ToxFAQs™ for Chlorine Dioxide and Chlorite
de Cloro y Clorito
CAS#: 10049-04-4 (Chlorine Dioxide); 7758-19-2 (Chlorite)
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This fact sheet answers the most frequently
asked health questions about chlorine dioxide and chlorite.
For more information, you may call the ATSDR Information Center
at 1-888-422-8737. This fact sheet is one in a series of summaries
about hazardous substances and their health effects. This
information is important because this substance may harm you.
The effects of exposure to any hazardous substance depend
on the dose, the duration, how you are exposed, personal traits
and habits, and whether other chemicals are present.
is a gas that does not occur naturally in the environment.
It is used to disinfect drinking water and make it safe
to drink. Chlorite is formed when chlorine dioxide reacts
with water. High levels of chlorine dioxide can be irritating
to the nose, eyes, throat, and lungs. Chlorine dioxide
and chlorite have not been found in any of the 1,647 National
Priorities List sites identified by the Environmental
Protection Agency (EPA).
What are chlorine dioxide and chlorite?
Chlorine dioxide is a yellow to reddish-yellow
manufactured gas. It does not occur naturally in the environment.
When added to water, chlorine dioxide forms chlorite ion,
which is also a very reactive chemical.
Chlorine dioxide is used as a bleaching
agent at paper manufacturing plants, and in public water treatment
facilities to make water safe to drink. In 2001, chlorine
dioxide and chlorite were used to decontaminate a number of
public buildings following the release of anthrax spores in
the United States.
What happens to chlorine dioxide and chlorite when
they enter the environment?
- Chlorine dioxide is a very reactive compound and breaks
down quickly in the environment.
- In air, sunlight rapidly breaks down chlorine dioxide
into chlorine gas and oxygen.
- In water, chlorine dioxide quickly forms chlorite.
- Chlorite in water may move into groundwater, although
reactions with soil and sediments may reduce the amount
of chlorite reaching groundwater.
- Neither chlorine dioxide or chlorite build up in the food
How might I be exposed to chlorine dioxide and chlorite?
Chlorine dioxide is added to drinking
water to protect people from harmful bacteria and other microorganisms.
Most people are exposed to small amounts of chlorine dioxide
and chlorite by drinking treated water.
Individuals who are employed at pulp
and paper mills, municipal water treatment facilities, and
other facilities that use chlorine dioxide and chlorite as
a disinfectant may have high exposures to chlorine dioxide
and chlorite (ions or salts).
How can chlorine dioxide and chlorite affect my health?
Both chlorine dioxide and chlorite react
quickly in water or moist body tissues. Breathing air containing
chlorine dioxide gas may cause nose, throat, and lung irritation.
Eating or drinking large amounts of chlorite salts may cause
irritation in the mouth, esophagus, or stomach. There is no
evidence that chlorine dioxide or chlorite affect reproduction
Studies in animals exposed to high amounts
of chlorine dioxide or chlorite have shown effects similar
to those seen in exposed people.
How likely are chlorine dioxide and chlorite to cause cancer?
There are no studies on cancer in humans
exposed to chlorine dioxide or chlorite. Based on inadequate
information in humans and in animals, the International Agency
for Research on Cancer (IARC) and the EPA have determined
that chlorine dioxide and sodium chlorite are not classifiable
as to human carcinogenicity.
How can chlorine dioxide and chlorite affect children?
Children exposed to large amounts of
chlorine dioxide and chlorite would be expected to be affected
in the same manner as adults.
Studies in rats have shown that exposure
of pregnant animals to chlorine dioxide or exposure of pups
shortly after birth may cause delays in the development of
the brain. However, the exposure levels in these studies were
much higher than what humans are usually exposed to these
compounds in the drinking water. There are no reliable studies
of effects of chlorine dioxide or chlorite in developing humans.
How can families reduce the risk of exposure to chlorine dioxide and chlorite?
Families that drink water treated with
chlorine dioxide may reduce their exposure by drinking bottled
water that has not been treated with these chemicals.
Is there a medical test to show whether I've been
exposed to chlorine dioxide and chlorite?
There are no routine medical tests available
to measure chlorine dioxide or chlorite in the body. There
is a special test to measure chlorite in tissues, blood, urine,
and feces, but the test cannot tell the extent of the exposure
or whether harmful effects will occur.
Has the federal government made recommendations to protect human health?
The EPA has set a maximum contaminant
level of 1 milligram of chlorite per liter (1 mg/L) and 0.8
mg/L for chlorine dioxide in drinking water. However, the
concentration of both of these chemicals may be higher or
lower in your drinking water.
The Occupational Safety and Health Administration
(OSHA) has set a limit of 0.1 parts of chlorine dioxide or
chlorite per million parts of air (0.1 ppm) in the workplace
during an 8-hour shift, 40-hour workweek.
Agency for Toxic Substances and Disease Registry (ATSDR). 2004.
Toxicological Profile for Chlorine Dioxide and Chlorite. Atlanta, GA: U.S. Department of Health and Human Services, Public Health
Where can I get more information?
If you have questions or concerns, please contact your community or state health or environmental quality department or:
For more information, contact:
Agency for Toxic Substances and Disease Registry
Office of Innovation and Analytics, Toxicology Section
4770 Buford Highway
Chamblee, GA 30341-3717
Phone: 1-800-CDC-INFO 888-232-6348 (TTY)
Email: Contact CDC-INFO
ATSDR can also tell you the location of occupational and environmental health clinics. These clinics specialize in recognizing, evaluating, and treating illnesses resulting from exposure to hazardous substances.