Chlorination disinfection by-products and pancreatic cancer risk

Chlorination disinfection by-products (CDBPs) are produced during the treatment of water with chlorine to remove bacterial contamination. CDBPs have been associated with an increased risk of bladder cancer. There is also some evidence that they may increase the risk of pancreatic cancer. We report results from a population-based case-control study of 486 incident cases of pancreatic cancer and 3,596 age- and sex-matched controls. Exposure to chlorination by-products was estimated by linking lifetime residential histories to two different databases containing information on CDBP levels in municipal water supplies. Logistic regression analysis found no evidence of increased pancreatic cancer risk at higher CDBP concentrations (all odds ratios < 1.3). Null findings were also obtained assuming a latency period for pancreatic cancer induction of 3, 8, or 13 years.     

饮用水消毒副产物暴露评价研究进展

介绍了饮用水消毒副产物暴露评价的基本定义,对饮用水暴露评价的主要消毒副产物进行了归纳总结,综述了现阶段饮用水消毒副产物暴露评价方法的进展及不足,并结合具体案例对饮用水消毒副产物暴露评价的具体步骤进行较为详细阐述,并对饮用水消毒副产物暴露评价研究的发展趋势及将来研究的重点进行了展望。     

Drinking water disinfection by-products and time to pregnancy

BACKGROUND: Laboratory evidence suggests tap water disinfection by-products (DBPs) could have an effect very early in pregnancy, typically before clinical detectability. Undetected early losses would be expected to increase the reported number of cycles to clinical pregnancy. METHODS: We investigated the association between specific DBPs (trihalomethanes, haloacetic acids, brominated-trihalomethanes, brominated-haloacetic acids, total organic halides, and bromodichloromethane) and time to pregnancy among women who enrolled in a study of drinking water and reproductive outcomes. We quantified exposure to DBPs through concentrations in tap water, quantity ingested through drinking, quantity inhaled or absorbed while showering or bathing, and total integrated exposure. The effect of DBPs on time to pregnancy was estimated using a discrete time hazard model. RESULTS: Overall, we found no evidence of an increased time to pregnancy among women who were exposed to higher levels of DBPs. A modestly decreased time to pregnancy (ie, increased fecundability) was seen among those exposed to the highest level of ingested DBPs, but not for tap water concentration, the amount absorbed while showering or bathing, or the integrated exposure. CONCLUSIONS: Our findings extend those of a recently published study suggesting a lack of association between DBPs and pregnancy loss.     

Bladder cancer and exposure to water disinfection by-products through ingestion, bathing, showering, and swimming in pools

Bladder cancer has been associated with exposure to chlorination by-products in drinking water, and experimental evidence suggests that exposure also occurs through inhalation and dermal absorption. The authors examined whether bladder cancer risk was associated with exposure to trihalomethanes (THMs) through ingestion of water and through inhalation and dermal absorption during showering, bathing, and swimming in pools. Lifetime personal information on water consumption and water-related habits was collected for 1,219 cases and 1,271 controls in a 1998-2001 case-control study in Spain and was linked with THM levels in geographic study areas. Long-term THM exposure was associated with a twofold bladder cancer risk, with an odds ratio of 2.10 (95% confidence interval: 1.09, 4.02) for average household THM levels of >49 versus < or =8 micro g/liter. Compared with subjects not drinking chlorinated water, subjects with THM exposure of >35 micro g/day through ingestion had an odds ratio of 1.35 (95% confidence interval: 0.92, 1.99). The odds ratio for duration of shower or bath weighted by residential THM level was 1.83 (95% confidence interval: 1.17, 2.87) for the highest compared with the lowest quartile. Swimming in pools was associated with an odds ratio of 1.57 (95% confidence interval: 1.18, 2.09). Bladder cancer risk was associated with long-term exposure to THMs in chlorinated water at levels regularly occurring in industrialized countries.     

