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PUBLIC HEALTH STATEMENT 

Chlorine Dioxide and Chlorite 

CAS#: 10049-04-4 and 7758-19-2 

Division of Toxicology September 2004 

This Public Health Statement is the summary 

chapter from the Toxicological Profile for Chlorine 

Dioxide and Chlorite. It is one in a series of Public 

Health Statements about hazardous substances and 

their health effects. A shorter version, the 

ToxFAQsTM, is also available. This information is 

important because these substances 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. For more information, 

call the ATSDR Information Center at 1-888-422-

8737. 

This public health statement tells you about chlorine 

dioxide and chlorite and the effects of exposure to 

them. 

The Environmental Protection Agency (EPA) 

identifies the most serious hazardous waste sites in 

the nation. These sites are then placed on the 

National Priorities List (NPL) and are targeted for 

long-term federal clean-up activities. Chlorine 

dioxide and chlorite have not been found in any of 

the 1,647 current or former NPL sites. Although 

the total number of NPL sites evaluated for these 

substances is not known, the possibility exists that 

chlorine dioxide and chlorite may be found in the 

future as more sites are evaluated. This information 

is important because these sites may be sources of 

exposure and exposure to these substances may 

harm you. 

When a substance is released either from a large 

area, such as an industrial plant, or from a container, 

such as a drum or bottle, it enters the environment. 

Such a release does not always lead to exposure. 

You can be exposed to a substance only when you 

come in contact with it. You may be exposed by 

breathing, eating, or drinking the substance, or by 

skin contact. 

If you are exposed to chlorine dioxide or chlorite, 

many factors will determine whether you will be 

harmed. These factors include the dose (how 

much), the duration (how long), and how you come 

in contact with them. You must also consider any 

other chemicals you are exposed to and your age, 

sex, diet, family traits, lifestyle, and state of health. 

1.1 WHAT ARE CHLORINE DIOXIDE AND 

CHLORITE? 

Chlorine dioxide is a yellow to reddish-yellow gas 

that can decompose rapidly in air. Because it is a 

hazardous gas, chlorine dioxide is always made at 

the location where it is used. Chlorine dioxide is 

used as a bleach at pulp mills, which make paper 

and paper products, and in public water-treatment 

facilities, to make water safe for drinking. It has 

also been used to decontaminate public buildings. 

Chlorine dioxide is soluble in water and will react 

rapidly with other compounds. When it reacts in 

water, chlorine dioxide forms chlorite ion, which is 

also a very reactive chemical. Because chlorine 

dioxide is very reactive, it is able to kill bacteria and 

microorganisms in water. About 5% of large watertreatment facilities (serving more than 100,000 

persons) in the United States use chlorine dioxide to 

treat drinking water. An estimated 12 million 

persons may be exposed in this way to chlorine 

dioxide and chlorite ions. In communities that use 

chlorine dioxide to treat drinking water, chlorine 

dioxide and its by-product, chlorite ions, may be 

present at low levels in tap water. 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

 

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PUBLIC HEALTH STATEMENT 

Chlorine Dioxide and Chlorite 

CAS#: 10049-04-4 and 7758-19-2 

Division of Toxicology September 2004 

In this profile, the term “chlorite” will be used to 

refer to “chlorite ion,” which is a water-soluble ion. 

Chlorite ion can combine with metal ions to form 

solid salts (e.g., sodium chlorite). Sodium chlorite 

dissolves in water and forms chlorite ions and 

sodium ions. More than 80% of all chlorite (present 

as sodium chlorite) is used to make chlorine dioxide 

to disinfect drinking water. Sodium chlorite is also 

used as a disinfectant to kill germs. 

1.2 WHAT HAPPENS TO CHLORINE 

DIOXIDE AND CHLORITE WHEN THEY 

ENTER THE ENVIRONMENT? 

Chlorine dioxide is a very reactive compound. In 

air, sunlight quickly breaks chlorine dioxide apart 

into chlorine gas and oxygen. In water, chlorine 

dioxide reacts quickly to form chlorite ions. When 

chlorine dioxide reacts with dissolved organic 

compounds in water-treatment systems, it forms 

disinfection by-products, such as chlorite and 

chlorate ions. 

Like chlorine dioxide, chlorite is very reactive. 

