EPA legal limit
No federal limit
Maximum Contaminant Level
EWG health guideline
0.06 ppb
Science-based, stricter target
IARC classification
Group 2A — probable human carcinogen
Cancer research classification
Health effects
BDCM is classified as a probable human carcinogen (Group 2A) by IARC — the strongest classification given to any of the four TTHM compounds. Animal studies have shown liver, kidney, and large intestinal tumours. Epidemiological evidence links BDCM exposure with bladder cancer. Reproductive effects include adverse pregnancy outcomes — particularly associated with showering and bathing exposure in addition to ingestion.
Where it comes from
Formed during chlorine disinfection when bromide naturally present in source water reacts with chlorinated intermediates. Higher bromide levels in coastal water supplies or water from industrial areas with bromide discharges lead to higher BDCM formation relative to chloroform.
How it's regulated
No individual EPA MCL — regulated under the combined TTHM limit of 80 ppb. EWG health guideline: 0.06 ppb, based on a 1-in-1-million cancer risk. The EWG guideline is stricter than for chloroform because of BDCM's higher carcinogenic potency per unit exposure.
How to filter bromodichloromethane
Not all filters address bromodichloromethane. Look for independently certified filters — NSF International certification means the removal claim has been independently verified.
BDCM is not removed by water ionization. An NSF 53 certified activated carbon block filter addresses TTHM compounds including BDCM.
Frequently asked questions
What is bromodichloromethane?
Bromodichloromethane (BDCM) is the second most prevalent trihalomethane compound in chlorinated drinking water, forming when chlorine reacts with naturally occurring organic matter in the presence of bromide ions. It is found at the highest concentrations in utilities that draw from surface water sources containing elevated bromide.
What are the health effects of bromodichloromethane?
BDCM is classified as a probable human carcinogen (Group 2A) by IARC — the strongest classification given to any of the four TTHM compounds. Animal studies have shown liver, kidney, and large intestinal tumours. Epidemiological evidence links BDCM exposure with bladder cancer. Reproductive effects include adverse pregnancy outcomes — particularly associated with showering and bathing exposure in addition to ingestion.
Is bromodichloromethane regulated in drinking water?
No individual EPA MCL — regulated under the combined TTHM limit of 80 ppb. EWG health guideline: 0.06 ppb, based on a 1-in-1-million cancer risk. The EWG guideline is stricter than for chloroform because of BDCM's higher carcinogenic potency per unit exposure.
Where does bromodichloromethane come from?
Formed during chlorine disinfection when bromide naturally present in source water reacts with chlorinated intermediates. Higher bromide levels in coastal water supplies or water from industrial areas with bromide discharges lead to higher BDCM formation relative to chloroform.
How do I remove bromodichloromethane from tap water?
The most effective methods for removing bromodichloromethane are: Activated carbon block filter, NSF 53 certified filter, Reverse osmosis (RO). Look for NSF-certified systems — independent certification confirms removal claims have been verified.
Is bromodichloromethane in your water?
Enter your ZIP code to see the measured level in your specific utility.