Multipathway risk assessment on disinfection by-products of drinking water in Hong Kong

The lifetime cancer risk and the hazard index of trihalomethanes (THMs) through oral ingestion, dermal absorption, and inhalation exposure from tap water in 19 districts in Hong Kong are estimated. The most dominant THMs are chloroform and bromodichloromethane (BDCM) in Hong Kong tap water. Among the three different pathways, residents have a higher risk of cancer through oral ingestion than through the other two pathways. The lifetime cancer risks through oral ingestion and dermal absorption for BDCM make the highest percentage contribution (59%) to total risks, followed by chloroform (24%). The chloroform and BDCM are at or above the negligible risk level of 10(-6) by a factor of 10 or more in most districts. Among the 19 districts, people living in Sai Kung have the highest risk of cancer due to the THM exposure through the multipathways, mainly because of the exposure to BDCM and dibromochloromethane (DBCM). The total cancer risk analysis indicates that each year approximately 10 out of the seven million Hong Kong residents could get cancer from the daily intake of water.     

Exposure to drinking water disinfection by-products and pregnancy loss

Previous research has suggested that exposure to elevated levels of drinking water disinfection by-products (DBPs) may cause pregnancy loss. In 2000-2004, the authors conducted a study in three US locations of varying DBP levels and evaluated 2,409 women in early pregnancy to assess their tap water DBP concentrations, water use, other risk factors, and pregnancy outcome. Tap water concentrations were measured in the distribution system weekly or biweekly. The authors considered DBP concentration and ingested amount and, for trihalomethanes only, bathing/showering and integrated exposure that included ingestion. On the basis of 258 pregnancy losses, they did not find an increased risk of pregnancy loss in relation to trihalomethane, haloacetic acid, or total organic halide concentrations; ingested amounts; or total exposure. In contrast to a previous study, pregnancy loss was not associated with high personal trihalomethane exposure (> or =75 micro g/liter and > or =5 glasses of water/day) (odds ratio = 1.1, 95% confidence interval: 0.7, 1.7). Sporadic elevations in risk were found across DBPs, most notably for ingested total organic halide (odds ratio = 1.5, 95% confidence interval: 1.0, 2.2 for the highest exposure quintile). These results provide some assurance that drinking water DBPs in the range commonly encountered in the United States do not affect fetal survival.     

Validation of urinary trichloroacetic acid as a biomarker of exposure to drinking water disinfection by-products

Disinfection by-products (DBPs) in drinking water represent a public health issue and a challenge for epidemiology to provide evidence towards the causation of various hypothesized health effects. Validation of a biomarker of exposure to DBPs is a strategy to achieve progress which has been advocated. The objective of this study was to validate urinary trichloroacetic acid (TCAA) excretion as a biomarker of exposure to DBPs in an experimental exposure cohort. A total of 52 healthy women participated in the study. Participants consumed supplied tap water for 15 d and provided urine and blood samples for TCAA measurements. The findings revealed that (1) background levels of TCAA in urine and blood were readily detectable, (2) TCAA levels in blood and urine increased with increased amounts of TCAA ingested, (3) the correlations between measurements of TCAA ingestion and urinary excretion were modest (r=0.66, p<0.001) based on one days' sampling and high (r=0.77–0.83, p<0.001) based on two to four days' sampling, (4) the correlations between measurements of TCAA ingestion and blood TCAA concentration were high (r=0.80, p<0.001) and (5) multiple days' urinary TCAA measures improved the prediction of TCAA ingestion through urinary TCAA excretion. TCAA can be a valid biomarker of exposure for DBPs in drinking water.     

Health impacts of long-term exposure to disinfection by-products in drinking water in Europe: HIWATE

There appears to be very good epidemiological evidence for a relationship between chlorination by-products, as measured by trihalomethanes (THMs), in drinking water and bladder cancer, but the evidence for other cancers, including colorectal cancer appears to be inconclusive and inconsistent. There appears to be some evidence for a relationship between chlorination by-products, as measured by THMs, and small for gestational age (SGA)/intrauterine growth retardation (IUGR) and preterm delivery, but evidence for other outcomes such as low birth weight (LBW), stillbirth, congenital anomalies and semen quality appears to be inconclusive and inconsistent.     

