Disinfection Byproducts in Drinking Water – What They Are and How to Avoid Them

Disinfection Byproducts in Drinking Water – What They Are and How to Avoid Them

Posted by Kenton Jones on Jun 18th 2018

Tap water from municipal water treatment facilities undergoes a disinfection process to remove microbial contaminants and keep communities safe. Although this process reduces the bacteria, viruses, and other harmful microbiological contaminants from the water supply, it can also form byproducts that pose risks. When some of the chemicals used in disinfection interact with other compounds found in the water during the disinfection process, they can form disinfection byproducts (DBPs).

Disinfection byproducts in drinking water include a range of contaminants that may have potentially negative consequences on human health. This guide describes the potential risks of disinfection byproducts and outlines how to avoid these contaminants to maintain your family's health.

What Are Disinfection Byproducts?

Disinfection byproducts are contaminants formed by the reaction between disinfectants and natural organic compounds found in water. People may unknowingly consume DBPs in their drinking water, breathe in contaminants in the air, or absorb them through their skin when swimming or bathing.

The disinfection processes used in public water treatment systems can cause DBPs when certain chemicals like chlorine are added to the water. Disinfection byproducts in water arise when disinfectants react with organic materials in the water, creating unintended contaminants that may adversely affect health.

Common Disinfection Byproducts

Scientists have identified over 700 disinfection byproducts, though the United States Environmental Protection Agency (EPA) only regulates 11. The most common types of disinfection byproducts are:

  • Trihalomethanes
  • Haloacetic acids
  • Bromate
  • Chlorite and chlorate


Trihalomethanes are a result of chlorine-based disinfectants reacting with compounds in water. This group of disinfectant byproducts includes four individual trihalomethanes:

  1. Bromodichloromethane (BDCM)
  2. Tribromomethane (bromoform)
  3. Trichloromethane (chloroform)
  4. Dibromochloromethane (DBCM)

The National Cancer Institute (NCI)labeled trihalomethanes as carcinogens, prompting the EPA to establish the Disinfection and Disinfectant Byproducts Rule (DBPR) limiting acceptable trihalomethane levels.

Haloacetic Acids

One of the newer disinfection byproducts to be discovered in drinking water, haloacetic acids, form when the chlorine used to disinfect the water reacts with other organic matter existing in the water. The formation of haloacetic acid byproducts can also be influenced by the dosage and acidity of the chlorine, length of time in contact, and concentration of bromide ions, another disinfectant.

Haloacetic acids are a group that includes five distinct varieties:

  1. Chloroacetic Acid
  2. Trichloroacetic Acid
  3. Bromoacetic Acid
  4. Dichloroacetic Acid
  5. Dibromoacetic Acid

Stage One of guidelines established by the EPA and other government agencies requires regular testing at water treatment plants, ranging in frequency depending on the origin of the water.

To further protect individuals from these contaminants, NSF created two different standards for drinking water filters. The first is NSF/ANSI Standard 42, which certifies that a filter reduces chlorine taste and odor in water. The second is NSF/ANSI Standard 53, which focuses on the treatment of DBPs such as haloacetonitriles and trihalomethanes.


Bromates are primarily the result of bromides interacting with the ozone that some public water systems add as a disinfectant. Bromates may also form because of oxidation in direct sunlight, such as in open-water reservoirs.

Animal experiments have linked the ingestion of bromate in drinking water with tumor formation. Although there are no studies on the long-term effects of bromate exposure, the EPA requires monthly testing for the disinfection byproduct at water treatment plants.

Chlorite and Chlorate

Chlorites and chlorates are disinfection byproducts created using chlorine dioxide or bleach in drinking water for disinfecting or controlling water's odor or taste. Public water systems frequently use chlorine dioxide to kill microorganisms and bacteria in water.

Chlorine dioxide and chlorite have been found to affect the development of organs and cause respiratory issues. An estimated 12 million people may be exposed to chlorine dioxide in the U.S. due to its use in water treatment facilities. The EPA issued regulations for chlorite and chlorine dioxide levels in drinking water plants to help limit exposure.

Why Are Disinfectants Used in Water Today?