Since chlorite is an ionic compound, it will exist 

primarily in water. Chlorite ions are mobile in 

water, and may move into groundwater. However, 

the reaction of chlorite ions with soils and 

sediments may reduce the concentration of chlorite 

ions capable of reaching groundwater. 

1.3 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 will be exposed to 

chlorine dioxide and its disinfection by-product, 

chlorite ions, when they drink water that has been 

treated with chlorine dioxide. The EPA has set the 

maximum concentration in the drinking water at 

0.8 milligrams per liter (mg/L) for chlorine dioxide 

and 1.0 mg/L for chlorite ion. The concentrations 

of chlorine dioxide and chlorite ion in your drinking 

water, however, may be lower or higher than these 

levels. 

1.4 HOW CAN CHLORINE DIOXIDE AND 

CHLORITE ENTER AND LEAVE MY 

BODY? 

Chlorine dioxide and chlorite usually enter the body 

when people drink water that has been disinfected 

with chlorine dioxide. Because chlorine dioxide 

rapidly breaks down in air to chlorine gas and 

oxygen, you would not likely breathe air containing 

dangerous levels of chlorine dioxide, but if you did, 

it could be absorbed across your lungs. You are not 

likely to encounter chlorite in the air you breathe. 

Whether chlorine dioxide or chlorite on your skin 

would be absorbed to any great extent is not known. 

Both chlorine dioxide and chlorite act quickly when 

they enter the body. Chlorine dioxide quickly 

changes to chlorite ions, which are broken down 

further into chloride ions. The body uses these ions 

for many normal purposes. Some chloride ions 

leave the body within hours or days, mainly in the 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

 

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PUBLIC HEALTH STATEMENT 

Chlorine Dioxide and Chlorite 

CAS#: 10049-04-4 and 7758-19-2 

Division of Toxicology September 2004 

urine. Most chlorite that is not broken down also 

leaves the body in the urine within a few days after 

exposure to chlorine dioxide or chlorite. 

1.5 HOW CAN CHLORINE DIOXIDE AND 

CHLORITE AFFECT MY HEALTH? 

Both chlorine dioxide and chlorite react quickly in 

water and moist body tissues. If you were to 

breathe air containing chlorine dioxide gas, you 

might experience irritation in your nose, throat, and 

lungs. If you were to eat or drink large amounts of 

chlorine dioxide or chlorite, you might experience 

irritation in the mouth, esophagus, or stomach. 

Most people will not be exposed to chlorine dioxide 

or chlorite in amounts large enough to damage other 

parts of the body, but if you were, you might 

experience shortness of breath and other respiratory 

problems because of damage to the substances in 

blood that carry oxygen throughout the body. 

Scientists use many tests to protect the public from 

harmful effects of toxic chemicals and to find ways 

for treating persons who have been harmed. 

One way to learn whether a chemical will harm 

people is to determine how the body absorbs, uses, 

and releases the chemical. For some chemicals, 

animal testing may be necessary. Animal testing 

may also help identify health effects such as cancer 

or birth defects. Without laboratory animals, 

scientists would lose a basic method for getting 

information needed to make wise decisions that 

protect public health. Scientists have the 

responsibility to treat research animals with care 

and compassion. Scientists must comply with strict 

animal care guidelines because laws today protect 

the welfare of research animals. 

Animal studies have shown effects of chlorine 

dioxide and chlorite that are similar to those seen in 

people exposed to very high amounts of these 

chemicals. In addition, exposure to high levels of 

chlorine dioxide and chlorite in animals both before 

birth and during early development after birth may 

cause delays in brain development. The levels to 

which the animals were exposed were much higher 

than levels that would likely be found in drinking 

water that has been disinfected with chlorine 

dioxide. 

1.6 HOW CAN CHLORINE DIOXIDE AND 

CHLORITE AFFECT CHILDREN? 

This section discusses potential health effects in 

humans from exposures during the period from 

conception to maturity at 18 years of age. 

