Bromodichloromethane
BDCM·Affects liver, kidneys, reproductive
A trihalomethane formed when chlorine reacts with bromide-containing source water. EPA-regulated, classified as a probable human carcinogen.
BDCM
EPA limit
0.080 mg/L (combined THMs)
Most at risk
Long-term consumers, pregnant women, coastal water systems
Found in
City water
AquaOx filters
YesActivated coconut shell carbon
What it does to you
Health effects
Bromodichloromethane is one of the four regulated trihalomethanes (THMs). The EPA classifies it as a probable human carcinogen based on animal studies showing kidney and liver tumors. In epidemiological work, elevated BDCM in drinking water correlates with increased risk of bladder and colorectal cancer over decades of exposure.
BDCM and the other brominated THMs are generally considered more concerning than pure chloroform on a per-microgram basis. Reproductive studies have linked higher THM exposure during pregnancy to lower birth weight, stillbirth, and certain birth defects.
As with all THMs, dermal absorption and inhalation in the shower contribute meaningfully to total exposure.
Where it comes from
How it gets into your water
BDCM forms the same way chloroform does: chlorine reacts with natural organic matter in source water. The difference is the bromide. When source water contains bromide (common in coastal areas, areas with seawater intrusion, or water sources affected by mining/oil operations), the chlorine-organic reaction produces brominated THMs like BDCM instead of pure chloroform.
Distribution pipes continue the reaction as water travels from the plant to your tap, so BDCM levels are often highest at the periphery of a water system.
Chlorinated treatment plants
Chlorine + bromide + organic matter
Distribution pipes
Reaction continues in transit
Bromide-rich source water
Coastal areas and oil/mining regions
Find out for yourself
Is it in your water?
If your city uses chlorine for disinfection and your source water contains any bromide, you have BDCM. The EPA combines it with the other three THMs (chloroform, dibromochloromethane, bromoform) under a single 80 ppb limit, so utilities report a combined number rather than BDCM specifically.
If you're in a coastal city or near oil/gas operations, check your utility's CCR for both the combined THM total and any individual breakdown they provide. The brominated species ratio is often higher in these areas.
The fix
How AquaOx filters it
Activated carbon filters all four regulated THMs with similar efficiency. The Centaur catalytic carbon and coconut shell carbon stages in The AquaOx capture BDCM as water passes through, with independent test reductions typically above 90%.
Because The AquaOx is installed at the main water line, BDCM is filtered before water reaches any shower, faucet, or appliance, which eliminates the inhalation and skin-absorption exposure routes that fridge or pitcher filters cannot address.
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