Chemical Emergencies

Technological Hazards

Chemical Emergencies

Prepared by TESEC – European Centre of Technological Safety (Kiev, Ukraine)
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The terms “chemical accident” and “chemical emergency” are used to refer to an event or dangerous occurrence resulting in the release of hazardous substances affecting human health and/or the environment in the short or the long term. Such events or occurrences include fires, explosions, leakages or releases of toxic substances that can cause illness, injury, disability or death to a large number of human beings. The population may be affected through contamination of air, water or the food chain resulting from a chemical accident. Those exposed are frequently either inside an industrial site or close to it. In an urban area, a community may be exposed to hazardous substances escaping from a breached tanker vehicle that has been transporting them. In rarer cases, the exposed population may be at some distance from the accident site, including beyond national borders. In addition to human health effects, chemical accidents may result in extensive and long-term damage to the environment, with considerable economic costs.

The term “chemical emergency” is used to refer to an event or dangerous occurrence resulting in the release of a substance or substances that are hazardous to human health and/or the environment in the short or the long term. Such events or occurrences include fires, explosions, leakages or releases of toxic substances that can cause illness, injury, disability or death, often for a large number of people.

This definition needs to be set alongside the concept of a “chemical accident”, in which exposure arising from releases of a substance or substances may result in illness or the possibility of illness. The number of people affected by a chemical accident may be very few (even none), and illness, disability or death may occur a considerable time (for example, several years) after the exposure.

From the health perspective, there are a number of ways of classifying chemical emergencies, and none of them is comprehensive or excludes all others. Classification could be based on: 

  • the chemical(s) involved, the amount released, their physical form, and where and how the release occurred;
  • the sources of the release;
  • the extent of the contaminated area;
  • the number of people exposed or at risk;
  • the routes of exposure;
  • the health or medical consequences of exposure.

The key channels for human exposure in the case of chemical accident are air or water dispersion of hazardous materials (such as flammable, explosive, corrosive, oxidising, asphyxiating, bio-hazardous, toxic, pathogenic or allergenic).

The hazardous chemicals present in communities around the world are mainly in industrial facilities and in transit via highways, rail and waterways. If not properly used, they can endanger our health and poison our environment. Accidents (including fires, explosions and leakages) resulting in the release of these substances can have adverse effects on human health, property and the environment. Human exposure to hazardous substances can cause injury or even death for a large number of people.

The production and use of chemicals are fundamental factors in the economic development of all countries, whether they are industrialised or developing countries. In one way or another, chemicals directly or indirectly affect all humans and are essential to our food production and consumption (eg fertilisers, pesticides, food additives, packing), our healthcare (eg pharmaceuticals, cleaning materials) or our well-being (eg appliances, fuels). Chemicals have become a part of our life, sustaining many of our activities, preventing and controlling many diseases and increasing agricultural productivity.
It is not just the worker handling chemicals who is at risk. We may be exposed in our homes through misuse or by accidents or be contaminated via consumer products such as food.

Most chemical accidents are limited in their impact but some of them have been on the scale of disasters:

  • the 1984 gas leak in Bhopal (India) with thousands of deaths and many people permanently disabled (http://www.bhopal.com);
  • the 2000 explosions at the Fireworks S.E. company which stored and assembled fireworks in the city of Enschede (Netherlands) caused the death of 22 people and injured almost 1,000 more. The incident caused extensive damage to a large area immediately surrounding the factory, including a residential area and also the Grolsch brewery (containing a large ammonia refrigeration system);
  • the 2001 AZF fertilizer plant accident in Toulouse (France) in which the explosion of 300 tons of ammonium nitrate resulted in 30 deaths and around 10,000 injuries.

The environment may be affected: chemicals can pollute the air we breathe, the water we drink and the food we eat; they can also affect forests and lakes, destroying wildlife and degrading ecosystems. 

Human exposure may occur directly through skin or eye contact, inhalation or ingestion of hazardous chemicals.

The harmful effects of chemical substances depend on the toxicity of the chemical and exposure to it. Toxicity is a property of the chemical substance, while exposure depends on the way the chemical is used. The level of exposure depends on the concentration of the hazardous chemical and the period of contact time. Many substances do not give any warning by odour, even though they may be present at dangerous concentrations in the air.

