Alterations to biomarkers related to long-term exposure to diesel exhaust at concentrations below occupational exposure limits in the European Union and the USA

Previously, occupational exposure to diesel engine exhaust (DEE) was associated with alterations to 19 biomarkers that potentially reflect the mechanisms of carcinogenesis. However, it is unclear whether DEE is associated with biological alterations at concentrations under existing or recommended occupational exposure limits (OEL). In a cross-sectional study of 54 factory workers exposed long-term to DEE and 55 unexposed controls, 19 previously identified biomarkers were reanalyzed. Multivariable linear regression was used to compare biomarker levels between DEE-exposed versus unexposed subjects and to assess elemental carbon (EC) exposure-response relationships, adjusted for age and smoking status. Below the MSHA OEL, 17 biomarkers were altered between DEE-exposed workers and unexposed controls. Below the EU OEL, DEE-exposed workers had elevated lymphocytes, decreased C-reactive protein, macrophage inflammatory protein-1β, and miR-122-5p. Even at EC concentrations under the ACGIH recommendation, some evidence of exposure-response relationships for miR-423-3p and gene expression were noted. In general, DEE exposure under existing or recommended OEL could be associated with biomarkers reflective of cancer-related processes, including inflammatory/immune response.