Chlorine is a chemical element with symbol Cl and atomic number 17. Under standard condition, the element is a yellow-green gas with a characteristic pungent odour, where it forms diatomic molecules. At approximately -34 degrees C (-29.2 degrees F) or at high pressures, chlorine condenses to an amber liquid. It has the highest electron affinity and the third highest electronegativity of all the elements; for this reason, chlorine is a strong oxidising agent. Free chlorine is rare on Earth, and is usually a result of direct or indirect oxidation by oxygen. [fusion_builder_container hundred_percent=”yes” overflow=”visible”][fusion_builder_row][fusion_builder_column type=”1_1″ background_position=”left top” background_color=”” border_size=”” border_color=”” border_style=”solid” spacing=”yes” background_image=”” background_repeat=”no-repeat” padding=”” margin_top=”0px” margin_bottom=”0px” class=”” id=”” animation_type=”” animation_speed=”0.3″ animation_direction=”left” hide_on_mobile=”no” center_content=”no” min_height=”none”][1,2]


Uses [3]


Chlorine is typically used in industrial plastic production, metal degreasing and dry cleaning solvents, textiles, agrochemicals and many more industrial and consumer products. It is used in bromine extraction and production of chlorates. In addition, chlorine is involved in water purification, disinfecting agents, especially as bleach. Typical household bleach does not contain pure chlorine, but does contain sodium hypochlorite, which is created from reacting chlorine and sodium hydroxide. Drinking water and public pools are disinfected by chlorine in hypochlorous acid.


Sources of Emission & Routes of Exposure


Sources of Emission [4]


  • Because chlorine is so reactive, it is not normally detected in the environment except for very low levels in the air above seawater.
  • You may be exposed through breathing, skin and eye contact if accident involving chlorine takes place nearby, such as a liquid chlorine spill, a leak from a chlorine tank, or a leak from a facility that produces or uses chlorine.
  • You may also be exposed to chlorine if you mix household chemicals such as toilet cleaner with bleach. Mixing household cleaners containing ammonia with bleach may also release dangerous chemicals into the air.
  • You may be exposed to chlorine gas through the improper use of swimming pool chemicals.
  • People who work in places where chlorine is made or used may be exposed to low levels over a period of time


Routes of Exposure [2]


Exposure to chlorine can occur through:

  • inhalation;
  • ingestion;
  • contact with the eyes;
  • contact with the skin


Health Effects [5]


Acute Effects


Chlorine is a potent irritant in humans to the eyes, the upper respiratory tract, and the lungs. Several acute (short-term) studies have reported the following effects: tickling of the nose at 0.014 to 0.054 parts per million (ppm); tickling of the throat at 0.04 to 0.097 ppm; itching of the nose and cough, stinging, or dryness of the nose and throat at 0.06 to 0.3 ppm; burning of the conjunctiva and pain after 15 minutes at 0.35 to 0.72 ppm; and discomfort ranging from ocular and respiratory irritation to coughing, shortness of breath, and headaches above 1.0 ppm. Higher levels of chlorine have resulted in the following effects in humans: mild mucous membrane irritation at 1 to 3 ppm; chest pain, vomiting, dypsnea, and cough at 30 ppm; and toxic pneumonitis and pulmonary oedema at 46 to 60 ppm. Chlorine is extremely irritating to the skin and can cause severe burns in humans. Acute animal tests in rats and mice have shown chlorine to have high acute toxicity via inhalation.


Chronic Effects


Workers chronically exposed to chlorine gas have exhibited respiratory effects, such as eye and throat irritation, and airflow obstruction. Animal studies have reported decreased body weight gain, eye and nose irritation, and non-neoplastic lesions and respiratory epithelial hyperplasia from chronic inhalation exposure to chlorine. The Reference Dose (RfD) for chlorine is 0.1 milligrams per kilogram body weight per day (mg/kg/d) based on no observed adverse effects in rats. EPA has not established a Reference Concentration (RfC) for chlorine. CalEPA has established a chronic reference exposure level of 0.00006 milligrams per cubic metre (mg/m3) based on respiratory epithelial lesions in rats.


