Use of urinary trichloroacetic acid as an exposure biomarker of disinfection by-products in cancer studies

Exposure to haloacetic acid disinfection by-products and male steroid hormones: An epidemiological and in vitro study

Haloacetic acids (HAAs) are ubiquitous in drinking water and have been associated with impaired male reproductive health. However, epidemiological evidence exploring the associations between HAA exposure and reproductive hormones among males is scarce. In the current study, the urinary concentrations of dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA), the internal exposure markers of HAAs, as well as sex hormones (testosterone [T], progesterone [P], and estradiol [E2]) were measured among 449 Chinese men. Moreover, in vitro experiments, designed to simulate the real-world scenarios of human exposure, were conducted to assess testosterone synthesis in the Leydig cell line MLTC-1 and testosterone metabolism in the hepatic cell line HepG2 in response to low-dose HAA exposure. The DCAA and TCAA urinary concentrations were found to be positively associated with urinary T, P, and E2 levels (all p < 0.001), but negatively associated with the ratio of urinary T to E2 (p < 0.05). Combined with in vitro experiments, the results suggest that environmentally-relevant doses of HAA stimulate sex hormone synthesis and steroidogenesis pathway gene expression in MLTC-1 cells. In addition, the inhibition of the key gene CYP3A4 involved in the testosterone phase Ⅰ catabolism, and induction of the gene UGT2B15 involved in testosterone phase Ⅱ glucuronide conjugation metabolism along with the ATP-binding cassette (ABC) transport genes (ABCC4 and ABCG2) in HepG2 cells could play a role in elevation of urinary hormone excretion upon low-dose exposure to HAAs. Our novel findings highlight that exposure to HAAs at environmentally-relevant concentrations is associated with increased synthesis and excretion of sex hormones in males, which potentially provides an alternative approach involving urinary hormones for the noninvasive evaluation of male reproductive health following exposure to DBPs.

Urinary biomarkers of drinking-water disinfection byproducts in relation to diminished ovarian reserve risk: A case-control study from the TREE cohort

BACKGROUND

Disinfection byproducts (DBPs) as ovarian toxicants have been documented in toxicological studies. However, no human studies have explored the effects of exposure to DBPs on diminished ovarian reserve (DOR).

OBJECTIVE

To assess whether urinary biomarkers of exposure to drinking-water DBPs were associated with DOR risk.

METHODS

A total of 311 women undergoing assisted reproductive technology were diagnosed with DOR in the Tongji Reproductive and Environmental (TREE) cohort from December 2018 to August 2021. The cases were matched to the controls with normal ovarian reserve function by age in a ratio of 1:1. Urinary trichloroacetic acid (TCAA) and dichloroacetic acid (DCAA) were quantified as biomarkers of drinking-water DBP exposures. The conditional logistic regression and restricted cubic spline (RCS) were used to explore urinary biomarkers of drinking-water DBP exposures in associations with the risk of DOR.

RESULTS

Elevated urinary DCAA levels were associated with higher DOR risk [adjusted odds ratio (OR) = 1.87; 95 % confidence interval (CI): 1.16, 3.03 for the highest vs. lowest quartiles; P for trend = 0.016]. The association was confirmed in the RCS model, with a linear dose-response curve (P for overall association = 0.029 and P for non-linear association = 0.708). The subgroup analysis by age and body mass index (BMI) showed that urinary DCAA in association with DOR risk was observed among women ≥35 years old and leaner women (BMI < 24 kg/m2), but the group differences were not statistically significant. Moreover, a U-shaped dose-response curve between urinary TCAA and DOR risk was estimated in the RCS model (P for overall association = 0.011 and P for non-linear association = 0.004).

CONCLUSIONS

Exposure to drinking-water DBPs may contribute to the risk of DOR among women undergoing assisted reproductive technology.

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.

Insights to estimate exposure to regulated and non-regulated disinfection by-products in drinking water

BACKGROUND

Knowledge about human exposure and health effects associated with non-routinely monitored disinfection by-products (DBPs) in drinking water is sparse.

OBJECTIVE

To provide insights to estimate exposure to regulated and non-regulated DBPs in drinking water.

