Disinfection Byproducts (DBPs)
Disinfection byproducts form when chlorine or other disinfectants react with naturally occurring organic matter in source water. The two main regulated groups are total trihalomethanes (TTHMs) and haloacetic acids (HAA5). They are an unavoidable tradeoff of water disinfection — the risk of not disinfecting far outweighs the risk of DBPs, but minimizing exposure is prudent.
Quick Reference · DBPs
Quick Answer
When utilities add chlorine to water to kill pathogens, it reacts with dissolved organic matter — leaves, algae, soil — to produce disinfection byproducts (DBPs). Over 600 DBPs have been identified. The EPA regulates two groups: total trihalomethanes (TTHMs, including chloroform) and haloacetic acids (HAA5). DBP levels tend to be highest in surface water systems and in warm months when organic matter is elevated.
Why Is DBPs in Drinking Water a Concern?
While DBPs are present at low levels in virtually all chlorinated water systems, long-term exposure has been associated with increased bladder cancer risk and reproductive effects. The EPA sets running annual averages to limit exposure, but individual quarterly samples can exceed averages.
Everyone on chlorinated public water has some DBP exposure. People who drink large amounts of tap water, swim in chlorinated pools, or take long showers in chlorinated water (which allows inhalation and skin absorption) have greater exposure. Pregnant women are advised to minimize exposure.
Health Effects of DBPs in Drinking Water
Increased bladder cancer risk with decades of high-level exposure
Adverse reproductive outcomes — miscarriage, low birth weight (at elevated levels)
Possible colorectal cancer association (research ongoing)
Liver and kidney stress at high concentrations
How Does DBPs Get Into Drinking Water?
Reaction between chlorine disinfectant and natural organic matter
Surface water sources (rivers, reservoirs) with high organic content
Seasonal algae blooms increasing precursor material
Chloramines (alternative disinfectant) producing different DBP profile
Distribution system aging — water that sits longer forms more DBPs
Regulatory Limit
EPA Maximum Contaminant Level (MCL)
80 µg/L (TTHMs) / 60 µg/L (HAA5)
The EPA limits total trihalomethanes (TTHMs) to 80 micrograms per liter (µg/L) and haloacetic acids (HAA5) to 60 µg/L, measured as annual running averages across all monitoring points in the system. These limits were set under the Stage 2 Disinfectants and Disinfection Byproducts Rule (2006). Some international standards are more stringent.
How to Test for DBPs in Your Water
DBPs are routinely monitored by public water systems and reported in Consumer Confidence Reports. Results are reported as system-wide running annual averages. Individual samples at your tap may vary — distribution system age and distance from the treatment plant affect DBP levels.
How to Remove DBPs from Drinking Water
These treatment methods have demonstrated effectiveness for DBPs removal.
Reverse Osmosis
Reverse osmosis (RO) is the most comprehensive point-of-use water treatment technology available for residential use. It removes 90–99% of dissolved contaminants including PFAS, lead, arsenic, nitrates, and disinfection byproducts by forcing water through a semi-permeable membrane with pores of approximately 0.0001 microns.
Activated Carbon
Activated carbon is the most widely used residential water treatment technology. It removes chlorine, taste and odor compounds, disinfection byproducts, many volatile organic compounds (VOCs), and — with NSF/ANSI 53 certification — lead and some PFAS. It is available as pitcher filters, under-sink units, and whole-house systems.
Utilities With DBPs Violations(8+ in database)
These utilities have reported DBPs-related violations in EPA SDWIS. Ordered by population served.
Mdwasa - Main System
FL · 2.4M served
City of Baltimore
MD · 1.6M served
Atlanta
GA · 1.1M served
Aqua Pa Main System
PA · 823K served
City of Tucson
AZ · 733K served
Kentucky-american Water Co
KY · 669K served
Milwaukee Waterworks
WI · 626K served
Baton Rouge Water Company
LA · 597K served
Frequently Asked Questions
From DBPs to Action
Find a certified lab to test for DBPs
State-certified labs for PFAS, lead, nitrate, bacteria, and more
Reverse osmosis — removes DBPs
NSF certification details, cost range, and maintenance notes
Activated carbon filters — DBPs reduction
NSF certification details, cost range, and maintenance notes
Look up your specific utility's records
Search by ZIP code or utility name for compliance and PFAS data
DBPs in California
State-specific violations, utilities, and testing guidance
DBPs in Texas
State-specific violations, utilities, and testing guidance
DBPs in Florida
State-specific violations, utilities, and testing guidance
DBPs in Arizona
State-specific violations, utilities, and testing guidance
Data sources and methodology
How EPA compliance and UCMR 5 monitoring data is sourced and validated
Questions About DBPs in Drinking Water
How do I test my water for DBPs?
Find state-certified labs — confirm EPA Method 533/537.1 for PFAS
Which utilities have DBPs violations?
Search by ZIP code or utility name for official EPA compliance records
What removes DBPs from tap water?
Reverse Osmosis Filtration — NSF certification details, cost, and maintenance
How is DBPs data sourced on this site?
EPA SDWIS, UCMR 5, and CCR data sources — update cadence and accuracy notes
Related Pages
Data Sources & Provenance
All data on this page is sourced from official U.S. government or public datasets.
Quick Reference
Category
Disinfection Byproducts
Risk Level
moderate
EPA Limit
80 µg/L (TTHMs) / 60 µg/L (HAA5)
Most at Risk
Everyone on chlorinated public water has some DBP exposure.
Well Water Relevant
No
DBPs by State
Treatment Options