Recent surveys suggest that, in the USA alone, as many as 50,000 units processing chemicals were not designed to prevent the leaking of hazardous substances should the unit get out of control, although it is admittedly unlikely that such runaway reactions would or could occur in any but a minority of cases. Most emergency relief systems in the chemical industry have serious design problems (with potentially devastating consequences) and virtually all are inadequate. Emergency and safety systems are not given priority in industry or in undergraduate curricula; none of the 145 undergraduate chemical engineering programmes in the USA requires a course in safety. Although the chemical industry is thought to be 'high-tech', much of the equipment used is antiquated and imprecise. Changes to improve matters would be costly—but not as costly as dealing with an accident should it occur.
Exposure to hazardous chemicals can result from industrial and transportation accidents and from inadequate management and disposal of wastes, particularly hazardous wastes.
Recent industrial accidents have broken records for the release of strong toxic substances. One, at the nuclear power reactor in Harrisburg, Pennsylvania (US), was the first known case of radioactive materials escaping into the environment resulting from commercial use of atomic energy. The Three Mile Island plant remains hazardous and problems of detoxification have not all been solved. Cancer, birth defects and other radiation-related illnesses have now begun to show higher incidences in the Harrisburg area. The full extent of human damage is not yet known however. The greatest industrial disaster of all time occurred in July, 1984 at Bhopal, India, where a transnational corporation's chemical factory malfunctioned leaking methyl isocyanate. Casualties may have exceeded 20,000 persons whose injuries include total or partial blindness, vision impairments, lung damage and other disorders. Genetic damage is also feared.