Before the days of factory dust control, asbestosis was first observed in the relatively few workers in asbestos factories where the concentration of asbestos particles was heavy. The resultant pneumoconiosis was intense and developed rapidly. Tuberculosis and bacterial complications were common, although the duration of the disease was short. Production of asbestos subsequently increased and is now over 3 million tons per year, equal in amount to the total production from 1920 through 1929. Approximately one quarter of the world's production is consumed in the United States, and more workers are exposed to small quantities of asbestos dust over longer time periods in factories other than asbestos factories. Asbestos is now a hazard in an increasing variety of occupations involving asbestos or asbestos-containing products, such as asbestos cement, insulation, paint and plastic, ship building and ship breaking, and in the construction industry.
The asbestosis observed in these workers is usually