Chlorine [factsheet]

CHLORINE

Please Note: The main source of information for this fact sheet is EPA's Drinking Water Criteria Document for Chlorine, Hypochlorous Acid and Hypochlorite Ion. Other secondary sources include the Hazardous Substances Data Bank (HSDB), a database of summaries of peer-reviewed literature, and the Registry of Toxic Effects of Chemical Substances (RTECS), a database of toxic effects that are not peer reviewed.

Environmental/Occupational Exposure

* Workers may be exposed to chlorine in industries where it is produced or used, particularly in the food and paper industries. In addition, persons breathing air around these industries may be exposed to chlorine. (1)

* Exposure to chlorine may also occur through drinking water and swimming pool water, where it is used as a disinfectant. (2)

* Accidental releases are another potential source of chlorine exposure. (3)

Assessing Personal Exposure

* No data were located regarding detection of personal exposure to chlorine.

Health Hazard Information

Acute Effects:

* Chlorine is a potent irritant in humans to the eyes, the upper respiratory tract, and the lungs. Several studies have reported the following effects: 0.014 to 0.054 ppm: tickling of the nose; 0.04 to 0.097 ppm: tickling of the throat; 0.06 to 0.3 ppm; itching of the nose and cough, stinging, or dryness of the nose and throat; 0.35 to 0.72 ppm: burning of the conjunctiva and pain after 15 minutes; above 1.0 ppm: discomfort ranging from ocular and respiratory irritation to coughing, shortness of breath, and headaches. (4)

* Higher levels of chlorine have resulted in the following effects in humans: 1 to 3 ppm: mild mucous membrane irritation; 30 ppm: chest pain, vomiting, dypsnea, cough; 46 to 60 ppm: toxic pneumonitis and pulmonary edema; 430 ppm: lethal after 30 minutes; 1,000 ppm: fatal within a few minutes. (3)

* Chlorine is extremely irritating to the skin and can cause severe burns. (3)

* Acute animal tests, such as the LC₅₀ test in rats and mice, have shown chlorine to have high acute toxicity. (5)

* EPA'sOffice of Air Quality Planning and Standards, for a hazard ranking under Section 112(g) of the Clean Air Act Amendments, considers chlorine to be a "high concern" pollutant based on severe acute toxicity. (6)

Chronic Effects (Noncancer):

* Several studies in the older literature reported that chronic exposure to chlorine concentrations of around 5 ppm caused respiratory complaints, corrosion of the teeth, inflammation of the mucous membranes of the nose, and increased susceptibility to tuberculosis in workers. (7)

* Animal studies have reported decreased body weight gain, eye and nose irritation, and effects on the respiratory tract, liver, and kidney from chronic inhalation exposure to chlorine. (4)

* Other studies have indicated that exposure to chlorine, via inhalation, may alter disease resistance in animals, with higher incidences of emphysema, pneumonia, and tuberculosis reported. (4)

* The RfC and the RfD for chlorine are under review by EPA. (8)

Reproductive/Developmental Effects:

* No information is available on the developmental or reproductive effects of chlorine in humans or animals via inhalation exposure.

* No adverse effects on growth, lifespan, or fertility were reported in rats exposed to 100 ppm chlorine in their drinking water for their entire lifespan, over seven generations. (4)

* Since chlorine is highly reactive, uptake at sites such as the ovaries and testes which are remote from the respiratory tract, is anticipated to be minimal. (2)

Cancer Risk:

* No information is available on the carcinogenic effects of chlorine in humans from inhalation exposure.

* Several human studies have investigated the relationship between exposure to chlorinated drinking water and cancer. These studies were not designed to assess whether chlorine itself causes cancer, but whether trihalomethanes or other organic compounds occurring in drinking water as a result of chlorination are associated with an increased risk of cancer. These studies show an association between bladder and rectal cancer and chlorination byproducts in drinking water. (5)

* Chlorine has not been found to be carcinogenic in animals; no tumors were noted in a study where rats were exposed to 100 ppm chlorine in their drinking water over their lifespan, for 7 generations (see Reproductive/Developmental Effects section). (4)

* Another study evaluated the potential carcinogenicity of chlorinated drinking water in rats and mice and found no statistically significant increase in tumors that could be related to the chlorinated water. (2)

