Silica, or silicon dioxide (SiO2), is a mineral that occurs naturally in crystalline or non-crystalline form. The most abundant crystalline form is α-quartz, which is the most common silicate mineral in the earth’s crust. It is found in sand, sandstone, shale and granite. Drilling, crushing, cutting, chipping, breaking, sawing or polishing materials containing crystalline silica can create a large amount of respirable dust.
Silicosis is a lung disease caused by the inhalation of crystalline silica dust. Leading to inflammation and scarring in the form of nodular lesions in the upper lobes of the lungs.
Approximately 2.3 million workers are exposed to respirable crystalline silica in the workplace. This includes 2 million workers in construction and roughly 300,000 workers in general industry, maritime and hydraulic fracturing.
Such jobs include:
- Jack hammering
- Rock drilling, cutting, chipping or polishing
- Brick or tile cutting and sawing
- Concrete drilling, sawing, grinding and polishing
- Asphalt milling
- Stone countertop fabrication
- Diatomaceous earth processing
- Pottery production
- Work on linings of rotary kilns and cupola furnaces
- Hydraulic fracturing
In 2016, OSHA established a new rule for Crystalline Silica Exposure: The new rule lowers the permissible exposure limit (PEL) to 50 ug/m3 averaged over an 8-hour Shift. https://www.osha.gov/dsg/topics/silicacrystalline/
The OSHA Standard (29 CFR 1926.1153) requires employers to limit worker exposures to respirable crystalline silica and to take other steps to protect workers.
See Table 1 of OSHA’s new rule on respirable silica dust in construction