Water treatment facilities continue to use disinfectants because drinking water may contain various pathogenic contaminants, including bacteria, viruses, and other microorganisms. Adding disinfectants to the public water supply effectively reduces or neutralizes these contaminants to levels that are unlikely to cause adverse health effects. Chlorine provides protection against waterborne diseases and associated symptoms like nausea, diarrhea, and vomiting.

The disinfectants used in the water treatment process are only one of several factors affecting the amount of disinfectant byproducts that can be present in drinking water. Other factors include:

  • The organic compounds present in the water.
  • The treatments used to remove the water's organic matter and other particles.
  • The concentration of disinfectants.

The most common chemical for disinfecting water is chlorine. Its use as a water disinfectant dates back to London in 1850 during the cholera epidemic, and it has seen widespread use since the early 1900s. However, recent questions related to the effects of chlorine in water have many questioning the continued usage of chlorine.

How Disinfection Byproducts Harm Human Health

While disinfectants are useful for removing microbial contaminants, their byproducts can harm human health. Long-term exposure to various disinfection byproducts is believed to increase the risk of adverse health consequences, including the following:

1. Cancer

The EPA classified trihalomethanes as Cancer Group B carcinogens. Drinking tap water containing these disinfection byproducts over a person's lifetime may increase their risk of colorectal and bladder cancer. Other studies have also demonstrated that trihalomethanes can damage the central nervous system, lungs, heart, kidneys, and liver. Additionally, the EPA found that trihalomethanes promoted liver and colon tumors.

The Centers for Disease Control and Prevention's (CDC) Agency for Toxic Substances and Disease Registry warns that drinking water with chloroform, a common trihalomethane, has been associated with a possible increase in the bladder, rectal, and colon cancers. You can absorb chloroform through your skin while showering or swimming in a public pool.

2. Reproductive Problems and Developmental Issues

There have been reports in scientific literature linking disinfection byproducts with birth defects and fetal developmental delays, with some studies indicating a link between trihalomethanes and miscarriages when ingested in high levels in drinking water.

Similarly, studies involving animals have demonstrated that high exposure to haloacetic acids can lead to developmental defects and lower birth weights.

3. Other Health Problems

According to the CDC, long-term exposure to high levels of chloroform can affect the central nervous system, liver, and kidneys. Exposure to even small amounts of haloacetic acids can cause eye and skin irritation that may be severe, depending on the levels of disinfection byproduct present.

Bromates are another contaminant that can cause various health issues. Ingesting bromates in large amounts over time can cause symptoms such as:

  • Nausea
  • Diarrhea
  • Vomiting
  • Hearing loss
  • Kidney issues
  • Abdominal pain
  • Nervous system problems

Alternate Water Disinfectant Practices

Water contaminants and disinfection byproducts are a much bigger problem than a simple case of residual chlorine in drinking water possibly affecting the smell or taste of the water you drink. The EPA studies on trihalomethanes conclude that the carcinogenic effects of a chemical mixture are "difficult to predict." Eliminating these risks by reducing exposure to disinfection byproducts provides invaluable peace of mind.

Alternate water disinfectant practices have developed over time, becoming more efficient at contaminant reduction. For example, boiling water is the most widely-used way of disinfecting water at home. People can also add flocculation disinfectant powder to water, which creates solids that can then be removed. Solar disinfection is another relatively new method that uses UV rays and heat to kill parasites and bacteria. Many households have opted to use water filters, as many have proven effective at reducing chemicals and DBPs.

Eliminate Chemicals With a Multipure Drinking Water System

As an environmentally-conscious consumer and health-conscious homeowner, you now have some power to control your family's exposure to drinking, showering in, and cooking with tap water contaminated by disinfection byproducts. An effective step for reducing your risk of exposure to potentially harmful contaminants in your local water supply is investing in an effective water filtration system.

At Multipure, we provide point-of-use drinking water filtration systems as well as systems for your entire home. Our water filtration systems offer filtration of numerous contaminants, so you can drink, cook, or bathe in your water with confidence that it's good for you and your family's health. Contact us today to do something to make a difference in the level of disinfection byproducts in your water.