Water - Disinfection Byproduct Health Effects

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Disinfection Byproduct Health Effects

September 20, 1999

http://www.epa.gov/enviro/html/icr/dbp_health.html

Since the discovery of chlorination byproducts in drinking water in

1974, numerous toxicological studies (studies on the health effects from

exposure to high dosages contaminants usually involving animals in a

lab) have been conducted. These studies have shown several disinfection

byproducts(1) to be carcinogenic in laboratory animals (e.g., including

bromate(2), certain trihalomethanes(3) and haloacetic acids(4)). Some

disinfection byproducts have also been shown to cause adverse

reproductive or developmental effects in laboratory animals (e.g.,

chlorite(5) and certain trihalomethanes(6) and haloacetic acids(4)).

However, there is considerable uncertainty involved in using the results

of high-dose, toxicological studies of some byproducts occurring in

disinfected drinking water to estimate the risk to humans from chronic

exposure to low doses of these and other byproducts.

In the area of epidemiology (studies of the factors that influence

disease in human populations), a number of studies have been completed

investigating the relationship between exposure to chlorinated surface

water and cancer. Some have suggested an increased cancer risk to those

exposed to chlorinated waters while others have demonstrated none. In

issuing the Stage 1 Disinfectants/Disinfection Byproducts Rule(7) based

on evidence then available, EPA stated that while the agency cannot

conclude there is a causal link between exposure to chlorinated surface

water and cancer, these studies have suggested an association, albeit

small, between bladder, rectal, and colon cancer and exposure to

chlorinated surface water. There are fewer epidemiology studies

evaluating the association between exposure to disinfection byproducts

and reproductive and developmental effects. Again, some have suggested

an increased risk from exposure to disinfection byproducts while others

have shown none. There remains considerable debate in the scientific

community on the significance of these contradictory findings concerning

chlorinated water and disinfection byproducts. As with cancer, EPA

stated in its Stage 1 Disinfectants/Disinfection Byproducts Rule that,

based on data then available, the agency can not conclude there is a

causal link between exposure to disinfection byproducts and reproductive

and developmental effects. In sum, EPA believes the weight-of-evidence

presented by the available epidemiological studies on chlorinated

drinking water and toxicological studies on individual disinfection

byproducts support a potential hazard concern and warrant regulatory

action at this time such as that taken in the Stage 1

Disinfectants/Disinfection Byproducts Rule.

An extensive research effort (1997 Update to ORD's Strategic Plan(8),

National Toxicology Program(9)) is currently underway to better

understand the potential risks attending exposure to disinfection

byproducts. While this research is being completed, an agreement among

water suppliers, environmental groups, consumer groups, and regulatory

agencies has been reached, resulting in the publication of a Stage 1

Disinfectants/Disinfection Byproducts Rule by EPA in the Federal

Register in December 1998. The participants recommended that while

additional information, especially on health effects, is needed, the

Stage 1 Disinfectants/Disinfection Byproducts Rule was considered the

best course of action to reduce potential risks from disinfection

byproducts in the near term.

(1)http://www.epa.gov/enviro/html/icr/gloss_dbp.html#dbp

(2)http://www.epa.gov/enviro/html/icr/gloss_dbp.html#tthm'>http://www.epa.gov/enviro/html/icr/gloss_dbp.html#tthm

(3)http://www.epa.gov/enviro/html/icr/gloss_dbp.html#hha'>http://www.epa.gov/enviro/html/icr/gloss_dbp.html#hha

(4)http://www.epa.gov/enviro/html/icr/gloss_dbp.html#chlorite

(5)http://www.epa.gov/enviro/html/icr/gloss_dbp.html#tthm'>http://www.epa.gov/enviro/html/icr/gloss_dbp.html#tthm

(6)http://www.epa.gov/enviro/html/icr/gloss_dbp.html#hha'>http://www.epa.gov/enviro/html/icr/gloss_dbp.html#hha

(7)http://www.epa.gov/OGWDW/mdbp/dbpfr.html

(8)http://www.epa.gov/ORD/WebPubs/stratplan/page1-20.pdf

(9)http://ntp-server.niehs.nih.gov/