Disinfection byproducts form as a result of chemical treatments that water companies use to keep water free of dangerous pathogens. Some byproducts may increase the risk of cancer.
In the United States, the Environmental Protection Agency (EPA) currently regulates four categories of disinfection byproducts for safety. However, researchers believe there may be hundreds—if not thousands—of unregulated byproducts lurking in the tap water that millions of people drink. The health effects of those chemicals are largely unknown.
Sourcing Public Drinking Water
In larger cities, water treatment plants typically pull water from surface water sources such as lakes, rivers, or reservoirs; groundwater; or a combination of both. Small towns tend to source drinking water from groundwater.Some locations may use recycled water, which comes from municipal wastewater, stormwater, or agricultural runoff.
Treating Public Drinking Water
Regardless of where it comes from, water supplied to the public goes through several treatment processes involving the addition of chemicals to remove small particles and filtration to ensure it is safe to drink.During the treatment process, water companies must strike a balance. They must add sufficient chemicals to the water to ensure safety, without exceeding EPA limits for treatment chemicals and their byproducts.
- Coagulation: Adding chemicals such as salts, iron, or aluminum to bind small particles.
- Flocculation: Mixing the water to help particles form larger clumps, sometimes with the addition of other chemicals.
- Sedimentation: Allowing large, heavy clumps to settle to the bottom of storage containers.
- Filtration: Passing the remaining clear water through several filters to remove residual particles, parasites, bacteria, and viruses. Some water treatment plants may use reverse osmosis, especially when treating recycled water.
- Disinfection: Using chemicals such as chlorine or chloramine to kill harmful germs and prevent waterborne illnesses such as cholera and typhoid.
Health Concerns With Disinfection Byproducts
According to a 2024 EPA report, although disinfection chemicals are effective, they can react with compounds present in water and create harmful byproducts, which treatment plant operators must remove during the water treatment process. EPA disinfection rules require utilities to monitor treated water for four disinfectant byproducts, including:- Trihalomethanes
- Haloacetic acids
- Chlorite
- Bromate
“There are consistent associations between disinfection byproducts and bladder cancer, also some associations with colorectal cancer,” Susan D. Richardson, a professor of chemistry at the University of South Carolina, told The Epoch Times. She also cited associations between disinfection byproducts and miscarriage and birth defects.
“While previous studies have looked at the fate of regulated disinfection byproducts in distribution systems, very few have investigated the more toxic, unregulated byproducts,” Richardson said.
The paper’s findings prompted Richardson and her colleagues to recommend that unregulated byproducts—specifically haloacetonitriles and iodoacetic acids—be considered for regulation, as they were the main drivers of toxicity in drinking water in this U.S.-based study.
Richardson told The Epoch Times her group’s latest research, expected to be published soon, investigated the fate of 66 disinfection byproducts as the treated water travels through pipes from the treatment plant to people’s homes.
She said that water distribution pipes are like reactors where disinfection byproducts can continue to form or degrade, and some transform into other byproducts over time.
Reducing Exposure to Disinfection Byproducts
A recent Environmental Working Group (EWG) study found that advanced per- and polyfluoroalkyl (PFAS) treatment technologies reduced trihalomethanes by 42 percent on average and lowered haloacetic acid levels by 50 percent.However, only 8 percent of U.S. water treatment plants currently have these systems.
Steve Via, director of federal relations for the American Water Works Association, told The Epoch Times there are several technologies utilities use in combination with chlorine or chloramines to produce fewer byproducts.
However, he noted that there are no alternatives to chlorine or chloramines for maintaining water sanitation during distribution to homes, as mandated by the EPA’s Surface Water Treatment Rule. These methods are generally considered best practice for water systems.
While most people have no control over what happens to their drinking water at the treatment plant, reducing exposure to potentially harmful byproducts at home is possible.
Richardson noted that reverse osmosis is particularly effective for charged byproducts such as haloacetic acids and for larger molecules.
Water pitcher filters can also help reduce exposure.
Via advised that before purchasing a water treatment device, consumers should confirm it is certified to NSF standards for the contaminant of concern and install and maintain the device according to the manufacturer’s instructions.
Activated carbon filters are typically installed where the water pipe enters the house (point of entry) or in the pipes leading to a faucet. Reverse osmosis systems are usually installed under a sink and connected to the faucet. Most commercially available filter systems combine carbon filtration and reverse osmosis to maximize chemical removal.
Installing filtration systems or using pitcher filters may help reduce disinfection byproducts, but these options can be costly. However, there are low- or no-cost ways to lower exposure.
“Setting aside drinking water in a pitcher in the refrigerator allows disinfection byproducts to dissipate, so that is one option,” Via said.
Reports typically show levels of the four regulated byproducts, and inorganic contaminants like arsenic, fluoride, and nitrate. They may also reveal lead and copper levels, PFAS, and radioactive contaminants like uranium. Reports often indicate whether the water came from surface water, ground water, or recycled water.