Children exposed to large amounts of chlorine 

dioxide or chlorite would likely be affected in the 

same manner as adults. Exposure to chlorine 

dioxide gas in young children, however, might more 

quickly reduce the ability of blood to carry oxygen 

than in adults, making breathing more difficult. If 

infants or babies still in their mother’s womb were 

exposed to large amounts of chlorine dioxide, it 

might cause parts of their brains to develop more 

slowly. This has been seen in young animals, but 

has not actually been seen in humans. 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

 

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PUBLIC HEALTH STATEMENT 

Chlorine Dioxide and Chlorite 

CAS#: 10049-04-4 and 7758-19-2 

Division of Toxicology September 2004 

1.7 HOW CAN FAMILIES REDUCE THE 

RISK OF EXPOSURE TO CHLORINE 

DIOXIDE AND CHLORITE 

If your doctor finds that you have been exposed to 

substantial amounts of chlorine dioxide or chlorite, 

ask whether your children might also have been 

exposed. Your doctor might need to ask your state 

health department to investigate. 

Families that drink water treated with chlorine 

dioxide may reduce the risk of exposure to chlorine 

dioxide and chlorite ions by drinking bottled water 

that has not been treated with chlorine dioxide or 

chlorite ions. 

1.8 IS THERE A MEDICAL TEST TO 

DETERMINE WHETHER I HAVE BEEN 

EXPOSED TO CHLORINE DIOXIDE 

AND CHLORITE? 

Although no medical tests are available to 

determine whether you have been exposed to 

chlorine dioxide or chlorite, exposure to very large 

amounts may result in damage to red blood cells 

that can be observed through routine blood tests. 

1.9 WHAT RECOMMENDATIONS HAS THE 

FEDERAL GOVERNMENT MADE TO 

PROTECT HUMAN HEALTH? 

The federal government develops regulations and 

recommendations to protect public health. 

Regulations can be enforced by law. The EPA, the 

Occupational Safety and Health Administration 

(OSHA), and the Food and Drug Administration 

(FDA) are some federal agencies that develop 

regulations for toxic substances. Recommendations 

provide valuable guidelines to protect public health, 

but cannot be enforced by law. The Agency for 

Toxic Substances and Disease Registry (ATSDR) 

and the National Institute for Occupational Safety 

and Health (NIOSH) are two federal organizations 

that develop recommendations for toxic substances. 

Regulations and recommendations can be expressed 

as “not-to-exceed” levels, that is, levels of a toxic 

substance in air, water, soil, or food that do not 

exceed a critical value that is usually based on 

levels that affect animals; they are then adjusted to 

levels that will help protect humans. Sometimes 

these not-to-exceed levels differ among federal 

organizations because they used different exposure 

times (an 8-hour workday or a 24-hour day), 

different animal studies, or other factors. 

Recommendations and regulations are also updated 

periodically as more information becomes available. 

For the most current information, check with the 

federal agency or organization that provides it. 

Some regulations and recommendations for chlorine 

dioxide and chlorite include the following: 

OSHA regulates the level of chlorine dioxide in 

workplace air. The occupational exposure limit for 

an 8-hour workday, 40-hour workweek is 0.1 parts 

per million (0.28 milligrams per cubic meter 

[mg/m3

]). The EPA has set a maximum 

contaminant level of 1 mg/L for chlorite in drinking 

water and a goal of 0.8 mg/L for both the maximum 

residual disinfectant level for chlorine dioxide and 

the maximum contaminant level for chlorite in 

drinking water that has been treated with chlorine 

dioxide as a disinfectant. 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

 

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PUBLIC HEALTH STATEMENT 

Chlorine Dioxide and Chlorite 

CAS#: 10049-04-4 and 7758-19-2 

Division of Toxicology September 2004 

1.10 WHERE CAN I GET MORE 

INFORMATION? 

If you have any more questions or concerns, please 

contact your community or state health or 

environmental quality department, your regional 

Nuclear Regulatory Commission office, or contact 

ATSDR at the address and phone number below. 

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. 

Toxicological profiles are also available on-line at 

www.atsdr.cdc.gov and on CD-ROM. You may 

request a copy of the ATSDR ToxProfilesTM 

CD-ROM by calling the information and technical 

assistance toll-free number at 1-888-42ATSDR 

(1-888-422-8737), by email at atsdric@cdc.gov, or 

by writing to: 

Agency for Toxic Substances and Disease Registry 

Division of Toxicology 

1600 Clifton Road NE 

 Mailstop F-32 

Atlanta, GA 30333 

 Fax: 1-770-488-4178 

For-profit organizations may request a copy of final 

profiles from the following: 

National Technical Information Service (NTIS) 

5285 Port Royal Road 

Springfield, VA 22161 

Phone: 1-800-553-6847 or 1-703-605-6000 

Web site: http://www.ntis.gov/ 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov