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Epidemiological assessment of health effects from chemical incidents
  1. Paul Cullinan
  1. Correspondence to:
 Dr Paul Cullinan, Department of Occupational and Environmental Medicine, National Heart & Lung Institute, Emmanuel Kaye Building, 1b Manresa Road, London SW3 6LR, UK;

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A chemical incident is the unexpected release of industrial material that is (potentially) hazardous either to humans, other animals or the environment. Common synonyms include the term “accident” but this presupposes an anticipated failure of control; “incidents” include also unanticipated disasters resulting from mechanical or organisational failures, and occasionally even sabotage.

The essence of a chemical incident is in its unexpectedness; the term is not used to describe predictable, continuing, and regulated releases of toxic substances from industrial sources. Neither does it generally include toxic releases contained entirely within an occupational setting where only employees are affected, although the principles of management are very similar. Such “industrial incidents” are usually managed by occupational health services. Major chemical incidents are those which pose a threat to a large number of people. This will depend on the size of the release, its area of distribution, and the magnitude of the population at risk.


The frequency of major chemical incidents is unmeasured although they are perhaps more frequent than many imagine; in the years 1975–77, for example, 30 were recorded.1 In principle they are more likely to occur where there are situations combining both high hazard and high vulnerability. There is mounting concern, for example, that heavy industrialisation in some parts of the world is proceeding faster than appropriate regulatory and surveillance measures. At the same time, many of the most devastating chemical incidents have occurred in countries with a long industrial history. A list of some infamous incidents is provided in table 1.

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Table 1

Selected, major chemical incidents

Chemical incidents are most obviously “agent oriented”2—that is, they come to light following the unexpected release of a toxic agent. Infamous examples include those in Bhopal (India) (fig 1), Chernobyl (former USSR), and Meda (Seveso, Italy). “Effect oriented” incidents are manifest initially …

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