Page 339 - CHEF Guide

Appendix A 299

A.3 Union Carbide, Bhopal, India – 1984 [89, pp. 25-30]

In 1984, at the Union Carbide plant in India, a storage tank containing methyl isocyanate (MIC) was contaminated with
water leading to a runaway reaction causing the release of more than 40 tons of toxic MIC gas through a relief valve. The
incident killed more than 3,000 people and injured hundreds of thousands more. This was arguably the worst chemical industry
incident in terms of people affected.

After investigation, the prevailing conclusion is that water was deliberately introduced to an MIC storage vessel through an
instrument connection. MIC is extremely water reactive, and a runaway reaction ensued.

There were a number of confounding factors that led to the Bhopal disaster:
 The vessel refrigeration system was down for six months to save money; its Freon was being used elsewhere.
 A relief effluent system caustic scrubber was inactive (said to be down for maintenance).
 The downstream flare for a scrubber was also shut down (said to be awaiting replacement of corroded pipe work).
 A fixed water curtain used to absorb MIC vapors was insufficient to reach the cloud.
 Supervision was slow to react to initial reports of MIC odor in the area; this was coffee break time (up to an hour may
have been lost here).
 A shanty town had been allowed to form along the plant perimeter over a number of years.
 An effective emergency communication/response system was not in place.

In most of Bhopal’s causal factors, you can see glaring deficiencies in the major process safety management elements of
hazard analysis, mechanical integrity, operating procedures, and management of change.
As a direct response to Bhopal, many regulatory initiatives were implemented worldwide. In India, this event led to the
Environment Protection Act (1986), the Air Act (1987), the Hazardous Waste (Management and Handling) Rules (1989), the
Public Liability Insurance Act (1991) and the Environmental Protection (Second Amendment) Rules (1992). In the US, the
Emergency Planning and Community Right-to-Know Act (EPCRA) was promulgated in 1986, and the Clean Air Act Amendments
(CAAA) were signed into law in 1990.

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