The effects of chemicals on humans may be acute: after brief exposure an immediate effect may be experienced. Chronic effects usually require repeated exposure and involve a delay between the first exposure and the appearance of adverse health effects. A substance may have both acute and chronic effects. Both acute and chronic conditions can result in permanent injury. Exposure to solvents may cause contact dermatitis, headache or nausea and these effects could be both acute and temporary.

Consequences of chemical accidents are not limited to direct human exposure, death or injury but also include environmental contamination requiring decontamination and recovery. In the case of severe accidents (like Bhopal in 1984, Enschede in 2000 or Toulouse in 2001) with thousands of victims, there are also psychological, economic and social consequences to be taken into account.

The prevention of chemical accidents and protection of communities and environments from chemical emergencies is based on an Integrated Emergency Management System having as key elements: prevention, preparedness, response and relief. 

Prevention has the main objective of preventing accidents involving hazardous substances and limiting any adverse health consequences if an accident occurs. 
The management of a hazardous facility has the primary responsibility for designing, constructing and operating it and for developing the means to do so. 

Public authorities, including health authorities in different countries, should co-operate and exchange information which could help to prevent accidents or human exposure to chemicals. Health/medical professionals should be involved in decision-making related to the prevention of chemical accidents. 

Preparedness, response and relief are the main tools for minimising the consequences of Chemical Emergencies.

Emergency preparedness has as a main objective the minimisation of negative consequences of an accident. The roles and responsibilities of individuals and organisations expected to be involved in emergency response activities should be clearly defined in emergency plans (including learning the warning signals and knowing what to do during an emergency). As part of the emergency planning process, there should be an identification of potential risks and the geographical zones where effects are likely to occur in the event of an accident. It is only through knowledge of the sources and nature of chemical risk that safety can be ensured. 

Preparedness and response planning should take into consideration the nature of possible clinical (and also psychological) effects on those potentially affected, including response personnel, workers and the local population. 
Hospitals and other treatment facilities, which may be called on during response to an accident involving hazardous substances, should develop systems for receiving and handling large numbers of patients at one time. 

Emergency response and relief has as a primary objective the protection of oneself and that of others from harm. On-site emergency management should decide on the immediate actions to take, including actions intended to avoid or limit exposure to hazardous substances, based on preliminary information concerning the site, the nature of the release, the hazardous substance(s) involved and any related analyses. Health/medical personnel should provide assistance, upon request, when such decisions have to be taken. Efforts should be made by public authorities and industry to improve public awareness of chemical hazards in the community and of how to respond in the event of an accident (for example through an understanding of the procedures related to possible evacuations and to sheltering in situ). If an accident occurs, the public should be given specific information in real time on the appropriate conduct and safety measures to adopt. 

Appropriate epidemiological and medical follow-up of chemical accidents should be initiated after the release of toxic chemicals. Persons who may have been significantly exposed to toxic chemicals during an accident (whether they are actually affected or not) should be examined and properly registered to allow for short- and long-term follow-up. It may be advisable to take biological samples for immediate and later analysis. 

The harmful effects of chemical substances depend on the toxicity of the chemical and exposure to it. Toxicity is a property of the chemical substance, while exposure depends on the way the chemical is used. The level of exposure depends on the concentration of the hazardous chemical and the period of contact time. Many substances do not give any warning (by odour for example), even though they may be present at dangerous concentrations in the air.

The first and most essential step in the safe use of chemicals is to know what they are, their potential impact on health and the environment and how to control them. That knowledge should be available for all. Furthermore, that inherently complex knowledge must be organised in such a way that essential information on chemical hazards and corresponding protective measures can be identified and conveyed to the user in a form that is easy to understand. 

The protection of the population and environment from Chemical Emergencies is a key aim of an Emergency Management System. The management of a hazardous facility has the primary responsibility for designing, constructing and operating it safely and for developing the means to do so. 
No chemical substance can cause adverse effects without first entering the body or coming into contact with it.

