Investigation on manganese exposure of workers in an electric welding enterprise in Qingpu District of Shanghai

Objective The occupational manganese exposure level of workers engaged in welding jobs in a motorcycle manufacturer was investigated to provide basic information for the intervention of manganese hazards in these workplaces.

Methods  Totally 118 welding-related jobs in a motorcycle manufacturer in Qingpu District of Shanghai were surveyed in 2016. Individual air samplers were used to measure the concentration of welding fume and manganese in the air of the workplaces, and their exposure concentrations(C_TWA) were calculated.

Results  The median value of manganese concentration(C_TWA) in 118 sites was 0.04 mg/m³(P₂₅, 0.02 mg/m³ and P₇₅, 0.10 mg/m³). There was no significant difference of manganese concentrations between morning and afternoon(P>0.05). The median value of welding fume concentration(C_TWA) was 11.25 mg/m³(P₂₅, 2.46 mg/m³ and P₇₅, 20.52 mg/m³). Spearman correlation analysis showed that there was a positive correlation between welding fume and manganese concentrations in the workplaces (r=0.61, P < 0.01). The concentrations of manganese in different types of work showed significant difference(P < 0.01), and manganese levels of workers engaged in manual welding positions were higher than workers engaged in robotic welding and auxiliary welding (P < 0.01). Of 118 inspection samples, the concentrations of 20 samples (16.95%) were higher than the national standard, and welding types, welding area and distances from pollution sources played an important role(P < 0.01).

Conclusion  The hazards of manganese of the welding workplaces in this enterprise were not optimistic, there was the risk of manganese over-exposure and poisoning. The workers engaged in manual welding and near pollution sources should be given much attention.