METHODS

We collected tap water from homes (N = 42), bottled water (N = 10), filtered tap water with domestic activated carbon jars (N = 6) and reverse osmosis (N = 5), and urine (N = 39) samples of participants from Barcelona, Spain. We analyzed 11 haloacetic acids (HAAs), 4 trihalomethanes (THMs), 4 haloacetonitriles (HANs), 2 haloketones, chlorate, chlorite, and trichloronitromethane in water and HAAs in urine samples. Personal information on water intake and socio-demographics was ascertained in the study population (N = 39) through questionnaires. Statistical models were developed based on THMs as explanatory variables using multivariate linear regression and machine learning techniques to predict non-regulated DBPs.

RESULTS

Chlorate, THMs, HAAs, and HANs were quantified in 98-100% tap water samples with median concentration of 214, 42, 18, and 3.2 μg/L, respectively. Multivariate linear regression models had similar or higher goodness of fit (R2) compared to machine learning models. Multivariate linear models for dichloro-, trichloro-, and bromodichloroacetic acid, dichloroacetonitrile, bromochloroacetonitrile, dibromoacetonitrile, trichloropropnanone, and chlorite showed good predictive ability (R2 = 0.8-0.9) as 80-90% of total variance could be explained by THM concentrations. Activated carbon filters reduced DBP concentrations to a variable extent (27-80%), and reverse osmosis reduced DBP concentrations ≥98%. Only chlorate was detected in bottled water samples (N = 3), with median = 13.0 µg/L. Creatinine-adjusted trichloroacetic acid was the most frequently detected HAA in urine samples (69.2%), and moderately correlated with estimated drinking water intake (r = 0.48).

SIGNIFICANCE

Findings provide valuable insights for DBP exposure assessment in epidemiological studies. Validation of predictive models in a larger number of samples and replication in different settings is warranted.

IMPACT STATEMENT

Our study focused on assessing and describing the occurrence of several classes of DBPs in drinking water and developing exposure models of good predictive ability for non-regulated DBPs.

Exposure to disinfection by-products and reproductive hormones among women: Results from the Tongji Reproductive and Environmental (TREE) study

BACKGROUND

Disinfection by-products (DBPs) have been shown to impair female reproductive function. However, epidemiological evidence on reproductive hormones is scarce.

OBJECTIVE

To investigate the associations between DBP exposures and reproductive hormones among women undergoing assisted reproductive technology.

METHODS

We included 725 women from the Tongji Reproductive and Environmental (TREE) Study, an ongoing cohort conducted in Wuhan, China during December 2018 and January 2020. Urine samples collected at recruitment were quantified for dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) as biomarkers of DBP exposures. At day 2-5 of menstruation, serum reproductive hormones including luteinizing hormone (LH), estradiol (E₂), total testosterone (T), progesterone (PRGE), and prolactin (PRL) were determined. Multivariate linear regression models were performed to assess the associations of urinary DCAA and TCAA concentrations with reproductive hormone levels. Dose-response relationships were investigated using natural cubic spline (NCS) and restricted cubic spline (RCS) models.

RESULTS

After adjusting for relevant confounders, we observed that higher urinary DCAA levels were associated with increased serum PRGE (9.2%; 95% CI: -0.55%, 19.8% for the highest vs. lowest tertile; P for trend = 0.06). Based on NCS models, we observed U-shaped associations of urinary DCAA with serum PRGE and PRL; each ln-unit increment in urinary DCAA concentrations above 3.61 μg/L and 6.30 μg/L was associated with 18.9% (95% CI: 4.8%, 34.7%) and 23.3% (95% CI: -0.92%, 53.5%) increase in serum PRGE and PRL, respectively. The U-shaped associations were further confirmed in RCS models (P for overall association ≤0.01 and P for non-linear associations ≤0.04). We did not observe evidence of associations between urinary TCAA and reproductive hormones.

CONCLUSION

Urinary DCAA but not TCAA was associated with altered serum PRGE and PRL levels among women undergoing assisted reproductive technology.

