Background The complex and diverse occupational disease hazards in automobile manufacturing industry pose high occupational health risks to workers.

Objective To explore the methods that can accurately reflect the workplace health risk grade of automobile manufacturing enterprises, and to guide enterprises to practice risk classification management.

Methods Comprehensive index method, International Commission on Mining and Metals occupational health risk assessment method (ICMM method), and risk index method were used toassess health risks of occupational disease hazards in major workstations such as welding, polishing, and painting in three automobile manufacturing enterprises in Hunan Province. Kappa consistency test was used to test the grading results of the three assessment methods. The re-examine results and detection rate of contraindications of occupational health examinations in the past three years were used to verify the assessment results.

Results The results of comprehensive index method showed that the hazards of each selected workstation in enterprises A and B were evaluated as grade 2-3, among which NO₂ in enterprise A was grade 3, and welding fume, NO₂, and formaldehyde in enterprise B were all grade 3. The hazards of each selected workstation in enterprise C were grade 3-4, among which NO₂ and benzene in were grade 4, and welding fume, manganese and its compounds, grinding wheel dust, and xylene were grade 3. The hazards evaluated by ICMM quantitative method were grade 2 and grade 5, among which manganese and its compounds in enterprise A and welding fume, grinding wheel dust, and benzene series in enterprise C were graded as grade 5. The hazards evaluated by risk index method were grade 1-4, among which manganese and its compounds in enterprises A and B were grade 3, and manganese and its compounds and benzene in enterprise C were grade 4. The Kappa value between comprehensive index method and ICMM method was 0.084 (P>0.05), that between comprehensive index method and risk index method was −0.046 (P>0.05), and that between ICMM method and risk index method was 0.014 (P>0.05), indicating poor consistency. By comparing the results of occupational health surveillance with the results of occupational health risk assessment, one worker was found to have occupational contraindication of manganese exposure and 1 worker was found to have excessive manganese in hair in enterprise A. However, the comprehensive index method graded low risk for manganese and its compounds in enterprise A and the result is conservative. The key workstations identified by ICMM method were consistent with the occupational health examination results, but the assessment grades were all extremely high risk, and the results were too strict. One worker was found to be contraindicated to welding fumes, and 2 polishers were found to have severe mixed pulmonary ventilation dysfunction in enterprise C. Mild and moderate pulmonary ventilation dysfunction was found to be common in welding and polishing workstations in each enterprise. The assessment results of welding fumes and grinding wheel dust by the risk index method were negligible risks, which were inconsistent with the occupational health examination results.

Conclusion The comprehensive index method, ICMM method, and risk index method can basically identify workstations with serious occupational hazards, but they have certain limitations and applicability. In general, the evaluation results of the comprehensive index method were generates more consistent with the results with occupational health surveillance than the other two methods, is more comprehensive and objective in consideration, and is more suitable for health risk assessment of automobile manufacturing enterprises.