This is a fact sheet about a chemical that may be found in some public or
private drinking water supplies. It may cause health problems if found
in amounts greater than the health standard set by the United States
Environmental Protection Agency (EPA).
What is Benzo(a)pyrene and how is it used?
Benzo(a)pyrene, or BaP, is one of a group of compounds called
polycyclic aromatic hydrocarbons (PAHs). They are not produced or used
commercially but are very commonly found since they are formed as a
result of incomplete combustion of organic materials.
Trade Names and Synonyms:
Why is Benzo(a)pyrene being regulated?
In 1974, Congress passed the Safe Drinking Water Act. This law requires
EPA to determine safe levels of chemicals in drinking water which do or
may cause health problems. These non-enforceable levels, based solely on
possible health risks and exposure, are called Maximum Contaminant Level
The MCLG for benzo(a)pyrene has been set at zero because EPA
believes this level of protection would not cause any of the potential
health problems described below.
Based on this MCLG, EPA has set an enforceable standard called a
Maximum Contaminant Level (MCL). MCLs are set as close to the MCLGs as
possible, considering the ability of public water systems to detect and
remove contaminants using suitable treatment technologies.
The MCL has been set at 0.2 ppb because EPA believes, given
present technology and resources, this is the lowest level to which
water systems can reasonably be required to remove this contaminant
should it occur in drinking water.
These drinking water standards and the regulations for ensuring
these standards are met, are called National Primary Drinking Water
Regulations. All public water supplies must abide by these regulations.
What are the health effects?
Short-term: EPA has found benzo(a)pyrene to potentially cause the
following health effects when people are exposed to it at levels above
the MCL for relatively short periods of time: red blood cell damage,
leading to anemia; suppressed immune system.
Long-term: Benzo(a)pyrene has the potential to cause the following
effects from a lifetime exposure at levels above the MCL: developmental
and reproductive effects; cancer.
How much Benzo(a)pyrene is produced and released to the environment?
PAHs are found in exhaust from motor vehicles and other gasoline and
diesel engines, emission from coal-, oil-, and wood-burning stoves and
furnaces, cigarette smoke; general soot and smoke of industrial,
municipal, and domestic origin, and cooked foods, especially
charcoal-broiled; in incinerators, coke ovens, and asphalt processing
There are two major sources of PAHs in drinking water: 1)
contamination of raw water supplies from natural and man-made sources,
and 2) leachate from coal tar and asphalt linings in water storage tanks
and distribution lines. PAHs in raw water will tend to adsorb to any
particulate matter and be removed by filtration before reaching the tap.
PAHs in tap water will mainly be due to the presence of PAH-containing
materials in water storage and distribution systems.
Though few data are available for estimating the potential for PAH
release to water from these materials, there are reports that levels
can reach 0.01 mg/L with optimum leaching conditions.
What happens to Benzo(a)pyrene when it is released to the environment?
Released benzo(a)pyrene is moderately persistent in the environment. It
readily binds to soils and should not leach to ground water, though it
has been detected in some ground water. If released to water, it will
adsorb very strongly to sediments and particulate matter. In most waters
and in sediments it will resist breakdown by microbes or reactive
chemicals, but it may evaporate or be degraded by sunlight.
Benzo(a)pyrene is expected to bioconcentrate in aquatic organisms that
can not metabolize it, including plankton, oysters and some fish.
How will Benzo(a)pyrene be detected in and removed from my drinking
The regulation for BaP became effective in 1994. Between 1993 and 1995,
EPA required your water supplier to collect water samples every 3 months
for one year and analyze them to find out if BaP is present above 0.02
ppb. If it is present above this level, the system must continue to
monitor this contaminant.
If contaminant levels are found to be consistently above the MCL,
your water supplier must take steps to reduce the amount of BaP so that
it is consistently below that level. The following treatment methods
have been approved by EPA for removing BaP: Granular activated charcoal.
How will I know if Benzo(a)pyrene is in my drinking water?
If the levels of BaP exceed the MCL, 0.2 ppb, the system must notify the
public via newspapers, radio, TV and other means. Additional actions,
such as providing alternative drinking water supplies, may be required
to prevent serious risks to public health.
This is a factsheet about a chemical that may be found in some
public or private drinking water supplies. It may cause health problems
if found in amounts greater than the health standard set by the United
States Environmental Protection Agency (EPA).
Drinking Water Standards:
Mcl: 0.2 ppb (parts per billion)
* Water/Land totals only include facilities with releases greater
than a certain amount - usually 1000 to 10,000 lbs.
Note: This fact sheet is part of a larger publication
adapted from U.S. EPA publication: EPA National Primary Drinking Water