Respirable crystalline silica

Abstract

Crystalline silica is abundant in nature and used in a variety of industries, e.g., mining, farming, construction, foundry processes and production of glass, artificial stone, ceramics and cement. When cut or crushed, dust containing respirable crystalline silica (RCS) particles is released in the air and cause severe diseases including silicosis and lung cancer. Recent epidemiological studies have shown excess lung cancer risks among workers exposed to RCS even in the absence of silicosis although silicosis increases the risk of developing lung cancer. The Dutch Expert Committee on Occupational Safety (DECOS) and the Nordic Expert Group for Criteria Documentation of Health Risks from Chemicals (NEG) evaluated the health hazards and calculated cancer risk of occupational exposure to RCS and decided to use lung cancer as the critical effect (the adverse health effect that occurs first at increasing exposure). As a direct genotoxic mechanism cannot be excluded, a non-threshold (risk-based) approach was used to calculate the risk for lung cancer. Two cancer risk levels were calculated: - A target risk level (low level), the level below which no extra protective measures have to be taken: 4 additional deaths of lung cancer per 100 000 workers for 40 years of occupational exposure, equal to 0.0004 mg/m3. - A prohibition risk level (high level) that should not be exceeded: 4 additional deaths of lung cancer per 1 000 workers for 40 years of occupational exposure, equal to 0.04 mg/m3. These recommended risk levels are considerably lower than the current legal occupational exposure limits in the Netherlands, Denmark, Finland, Norway and Sweden.