High-Performance Trichloroacetic Acid Sensor Based on the Intramolecular Hydrogen Bond Formation and Disruption of a Specially Designed Fluorescent o-Carborane Derivative in the Film State

Discriminative and sensitive detection of environmentally important and health-related trichloroacetic acid (TCA) suffers from various problems such as bulky instruments and time-consuming operation as well as complex sample processing. Herein, we present a rapid, sensitive, and specific method for the detection of gaseous TCA using a fluorescent single-molecule array. An o-carborane-based benzothiazole derivative (CB-BT-OCH₃) with specific fluorescence properties was specifically designed and utilized to fabricate a film-based single-molecule array. It was revealed that the fluorescent film is photochemically stable and extremely sensitive to TCA vapor, depicting an observable fluorescence color change from green to blue. The experimental detection limit is 0.2 ppm, which is lower than the safety limit (1 ppm) required by the threshold limit values and biological exposure indices. In addition, the film could show detectable intensity change within 0.2 s. On the basis of multiple signal responses, a conceptual two-channel-based fluorescent TCA sensor was developed. Importantly, the proposed conceptual sensor paves a new route to the development of specific fluorescent film-based sensor arrays with a single fluorophore as sensing units.

Associations of urinary dichloroacetic acid and trichloroacetic acid exposure with platelet indices: Exploring the mediating role of blood pressure in the general population

Human exposure to drinking water disinfection by-products (DBPs) is potentially linked to high blood pressure (BP), which may be associated with abnormal platelet activation. This study investigated whether the relationship between DBP exposure with platelet change was mediated by BP. DBP biomarkers, such as urinary dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA), BP and platelet indices from 505 adults from a hospital in Shijiazhuang, China were measured. The cross-sectional associations among DCAA and TCAA exposure, BP and platelet indices were explored through multivariable linear regressions, and the mediation effect of BP was evaluated using the Sobel-Goodman test. We observed that DCAA and TCAA were positively associated with systolic BP (all p for trends < 0.01), which was positively associated with platelet count (PLC) (p for trend < 0.05). Mediation analysis indicated that systolic BP fully mediated the associations of DCAA and TCAA with PLC. When BP was controlled, a previously inverse significant relation between DCAA and platelet distribution width (PDW) remained significant (p < 0.05). Obtained results suggested that exposure to DCAA may contribute to decreased PDW in humans. Systolic BP is a possible mediator of the association between DCAA exposure and PLC. TCAA may indirectly positively affect PLC by increasing systolic BP.

The role of residential history in cancer research: A scoping review

The role of residential history in cancer prevention, diagnosis, treatment, and survivorship is garnering increasing attention in cancer research. To our knowledge, there is no comprehensive synthesis of the current state of knowledge in the field. We reviewed the extant literature on this topic and conducted a scoping analysis to examine two main research questions: (a) To what degree, and how, have researchers accounted for residential history/mobility in cancer research? and (b) What are the gaps in the literature based on a knowledge synthesis using scoping review and concept mapping? To answer these questions, this scoping analysis focuses on how researchers compile, analyze and discuss residential history/mobility in studies on cancer. The study is focused on peer-reviewed articles from 6 different datasets (PubMed, Cinahl, Scopus, Web of Science and JSTOR, ERIC) from 1990 to August 2020. The review captured 1951 results in total, which was scoped to 281 relevant peer-reviewed journal articles. First, we examined these articles based on cancer continuum, cancer type and the main theme. Second, we identified 21 main themes and an additional 16 sub-themes in the pool of the selected articles. We utilized concept mapping to provide a conceptual framework and to highlight the underlying socioecological assumptions and paradigms. Results show that cancer research incorporating residential histories is primarily focused on incidence and estimating cumulative exposure, with little consideration across the cancer continuum. Additionally, our review suggests that although the social environment plays an important role across the cancer continuum, a small number of articles were focused on such factors and this area remains relatively unexplored. Additionally, the expansion of interdisciplinary research on residential mobility before and after cancer diagnosis will enhance understanding of the role of environmental and socioeconomic characteristics and exposures on cancer continuum.

Effects of exposure to water disinfection by-products in a swimming pool: A metabolome-wide association study

BACKGROUND

Exposure to disinfection by-products (DBPs) in drinking water and chlorinated swimming pools are associated with adverse health outcomes, but biological mechanisms remain poorly understood.

OBJECTIVES

Evaluate short-term changes in metabolic profiles in response to DBP exposure while swimming in a chlorinated pool.

MATERIALS AND METHODS

The PISCINA-II study (EXPOsOMICS project) includes 60 volunteers swimming 40min in an indoor pool. Levels of most common DBPs were measured in water and in exhaled breath before and after swimming. Blood samples, collected before and 2h after swimming, were used for metabolic profiling by liquid-chromatography coupled to high-resolution mass-spectrometry. Metabolome-wide association between DBP exposures and each metabolic feature was evaluated using multivariate normal (MVN) models. Sensitivity analyses and compound annotation were conducted.

