Rationale, design and baseline results of the Guangxi manganese-exposed workers healthy cohort (GXMEWHC) study

Objective: To determine the relationship between biomarkers of exposure, disease and susceptibility, and early health effects and long-term diseases related to occupational manganese (Mn) exposure. Design: Baseline survey of a longitudinal cohort study of workers in a ferromanganese refinery. Participants: A total of 1888 individuals (1197 men, 691 women; average seniority 15.34 years) were enrolled in the Guangxi manganese-exposed workers healthy cohort (GXMEWHC) study. Participants were between 18 and 60 years of age (mean 40.31 years), had worked in the ferromanganese refinery for at least 1 year and lived in the local area. Results: The GXMEWHC study included a baseline survey. Participants were divided into four groups according to manganese (Mn) cumulative exposure index (Mn-CEI) levels: an internal control group (MnCEI <1.0 mg/m(3) year), a low exposure group (1.0 mg/m(3) year <= Mn-CEI<2.0 mg/m(3) year), a medium exposure group (2.0 mg/m(3) year <= Mn-CEI<5.0 mg/m(3) year) and a high exposure group (Mn-CEI >= 5.0 mg/m(3) year). Genome-wide association studies of quantitative trait loci and binary trait loci in 500 Mn-exposed workers were performed using Illumina Infinium HumanExome BeadChip arrays. Stored plasma, DNA, hair and urine are available for further study. Participants will be followed up every 3 years. Conclusions: The GXMEWHC study provides abundant data for exploring the systemic health effects of occupational Mn exposure using biomarkers of exposure, disease and susceptibility.