experiments. Therefore, our results provided unprecedented insight into metabolic, co-metabolic and RDase-active-only dehalogenation of varied organohalides by specific OHRB, which could guide future screening of OHRB for remediation of sites contaminated by HCBD and other POPs.

No interactions among three methane inhibitors on in vitro methane production

ABSTRACT Two experiments (Exps.) were conducted to examine the interactions among methane inhibitors on 24 h in vitro methane production using monensin (MON), fumaric acid (FA), and bromochloromethane (BCM). Donor goats and in vitro fermentation incubations were both treated with a 50:50 concentrate:forage diet (DM basis). In Exp. 1, MON (0, 60, or 120 mg/kg DM) and FA (0, 3.44, or 6.89 mM) were used to examine their two-way interaction, and no interaction was found on methane production (P > 0.05). In Exp. 2, MON (0 or 60 mg/kg DM), FA (0 or 6.89 mM), and BCM (0 or 3.08 μM) were used to examine their three-way interaction, and no three-way interaction was observed (P > 0.05). The correlation was significant under the MON and FA treatments without BCM (r = 0.55, P < 0.05), and under the MON, FA, and BCM treatments, the correlation was also significant (r = 0.59, P < 0.05). Collectively, no two- or three-way interactions were observed among MON, FA, and BCM. Regression analyses showed that MON, FA, and BCM were independent from each other, and the inhibitory effects of the three methane inhibitors on methanogenesis to a certain range are additive.

Insights into graphene oxide/ferrihydrite adsorption as pretreatment during ultrafiltration: Membrane fouling mitigation and disinfection by-product control

In this study, a novel adsorbent of graphene oxide (GO) incorporated ferrihydrite (FH) was fabricated and integrated with ultrafiltration (UF) to remove natural organic matter (NOM), the crucial cause of membrane fouling and major precursor of disinfection by-products (DBPs). Compared with FH and powdered activated carbon (PAC), GO/FH exhibited superior removal for high molecular weight (HMW) humic- and fulvic-like substances and low molecular weight (LMW) protein. The cake layer formed by GO/FH alleviated the deposition of NOM on membrane surface or inside membrane pores. Therefore, GO/FH reduced 89% and 95% total fouling resistance and irreversible membrane resistance, respectively, together with the lowest increment of transmembrane pressure. Pearson correlation analysis indicated that DOC, rather than specific ultraviolet absorbance (SUVA) and UV254, was significantly correlated to the formation of trihalomethanes (THMs) and haloacetic acids (HAAs) when SUVA was below 4 L/mg-C.m. Whilst the HMW NOM (1–20 kDa) was highly related to dibromochloromethane (DBCM) (r = 0.98–1), the LMW fraction (< 1 kDa) was correlated with dibromochloromethane (TCAA) and dichloroacetic acid (DCAA) (r = 0.88–0.98). Inspiringly, GO/FH-UF reduced 90% of carbonaceous DBPs, the concentrations of which well met the WHO Guidelines. In summary, GO/FH-UF substantially alleviated membrane fouling and dramatically reduced DBP formation potential.

Evaluation of Trihalomethane Formation Risk Analysis in Swimming Pools in Eskisehir, Turkey

