Occupational exposure limit compliance may underestimate health risks in silica dust-exposed workplaces

Abstract Occupational exposure limits (OELs) are widely used to judge the acceptability of workplace dust exposure, but their ability to capture the full health risk of respirable crystalline silica (RCS) remains uncertain. This study evaluated the concordance between OEL compliance and semi-quantitative occupational health risk classification among dust-exposed workplaces in Yongchuan District, Chongqing, China. Occupational hygiene data were collected from 42 enterprises, 212 silica dust-exposed positions and 1,060 occupational air samples, including total dust and respirable dust samples. Silica dust was the predominant hazard, accounting for 100% of assessed positions. Although 764 samples (72.1%) complied with occupational exposure limits, 317 samples (29.9%) were classified as high or very high risk by semi-quantitative assessment. At the position level, 110 of 212 silica dust-exposed positions (51.9%) were classified as high or very high risk, including 12 of 108 OEL-compliant positions (11.1%). Non-metallic mineral mining had a particularly high risk burden, and drilling, crushing, loading or transportation, sand cleaning, moulding sand handling, and dry cutting were the main high-risk processes. Wet operations showed substantially lower risk. These findings indicate that OEL compliance alone may underestimate silica-related occupational health risks, particularly in jobs with high free crystalline silica (SiO₂) content. Combining exposure-limit compliance with semi-quantitative risk assessment may improve risk stratification and support more targeted silicosis prevention.