Benzo(a)pyrene
BaP·Affects liver, lungs, reproductive
A polycyclic aromatic hydrocarbon (PAH) and IARC Group 1 known human carcinogen. The EPA's marker compound for PAH contamination in drinking water.
BaP
EPA limit
0.0002 mg/L (MCL)
Most at risk
Households near coal-tar sealed parking lots, creosote operations, or former manufactured gas plants
Found in
City water · Well water · Industrial areas
AquaOx filters
YesActivated coconut shell carbon
What it does to you
Health effects
Benzo(a)pyrene (BaP) is classified by the International Agency for Research on Cancer as a Group 1 known human carcinogen, the highest category. It is the most studied of the polycyclic aromatic hydrocarbons (PAHs) and serves as the indicator compound the EPA uses to regulate PAH exposure in drinking water. The compound is metabolized in the body to a highly reactive epoxide that binds DNA and causes the mutations linked to lung, skin, and digestive-tract cancers.
Beyond cancer, BaP is a documented reproductive and developmental toxicant. Animal studies show reduced fertility, fetal malformations, and immune system effects at sustained exposure. The lungs are a primary non-cancer target.
The EPA's MCL of 0.2 micrograms per liter is one of the lowest drinking-water limits because of BaP's potency as a carcinogen at very low doses. The MCLG is zero.
Where it comes from
How it gets into your water
Benzo(a)pyrene forms during incomplete combustion of organic matter: coal, oil, wood, tobacco, and gasoline all produce it. Urban runoff from coal-tar-sealed parking lots and driveways is the largest non-point source in many watersheds; these sealants contain PAHs at percent-level concentrations and erode into stormwater systems.
Industrial sources include former manufactured gas plants (MGP sites), coke ovens, aluminum smelting, asphalt and roofing operations, and creosote-treated wood facilities. Old MGP sites are particularly persistent PAH sources, with contamination from operations that ceased decades ago still affecting nearby groundwater.
BaP can also leach into water from coal-tar-coated cast iron and steel pipes used in older distribution systems.
Coal-tar sealants
Parking lot and driveway runoff
Former gas plants
Legacy MGP site groundwater
Contaminated wells
Near industrial or creosote sites
Coal-tar-lined pipes
Older distribution mains
Find out for yourself
Is it in your water?
Public water utilities are required to test for benzo(a)pyrene and report results in the annual Consumer Confidence Report. Most municipal systems report non-detect, but utilities serving areas with legacy industrial contamination or coal-tar-lined distribution pipes occasionally report detections at or near the MCL.
Private well owners near former manufactured gas plants, coal-tar facilities, creosote yards, aluminum smelters, or coke ovens should request PAH testing using EPA Method 525, which detects BaP at sub-microgram-per-liter levels.
The fix
How AquaOx filters it
Activated carbon is highly effective at filtering benzo(a)pyrene and other PAHs from drinking water. The Centaur catalytic carbon and coconut shell activated carbon stages in The AquaOx adsorb BaP strongly because of its large, hydrophobic molecular structure that binds tightly to carbon.
For households on wells with confirmed PAH contamination, we recommend pairing The AquaOx with the under-sink RO at the kitchen tap for a final-stage barrier on drinking and cooking water.