Occupational exposure to respirable crystalline silica and incident glomerulonephritis

OBJECTIVES: Occupational exposure to respirable crystalline silica has been suggested by previous studies to increase the risk of kidney-related diseases. This study investigated the association between occupational exposure to crystalline silica and the risk of glomerulonephritis.

METHODS: Prospective cohort study with 2,955,863 Danish workers followed from 1994 to 2015. All cohort members were assigned an annual level of exposure to crystalline silica by linking a job exposure matrix with each individual's work history. We identified cases of glomerulonephritis by ICD-10 codes N00, N01, N02 and N05 in the Danish National Patient Registry. Exposure-response relations were examined for cumulative exposure to silica, highest attained exposure, and exposure duration using a discrete time hazard model. We adjusted for age, sex, calendar year, education and chronic infections and censored when diseases strongly associated with glomerulonephritis occurred.

RESULTS: We identified 3054 cases of glomerulonephritis. Analyses showed no increase in risk with increasing cumulative exposure with an incidence rate ratio (IRR) of 1.01 (95 % confidence interval (CI): 0.97-1.05) per 50 (μg/m3-years). The IRR in the highest exposure tertile compared to the non-exposed group was 1.12 (95 % CI: 0.93-1.35). Comparable results were found for highest attained exposure and exposure duration.

CONCLUSION: Our findings do not suggest a causal relation between occupational exposure to crystalline silica and glomerulonephritis. However, further research is needed to confirm these findings.