Disinfection by-products in drinking water
What are disinfection by-products?
Disinfection by-products (DBPs) are chemicals that can be formed when chlorine is used for disinfecting drinking water to prevent disease. The chlorine reacts with decaying organic matter, like leaves or vegetation, from lakes and rivers to form DBPs. 2 of the most common types of DBPs found in chlorinated drinking water are trihalomethanes (THMs) and haloacetic acids (HAAs).
Are there immediate health risks?
The use of chlorine to treat drinking water has almost completely eliminated waterborne bacteria and diseases like typhoid fever, cholera, dysentery, and other gastrointestinal diseases. Chlorine is the most commonly used drinking water disinfectant. It has been used to disinfect water and make it suitable for drinking for more than 100 years.
Some studies have suggested that long-term exposure to consistent high levels of THMs and/or HAAs might increase the risk of cancer. Experts agree that any health concern from these DBPs will come from exposure over many years.
The benefits of disinfecting drinking water with chlorine are much greater than the potential health risks of being exposed to higher levels of THMs and HAAs.
How are people exposed to DBPs?
You can come in contact with THMs and HAAs when drinking or bathing in affected water or breathing in steam when showering. Higher levels of THMs and HAAs often happen in summer and fall when there is more organic matter in a community's source water.
What can I do in my home if my community's water shows high levels of THMs or HAAs?
If the water in your community has elevated levels of THMs or HAAs, you can reduce your exposure by:
- opening a window or using a fan when bathing/showering
- taking baths of less than 30 minutes per day, or taking showers of less than 10 minutes per day
- using a pour-over filtration water pitcher for drinking
- using a safe alternative to tap water for drinking (do not drink water straight from a lake or river)
- using a treatment device in your home that is certified to remove THMs
- look for a filter that is labeled with the "NSF/ANSI 53" certification mark
- to keep your water clean, it is important to install and maintain the treatment device following the manufacturer's instructions (for example, filters should be replaced regularly)
You don't have to stop using tap water. You can still:
- brush your teeth
- wash fruits and vegetables
- use tap water to prepare foods
- wash dishes and clothes
For more information
For more information on disinfection by-products, please contact your community's environmental public health officer.