Silica has recently been in the news because this past August the US Occupational Safety and Health Administration
(OSHA) proposed a new rule lowering the occupational limit from 0.1 mg/m3 (0.25 mg/m3 for the construction industry) to
0.05 mg/m3.1 The current standard was set in 1971. Although regulation of occupational exposures at the current standard
has substantially reduced silicosis death rates in the United States, new cases of silicosis continue to be diagnosed, some among
younger individuals who entered the workforce well after the existing standard was in place. Risk assessments estimate that
lowering occupational exposure limits from the current to the proposed standard will reduce silicosis and lung cancer mortality
to about one-half of the rates predicted under the current standard.
OSHA estimates that 2.2 million US workers are exposed to silica, 1.85 million of these in the construction industry. This
translates into approximately 1 to 2 workers per every 100 workers. In addition to workers currently exposed to silica, many
more have been exposed to silica in the past. Patients may develop symptoms of silicosis years after their occupational exposure
to silica has ended. Patients who smoke and have a history of silica exposure, and particularly those with silicosis, can reduce their
risk of lung cancer by smoking cessation. Current and former long-term smokers with a history of silica exposure may meet lifetime
risk guidelines for computed tomography (CT) screening for lung cancer, when their increased risk due to silica exposure is
taken into account. For all these reasons, it is important for clinicians to be aware of occupations with potential silica exposure,
the symptoms and diagnostic criteria for silicosis, and the risk of lung cancer associated with silica exposure and silicosis.