Swimming pools are popular entertainment and sport areas that people often use. For this reason, it is crucial to determine the physicochemical properties and Trihalomethanes (THMs) concentrations of swimming pools and the effect of THMs on swimmer health. This study focuses on the physicochemical parameters and THM concentrations of six swimming pools in Eskisehir and the impacts of THMs on human health. Within the study context, physicochemical parameters were examined and swimming pool water standards of various countries and organizations were evaluated. The alkalinity, pH, temperature, hardness, and free chlorine values of the swimming pools were determined to compare with the current standards. Concentrations of chloroform (TCM), bromodichloromethane (BDCM), and dibromochloromethane (DBCM) were also determined in the collected samples. Concentrations were found to be in the range of 11.6-100.1 µg/l for BDCM, 151.5-366.4 µg/l for TCM, ND-6.95 µg/l for DBCM, and 172.1-380.7 µg/l for TTHM. From the results, it was determined that TTHM concentrations were above the limit values defined by WHO, while chloroform (except P1 and P5 pools), BDCM (except P3 pool), and DBCM concentrations were significantly below the limit values. TTHMs and chloroform concentrations were high in tap water using sodium hypochlorite as a disinfectant. BDCM and DBCM concentrations were high in pools where groundwater was used. Health risks of THMs in pools through ingestion and dermal absorption were also estimated for both women and men. In the interpretation of the result, it was also found that high concentrations of TTHMs increased the risk, and women’s ingestion-based risk values are slightly higher than men’s ingestion-based risk values. Fingerprints of THM formation in pool water are precursor parameters and it is of great importance to constantly control and take precautions. It has been observed that the use of groundwater as a water source and NaCl as a disinfectant significantly reduces THM formation in swimming pools. However, in order to reduce the BDCM and DBCM concentrations in the use of groundwater, it is recommended to measure the precursor bromide and establish the relevant limit values. The use of hypochlorite disinfectants in pools where tap water is used as a water source increases THM formation. For this reason, it is necessary to determine the amount of organic carbon as a precursor for pools using tap water as a water source and add it to the limit values. In addition, the use of calcium hypochlorite disinfectant instead of sodium hypochlorite reduces THM formation. Highlight Physicochemical properties and THMs concentrations of swimming pools and effects of trihalomethanes (THMs) on the health of swimmers. Physicochemical parameters and THM concentrations of six swimming pools were determined, and the effects of THMs’ on human health. Physicochemical parameters (alkalinity, pH, temperature, and hardness), chloroform (TCM), bromodichloromethane (BDCM), and dibromochloromethane (DBCM) were studied. As a result of the study, total THMs and TCM concentrations were high in pools where tap water, and sodium hypochlorite were used. BDCM and DBCM concentrations were high in pools where groundwater was used. High THM concentrations increase the risk, and at the same time, women’s ingestion-based risk values are slightly higher than men’s ingestion-based risk values.

Effect of elevated atmospheric CO2 concentration and temperature on volatile halogenated organic compound content in soils of Schima superba and Cunninghamia lanceolata seedlings.

Global changes caused by the increases of atmospheric CO2 concentration and temperature have important effects on soil biogeochemical processes. The synthesis and release of volatile halogenated organic compounds (VOXs) is an important pathway for soil to participate in the global material cycle and energy flow. In this study, Schima superba and Cunninghamia lanceolata seedlings in the southern subtropics were selected as the research objects. Four treatments, including control (CK), elevated CO2 concentration (EC), elevated temperature (ET) and elevated both factors (EC+ET) were set up. The effects of EC and ET on soil VOXs formation were studied by an open-top chamber system coupled with a purging and trapping gas chromatography/mass spectrometry. The results showed that VOXs content in the soil of S. superba seedlings was 0.065-0.252 ng·g-1, which was higher than that of C. lanceolata (0.038-0.136 ng·g-1). At the EC, ET and EC+ET treatments, VOXs contents were reduced in soils of both species. The effect of ET was the most significant, with the decrease rates of 74.2% and 72.1% in both soils, respectively. The change of VOXs content with increasing temperature mainly attributed to the changes of soil moisture and nitrogen content. The content of VOXs in the soils of S. superba seedlings decreased more than that of C. lanceolata under different treatments. In CK, EC, ET and EC+ET treatment, bromodichloromethane (BDCM) (27.5%, 36.7%, 32.9%, 32.6%) and tetrachloromethane (TCM) (9.0%, 16.8%, 22.7%, 15.8%) were the main VOXs in the soil of S. superba seedlings, respectively, while BDCM and dibromomethane (DBM) were the main VOXs in the soil of C. lanceolata seedlings. BDCM accounted for 31.9%, 38.2%, 40.9% and 37.2% of the VOXs content in each treatment, and DBM accounted for 17.9%, 16.5%, 19.2% and 16.0% of the VOXs content, respectively. Simulating elevated atmospheric CO2 concentration and temperature was conducive to more comprehensive reflection of the ecological effect of global climate change, and it could provide data support for improving the VOCs flux model.

Integration of fluorescence quenching correction into trihalomethane formation prediction models.

