Chlorine

Primary reference(s)

IPCS, 1982. Environmental Health Criteria 21: Chlorine and hydrogen chloride. International Programme on Chemical Safety (IPCS). Accessed 2 December 2019.

PHE, 2019. Chlorine: health effects, incident management and toxicology. Public Health England (PHE). Accessed 2 December 2019.

Annotations

Key relevant UN convention / multilateral treaty

World Health Organization (WHO) International Health Regulations (WHO, 2016).

Organisation for the Prohibition of Chemical Weapons (OPCW), Chemical Weapons Convention. (OPCW, 2024a; b)

Drivers

Chlorine contamination is caused by anthropogenic activities that include accidents or misuse in industrial and similar settings, leading to significant health and environmental impacts. 

Documented accidents involving chlorine, a highly reactive and toxic gas, have occurred in various industries and settings, leading to significant health and environmental impacts. Chlorine can be related to: (1) Industrial Accidents, (2) Natural hazards, (3) Urban Environments, (4) Terrorism and Sabotage, (5) Transport and Storage. 

Chlorine Release Accidents in Chemical Plants:  

Accidental releases of chlorine gas can occur in chemical manufacturing facilities, particularly those involved in the production of chlorinated chemicals such as PVC (polyvinyl chloride) and chlorine bleach. Chlorine gas is highly toxic and can cause respiratory irritation, lung damage, and even death at high concentrations (CDC, 2023 - https://emergency.cdc.gov/agent/chlorine/basics/facts.asp). 

Chlorine is transported in railcars and tanker trucks for various industrial applications. Accidents involving derailments, collisions, or leaks during transportation can result in the release of chlorine gas into the environment. These incidents pose risks to nearby communities and emergency responders, who may be exposed to the toxic gas (USDT PHMSA, 2024, UK HSA, 2024). 

Chlorine is commonly used in water treatment facilities to disinfect drinking water supplies. Accidental over-chlorination or equipment failures can lead to the release of excess chlorine into the water distribution system, resulting in elevated chlorine levels in drinking water and potential health risks for consumers. These documented accidents underscore the importance of proper handling, storage, and transportation of chlorine, as well as emergency preparedness and response measures, to prevent and mitigate the impacts of chlorine-related incidents on public health and safety. 

Impacts

Minor exposures to chlorine may result in a burning sensation of the eyes and throat. More substantial exposure may cause coughing or breathing difficulties. Exposure to high concentrations of chlorine gas can damage the lungs and airways, hours after the exposure, potentially without preceding warning symptoms; this may cause a build-up of fluid in the lungs (oedema) which can be fatal. Following severe injuries from inhaling chlorine, there may be a shock, coma and death, or when surviving, a chronic disorder of the lungs. Those exposed during physical exertion appear especially vulnerable (IPCS, 1982; PHE, 2019). 

Owing to its hazardous nature, the majority of chlorine is transported by rail (ILO, 2004). 

The modern use of chemical weapons began with World War I, when both sides in the conflict used poisonous gas to inflict agonising suffering and cause significant battlefield casualties. Such weapons basically consisted of well-known commercial chemicals put into standard munitions such as grenades and artillery shells. Chlorine was a common chemical used in this way historically and still presents a risk (United Nations Office for Disarmament Affairs, no date; OPCW, 2024a; b; c).

Multi-hazard context

The figure below summarises common interactions between chlorine and other hazards. This information should be used with caution and not be solely relied upon in Disaster Risk Management, particularly as some interactions may not have been included. Note that hazardous events occurring together or locally in space or time may not necessarily cause, amplify or be otherwise related to each other. Specific examples of multi-hazard context can be found in the ‘Hazard drivers’ and ‘Impacts’ sections above.

Multi-hazard diagram

Risk Management

Spillages and run-off should be prevented from entering watercourses as chlorine is harmful to the natural environment; evacuation should be considered in a written emergency plan for significant spills and leaks of chlorine such as from tanks; and harmonised labelling and transport approaches should be adhered to.

Monitoring

The section and the table below offer an overview of monitoring chlorine. This information can be used for forecasting within a national early warning system (EWS). Since EWS capacities and processes differ across countries, the most current and specific information regarding EWS should be obtained from the appropriate national or regional agency/authority responsible for disaster management.