7. Consequences of chemical releases

To help district/local administration to act effectively and efficiently in response to emergency situations which has an impact on people's health and other services during industrial disasters, industry is characterised by the following components:

  • Storage vessels of chemicals, these chemicals may be toxic or inflammable in nature.
  • Piping systems for transportation of the chemicals, solvents, water, steams, etc. to the process area.
  • Process area where reaction takes places at various temperature, pressure in reaction vessels.
  • Topography and land use pattern along with the local community in the area.

There are always possibilities of the release of these chemicals either due to material failure of the pipes or vessels or due to high pressure and high temperature. Release is also due to human faults. The released chemical may be of toxic in nature like chlorine, ammonia, etc or inflammable like hydrogen, LPG, etc. creating losses to human life environment and property.

The behaviour of the released chemical is depicted in flow diagram as Fig-2. In summary the consequence of the released chemical will be either fire or explosion if it is flammable. The term like BLEVE, VCE used in the flow diagram are discussed in other modules. The toxic chemical will spread in the form of toxic cloud and the behaviour of the cloud will depend on the climatic conditions and on the amount of the released chemical.

Industrial and transportation accidents involving toxic chemicals and pollution incidents associated, occur at various places. Sudden acute incidents may occur as a result of a fire, explosion or other accident in the handling of chemicals at an industrial or storage site, the impact of a natural disaster or terrorist attack on such sites, or during the transportation of hazardous chemicals.


Industrial Fire
Silent releases may occur from industrial or storage sites due to undetected leaks, or from waste sites. Outbreaks of illness may be the first sign of such releases. Exposure may be limited to people within the site, or extend to the public outside via air or water pollution or, more slowly, through the contamination of soil and food.


Problems are compounded when pre-emergency medical and paramedical services are lacking and occupational health is undeveloped as a medical specialty.

7.1 Typical impacts on health

Direct impacts

  • Deaths and serious injuries from explosions, building collapses and transport accidents.
  • Burns.
  • Deaths and illness/internal damage from exposure to toxic chemicals, during the release, from direct dermal exposure and inhalation later: from dermal exposure through contact with contaminated objects and ingestion of contaminated food or water.

Some effects, e.g. eye or skin irritation, broncho constriction or central nervous system depression, can occur within a few minutes or hours of exposure. Others may be delayed, e.g. chronic lung damage, respiratory difficulties and cancers.

Accidents involving volatile hydrocarbon compounds, herbicides, ammonia or chlorine have particularly serious public health effects.

Low socio-economic status populations living near hazardous sites (including storage sites) are particularly at risk. People with diabetes or asthma, and smokers, may be particularly susceptible.

Indirect impact

  • Psychological and psychosocial effects: fear and anxiety, increase in disease and non-specific medical symptoms
  • Social disruption if people are displaced; economic costs

7.2 Typical demands on health services

In case of an explosion or transport accident:

  • treatment of casualties
  • psychological trauma care

In case of an incident involving release of toxic chemicals:

  • assessment of public health risks, decision on 'best outcome' approach to managing the situation, implementation of measures to protect people and their environment (by public health services)
  • treatment and monitoring of exposed people (by medical services)
  • None (unless a health facility or staff and directly affected)

7.3 What the assessment IC should focus on

  1. Number of casualties requiring treatment for injuries or burns
  2. When there is a (suspected) chemical emergency:
  • The source and type of contaminants, the magnitude of the release, the likely dispersion pattern, the specific public health risks and the populations at risk.
  • The exposure of individual people at the site, first responders, surrounding population (through environmental and personal/ biological monitoring based on sampling, questionnaires and surrogate markers).
  • Health effects, initially acute effects then longer-term effects (data on functional, physical, morbidity and mortality outcomes).
  • The capacity of local services to respond appropriately with qualified personnel protective equipment, specific antidotes, diagnostic capacity, decontamination facilities, etc.

7.4 Interventions/Response likely to be needed: Specific health/medical interventions

Registration, diagnostic testing, treatment and monitoring of exposed individuals, with advice from the nearest poison centre (in case of chemical poisoning).

7.5 Other critical public health interventions

  • Analysis of options to manage the situation and selection of the 'best public health outcome option' taking account of weather forecasts and environmental modelling predictions of the likely dispersion of chemical pollutants in the area and/or water courses.
  • Definition of 'hot', 'warm' and 'cold' zones around the scene of the accident; excluding all persons without protective clothing from the hot and warm zones.
  • Information to the public on risks and precautions: e.g. sheltering from air pollution (staying indoors and closing all windows), restrictions if water, soil or food supplies are contaminated.
  • Evacuation, if necessary, and provision of essential services at the evacuation sites (if health risks are acute).
  • Prevention or containment of fire-fighting water run-off (using drainage ditches or holding tanks).
  • Monitoring the source of contamination and likely contaminated media well beyond the moment at which the release is thought to have been controlled.
  • Remediation measures to make the environment safe and clean a range of specialist information and services are required including chemical and medical toxicology (including laboratories), environmental and medical epidemiology, and environmental and biological monitoring.


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