RESULTS

Exposure levels of all DBPs in exhaled breath were higher after the experiment. A total of 6,471 metabolic features were detected and 293 features were associated with at least one DBP in exhaled breath following Bonferroni correction. A total of 333 metabolic features were associated to at least one DBP measured in water or urine. Uptake of DBPs and physical activity were strongly correlated and mutual adjustment reduced the number of statistically significant associations. From the 293 features, 20 could be identified corresponding to 13 metabolites including compounds in the tryptophan metabolism pathway.

CONCLUSION

Our study identified numerous molecular changes following a swim in a chlorinated pool. While we could not explicitly evaluate which experiment-related factors induced these associations, molecular characterization highlighted metabolic features associated with exposure changes during swimming.

Formation and control of nitrogenous DBPs from Western Australian source waters: Investigating the impacts of high nitrogen and bromide concentrations

We studied the formation of four nitrogenous DBPs (N-DBPs) classes (haloacetonitriles, halonitromethanes, haloacetamides, and N-nitrosamines), as well as trihalomethanes and total organic halogen (TOX), after chlorination or chloramination of source waters. We also evaluated the relative and additive toxicity of N-DBPs and water treatment options for minimisation of N-DBPs. The formation of halonitromethanes, haloacetamides, and N-nitrosamines was higher after chloramination and positively correlated with dissolved organic nitrogen or total nitrogen. N-DBPs were major contributors to the toxicity of both chlorinated and chloraminated waters. The strong correlation between bromide concentration and the overall calculated DBP additive toxicity for both chlorinated and chloraminated source waters demonstrated that formation of brominated haloacetonitriles was the main contributor to toxicity. Ozone-biological activated carbon treatment was not effective in removing N-DBP precursors. The occurrence and formation of N-DBPs should be investigated on a case-by-case basis, especially where advanced water treatment processes are being considered to minimise their formation in drinking waters, and where chloramination is used for final disinfection.

In vitro bioacessibility and transport across Caco-2 monolayers of haloacetic acids in drinking water

Water disinfection plays a crucial role in water safety but it is also a matter of concern as the use of disinfectants promotes the formation of disinfection by-products (DBPs). Haloacetic acids (HAAs) are one of the major classes of DBPs since they are frequently found in treated water, are ubiquitous, pervasive and have high water solubility, so a great concern emerged about their formation, occurrence and toxicity. Exposure to HAAs is influenced by consumption patterns and diet of individuals thus their bioavailability is an important parameter to the overall toxicity. In the current study the bioacessibility of the most representative HAAs (chloroacetic acid - MCAA, bromoacetic acid - MBAA, dichloroacetic acid - DCAA, dibromoacetic acid - DBAA, and trichloroacetic acid - TCAA) after simulated in vitro digestion (SIVD) in tap water and transport across Caco-2 monolayers was evaluated. Compounds were monitored in 8 points throughout the digestion phases by an optimized LC-MS/MS methodology. MCAA and MBAA were not bioaccessible after SIVD whereas DCAA, DBAA and TCAA are highly bioaccessible (85 ± 4%, 97 ± 4% and 106 ± 7% respectively). Concerning transport assays, DCAA and DBAA were highly permeable throughout the Caco-2 monolayer (apparent permeability and calculated fraction absorbed of 13.62 × 10(-6) cm/s and 90% for DCAA; and 8.82 × 10(-6) cm/s and 84% for DBAA), whereas TCAA showed no relevant permeability. The present results may contribute to efficient risk analysis studies concerning HAAs oral exposure from tap water taking into account the different biological behaviour of these chemically similar substances.

Environmental and personal determinants of the uptake of disinfection by-products during swimming

BACKGROUND

Trihalomethanes (THMs) in exhaled breath and trichloroacetic acid (TCAA) in urine are internal dose biomarkers of exposure to disinfection by-products (DBPs) in swimming pools.

OBJECTIVE

We assessed how these biomarkers reflect the levels of a battery of DBPs in pool water and trichloramine in air, and evaluated personal determinants.

