What is Chlorine?

Chlorine is a yellow-green diatomic gas at room temperature with a strong, pungent odour. Highly reactive, it acts as a powerful oxidizer and is typically found in combined forms due to its instability in nature. It condenses to a liquid at -34°C and is rarely found in its free form except when produced through industrial or oxidative processes.

What is Chlorine used for?

Chlorine is widely used in:

• Plastic manufacturing
• Metal degreasing & dry cleaning
• Textile & agrochemical production
• Bromine extraction & chlorate synthesis
• Water treatment (drinking water & pools)
• Household bleach (via sodium hypochlorite)

Sources of Emission & Route of Exposure

Sources of Emission

• Natural: Low levels above seawater
• Accidental: Spills, leaks from tanks/facilities
• Household: Mixing bleach with toilet cleaner or ammonia
• Pools: Improper use of pool chemicals
• Workplace: Manufacturing or handling chlorine

Routes of Exposure

• Inhalation
• Skin & eye contact
• Ingestion

Health Effects

Acute Effects

• Low doses (0.014–1 ppm): Nose/throat tickling, eye irritation
• Moderate (1–3 ppm): Mucosal irritation
• High (30–60 ppm): Vomiting, chest pain, pulmonary oedema
• Skin contact may cause severe burns
• Highly toxic via inhalation in animals

Chronic Effects

• Human: Airway inflammation, chronic respiratory symptoms
• Animal: Eye/nose irritation, weight loss, respiratory lesions
• RfD: 0.1 mg/kg/day (EPA)
• Chronic REL: 0.00006 mg/m³ (CalEPA)

Reproductive/Developmental Effects

• No evidence of effects via inhalation
• Uptake in reproductive organs is unlikely due to high reactivity

Cancer Risk

• No direct link in humans
• Drinking water studies suggest links to bladder/rectal cancer from by-products
• Not classified as a carcinogen by EPA

Safety

First Aid Measures

• Inhalation:

Move the affected person to fresh air immediately. Avoid direct exposure yourself. Remove contaminated clothing, and keep the patient warm and at rest. If breathing is difficult or the patient appears cyanotic (bluish skin), clear airways and administer oxygen if qualified. Begin CPR if not breathing. Seek urgent medical care.

• Skin Contact:

Remove contaminated clothing promptly. Wash affected areas with running water and soap. Seek medical help if irritation, blistering, or burns occur. Cover burns with a clean, dry dressing. Launder clothing before reuse.

• Eye Contact:

Rinse eyes continuously with running water while holding eyelids open. Continue flushing for at least 15 minutes or until advised by a medical professional.

• Ingestion:

Rinse mouth thoroughly. Do not induce vomiting. Offer water to drink. Get immediate medical attention.

• Medical Attention & Special Treatment:

Treat symptomatically. Effects may be delayed—watch for pulmonary edoema (fluid in lungs).

Exposure Controls

• Use adequate ventilation to maintain air concentrations below permissible exposure limits.
• If vapours are present, apply local exhaust ventilation or use air-supplied respirators.
• Prevent vapour accumulation in low-lying areas such as hollows or pits.
• Avoid confined spaces where chlorine vapour may concentrate.

Personal Protective Equipment

The right PPE depends on a full risk assessment considering exposure type, chemical state, handling process, and the environment. Generally recommended:

• Overalls
• Chemical safety goggles
• Full-face shield
• Elbow-length impervious gloves
• Air-supplied mask (AS/NZS 1715 & 1716 compliant) if there's inhalation risk

Good Hygiene Practices:

• Always wash hands before eating, drinking, smoking, or using the toilet.
• Decontaminate and store PPE properly after use.

Regulation

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]. 

Australia

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)