Disinfection Byproducts (DBPs) in Water

If your water comes from a municipal supplier, there’s a high chance that it contains disinfection byproducts (DBPs). These invisible contaminants have a number of known health effects when found in water.

In this glossary, we’ve discussed everything you need to know about disinfection byproducts in drinking water, including how they’re formed, their health risks, and how to protect your family from these contaminants.

❔ What are Disinfection Byproducts?

Disinfection byproducts (DBPs) are organic, inorganic, or chemical substances that are formed when disinfectants (such as chlorine) come into contact with inorganic or organic matter.

💡 These contaminants were discovered in the 1970s by scientists who conducted gas chromatography testing. Since this discovery, some action has been taken to reduce the risk of DBPs in water, but they’re still widely present in public drinking water supplies today.

Disinfection byproducts are most commonly found in chlorinated drinking water. There are around 600 known DBPs, but only a handful of these have clear data on their health effects and treatment options. Common disinfection byproducts are bromate, chlorate, chlorite, haloacetic acids, and trihalomethanes (THMs). Each of these substances has its own set of health risks.

In Water As	Bromate Chlorite Haloacetic acids (HAA) Trihalomethanes (THM)
Sources	Disinfection in public drinking water supplies
Maximum Contaminant Levels (MCLs)	US EPA: Bromate - 0.010 mg/L Chlorite - 1.0 mg/L Haloacetic acids - 0.060 mg/L Total trihalomethanes - 0.080 mg/L
Potential Health Risks	Vomiting, nausea, diarrhea, abdominal pain Increased risk of bladder and colon cancer Potential carcinogen
Treatments	Granular Activated Carbon Reverse Osmosis Nanofiltration Water Distiller

🩺 What are the Potential Health Effects of Disinfection Byproducts?

Different disinfection byproducts have their own harmful health effects. The most common disinfection byproducts, and their health effects, are:

• Bromate: vomiting, nausea, diarrhea, abdominal pain, hearing loss, kidney effects, nervous system effects
• Chlorate: potential carcinogen, limits the blood’s ability to absorb oxygen, leading to kidney failure
• Chlorite: eye, nose, and throat irritation, coughing and shortness of breath
• Haloacetic acids: Increased risk of bladder, rectal, and colon cancer, birth defects, skin irritation, liver damage, nervous system effects
• Trihalomethanes: Increased risk of bladder and colon cancer, birth defects, reproductive problems

📌 Exposure to low levels of disinfection byproducts in the short term isn’t thought to have a known health risk. Somebody with an average drinking water consumption of 2 liters per day shouldn’t be adversely affected by DBPs. Generally, DBPs are most dangerous when they’re consumed in high concentrations over a prolonged period of time.

Although different DBPs have different health effects, most of them have one health risk in common: an excess cancer risk. The World Health Organization (WHO) International Agency for Research on Cancer has classified several disinfection byproducts based on their carcinogen status in this CDC article.

🚰 How Do Disinfection Byproducts Get Into Drinking Water?

Disinfection byproducts aren’t found naturally in surface or groundwater. These contaminants enter public drinking water supplies during disinfection .

If you drink disinfected drinking water from a municipal supplier, it’s likely that your water contains disinfectants – and disinfection byproducts.

All water delivered by a distribution system must be disinfected (typically with chlorine) to kill microorganisms like bacteria, viruses, and protozoans, for public health protection.

Disinfection byproducts are produced when disinfectants like chlorine, chlorine dioxide, chloramine, and bromate react with naturally occurring organic matter in tap water.

There’s no way to prevent the production of DBPs – as their name suggests, they’re a byproduct of chlorine disinfection. Disinfection byproducts continue to form as water travels through the distribution system to your home, so water treatment facilities can’t completely protect the public from these contaminants.

The types of disinfection byproducts that occur in municipal water depend on the disinfectant used to treat the water supply.

If you get your water from a private well, your risk of drinking disinfection byproducts is minimal. Private well supplies aren’t disinfected by public suppliers. Your own method of water disinfection will determine whether or not your water contains DBPs.

📉 Do Water Treatment Facilities Monitor Levels of Disinfection Byproducts in Drinking Water?

Yes, water treatment facilities are legally required to monitor and minimize the levels of disinfection byproducts in drinking water.

The Environmental Protection Agency (EPA) has established Disinfection Byproducts Rules to protect public health from these contaminants. These two rules apply to all community and non-community water systems, including those that serve less than 10,000 people.

The EPA’s Stage 1 Disinfectants and Disinfection Byproducts Rule (DBPR) reduces public exposure to disinfection by-products in drinking water systems. Stage 2 of the EPA’s DBPR tightens compliance monitoring requirements for two particular types of disinfection byproducts: haloacetic acids (HAA5), trihalomethanes (TTHM), and targets water supplies with the highest risk.