* EPA has not classified chlorine for carcinogenicity. (8)

Physical Properties

* Chlorine is a greenish-yellow gas that is slightly soluble in water. (7)

* Chlorine has a suffocating odor; the odor threshold is 0.31 ppm. (9)

* The chemical formula for chlorine is Cl₂, and its molecular weight is 70.90 g/mol. (4)

Uses

* Chlorine is used for water disinfection and for treatment of sewage effluent. It is also used to disinfect equipment and utensils in beverage and food processing plants, and as an intermediate in the manufacture of a number of organic products such as antifreeze, rubber, cleaning agents, and pharmaceuticals. (2,4)

Health Data from Inhalation Exposure

Concentration (mg/m³)	Health numbers^a	Regulatory, advisory numbers^b	Reference
1,000,000.0
_ _ _ _ 100,000.0
_ _ _ _ 10,000.0
_ _ _ _ 1,000.0
_ _ _ _ 100.0	* LC₅₀ (rats) (849 mg/m³) * LC₅₀ (mice) (397 mg/m³)		5 5
_ _ _ _ 10.0
_ _ _ _ 1.0		* OSHA PEL and ACGIH TLV (3 mg/m³) * OSHA PEL, ACGIH TLV, and NIOSH REL (1.5 mg/m³)	4 4

ACGIH TLVCAmerican Conference of Governmental and Industrial Hygienists' threshold limit value expressed as a time-weighted average; the concentration of a substance to which most workers can be exposed without adverse effects.

LC₅₀ (Lethal Concentration₅₀)CA calculated concentration of a chemical in air to which exposure for a specific length of time is expected to cause death in 50% of a defined experimental animal population.

NIOSH RELCNational Institute of Occupational Safety and Health's recommended exposure limit; NIOSH-recommended exposure limit for an 8- or 10-h time-weighted-average exposure and/or ceiling.

OSHA PELCOccupational Safety and Health Administration's permissible exposure limit expressed as a time-weighted average; the concentration of a substance to which most workers can be exposed without adverse effects averaged over a normal 8-h workday or a 40-h workweek.

^a Health numbers are toxicological numbers from animal testing or risk assessment values developed by EPA.

^b Regulatory numbers are values that have been incorporated in Government regulations, while advisory numbers are nonregulatory values provided by the Government or other groups as advice.

References

1. U.S. Environmental Protection Agency. Drinking Water Criteria Document for Chlorine, Hypochlorous Acid and Hypochlorite Ion. (External Review Draft.) Environmental Criteria and Assessment Office, Office of Health and Environmental Assessment, Cincinnati, OH. 1992.

2. U.S. Environmental Protection Agency. Integrated Risk Information System (IRIS) on Chlorine. Environmental Criteria and Assessment Office, Office of Health and Environmental Assessment, Office of Research and Development, Cincinnati, OH. 1993.

3. U.S. Department of Health and Human Services. Hazardous Substances Data Bank (HSDB, online database). National Toxicology Information Program, National Library of Medicine, Bethesda, MD. 1993.

4. E.J. Calabrese and E.M. Kenyon. Air Toxics and Risk Assessment. Lewis Publishers, Chelsea, MI. 1991.

5. R.D. Morris, A. Audet, I.F. Angelillo, T. C. Chalmers, and F. Mosteller. Chlorination, Chlorination by-products, and cancer: A meta-analysis. American Journal of Public Health, 82(7):955-977. 1992.

6. U.S. Environmental Protection Agency. Ambient Water Quality Criteria for Chlorine. EPA 440/5-84-030. Office of Water Regulations and Standards, Washington, DC. 1985.

7. American Council of Government of Industrial Hygienists (ACGIH). Documentation of the Threshold Limit Values. Fourth Edition. Cincinnati, OH. 1986.

8. U.S. Department of Health and Human Services. Registry of Toxic Effects of Chemical Substances (RTECS, online database). National Toxicology Information Program, National Library of Medicine, Bethesda, MD. 1993.

9. J.E. Amoore and E. Hautala. Odor as an aid to chemical safety: Odor thresholds compared with threshold limit values and volatilities for 214 industrial chemicals in air and water dilution. Journal of Applied Toxicology, 3(6):272-290. 1983.