METHODS

A total of 116 adults swam during 40min in a chlorinated indoor pool. We measured chloroform, bromodichloromethane, dibromochloromethane and bromoform in exhaled breath and TCAA in urine before and after swimming, trichloramine in air and several DBPs in water. Personal determinants included sex, age, body mass index (BMI), distance swum, energy expenditure, heart rate and 12 polymorphisms in GSTT1, GSTZ1 and CYP2E1 genes.

RESULTS

Median level of exhaled total THMs and creatinine adjusted urine TCAA increased from 0.5 to 14.4µg/m(3) and from 2.5 to 5.8µmol/mol after swimming, respectively. The increase in exhaled brominated THMs was correlated with brominated THMs, haloacetic acids, haloacetonitriles, haloketones, chloramines, total organic carbon and total organic halogen in water and trichloramine in air. Such correlations were not detected for exhaled chloroform, total THMs or urine TCAA. Exhaled THM increased more in men, urine TCAA increased more in women, and both were affected by exercise intensity. Genetic variants were associated with differential increases in exposure biomarkers.

CONCLUSION

Our findings suggest that, although affected by sex, physical activity and polymorphisms in key metabolizing enzymes, brominated THMs in exhaled breath could be used as a non-invasive DBP exposure biomarker in swimming pools with bromide-containing source waters. This warrants confirmation with new studies.

Predictors of Third Trimester Blood Trihalomethanes and Urinary Trichloroacetic Acid Concentrations among Pregnant Women

Prenatal exposure to disinfection byproducts (DBPs) has been associated with a variety of adverse birth outcomes. However, little is known about predictors of prenatal biomarkers of exposure to DBPs among pregnant women. We aimed to identify predictors of third trimester blood trihalomethanes (THMs) and urinary trichloroacetic acid (TCAA) concentrations, two biomarkers of exposure to DBPs, among pregnant women. Blood samples, urine samples, and questionnaires on individual characteristics and water-use activities were collected from 893 pregnant women in a Chinese cohort study. Maternal blood THM [chloroform (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), and bromoform (TBM)] and urinary TCAA concentrations were measured. We used multivariable linear regression to identify the predictors of third trimester blood THM and creatinine-adjusted urinary TCAA concentrations. The geometric mean of blood TTHM (sum of TCM, BDCM, DBCM, and TBM) and creatinine-adjusted urinary TCAA concentrations were 51.90 ng/L and 9.66 μg/g creatinine, respectively. Study city was the strongest significant predictors of blood THM and creatinine-adjusted urinary TCAA concentrations. Prenatal body mass index (BMI) was associated with decreased blood THM and decreased creatinine-adjusted urinary TCAA concentrations. Age was associated with increased blood Br-THM (sum of BDCM, DBCM, and TBM) concentrations. Intake of boiled water and passive smoking were associated with lower blood THM concentrations. The predictors of blood THM and urinary TCAA concentrations identified in this study provide potential health implications on how to reduce DBP exposure during pregnancy.

Blood trihalomethane levels and the risk of total cancer mortality in US adults

BACKGROUND

Although animal data have suggested the carcinogenic activity of trihalomethanes (THMs), there is inconsistent evidence supporting the link between THM exposure and cancers in humans.

OBJECTIVES

We investigated the association between specific and total blood THM levels with the risk of total cancer mortality in adults.

METHODS

We analyzed data from the 1999-2004 Third National Health and Nutrition Examination Survey and the Linked Mortality File of the United States. A total of 933 adults (20-59 years of age) with available blood THM levels and no missing data for other variables were included. Four different THM species (chloroform, bromodichloromethane (BDCM), dibromochloromethane (DBCM) and bromoform) were included, and the codes associated with cancer (malignant neoplasm) were C00 through C97, based on the underlying causes of death listed in the International Classification of Disease 10the Revision.

RESULTS

Compared with adults in the lowest DBCM, bromoform, and total brominated THM tertiles, those in the highest DBCM, bromoform, and total brominated THM tertiles exhibited adjusted hazard ratios (HR) of total cancer mortality of 4.97 (95% confidence interval (CI) = 1.59-15.50), 4.94 (95% CI = 1.56-15.61), and 3.42 (95% CI = 1.21-15.43) respectively. The risk of total cancer mortality was not associated with increases in blood chloroform and total THM levels.

CONCLUSIONS

We found that the baseline blood THM species, particularly brominated THMs, were significantly associated with total cancer mortality in adults. Although this study should be confirm by other studies, our findings suggest a possible link between THM exposures and cancer.