EPA legal limit
10 ppb
Maximum Contaminant Level
EWG health guideline
0.1 ppb
Science-based, stricter target
IARC classification
Group 2B — possibly carcinogenic to humans
Cancer research classification
Health effects
Bromate is classified as a probable human carcinogen (Group 2B) by IARC, based on kidney tumour evidence in animal studies. The EPA MCL of 10 ppb is set at the analytical detection limit for routine monitoring, not at a level representing no risk — the EWG health guideline of 0.1 ppb reflects the cancer risk at the 1-in-1-million level.
Where it comes from
Forms specifically during ozone disinfection of water with bromide present in source water. Not a chlorination byproduct. Most common in utilities that have adopted ozonation as an alternative disinfectant, including some large urban systems and groundwater utilities in coastal areas.
How it's regulated
EPA MCL: 10 ppb (running annual average). The EWG health guideline is 0.1 ppb — 100× stricter — based on cancer risk assessment. Bromate does not form in chlorinated water systems; it is specific to ozone treatment.
The EPA vs EWG gap
The legal limit (10 ppb) is 100× higher than the EWG health guideline (0.1 ppb). Water can be legally compliant while still exceeding the science-based threshold.
How to filter bromate
Not all filters address bromate. Look for independently certified filters—NSF International certification means the removal claim has been independently verified.
Frequently asked questions
What is bromate?
Bromate is a disinfection byproduct that forms when water containing naturally occurring bromide is treated with ozone. It is a particular concern for utilities that have switched to ozone disinfection to reduce chlorine-based byproducts (TTHMs and HAAs) — ozonation reduces one class of DBPs but creates bromate instead.
What are the health effects of bromate?
Bromate is classified as a probable human carcinogen (Group 2B) by IARC, based on kidney tumour evidence in animal studies. The EPA MCL of 10 ppb is set at the analytical detection limit for routine monitoring, not at a level representing no risk — the EWG health guideline of 0.1 ppb reflects the cancer risk at the 1-in-1-million level.
Is bromate regulated in drinking water?
EPA MCL: 10 ppb (running annual average). The EWG health guideline is 0.1 ppb — 100× stricter — based on cancer risk assessment. Bromate does not form in chlorinated water systems; it is specific to ozone treatment.
Where does bromate come from?
Forms specifically during ozone disinfection of water with bromide present in source water. Not a chlorination byproduct. Most common in utilities that have adopted ozonation as an alternative disinfectant, including some large urban systems and groundwater utilities in coastal areas.
How do I remove bromate from tap water?
The most effective methods for removing bromate are: Reverse osmosis (RO), NSF 58 certified RO system, Activated carbon block filter. Look for NSF-certified systems—independent certification confirms removal claims have been verified.
Is bromate in your water?
Enter your ZIP code to see the measured level in your specific utility.