Environmental Protection Agency concludes that there is no safe level of asbestos exposure
Most health information on asbestos has been derived from studies of workers who have been exposed to asbestos in the course of their occupation.
Asbestos fiber concentrations for these workers were many times higher than those encountered by the general public.
Although the risks associated with low-level non-occupational exposure are not as well established, the Environmental Protection Agency (EPA) concludes that there is no safe level of exposure to asbestos fibers.
Courtesy of the EPA

First diagnosed cases of asbestosis and lung cancer occurred in 1935.