Health effects of chlorine dioxide and chlorite

Introduction

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 water-treatment 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.

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.

Pathways for chlorine dioxide and chlorite in the environment

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 water-treatment 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.

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.

Exposure 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.

Pathways for chlorine dioxide and chlorite in the 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 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.

Health effects of chlorine dioxide and chlorite

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.

Health effects in children

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.

You should know that 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 such health effects 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.

Additionally, there are vigorous national and international efforts to develop alternatives to animal testing. The efforts focus on both in vitro and in silico approaches and methods. For example, the National Toxicology Program (NTP) at the National Institute of Environmental Health Sciences (NIEHS) created the NTP Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM) in 1998. The role of NICEATM is to serve the needs of high quality, credible science by facilitating development and validation—and regulatory and public acceptance—of innovative, revised test methods that reduce, refine, and replace the use of animals in testing while strengthening protection of human health, animal health and welfare, and the environment. In Europe, similar efforts at developing alternatives to animal based testing are taking place under the aegis of the European Centre for the Validation of Alternative Methods (ECVAM).

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.

Reducing 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.

Medical tests for exposure 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.

Further Reading

Disclaimer: This article is taken wholly from, or contains information that was originally published by, the Agency for Toxic Substances and Disease Registry. Topic editors and authors for the Encyclopedia of Earth may have edited its content or added new information. The use of information from the Agency for Toxic Substances and Disease Registry should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.

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Citation

(2008). Health effects of chlorine dioxide and chlorite. Retrieved from http://www.eoearth.org/view/article/51cbedfa7896bb431f695357

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