Despite there being numerous models of trihalomethane (THM) formation, they are limited by high estimation errors, which can be close to the regulatory limits for THMs, due to the fluorescence quenching effect. In this research, the estimation error for THM formation was reduced by correcting the quenching effect. The trihalomethane formation potential (THMFP) test was conducted in the presence of chlorine and bromine, individually and in mixtures. The THM precursors used in this study were protein (bovine serum albumin; BSA), amino acids (tryptophan and tyrosine), chlorine, bromine, and Suwannee River natural organic matter (SWNOM). BSA tended to form bromodichloromethane (BDCM) rather than trichloromethane (TCM) during chlorination in the presence of bromide (Br-). In contrast, SWNOM tended to form chlorinated THMs (TCM) rather than brominated THMs (BDCM and dibromochloromethane; DBCM), and no TBMs were formed in these processes. BSA with SWNOM decreased the formation of TCM due to the decrease in the amount of TCM precursor in SWNOM through binding with BSA. The concentration of each THM species was predicted from the fluorescence intensity of peak C, corrected fluorescence intensity of peak T, and Br- concentration. The use of humic-like and corrected protein-like fluorescence in the excitation-emission matrix model for predicting THM species reduced the prediction error. In this research, correction of the fluorescence quenching decreased the mean percentage estimation error for TCM, BDCM, and DBCM from 47%, 35%, and > 100% in classical approaches to 6.6%, 26.9%, and 2.0%, respectively. This study is expected to make contributions in reporting the relationship between the concentration of natural organic matter compositions and the formation of THM species.

Prenatal Exposure to Disinfection Byproducts and Intrauterine Growth in a Chinese Cohort.

Disinfection byproduct (DBP) exposure has been associated with birth size, pregnancy oxidative stress, and other adverse perinatal outcomes. However, little is known about the potential effect of prenatal DBP exposure on intrauterine growth. The present study included 1516 pregnant women from the Xiaogan Disinfection By-Products (XGDBP) birth cohort who were measured for four blood trihalomethanes [i.e., chloroform (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), and bromoform (TBM)] and two urinary haloacetic acids [i.e., dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA)] across pregnancy trimesters. Second- and third-trimester fetal ultrasound measures of the abdominal circumference (AC), head circumference, biparietal diameter, femur length, and estimated fetal weight and birth weight were converted into z-scores. After adjusting for potential confounders, linear mixed models showed a decreasing AC z-score across tertiles of blood brominated THM (Br-THMs, the sum of BDCM, DBCM, and TBM) and total THM (THM4, the sum of Br-THMs and TCM) concentrations (both p for trend <0.01). We also observed a decreasing AC z-score across categories of blood TBM during pregnancy trimesters (p for trend = 0.03). Urinary haloacetic acids were unrelated to fetal growth parameters. In summary, prenatal exposure to THMs, particularly during the first trimester, was associated with reduced fetal abdominal circumference.

Total organic halogen in two drinking water supply systems: Occurrence, variations, and relationship with trihalomethanes

The spatiotemporal presence of overall disinfection by-products (DBPs) in two full-scale drinking water supply systems (DWSSs) were investigated using quantification of total organic halogen (TOX). The relationships of TOX with water quality parameters (especially the most regulated DBPs, trihalomethanes (THMs)) were also evaluated. The TOX levels ranged between 2.6 and 70.3 μg Cl/L and between 46.6 and 205.9 μg Cl/L in raw water and distribution water, respectively. The TOX concentration in water increased by an average of nine times after water treatment and varied slightly during distribution, suggesting that TOX in drinking water was mainly formed during chlorination disinfection rather than distribution. No clear seasonality in TOX level was observed. Positive correlations were found between raw water dissolved organic carbon (DOC) with an increase in TOX in treated water and between DOC level with TOX content in distributed water, emphasizing a key role of organics in TOX formation. Chloroform (TCM) was the dominant THM, followed by bromodichloromethane (BDCM) in the drinking water, and the levels of the other two measured THMs (dibromochloromethane and bromoform) were negligible. THM2 (sum of TCM and BDCM) made up average of 18% of the TOX, and was weakly correlated with TOX content (rs = 0.321; P < 0.05), implying that THM is not a suitable surrogate measure for TOX in drinking water. This study provides basic data on the occurrence and variation of TOX within conventional DWSSs and highlights the importance of using TOX measurements to obtain more accurate information about DBP occurrence, for exposure assessment and regulatory determination.

Association of blood trihalomethane concentrations with asthma in US adolescents: nationally representative cross-sectional study.

BackgroundPopulation studies show that the use of swimming pools is associated with the risk of asthma and allergic diseases among children. Our objective was to explore the associations between blood trihalomethane (THM) concentrations and asthma among US adolescents, and assess to what extent the association is modified by active tobacco smoke exposure.MethodsWe included 2359 adolescents aged 12–19 years with measured blood concentrations of chloroform (trichloromethane (TCM)), bromodichloromethane (BDCM), dibromochloromethane (DBCM) and bromoform (tribromomethane (TBM)) from the National Health and Nutrition Examination Survey 2005–2012. Logistic regression models were fitted to assess the odds ratios for the association of blood THM concentrations (three or four categories) with the risk of self-reported current and ever (lifetime) asthma.ResultsBlood DBCM concentrations were associated with a higher risk of ever asthma among all adolescents (OR 1.54 (95% CI 1.07–2.21), comparing the extreme exposure categories). The relationship was stronger among adolescents exposed to tobacco smoke (OR 3.96 (95% CI 1.89–8.30), comparing the extreme exposure categories). We also found positive relationships between blood brominated THM concentrations (sum of BDCM, DBCM and TBM) and risk of ever asthma and between blood DBCM and brominated THM concentrations and risk of current asthma among adolescents with tobacco smoke exposure. The relative excess risk of ever asthma due to the interaction between high blood DBCM and brominated THM concentrations and tobacco smoke exposure was 1.87 (95% CI 0.30–3.43) and 0.78 (95% CI 0.07–1.49), respectively.ConclusionsExposure to THMs is associated with a higher risk of asthma in adolescents, particularly among those exposed to tobacco smoke.

Relationship between Blood Trihalomethane Concentrations and Serum Thyroid Function Measures in U.S. Adults.

Toxicological studies show that exposure to disinfection byproducts, including trihalomethanes (THMs), negatively affects thyroid function; however, few epidemiological studies have explored this link. This study included 2233 adults (ages ≥20 years) from the 2007-2008 National Health and Nutrition Examination Survey (NHANES) who were measured for blood THM concentrations [chloroform (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), or bromoform (TBM)] and serum thyroid function biomarkers [thyroid-stimulating hormone, free thyroxine (FT4), total thyroxine (TT4), free triiodothyronine (FT3), total triiodothyronine (TT3), thyroid peroxidase antibody (TPOAb), and thyroglobulin antibody (TgAb)]. Multivariable linear regression models showed positive associations between blood TCM, BDCM, and total THMs (the sum of all four THMs) concentrations and serum FT4, whereas inverse associations were found between blood DBCM and total brominated THM (Br-THM; the sum of BDCM, DBCM, and TBM) concentrations and serum TT3 (all p < 0.05). Besides, positive associations were observed between blood TCM concentrations and FT4/FT3 ratio, between BDCM, DBCM, and Br-THM concentrations and TT4/TT3 ratio, and between DBCM and Br-THM concentrations and FT3/TT3 ratio (all p < 0.05). Blood THM concentrations were unrelated to the serum levels of thyroid autoantibodies TgAb or TPOAb. In summary, exposure to THMs was associated with altered serum biomarkers of thyroid function but not with thyroid autoimmunity among U.S. adults.

Trihalomethanes in exhaled air, indoor air and water: A parallel design trial in chlorine and ozone-chlorine disinfected swimming pools

We measured the concentrations of Trihalomethanes (THMs), Chloroform (TCM), Bromodichloromethane (BDCM), Dibromochloromethane (DBCM) and Bromoform (TBM), in water, indoor air and exhaled air before and after using chlorine and ozone-chlorine disinfected swimming pools from September 2020 to January 2021. Two parallel panels of adult subjects swam for 60 min in a chlorine and an ozone-chlorine indoor swimming pool. The concentration of total THMs (tTHMs) in water samples of chlorine and ozone-chlorine swimming pools were in the ranges of 170.8–192.5 μg/L and 161.3–180.4 μg/L, respectively which exceeded the WHO guideline value. High levels of THMs were found in indoor air at the height of 10 cm compared to 150 cm above water surface. We found a statistically significant correlation between the concentration of THMs in water and indoor air samples. The results showed that the levels of all detected THMs in participant’ exhaled air after 60 min swimming were 11–13 times higher than those of before exposure. A statistically significant linear correlation was observed between THMs levels in the exhaled air and indoor air at the height of 10 cm above the water surface, but not with the levels at the height of 150 cm. We also found that the levels of THMs in exhaled air were associated with the energy expenditure, swimming distance and time, but not correlated with BMI and skin area.

Association of blood trihalomethane concentrations with asthma among U.S. Children: NHANES 2005-2012

BACKGROUND AND AIM: Population studies show that use of swimming pools is associated with risk of asthma and allergic diseases among children. However, few studies have examined exposure to disinfection by-products (DBP) from water chlorination with risk of asthma. To explore the associations between blood trihalomethane (THM) concentrations (a biomarker of DBP) and asthma among U.S. children and assess to what extent the association is modified by tobacco smoke exposure. METHODS: We included 2,359 children aged 12-19 years with measured blood concentrations of four THMs at baseline: chloroform (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), and bromoform (TBM) from the National Health and Nutrition Examination Surveys 2005-2012. Logistic regression models were fitted to assess the odds ratios (ORs) and 95% confidence intervals (CIs) for the association of THM concentrations (three or four categories) with the risk of self-reported lifetime and curent asthma. RESULTS:After adjusting for potential confounders, blood DBCM concentration was associated with a greater risk of ever asthma among all children (OR=1.54; 95% CI: 1.07, 2.21, comparing the extreme exposure categories). The relation was stronger among children exposed to tobacco smoke (OR=3.96; 95% CI: 1.89, 8.30, comparing the extreme exposure categories). We also found positive relationships between Br-THMs and risk of ever asthma (OR=3.28; 95% CI: 1.43, 7.53, comparing the extreme quartiles of exposure) and between DBCM and Br-THMs and risk of current asthma among children with tobacco smoke exposure (OR=3.72; 95% CI: 1.40, 9.89 and 3.79; 95% CI: 1.22, 11.79, resperctively, comparing the extreme exposure categories). CONCLUSIONS:Our findings provide novel evidence that exposure to disinfection by-products is associated with a greater risk of asthma in children, particularly among those exposed to tobacco smoke. KEYWORDS: Biomarkers of exposure, Water quality, Respiratory outcomes, Asthma, Environmental epidemiology

Association of Blood Trihalomethane Concentrations with Risk of All-Cause and Cause-Specific Mortality in U.S. Adults: A Prospective Cohort Study.

Water chlorination can lead to the formation of disinfection byproducts, including trihalomethanes (THMs). However, few epidemiologic studies have explored associations between THM exposure and mortality. This study included 6720 adults aged ≥40 years from the National Health and Nutrition Examination Survey 1999-2012 who had blood THM concentrations quantified. A higher risk of all-cause mortality was found across increasing quartile concentrations of blood chloroform (TCM) and total THMs (TTHMs; sum of all four THMs) (both p for trend = 0.02). Adults in the highest quartile of TCM and TTHM concentrations had hazard ratios (HRs) of 1.35 (95% confidence intervals: 1.05-1.74) and 1.37 (1.05-1.79), respectively, for all-cause mortality, compared with adults in the lowest quartile. When cause-specific mortality was evaluated, a positive relationship was found between blood bromodichloromethane (BDCM), dibromochloromethane (DBCM), bromoform (TBM), total brominated THMs (Br-THMs; sum of BDCM, DBCM, and TBM), and TTHM concentrations and risk of cancer death and between blood TCM and TTHMs and risk of other cause (noncancer/nonheart disease) mortality. Our findings suggest that higher exposure to Br-THMs was associated with increased cancer mortality risk, whereas TCM was associated with a greater risk of noncancer/nonheart disease mortality.

Radial basis function artificial neural network (RBF ANN) as well as the hybrid method of RBF ANN and grey relational analysis able to well predict trihalomethanes levels in tap water

Many models have been developed in previous studies for predicting the formation of disinfection by-products (DBPs) in drinking water. However, most of them were linear or log-linear regression models, and generated based on simulated disinfection of source water or treated water in a laboratory other than real tap water, which shows low application potential in practice. In this study, a radial basis function artificial neural network (RBF ANN) as well as the hybrid method of RBF ANN and grey relational analysis (GRA) was proposed to predict trihalomethanes (THMs) levels in real distribution systems. A total of 64 sets of data including THMs levels (trichloromethane (TCM), bromodichloromethane (BDCM) and total-THMs (T-THMs)) and 8 water quality parameters (temperature, pH, UV absorbance at 254 (UVA254), dissolved organic carbon, bromide, residual free chlorine, nitrite and ammonia) were used to train and verify the proposed model. As compared to linear and log-linear regression models (rp = 0.254–0.659; N25 = 46–78%), RBF ANNs for THMs (TCM, BDCM and T-THMs) prediction consistently show higher regression coefficients (rp = 0.760–0.925) and prediction accuracy (N25 = 92–98%), which indicates the high capability of RBF ANN to learn the complex non-linear relationships involved THMs formation. Further analysis shows that RBF ANNs using fewer water quality parameters based on GRA still make excellent performance in THMs prediction (rp = 0.760–0.946; N25 = 92–98%). This result demonstrates that GRA can be an effective technique to facilitate the generation of sound RBF ANN models with fewer factors.

Comparison of in vivo derived and scaled in vitro metabolic rate constants for several volatile organic compounds (VOCs)

Metabolic rate parameters estimation using in vitro data is necessary due to numbers of chemicals for which data are needed, trend towards minimizing laboratory animal use, and limited opportunity to collect data in human subjects. We evaluated how well metabolic rate parameters derived from in vitro data predict overall in vivo metabolism for a set of environmental chemicals for which well validated and established methods exist. We compared values of VmaxC derived from in vivo vapor uptake studies with estimates of VmaxC scaled up from in vitro hepatic microsomal metabolism studies for VOCs for which data were available in male F344 rats. For 6 of 7 VOCs, differences between the in vivo and scaled up in vitro VmaxC estimates were less than 2.6-fold. For bromodichloromethane (BDCM), the in vivo derived VmaxC was approximately 4.4-fold higher than the in vitro derived and scaled up VmaxC. The more rapid rate of BDCM metabolism estimated based in vivo studies suggests other factors such as extrahepatic metabolism, binding or other non-specific losses making a significant contribution to overall clearance. Systematic and reliable utilization of scaled up in vitro biotransformation rate parameters in PBPK models will require development of methods to predict cases in which extrahepatic metabolism and binding as well as other factors are likely to be significant contributors.

Distribution Characteristics of Disinfection By-Products and the Effects of Booster Chlorination in Long-Distance Water Supply Systems

It is difficult for waterworks that add chlorine into finished water once to maintain sufficient residual chlorine at unfavorable points of the pipe network that supply water for large areas of coverage. Therefore, booster chlorination was employed for a long-distance water distribution system. The study was performed in H City with a water supply system serving about 400 km2 of downtown and rural areas. The purpose of this work is to obtain the distribution characteristics of disinfection by-products (DBPs) in the booster chlorination disinfection pipe network through uniformly distributed sampling analysis. The results showed that detected DBPs include trichloromethane (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM) and tribromomethane (TBM), dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), dichloroacetonitrile (DCAN), bromochloroacetonitrile (BCAN), and trichloronitromethane (TCNM). The concentrations of the regulated DBPs were found to be lower than the standard limits specified in the Sanitary Standard for Drinking Water (GB5749-2006). Before booster chlorination, the average concentrations of the DBPs mentioned (expressed as mean±deviation) were (8.08±3.34), (9.77±2.91), (7.38±4.82), (2.65±2.02), (2.95±3.26), (6.02±6.06), (3.13±2.48), (1.61±2.05), and (0.15±0.10) μg·L-1, while afterwards, they were increased to (10.30±4.55), (11.73±3.60), (8.23±5.22), (2.95±2.45), (3.29±3.60), (8.15±7.58), (3.31±2.61), (1.33±2.04), and (0.12±0.06) μg·L-1, respectively. Trihalomethanes (THMs) and haloacetic acids (HAAs) increased by 6.32%-26.60% and 5.32%-42.71%, respectively, after booster chlorination. In addition, raw water quality and seasonal changes had a certain impact on the occurrence of DBPs. The levels of DBPs in summer were generally higher than those in spring or autumn. According to the analysis of DBP formation potential of source water, finished water, and tap water, it was found that the risk of DBPs exceeding the standard limit may exist in the water supply system of H City; therefore, further optimization of the treatment process should be considered to ensure water quality.

Blood and urinary biomarkers of prenatal exposure to disinfection byproducts and oxidative stress: A repeated measurement analysis

BackgroundToxicological studies have demonstrated that disinfection by-products (DBPs) can induce oxidative stress, a proposed mechanism that is relevant to adverse birth outcomes. ObjectiveTo examine the associations of blood trihalomethanes (THMs) and urinary haloacetic acids (HAAs) with urinary biomarkers of oxidative stress among pregnant women. MethodsFrom 2015 to 2017, a total of 4150 blood and 4232 urine samples were collected from 1748 Chinese women during pregnancy. We determined concentrations of 4 blood THMs [chloroform (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), and bromoform (TBM)] and 2 urinary HAAs [dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA)]. The summary measures of exposure for brominated THMs (Br-THMs; a molar sum of BDCM, DBCM, and TBM) and total THMs (TTHMs; a molar sum of TCM and Br-THMs) were also calculated. Associations of categorical (i.e., tertiles) and continuous measures of DBPs with urinary concentrations of oxidative stress (OS) biomarkers, 8-hydroxy-2-deoxyguanosine (8-OHdG), 4-hydroxy-2-nonenal-mercapturic acid (HNE-MA), and 8-iso-prostaglandin F2α (8-isoPGF2α), were assessed using linear mixed regression models. ResultsAfter adjusting for relevant confounding factors, we observed positive dose-response relationships between blood Br-THM tertiles and urinary HNE-MA (P for trend < 0.001). We also found positive associations between tertiles of blood TCM and TTHMs and urinary 8-OHdG and HNE-MA (all P for trend < 0.05). Urinary HAAs were also positively associated with 8-OHdG, HNE-MA, and 8-isoPGF2α in a dose-response manner (all P for trend < 0.001). These associations were further confirmed when we modeled DBP exposures as continuous variables in linear mixed regression models, as well as in penalized regression splines based on generalized additive mixed models. ConclusionsExposure to DBPs during pregnancy may increase maternal OS status.

Total Trihalomethane Levels in Major Watersheds across the United States

Trihalomethanes, such as chloroform, bromoform, dibromo(chloro)methane, and bromo(dichloro)methane, are present in the major watersheds across the United States. These chemicals play an important role in the development of cancer, have adverse reproductive outcomes, and were found to be present above the threshold established by the Environmental Protection Agency. To understand the impact of socioeconomic background on the quality of water and possible disparities, we have analyzed the levels of total trihalomethanes in the metropolitan areas in the major watersheds across the United States, in 2018, as they correlated to average household incomes. Our study found that Arkansas, Nevada, and Rhode Island demonstrated higher than federally mandated levels of total trihalomethanes in their watersheds. The median annual household and per capita incomes of the three states (Arkansas, Nevada, and Rhode Island) were lower than the national average. In addition, Delaware, New Hampshire, and Wisconsin, which had higher median income levels, demonstrated the lowest total trihalomethane levels across the United States.

Disinfection By-products and the Relevant Health Risk in the Water Supply System in H City of Zhejiang Province

The occurrence of 18 types of disinfection by-products (DBPs) in two waterworks and the corresponding water supply networks of H City in Zhejiang Province was determined by gas chromatography coupled with electron capture detector (GC-ECD). The correlation between DBPs and organic precursors, and health risks caused by DBPs, were discussed. Results showed that the disinfection by-products detected in drinking water in H City mainly include trihalomethanes (THMs), haloacetic acid (HAAs), haloacetonitrile (HANs) and trichloronitromethane (HNMs), with highest concentrations of THMs followed by HAAs. In the finish water of CX Waterworks and tap water supplied by CX Water works, concentrations of THMs ranged from 7.70 to 32.73μg·L-1and 9.00 to 51.42μg·L-1, respectively, and those of HAAs 3.05 to 21.30μg·L-1 and 6.00 to 26.79μg·L-1, respectively. The THMs in finished water and tap water of TH Waterworks were in the range 8.65-38.76μg·L-1 and 12.09-42.04μg·L-1, respectively, and those of HAAs were 2.42-14.79μg·L-1 and 2.80-33.40μg·L-1, respectively. The DBPs in the finished and tap water of the two waterworks were at lower levels than the limitations regulated by the Sanitary Standard for Drinking Water (GB 5749-2006). The index of dissolved organic carbon (DOC) and UV254 were adopted to describe the organic compounds, and it was found that trichloromethane (TCM) was significantly negatively correlated with DOC and UV254in tap water. Based on the EPA recommended health risk assessment model, the carcinogenic and non-carcinogenic risks of chlorine disinfection by-products in the oral intake route were calculated. It was found that the carcinogenic risks caused by the disinfection by-products in the finished water and tap water of H City were 5.94×10-6-4.76×10-5 and 5.94×10-6-5.56×10-5, respectively, while the non-carcinogenic risks were 0.91×10-2-4.20×10-2 and 1.26×10-2-4.72×10-2, respectively. The carcinogenic risk is mainly from THMs:bromodichloromethane (BDCM) contributes the highest cancer risk, and the non-carcinogenic risk is mainly from TCM.