Chlorination disinfection by-products in drinking water and the risk of adult leukemia in Canada

The authors conducted a population-based case-control study of 1,068 incident leukemia cases and 5,039 controls aged 20-74 years during 1994-1997 to examine the association between exposure to drinking water chlorination disinfection by-products and adult leukemia risk in Canada. Residence and drinking water source histories and data from municipal water supplies were used to estimate individual chlorination disinfection by-product exposure according to water source, chlorination status, and chlorination disinfection by-product levels during the 40-year period before the interview. The analysis included 686 cases and 3,420 controls for whom water quality information was available for at least 30 of these years. Increased risk of chronic myeloid leukemia was associated with increasing years of exposure to different chlorination disinfection by-product indexes, with an adjusted odds ratio of 1.72 (95% confidence interval: 1.01, 3.08) for the highest exposure duration to total trihalomethanes of more than 40 microg/liter. In contrast, the risk of the other studied leukemia subtypes was found to decrease with increasing years of exposure to chlorination disinfection by-products. A protective effect was noted for chronic lymphoid leukemia (odds ratio = 0.60, 95 percent confidence interval: 0.41, 0.87) associated with the highest exposure duration to total trihalomethanes of more than 40 microg/liter. More studies with long-term exposure measures and large enough to evaluate leukemia subtypes are needed to further understanding of the issue.     

江苏省城市饮用水氯化消毒副产物的健康风险评估

目的 了解江苏省城市饮用水中氯化消毒副产物三卤甲烷、卤乙酸暴露水平,评估饮用水中氯化消毒副产物经口摄入途径对人体健康潜在危害,为制定饮水安全保障政策提供参考.方法 2017-2019年,选取全省氯化消毒的市政水厂51座,在枯水期(3-5月)、丰水期(7-9月)采集出厂水、末梢水192份,检测水中三卤甲烷(三氯甲烷、一氯二溴甲烷、二氯一溴甲烷、三溴甲烷)、卤乙酸(二氯乙酸、三氯乙酸)暴露水平,使用美国环保署推荐的健康风险评价模型,对氯化消毒副产物经口摄入途径的健康风险进行评估.结果 所有水样氯化消毒副产物检出值均低于国标限值.氯化消毒副产物对成年男性、成年女性、儿童终身致癌风险分别为3.13×10-5、3.16×10-5、2.91×10-5,其中二氯一溴甲烷致癌风险最高,对成年男性、成年女性、儿童致癌风险分别为1.12×10-5、1.13×10-5、1.04×10-5,分别占总致癌风险的35.78％、35.76％、35.74％.副产物终身致癌风险液氯消毒高于次氯酸钠消毒,末梢水高于出厂水,丰水期高于枯水期.对成年男性、成年女性、儿童非致癌风险健康危害指数分别为7.30×10-2、7.40×10-2、6.80×10-2,其中三氯甲烷非致癌风险最高.结论 江苏省城市饮用水氯化消毒副产物终身致癌风险、非致癌风险均在可接受范围内,二氯一溴甲烷、一氯二溴甲烷是风险管理重点指标.     

Modelling exposure to disinfection by-products in drinking water for an epidemiological study of adverse birth outcomes

We are conducting an epidemiological study on the association between disinfection by-product concentrations in drinking water and adverse birth outcomes in the UK, using trihalomethane (THM) concentrations over defined water zones as an exposure index. Here we construct statistical models using sparse routinely collected THMs measurements to obtain quarterly estimates of mean THM concentrations for each water zone. We modelled the THM measurements using a Bayesian hierarchical mixture model, taking into account heterogeneity in THM concentrations between water originating from different source types, quarterly variation in THM concentrations and uncertainty in the true value of undetected and rounded measurements. Quarterly estimates of mean THM concentrations plus estimates of the water source type (ground, lowland surface or upland surface) were obtained for each water zone. THM concentration estimates were typically highest from July to September (third quarter), and varied considerably between water sources. Our exposure estimates were categorized into 'low', 'medium' and 'high' THM classes. Our modelled quarterly exposure estimates were compared to a simple alternative: annual means of the raw data for each water zone. In all, 15-25% of exposure estimates were classified differently. The modelled THM estimates led to slightly stronger and more precise estimates of association with risk of still birth and low birth weight than did the raw annual means. We conclude that our modelling approach enabled us to provide robust quarterly estimates of ecological exposure to THMs in a situation where the raw data were too sparse to base exposure assessment on empirical summaries alone.     

