Global assessment of chemical quality of drinking water: The case of trihalomethanes.

Background: Trihalomethanes (THM), a major class of disinfection by-products, are widespread and are associated with adverse health effects. We conducted a global evaluation of current THM regulations and concentrations in drinking water.

Methods: We included 120 countries (∼7000 million inhabitants in 2016), representing 94% of the world population.

Relationships between regulated DBPs and emerging DBPs of health concern in U.S. drinking water.

A survey was conducted at eight U.S. drinking water plants, that spanned a wide range of water qualities and treatment/disinfection practices.

Feel the Burn: Disinfection Byproduct Formation and Cytotoxicity during Chlorine Burn Events.

Nitrification and biofilm growth within distribution systems remain major issues for drinking water treatment plants utilizing chloramine disinfection. Many chloraminated plants periodically switch to chlorine disinfection for several weeks to mitigate these issues, known as "chlorine burns". The evaluation of disinfection byproduct (DBP) formation during chlorine burns beyond regulated DBPs is scarce.

Drivers of Disinfection Byproduct Cytotoxicity in U.S. Drinking Water: Should Other DBPs Be Considered for Regulation?

This study reveals key disinfection byproduct (DBP) toxicity drivers in drinking water across the United States. DBPs, which are ubiquitous in drinking water, form by the reaction of disinfectants, organic matter, bromide, and iodide and are generally present at 100-1000× higher concentrations than other contaminants. DBPs are linked to bladder cancer, miscarriage, and birth defects in human epidemiologic studies, but it is not known as to which DBPs are responsible.

Contributions of volatilization, photolysis, and biodegradation to N‑nitrosodimethylamine removal in conventional drinking water treatment plants.

N‑nitrosodimethylamine (NDMA) was detected in the source water of some Chinese drinking water treatment plants (DWTPs), which decreased in concentration along the treatment train. Volatilization, photolysis, and/or biodegradation were suspected of being capable of attenuating NDMA. In this study, the contribution of these mechanisms to NDMA removal was investigated by a field study in a conventional DWTP with aerated bio-pretreatment, as well as in laboratory-based experiments.

A one-year long survey of temporal disinfection byproducts variations in a consumer's tap and their removals by a point-of-use facility.

In order to better understand the occurrence of disinfection byproducts (DBPs) in tap water and their real impacts on consumers, this study made a one-year long survey of the temporal variations of a series of DBPs before and after a point-of-use (POU) treatment facility installed in a building serving for ∼300 people. Water samples were collected every week at a fixed location and time for 1 year, and frequent samplings were carried out every 6 h a day for 1 month at selected seasons, which ultimately amounted to 322 samples. The results show that the concentrations of DBPs were higher in the summer than other seasons, with the lowest DBP levels being observed in spring.

Trace determination and occurrence of eight chlorophenylacetonitriles: An emerging class of aromatic nitrogenous disinfection byproducts in drinking water.

Two chlorophenylacetonitriles (CPANs) (2-chloro- and 3,4-dichlorophenylacetonitrile), representatives of an emerging class of aromatic nitrogenous disinfection byproducts, were recently identified in chlor(am)inated drinking water with liquid/liquid extraction and gas chromatography/mass spectrometry (GC/MS). Due to their high cytotoxicity, they are potentially significant drinking water contaminants. The detection limit for these two CPANs with the previous method was 100 ng L.

Ingested nitrate, disinfection by-products, and risk of colon and rectal cancers in the Iowa Women's Health Study cohort.

Background: N-nitroso compounds (NOC) formed endogenously after nitrate/nitrite ingestion and disinfection by-products (DBPs) are suspected colorectal carcinogens, but epidemiologic evidence of these associations is limited.

Objectives: We investigated the relationship between drinking water exposures and incident colorectal cancers in a cohort of postmenopausal women.

Methods: Using historical nitrate-nitrogen (NO-N) measurements and estimates of total trihalomethanes (TTHM), the sum of 5 or 6 haloacetic acids (HAAs), and individual DBPs in public water supplies (PWS), we computed average exposures and years of exposure above one-half the U.

Formation and speciation of chlorinated, brominated, and iodinated haloacetamides in chloraminated iodide-containing waters.

