Crystalline silica is a naturally occurring mineral found throughout the earth’s crust. Quartz is the most commonly encountered form, ahead of tridymite and cristobalite. Industrial silica, as well as mineral materials and materials containing crystalline silica, are used as raw materials, additives or processing aids, with or without transformation, in a multitude of applications: glassware, foundry, chemicals, rubbers, paints, construction with, in particular, concrete, funeral facings, etc.
Exposure to crystalline silica in many industries
In France, nearly 365,000 workers are said to be exposed by inhalation to crystalline silica, in particular quartz. ANSES estimates that 23,000 to 30,000 workers would be exposed to levels exceeding the occupational exposure limit value (OEL) of 0.1 mg.m-3 currently in force in France, and more than 60,000 at levels exceeding the lowest OEL proposed at the international level established at 0.025 mg.m-3. More than two-thirds of these exposure levels relate to the construction sector; follow the sectors of manufacturing of non-metallic mineral products, metallurgy and mining.
High health risks for workers exposed to crystalline silica in France
Since the classification of crystalline silica as a carcinogen for humans by the IARC in 1997, all the studies published since have confirmed the link with the development of bronchopulmonary cancer (BPC). The risk is increased in the presence of pulmonary silicosis, but the available studies confirm the existence of a significant risk independently of silicosis.
If the causal link is now well established with silicosis, the expert report underlines the interest of revising the current definition of the disease from a medical point of view, including the early forms.
In addition to silicosis and bronchopulmonary cancer, ANSES’s expert appraisal confirms a significant association between exposure to crystalline silica and the risk of developing an autoimmune disease such as systemic scleroderma, systemic lupus erythematosus and polyarthritis rheumatoid. Similarly, exposure to crystalline silica increases the risk of developing non-malignant respiratory pathologies other than silicosis such as chronic obstructive pulmonary disease (COPD), emphysema, tuberculosis.
An association has been observed in studies between exposure to crystalline silica and the risk of kidney disease or diffuse infiltrating pneumonitis (PID) of the idiopathic pulmonary fibrosis (IPF) type, but currently available data are insufficient to explain these relationships in detail.
Given the health effects on the one hand, and the French exposure data collected on the other, ANSES’s expert appraisal concludes that there is a particularly high health risk for the occupational population exposed to silica crystalline at levels above or equivalent to the OEL of 0.1 mg.m-3 currently in force in France.
Recommendations to strengthen exposure prevention and medical surveillance
ANSES recommends a series of measures in terms of prevention and control of exposure in the workplace, medical surveillance and recognition of occupational diseases.
In terms of prevention, ANSES first recalls the need to apply the preventive measures defined by Directive 2004/37/EC on the protection of workers once morest the risks related to exposure to carcinogens or mutagens in work. Indeed, “work involving exposure to respirable crystalline silica dust from work processes” has been considered carcinogenic and listed in Annex I of this directive. Thus, ANSES recommends rapidly transposing the consequences of this listing into French law. It also recommends revising the OELs for crystalline silica, deemed insufficiently protective, without making a distinction between its different forms.
In terms of medical surveillance, ANSES recommends in particular changes in the diagnosis and screening of certain pathologies (silicosis, tuberculosis, kidney pathologies, etc.) for subjects exposed or having been occupationally exposed to crystalline silica.
Lastly, ANSES recommends that the tables of occupational diseases linked to crystalline silica be revised.
In addition, the agency also recommends conducting studies to improve knowledge of the prevalence of exposure, metrology and health effects.