Exposure estimates to disinfection by-products of chlorinated drinking water.

Exposure to disinfection by-products (DBPs) of drinking water is multiroute and occurs in households serviced by municipal water treatment facilities that disinfect the water as a necessary step to halt the spread of waterborne infectious diseases. Biomarkers of the two most abundant groups of DBPs of chlorination, exhaled breath levels of trihalomethanes (THMs) and urinary levels of two haloacetic acids, were compared to exposure estimates calculated from in-home tap water concentrations and responses to a questionnaire related to water usage. Background THM breath concentrations were uniformly low. Strong relationships were identified between the THM breath concentrations collected after a shower and both the THM water concentration and the THM exposure from a shower, after adjusting for the postshower delay time in collecting the breath sample. Urinary haloacetic acid excretion rates were not correlated to water concentrations. Urinary trichloroacetic acid excretion rates were correlated with ingestion exposure, and that correlation was stronger in a subset of individuals who consumed beverages primarily within their home where the concentration measurements were made. No correlation was observed between an average 48-hr exposure estimate and the urinary dichloroacetic acid excretion rate, presumably because of its short biological half-life. Valid biomarkers were identified for DBP exposures, but the time between the exposure and sample collection should be considered to account for different metabolic rates among the DBPs. Further, using water concentration as an exposure estimate can introduce misclassification of exposure for DBPs whose primary route is ingestion due to the great variability in the amount of water ingested across a population.     

潍坊市饮用水中消毒副产物的水平及其健康风险评价

目的了解潍坊市居民生活饮用水中消毒副产物的种类和分布水平,并对其健康风险进行评价。方法于2018年丰水期(8月)和枯水期(3月)采集潍坊市区12家市政水厂的出厂水和相应的末梢水水样共86份,对水样中18种消毒副产物进行浓度水平检测和健康风险评价。检测结果评价参考国家生活饮用水标准(GB5749—2006),并参照美国USEPA的致癌风险模型评估DBPs经饮水途径对潍坊市居民造成的健康危害。结果潍坊市饮用水中主要检测到的消毒副产物为THMs(TCM、BDCM、DBCM和TBM);丰水期与枯水期消毒副产物的浓度在不同季节分布均无差异(P>0.05);出厂水和末梢水中消毒副产物引起的致癌风险分别为11.1×10~(-7)～7.73×10~(-5)和7.86×10~(-7)～1.07×10~(-4),非致癌风险分别为1.82×10~(-3)～0.13和1.64×10~(-3)～0.18,致癌风险均来自三卤甲烷类物质。结论三卤甲烷是2018年潍坊市主城区饮用水中的主要消毒副产物。     

Diesel exhaust exposure and bladder cancer risk

A total of 136 cases of men with urinary bladder cancer and 272 matched hospital controls were examined for potential exposure to diesel exhaust. A lifetime occupational history was obtained for all subjects in the study and assessment of exposure to diesel exhaust was based on the job titles of the subject and self-reported exposure. The risk was assessed by odds ratios, with adjustment for confounding variables, in particular cigarette smoking. There was no evidence of elevated risk in occupations with possible or probable exposure (the ORs adjusted for smoking were 1.1. and 0.9 respectively). Truck driving alone was also not associated with elevated risk (adjusted OR=0.5). There was a weak positive crude association with any exposure, including self-reports (OR=1.4); however after adjustment for smoking, the estimate did not retain statistical significance (OR=1.2, 95% CI=0.8-2.0). This study provides little to support the hypothesis of an excess of bladder cancer risk from occupational exposure to diesel exhaust.Corresponding author.     

