An excess of laryngeal cancer has also been observed in some groups of exposed workers. No clear excess of cancer has been associated with the presence of asbestos fibers in drinking water. Both cigarette smoking and occupational exposure to asbestos fibers increase lung cancer incidence independently. When present together, they act multiplicatively. The primary routes of potential human exposure to asbestos are dermal contact, inhalation, and ingestion.
Asbestos is used so widely that the entire population is potentially exposed to some degree.
The number of workers exposed to asbestos since 1950 has greatly increased, but the intensity of occupational exposure has decreased. Worker exposure is a concern in the mining and milling of asbestos, during the manufacture of all asbestos products, and in the construction and shipbuilding industries. OSHA reported that about 2.5 million workers are estimated to have some potential exposure to asbestos. In addition, worker exposure occurs in asbestos end-product use occupations, e.g., asbestos insulation workers, brake repair and maintenance workers, building demolition workers, asbestos abatement workers, etc. The NOES estimated that 30,594 total workers, including 3,410 women, potentially were exposed to C hrysotile .