Haloacetamides (HAMs), an emerging class of disinfection by-products, have received increasing attention due to their elevated cyto- and genotoxicity. However, only limited information is available regarding the iodinated analogues. This study investigated the formation and speciation of iodinated haloacetamides (I-HAMs) and their chlorinated/brominated analogues during the chloramination of bromide and/or iodide-containing waters and a model compound solution over various time periods.

The stability of chlorinated, brominated, and iodinated haloacetamides in drinking water.

Haloacetamides (HAMs), a group of nitrogenous disinfection byproducts (N-DBPs), can decompose to form corresponding intermediate products and other DBPs. The stability of ten different HAMs, including two chlorinated, five brominated, and three iodinated species was investigated with and without the presence of chlorine, chloramines, and reactive solutes such as quenching agents. The HAM basic hydrolysis and chlorination kinetics were well described by a second-order kinetics model, including first-order in HAM and hydroxide and first-order in HAM and hypochlorite, respectively, whereas the HAM neutral hydrolysis kinetic was first-order in HAM.

Ingested nitrate and nitrite, disinfection by-products, and pancreatic cancer risk in postmenopausal women.

Nitrate and nitrite are precursors of N-nitroso compounds (NOC), probable human carcinogens that cause pancreatic tumors in animals. Disinfection by-products (DBP) exposures have also been linked with digestive system cancers, but few studies have evaluated relationships with pancreatic cancer. We investigated the association of pancreatic cancer with these drinking water contaminants and dietary nitrate/nitrite in a cohort of postmenopausal women in Iowa (1986-2011).

Case study approach to modeling historical disinfection by-product exposure in Iowa drinking waters.

In the 1980s, a case-control epidemiologic study was conducted in Iowa (USA) to analyze the association between exposure to disinfection by-products (DBPs) and bladder cancer risk. Trihalomethanes (THMs), the most commonly measured and dominant class of DBPs in drinking water, served as a primary metric and surrogate for the full DBP mixture. Average THM exposure was calculated, based on rough estimates of past levels in Iowa.

Ingested Nitrate, Disinfection By-products, and Kidney Cancer Risk in Older Women.

Background: N-nitroso compounds formed endogenously after nitrate/nitrite ingestion are animal renal carcinogens. Previous epidemiologic studies of drinking water nitrate did not evaluate other potentially toxic water contaminants, including the suspected renal carcinogen chloroform.

Methods: In a cohort of postmenopausal women in Iowa (1986-2010), we used historical measurements to estimate long-term average concentrations of nitrate-nitrogen (NO3-N) and disinfection by-products (DBP) in public water supplies.

Nitrate from Drinking Water and Diet and Bladder Cancer Among Postmenopausal Women in Iowa.

Background: Nitrate is a drinking water contaminant arising from agricultural sources, and it is a precursor in the endogenous formation of N-nitroso compounds (NOC), which are possible bladder carcinogens.

Objectives: We investigated the ingestion of nitrate and nitrite from drinking water and diet and bladder cancer risk in women.

Methods: We identified incident bladder cancers among a cohort of 34,708 postmenopausal women in Iowa (1986-2010).

Understanding and exploring the potentials of household water treatment methods for volatile disinfection by-products control: Kinetics, mechanisms, and influencing factors.

This study systematically evaluates the capabilities of five types of household water treatment (HWT) methods (including boiler heating, microwave irradiation, pouring, stirring, and shaking) on the removals of four regulated trihalomethanes (THM) and three iodinated halomethanes (IHMs) under a variety of conditions simulative of residential uses. Overall, the results clearly showed promising capabilities of all five HWT methods in controlling volatile disinfection by-products (DBPs), and heating with a boiler was the most effective approach among all methods due to the synergistic effects of water turbulence and bubbling phenomena. A contemporary boiler equipped with an automatic switch-off function reduced on average 92% of seven halomethanes (HM) at favourable conditions.

Veterinary antibiotics used in animal agriculture as NDMA precursors.

The formation of carcinogenic N-nitrosodimethylamine (NDMA) during chloramination at drinking water treatment plants has raised concerns as more plants have switched from chlorine to chloramine disinfection. In this study, a source of NDMA precursors that has yet to be investigated was examined. Veterinary antibiotics are used in large quantities at animal agricultural operations.

