A review on the 40th anniversary of the first regulation of drinking water disinfection by‐products

Abstract

Water disinfection, primarily by chlorination, is one of the greatest achievements of public health. However, more than half a century after its introduction, studies in the 1970s reported that (a) chlorine interacted with organic matter in the water to form disinfection by‐products (DBPs); (b) two DBPs, chloroform and bromoform, both trihalomethanes (THMs), were rodent carcinogens; (c) three brominated THMs were mutagenic; in six studies chlorinated drinking waters in the United States and Canada were mutagenic; and (d) in one epidemiological study there was an association between bladder cancer mortality and THM exposure. This led the U.S. Environmental Protection Agency to issue its first DBP regulation in 1979. Forty years later, >600 DBPs have been characterized, 20/22 have been shown to be rodent carcinogens, >100 have been shown to be genotoxic, and 1000s of water samples have been found to be mutagenic. Data support a hypothesis that long‐term dermal/inhalation exposure to certain levels of the three brominated THMs, as well as oral exposure to the haloacetic acids, combined with a specific genotype may increase the risk for bladder cancer for a small but significant population group. Improved water‐treatment methods and stricter regulations have likely reduced such risks over the years, and further reductions in potential risk are anticipated with the application of advanced water‐treatment methods and wider application of drinking water regulations. This 40‐year research effort is a remarkable example of sustained cooperation between academic and government scientists, along with public/private water companies, to find answers to a pressing public health question.

Effects of harmful algal blooms on regulated disinfection byproducts: Findings from five utility case studies

“…Disinfecting drinking water from all surface water sources is a critical treatment step for protecting public health against disease‐causing waterborne pathogens (Schoenen, 2002). However, chemical disinfectants can react with naturally occurring material in the water to form DBPs, potentially posing significant human health risks (DeMarini, 2020; USEPA, 2006; Regli et al, 2015; Rook, 1974). Key factors influencing DBP formation include source water organic material composition and concentrations; source water pH and temperature; precursor removal rates; distribution system residence time; and the amount, timing, and type of disinfectant used during treatment.…”

“…Epidemiological studies have shown associations between the development of bladder cancer and exposures to both chlorinated drinking water (Cantor et al, 1985, 1998; King & Marrett, 1996; McGeehin et al, 1993; Villanueva et al, 2003) and DBPs (Cantor et al, 2010; DeMarini, 2020; Hrudey et al, 2015; Villanueva et al, 2004, 2007). Toxicity studies have also indicated DBPs can be carcinogenic and genotoxic (Richardson et al, 2007).…”

Adsorption Studies of Waterborne Trihalomethanes Using Modified Polysaccharide Adsorbents

“…DBCM and bromoform were assigned to Group 3 Environmental Protection Agency (EPA) cancer potency factors because of their inconclusive carcinogenicity in humans and limited evidence from experimental studies on animals [ 1 , 8 ]. Besides carcinogenicity, animal studies indicate that chloroform in drinking water supplies may lead to low birth weight, prematurity, and intrauterine growth retardation [ 1 , 8 , 9 ]. Chloroform may cause acute and chronic ecological effects to aquatic life due to its moderate acute and chronic toxicity to aquatic organisms.…”

“…The United States (U.S.) EPA has published the Disinfection By-products Rule to regulate total THMs at a maximum allowable annual average level of 80 ppb for Stage 1 and 40 ppb in Stage 2 for water treatment processes [ 9 ]. The maximum acceptable concentration (MAC) for THMs in drinking water established by Health Canada is 100 ppb.…”

Inability of GSTT1 to activate iodinated halomethanes to mutagens in Salmonella

“…Drinking water disinfected primarily by chlorine has been ubiquitous in most regions of the world for a century; however, the potential health effects of disinfection by‐products (DBPs), which are formed by the reaction of chlorine with organics and halides in the water, were not recognized until the 1970s (DeMarini, 2020). Among the >700 DBPs identified, >100 have been tested and found to be genotoxic in vitro, and 20 out of 22 that have been tested are carcinogenic in rodents (Richardson et al, 2007; Wagner and Plewa, 2017; Cortés and Marcos, 2018; DeMarini, 2020).…”