Early in the 20th century, with the introduction of the automobile, an expanding petrochemical industry, and production line methods, the workplace environment changed from one of mainly small, isolated shops to one dominated by large factories employing many workers. In many cases, workers were crowded into buildings with poor ventilation and minimal safety controls, and the hazards of chemicals became more evident. Petroleum and mined materials, e.g., asbestos and metals, could now be removed from the earth, transported great distances, and introduced into a plethora of manufactured products. The nature of the workplace today is quite varied, from workers on large production lines in manufacturing plants to workers in small groups or individuals working alone such as in the application of pesticides. Regardless of the nature of employment, workers in virtually all places are potentially exposed to chemicals. In fact, the Occupational Safety and Health Administration (OSHA) estimated in 1987 that 32 million workers were potentially exposed to chemical hazards (OSHA, 1987).