Reproductive/Developmental Effects


No information is available on the developmental or reproductive effects of chlorine in humans or animals via inhalation exposure. Animal studies have demonstrated no evidence of reproductive or developmental effects from ingestion exposure to chlorine. 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.


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 by-products in drinking water. An NTP study reported no evidence of carcinogenic activity in male rats or male and female mice, and equivocal evidence, based on an increase in mononuclear cell leukaemia, in female rats, from ingestion of chlorinated or chloraminated water. EPA has not classified chlorine for carcinogenicity.




First Aid Measures [6]


  • Inhalation: Remove victim from area of exposure – avoid becoming a casualty. Remove contaminated clothing and loosen remaining clothing. Allow patient to assume most comfortable position and keep warm. Keep at rest until fully recovered. If patient finds breathing difficult and develops a bluish discolouration of the skin (which suggests a lack of oxygen in the blood – cyanosis), ensure airways are clear of any obstruction and have a qualified person give oxygen through a face mask. Apply artificial respiration if patient is not breathing. Seek immediate medical advice.
  • Skin Contact: If skin or hair contact occurs, immediately remove any contaminated clothing and wash skin and hair thoroughly with running water. If swelling, redness, blistering or irritation occurs seek medical assistance. For skin burns, cover with a clean, dry dressing until medical help is available. Launder contaminated clothing before reuse.
  • Eye Contact: If in eyes, hold eyelids apart and flush the eye continuously with running water. Continue flushing until advised to stop by a Poisons Information Centre or a doctor, or for at least 15 minutes.
  • Ingestion: Immediately rinse mouth with water. If swallowed, do NOT induce vomiting. Give a glass of water. Seek immediate medical assistance.
  • Medical attention and special treatment: Treat symptomatically. Effects may be delayed. Delayed pulmonary oedema may result.


Exposure Controls [6]


Ensure ventilation is adequate to maintain air concentrations below Exposure Standards. If inhalation risk exists: Use with local exhaust ventilation or while wearing air supplied mask. Vapour heavier than air – prevent concentration in hollows or sumps. DO NOT enter confined spaces where vapour may have collected.


Personal Protective Equipment [6]


The selection of PPE is dependant on a detailed risk assessment. The risk assessment should consider the work situation, the physical form of the chemical, the handling methods, and environmental factors. The following equipment is recommended with adequate ventilation:

  • Overalls;
  • Chemical goggles;
  • Full face shield;
  • Elbow-length impervious gloves;
  • If inhalation risk exists, wear air-supplied mask meeting the requirements of AS/NZS 1715 and AS/NZS 1716.
  • Always wash hands before smoking, eating, drinking or using the toilet.
  • Wash contaminated clothing and other protective equipment before storage or re-use.


Regulation [2,7,8]


Exposure Limits


United States

  • OSHA: The Occupational Safety and Health Administration’s permissible exposure limit (PEL) for chlorine is 1 ppm (3 milligrams per cubic metre (mg/m3) as a ceiling limit. A worker’s exposure to chlorine shall at no time exceed this ceiling level [29 CFR 1910.1000, Table Z-1].
  • NIOSH: The National Institute for Occupational Safety and Health has established a recommended exposure limit (REL) for chlorine of 0.5 ppm mg/m3 as a TWA for up to a 10-hour workday and a 40-hour workweek and a short-term exposure limit (STEL) of 1 ppm (3 mg/m m3)[NIOSH 1992].
  • ACGIH: The American Conference of Governmental Industrial Hygienists has assigned chlorine a threshold limit value (TLV) of 0.5 ppm (1.5 mg/m m3) as a TWA for a normal 8-hour workday and a 40-hour workweek and a short-term exposure limit (STEL) of 1.0 ppm (2.9 mg/m m3) for periods not to exceed 15 minutes. Exposures at the STEL concentration should not be repeated more than four times a day and should be separated by intervals of at least 60 minutes [ACGIH 1994, p. 15].



  • Safe Work Australia has established a TWA (parts per million) of 1 and a TWA (mg/m3) of 3
  • Australian Drinking Water Guidelines: Maximum of 1 mg/L (i.e. 0.001 g/L)