南昌市主城区饮用水中消毒副产物含量及其健康风险评价

目的 了解南昌市主城区饮用水中消毒副产物种类、分布,并评价其潜在健康风险。方法 于 2015年枯水期（11月）、2016年丰水期（6月）采集南昌市主城区 8家市政出厂水水样 16份 ,依据《生活饮用水标准检验方法》（GB/T5750 - 2006）检测水样中 13种消毒副产物含量;运用美国环保局健康风险评价模型评价消毒副产物通过饮水途径引起的健康风险。结果 出厂水中消毒副产物浓度均符合《生活饮用水卫生标准》（GB5749 - 2006）,卤乙酸（二氯乙酸、三氯乙酸）和三卤甲烷（三氯甲烷、二溴一氯甲烷）是南昌市主城区饮用水中主要消毒副产物。消毒副产物在丰水期浓度是枯水期浓度的4.16倍,丰水期二氯乙酸、三氯乙酸、三氯甲烷浓度高于枯水期,枯水期二溴一氯甲烷浓度高于丰水期（均P＜0.05）。消毒副产物引起的致癌风险为2.83×10 - 5/年～7.98×10 - 5/年,中值5.91×10 - 5/年,非致癌风险为6.21×10 - 2/年～1.86×10 - 1/年,中值为1.22×10 - 1/年。致癌风险主要来自二氯乙酸、三氯乙酸和二氯一溴甲烷,丰水期以三氯乙酸和三氯甲烷贡献最大;枯水期以二溴一氯甲烷和二氯一溴甲烷贡献最大;而二氯乙酸对非致癌风险贡献最大。结论 卤乙酸和三卤甲烷是南昌市主城区饮用水中的主要消毒副产物,出厂水中消毒副产物引起的致癌风险在可接受的范围,但需提出风险控制措施,丰水期消毒副产物浓度应该得到控制。     

The healthy men study: an evaluation of exposure to disinfection by-products in tap water and sperm quality

BACKGROUND: Chlorination of drinking water generates disinfection by-products (DBPs), which have been shown to disrupt spermatogenesis in rodents at high doses, suggesting that DBPs could pose a reproductive risk to men. In this study we assessed DBP exposure and testicular toxicity, as evidenced by altered semen quality. METHODS: We conducted a cohort study to evaluate semen quality in men with well-characterized exposures to DBPs. Participants were 228 presumed fertile men with different DBP profiles. They completed a telephone interview about demographics, health history, water consumption, and other exposures and provided a semen sample. Semen outcomes included sperm concentration and morphology, as well as DNA integrity and chromatin maturity. Exposures to DBPs were evaluated by incorporating data on water consumption and bathing and showering with concentrations measured in tap water. We used multivariable linear regression to assess the relationship between exposure to DBPs and adverse sperm outcomes. RESULTS: The mean (median) sperm concentration and sperm count were 114.2 (90.5) million/mL and 362 (265) million, respectively. The mean (median) of the four trihalomethane species (THM4) exposure was 45.7 (65.3) microg/L, and the mean (median) of the nine haloacetic acid species (HAA9) exposure was 30.7 (44.2) microg/L. These sperm parameters were not associated with exposure to these classes of DBPs. For other sperm outcomes, we found no consistent pattern of increased abnormal semen quality with elevated exposure to trihalomethanes (THMs) or haloacetic acids (HAAs). The use of alternate methods for assessing exposure to DBPs and site-specific analyses did not change these results. CONCLUSIONS: The results of this study do not support an association between exposure to levels of DBPs near or below regulatory limits and adverse sperm outcomes in humans.     

Effects of tap water processing on the concentration of disinfection by-products

Aim: This study examined the effects on disinfection by-product (DBP) concentrations of common household methods for processing drinking water.     

Chlorinated drinking water and bladder cancer: effect of misclassification on risk estimates

Data are presented from the Iowa portion of the National Bladder Cancer Case-Control Study demonstrating the effect of misclassification on depressing odds ratio estimates for years of exposure to chlorinated drinking water and bladder cancer. Four methods (METHODS 1 through 4) of quantifying chlorination exposure with sequentially decreasing degrees of misclassification are presented for the 268 bladder cancer cases and 658 population-based controls fulfilling criteria for inclusion in this study. Twenty-eight other risk factors for bladder cancer were considered along with chlorinated drinking water exposure estimated by METHOD 4. Stepwise regression models included as significant factors cigarette smoking (p less than .001), chlorination exposure (p = .038), and irradiation to the pelvic area (p = .040). Replacement of chlorinated drinking water exposure estimated by METHOD 4 with any of the remaining three methods resulted in models that included cigarette smoking and irradiation to the pelvic area, but not chlorination exposure. Thus, misclassification of chlorination exposure signified the difference between observing and not observing an association with bladder cancer.