Additionally, several disinfection byproducts are regulated by the EPA, which has set a Maximum Contaminant Level for each of these contaminants:

• Bromate: 0.010 mg/L
• Chlorite: 1.0 mg/L
• Haloacetic acids: 0.060 mg/L
• Total trihalomethanes: 0.080 mg/L

Some DBPs aren’t currently regulated by the EPA, but they are on the EPA’s Unregulated Contaminant Monitoring Rule (UCMR) list, and may be regulated in the future.

Additionally, many water treatment facilities have now switched from chlorine to chloramine for drinking water disinfection. Chloramine isn’t as reactive with naturally occurring organic matter as chlorine. This means that it produces far fewer disinfection byproducts when it’s used to treat drinking water.

There are several other alternative disinfection methods, but not all of them are suitable for large-scale use. Chloramine is a good alternative to chlorine because it’s still affordable and easy to use on an ongoing basis.

However, chloramine is known to produce trihalomethane (THMs) and n-nitrosodimethylamine (NDMAs), two water disinfection by-products that aren’t commonly produced by chlorine – so chloramine still has its faults.

🔎 How Can I Tell if Disinfection Byproducts Are in My Drinking Water?

DBPs don’t have a taste, smell, or appearance in drinking water. This means you have no way to know whether or not your water contains DBPs, and what concentration of DBPs are present.

Testing your water is the only way to learn of its disinfection byproducts levels. A private laboratory test is the most accurate, thorough testing method for DBPs. Many laboratories offer testing packages that detect a selection of the most common disinfection byproducts, so you can learn exactly what your water contains.

📌 Keep in mind that water testing will only tell you the presence of DBPs at a certain point in time. Disinfectant levels are known to fluctuate in water, and their byproducts will fluctuate, too. Your water’s DBPs concentration may increase or decrease on a day-to-day basis.

👩🏽‍⚕️ How Can I Protect My Family from Disinfection Byproducts in Drinking Water?

The best way to protect your family from disinfection byproducts in drinking water is to remove these contaminants from your water supply before you drink it.

There are several water systems that offer effective at-home treatment for disinfection byproducts removal:

• Granular activated carbon filters: A granular activated carbon (GAC) filter can remove both chlorine and its disinfection byproducts. GAC uses adsorption to trap contaminants in its pores. Granular activated carbon filters may be used alone (such as in a faucet filter or a water pitcher filter) or as a stage in a large, point of entry water system.
• Reverse osmosis systems: Reverse osmosis is one of the best methods of purifying water and significantly improving water quality. The RO treatment process involves sending water through several stages, including a semi-permeable membrane, which removes heavy metals, chemicals, organic matter, and DBPs. A reverse osmosis water system is usually installed underneath a kitchen sink or on a kitchen countertop. Whole home RO systems are also available.
• Nanofiltration: Any kind of nanofilter should be capable of removing nanoparticles like disinfection byproducts. A nanofilter is typically used in a countertop or under-sink water filter. The technology is very similar to reverse osmosis, using a membrane to separate contaminants and organic substances from water particles. Nanofiltration removes virtually all DBPs from water.
• Water distillers: A water distiller uses heat to remove virtually all impurities from drinking water. During distillation, water is boiled until it vaporizes. The majority of contaminants, including most DBPs, remain in the boiling chamber, while the water vapor condenses into a separate container. Any remaining contaminants are removed by an activated carbon filter. A distilled water system is typically used as a countertop unit.

Aside from installing a water treatment solution, you may also contact your local water treatment facility and express your interest in using chloramine instead of chlorine to disinfect your water.

While chloraminated water isn’t entirely free from DBPs, it contains far fewer of these impurities. Contacting your water supplier might do nothing, but your supplier may consider public interest if they’re considering switching from chlorine to chloramine for drinking water disinfection.

⚠️ How Else Can I Be Exposed to Disinfection Byproducts?

Aside from drinking DBPs in your tap water, other sources of exposure to these contaminants are:

• Eating foods that have been grown, stored, prepared, or cooked in chlorinated water containing disinfection byproducts
• Breathing in air containing disinfection byproducts (such as when you’re showering, swimming, or bathing)
• Absorbing DBPs through your skin when swimming in chlorinated water

You can reduce your risk of inhaling DBPs by installing a water filtration system at water’s point of entry into your home.

📝 Where Can I Get More Information?

You can get more information on disinfection byproducts in tap water, including how they’re formed and their potential risks, from the websites listed below:

• EPA: Stage 1 and Stage 2 Disinfectants and Disinfection Byproducts Rules
• WHO: Disinfectants and Disinfection Byproducts
• Science Direct: Disinfection Byproducts