Crystalline silica is a naturally occurring mineral in the Earth’s crust. It is most commonly found as quartz, followed by tridymite and cristobalite. Industrial silica, as well as mineral materials and materials containing crystalline silica, are used as raw materials, additives or processing aids in their original or processed form. They can be found in a variety of applications, including glassware, smelting, chemistry, rubbers, paints, construction (especially concrete), and headstones and monuments.
Crystalline silica exposure in various industries
In France, nearly 365,000 workers could potentially breathe in this mineral, mainly from quartz. ANSES estimates that 23,000 to 30,000 workers could be exposed to levels exceeding the occupational exposure limit (OEL) of 0.1 mg.m‑3 currently in force in France, and more than 60,000 workers to levels exceeding the lowest international OEL of 0.025 mg.m‑3. More than two thirds of exposures at these levels are in the construction sector, followed by non-metallic mineral products manufacturing, metallurgy and mining.
High health risks for workers exposed to crystalline silica in France
Since the International Agency for Research on Cancer (IARC) classified crystalline silica as a human carcinogen in 1997, all studies published since then have confirmed its connection to lung cancer development. Although having silicosis increases a person’s risk of developing cancer, the available studies confirm the existence of a significant risk even without silicosis.
While this causal link is well established, the expert appraisal underlines the importance of revising the current medical definition of silicosis to include early forms.
In addition to silicosis and lung cancer, the ANSES expert appraisal found a significant link between exposure to crystalline silica and the risk of developing an autoimmune disease such as systemic scleroderma, systemic lupus erythematosus or rheumatoid arthritis. Similarly, exposure to crystalline silica increases the risk of developing non-malignant respiratory diseases other than silicosis, such as chronic obstructive pulmonary disease (COPD), emphysema or tuberculosis.
Studies have shown an association between exposure to crystalline silica and the risk of kidney disease and idiopathic interstitial pneumonia in the form of idiopathic pulmonary fibrosis (IPF), but data are currently insufficient to ascertain the exact relationship between them.
Taking into account both the health effects and the data on exposure in France, the ANSES expert appraisal has concluded that there is an especially high health risk for workers exposed to crystalline silica at levels equal to or above the OEL of 0.1 mg.m‑3 currently in force in France.
Recommendations for enhanced exposure prevention and medical surveillance
ANSES recommends a series of measures in terms of preventing and controlling occupational exposure, ensuring medical surveillance and recognising occupational diseases.
With regard to prevention, ANSES recalls the need to apply the prevention measures as set out in Directive 2004/37/EC on the protection of workers from the risks related to exposure to carcinogens or mutagens at work. According to Annex I of this Directive, “work involving exposure to respirable crystalline silica dust generated by a work process” is considered to be a carcinogenic process. Accordingly, ANSES recommends rapidly transposing this condition into French law. It also recommends revising the OELs for crystalline silica, considered to be insufficiently protective, without distinguishing between its different forms.
In terms of medical surveillance, ANSES recommends changes in the diagnosis and screening processes for certain diseases (silicosis, tuberculosis, kidney diseases, etc.) for subjects currently or previously exposed to crystalline silica in their work environment.
Finally, ANSES recommends revising the occupational disease tables related to crystalline silica.
Additionally, the Agency recommends conducting studies to improve knowledge of the prevalence of exposure, metrology and the health effects.