2/24/2009 US EPA

WATER SYSTEMS, DISINFECTION BYPRODUCTS, AND THE USE OF

MONOCHLORAMINE

7) Why are disinfection byproducts a public health concern?

Drinking water research indicates that certain byproducts of water
disinfection have the potential to be harmful.1

•	Some research indicates that certain byproducts of water disinfection are
linked to increases in cancer incidence, including bladder cancer.

•	Some research indicates that certain byproducts of water disinfection can
be linked to liver, kidney, central nervous system problems, and
reproductive effects.

•	Some research indicates that certain byproducts of water disinfection can
be linked to anemia.2

Assessments of the risks of water disinfection can be highly uncertain.

•	Scientists from many organizations have conducted research on the
effects of disinfection byproducts.

•	In some cases research results are contradictory; some studies show links
to adverse health effects and others do not.

•	Regulatory documents describe the uncertainties in risk assessments of
disinfection byproducts.1

The Environmental Protection Agency considers risk and uncertainty in
establishing regulations for water disinfection.

•	Regulators weigh the public health benefits of disinfection against the risks
of the potentially harmful disinfection byproducts.3

•	EPA sets limits for certain disinfection byproducts which are linked to
health effects such as bladder cancer.1

•	EPA and other organizations continue to conduct research on disinfection
byproducts.

Additional Supporting Information:

1.	EPA has adopted enforceable regulations to limit occurrence of disinfection
byproducts in drinking water for a group of four total trihalomethanes (TTHMs)
(chloroform, bromodichloromethane (BDCM), dibromochloromethane (DBCM), and
bromoform), a group of five haloacetic acids (HAA5) (monochloroacetic acid (MCA),
dichloroacetic acid (DCA), trichloroacetic acid (TCA), monobromoacetic acid (MBA), and
dibromoacetic acid (DBA)), and the individual byproducts chlorite and bromate. The
maximum contaminant levels for these disinfection byproducts are: TTHMs (0.080
mg/L), HAA5 (0.060 mg/L), chlorite (1.0 mg/L), bromate (0.010 mg/L). See Stage 2
Disinfection Byproducts Rule (71 FR 388, January 4, 2006) for more information on
disinfection byproducts and discussion of uncertainties,
http://www.epa.qov/fedrqstr/EPA-WATER/2006/Januarv/Dav-04/w03.pdf.

2.	For more information on anemia and disinfection byproducts visit
http://www.epa.gov/oqwdw/hfacts.html.

3.	See question 8 for additional information on how EPA regulates disinfection
byproducts.

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