Low-level silica exposure ups overall, cause-specific mortality risk
Low-level occupational exposure to crystalline silica is associated with increased risk of mortality from respiratory diseases, pulmonary heart disease, lung cancer and ischaemic heart disease, among other complications, a new study has found.
The study included 44,087 Chinese workers (81.2 percent male) with histories of at least 1 year of pottery factory or metal mine work. Of these, 24,731 had never been exposed to silica and 20,076 had had a lifetime peak silica exposure of ≤0.35 mg/m3.
Participants who had ever been exposed to crystalline silica were further categorized into two according to the lifetime highest exposure: those with a lifetime peak exposure of ≤0.05 mg/m3 (n=4,038) and those with ≤0.10 mg/m3 (n=10,486).
Of participants in the ≤0.10 mg/m3 level, quartiles of silica exposure showed a significant and positive linear trend with overall mortality risk (hazard ratios [HRs] per quartile, 1.11, 1.23, 1.33 and 1.18; p<0.001 for linear trend).
Silica exposure also correlated significantly with higher mortality risks from malignant neoplasms (HR, 1.06; 95 percent CI, 1.03 to 1.09), lung cancer (HR, 1.08; 1.02 to 1.14), ischaemic heart disease (HR, 1.09; 1.02 to 1.16), pulmonary heart disease (HR, 1.08; 1.00 to 1.16) and respiratory disease (HR, 1.20; 1.14 to 1.26).
Trends were similar in the ≤0.05 and ≤0.35 mg/m3 level.
Over the follow-up period of 33.5 years, 8,506 all-cause deaths were reported, yielding an overall mortality rate of 594.0 per 100,000 person-years. The mortality rate for the group never exposed to silica was 550.7 per 100,000 person-years, while for those with a lifetime peak exposure of ≤0.35 mg/m3, the rate was 643.4 per 100,000 person-years.