The effect of natural organic matter polarity and molecular weight on NDMA formation from two antibiotics containing dimethylamine functional groups.

N-nitrosodimethylamine (NDMA) is a disinfection byproduct preferentially formed in chloraminated water. NDMA may be formed from certain chemicals containing dimethylamine (DMA) functional groups. This reaction may be slowed by the presence of natural organic matter (NOM).

Drinking Water Disinfection By-products, Genetic Polymorphisms, and Birth Outcomes in a European Mother-Child Cohort Study.

Background: We examined the association between exposure during pregnancy to trihalomethanes, the most common water disinfection by-products, and birth outcomes in a European cohort study (Health Impacts of Long-Term Exposure to Disinfection By-Products in Drinking Water). We took into account exposure through different water uses, measures of water toxicity, and genetic susceptibility.

Methods: We enrolled 14,005 mothers (2002-2010) and their children from France, Greece, Lithuania, Spain, and the UK.

Granular Activated Carbon Treatment May Result in Higher Predicted Genotoxicity in the Presence of Bromide.

Certain unregulated disinfection byproducts (DBPs) are more of a health concern than regulated DBPs. Brominated species are typically more cytotoxic and genotoxic than their chlorinated analogs. The impact of granular activated carbon (GAC) on controlling the formation of regulated and selected unregulated DBPs following chlorine disinfection was evaluated.

Occurrence of nitrosamines and their precursors in drinking water systems around mainland China.

N-Nitrosamines (NAs) in drinking water have attracted considerable attention in recent years due to their high carcinogenicity, frequent occurrence, and their potential regulation. During the past three years, we have collected about 164 water samples of finished water, tap water, and source water from 23 provinces, 44 cities from large cities to small towns, and 155 sampling points all over China. The occurrence of NAs in the finished and tap water was much higher in China than that in the U.

NDMA formation during drinking water treatment: A multivariate analysis of factors influencing formation.

The formation of the carcinogen N-nitrosodimethylamine (NDMA) during drinking water treatment has raised concerns in the drinking water industry. Many bench-scale laboratory tests and pilot plant studies have been completed to try to determine which factors during water treatment increase or decrease the amount of NDMA formed in drinking water. This study used data from over 20 drinking water treatment plants in the United States and Canada to determine which factors are most highly correlated with the NDMA concentration in delivered water using a mixed effects model with a random intercept.

Contribution of the Antibiotic Chloramphenicol and Its Analogues as Precursors of Dichloroacetamide and Other Disinfection Byproducts in Drinking Water.

Dichloroacetamide (DCAcAm), a disinfection byproduct, has been detected in drinking water. Previous research showed that amino acids may be DCAcAm precursors. However, other precursors may be present.

Applying the polarity rapid assessment method to characterize nitrosamine precursors and to understand their removal by drinking water treatment processes.

Some N-nitrosamines (NAs) have been identified as emerging disinfection by-products during water treatment. Thus, it is essential to understand the characteristics of the NA precursors. In this study, the polarity rapid assessment method (PRAM) and the classical resin fractionation method were studied as methods to fractionate the NA precursors during drinking water treatment.

Evaluating Evidence for Association of Human Bladder Cancer with Drinking-Water Chlorination Disinfection By-Products.

Exposure to chlorination disinfection by-products (CxDBPs) is prevalent in populations using chlorination-based methods to disinfect public water supplies. Multifaceted research has been directed for decades to identify, characterize, and understand the toxicology of these compounds, control and minimize their formation, and conduct epidemiologic studies related to exposure. Urinary bladder cancer has been the health risk most consistently associated with CxDBPs in epidemiologic studies.

Determinants of disinfectant pretreatment efficacy for nitrosamine control in chloraminated drinking water.

Utilities using chloramines need strategies to mitigate nitrosamine formation to meet potential future nitrosamine regulations. The ability to reduce NDMA formation under typical post-chloramination conditions of pretreatment with ultraviolet light from a low pressure mercury lamp (LPUV), free chlorine (HOCl), ozone (O3), and UV light from a medium pressure mercury lamp (MPUV) were compared at exposures relevant to drinking water treatment. The order of efficacy after application to waters impacted by upstream wastewater discharges was O3 > HOCl ≈ MPUV > LPUV.