There are four main ways for chemical substances to enter the human body: 

  • Inhalation (breathing in).
  • Absorption (through the skin or eyes).
  • Ingestion (eating, swallowing).
  • Transfer via the placenta of a pregnant woman to an unborn baby.


Most chemicals used in any location may be dispersed into the air in dust, mist, fumes, gas or vapour form and can then be inhaled. Workers at a facility, and also the local population not actually handling them but still within reach, can be exposed to a mixture of chemicals from various sources. 

The key manner of exposure for humans in the case of a chemical accident is therefore via air or water dispersion of hazardous materials. 
Air monitoring and liquid sampling is one of the most important activities in the prevention of and response to chemical incidents. 

Mitigation refers to the measures undertaken to limit the adverse impact of a Chemical Emergency.

It is based on two main components:

  • Planning for emergencies on the site of a hazardous facility and off-site;
  • Community awareness.


The on-site and off-site emergency plans should give details of the technical and organisational procedures applicable in the event of an accident to limit the effects on people, property and the environment both within the facility and outside it.

The off-site emergency plan and all relevant on-site emergency plans must be consistent and integrated. To form that common basis for off-site and on-site emergency planning, the management of a hazardous facility should identify and assess the full range of potential accidents (including low-probability, high-consequence accidents) in the installation. This information should be available in the emergency plans. Public authorities should take particular care to ensure that all hazardous facilities (including small and medium-sized enterprises and commercial users of hazardous substances) carry out such assessments and the appropriate emergency planning.

Public authorities should ensure, through the legal and procedural means they deem appropriate, that the potentially affected community is provided with:

  • general information on the nature, extent and potential off-site effects on human health and/or the environment (including property) of possible major accidents at existing or planned hazardous facilities;
  • specific and timely information on the appropriate conduct and safety measures they should adopt in the event of an accident involving hazardous substances;
  • access to other available information needed to understand the nature of the possible effects of an accident (such as information on hazardous substances capable of causing serious off-site damage);
  • capability to contribute effectively, as appropriate, to decisions concerning hazardous facilities and the development of community emergency preparedness plans.

Effective protection in the event of an accident or response depends on:

  • the nature of the incident (is it an air or a water release?);
  • the hazardous substances involved;
  • the potential severity of the incident;
  • the incident’s potential off-site effects; 
  • the quantity and type of the hazardous substance(s) involved;
  • the treatment facilities available for emergency response.


Notification from the hazardous facility should trigger the implementation of the off-site emergency response plan, beginning with an initial assessment of the situation leading to a decision on which response actions are required.

In the case of the release of a toxic substance, the decision on whether the potentially affected community should shelter indoors or be evacuated should be taken by the responsible person designated in the emergency plan. The decision made should be based on likely exposure and possible health effects.

Emergency warning alert systems should be available to warn the potentially affected public that an accident has occurred or that there is an imminent threat of an accident:

  • The system chosen may vary depending on local culture and conditions, providing that it is effective and timely. Suitable warning systems could include, for example, sirens, automatic telephone messages, mobile public address systems or a combination of systems.
  • The potentially affected community should be notified of the systems which will be used in an emergency, and the systems should be tested in advance.


Emergency warning alert signals and announcements should be fully understood by the public and the public should know how to respond appropriately in an emergency. Time and distance from the contamination source are important factors in limiting exposure to the public. The shorter the period of time an individual stays in a contaminated area and greater the distance from the source of contamination, the smaller the exposure received by them. 

While dispersed populations may be affected through contamination of water or the food chain resulting from a chemical accident, those exposed are frequently inside an industrial site. In an urban area, a community may be exposed to hazardous substances escaping from a breached tanker vehicle that has been transporting them. In rarer cases, the exposed population may be at some distance from the accident site, including beyond national borders. Potentially affected areas in neighbouring countries could include those with limited chemical emergency response plans or capabilities. 

The identification of potential risks and the geographical zones where effects are likely to occur in the event of an accident is a part of the emergency planning process. It should include general zoning and mapping of hazardous industrial activities, taking into account all aspects of protecting health and the environment (including property) and case-by-case decision-making concerning the siting of a new facility or proposed development near an existing facility.