Background Most of the studies on grading and classification of occupational health compre-hensive risks for specific employers still remain in the establishment and description of methodology, and practical application studies are rarely reported.

Objective To explore the application of an occupational disease hazards comprehensive risk assessment method issued by the National Disease Control and Prevention Bureau in conjunction with the National Health Commission and a self-developed occupational health grading and classification method in petroleum refining enterprises, and to provide practical experience for the implementation of differentiated law enforcement by relevant regulatory authorities.

Methods Two occupational health grading and classification methods were practiced in three petroleum refining enterprises in Guangdong Province. The occupational hazards comprehensive risk assessment method was provided by the Notice on Carrying out Pilot Work of Occupational Health Classification Supervision and Law Enforcement of the National Disease Control and Prevention Bureau and the National Health Commission. The principle was to derive the occupational health risk level according to nature of occupational hazards, exposure level, and number of workers exposed to them in an employer, and then to classify them into Class A, Class B, and Class C by combining with local occupational health management status level. The occupational health grading and classification method was self-developed according to available domestic and foreign occupational health risk assessment methods. Its principle was to calculate the risk level of each workstation in an employer based on published carcinogenicity classification or LD₅₀/LC₅₀ of chemical toxicants, level of noise, exposure parameters such as exposure level and exposure frequency, estimate the comprehensive risk R_o of the target employer by the Romanian comprehensive risk calculation method, and then calculate a comprehensive risk R_o' weighted by the occupational health management index of the target employer and classify it into class A, class B, and class C. Finally, assessment results, scope of application, inquired indicators, advantages,disadvantages and professional competence requirements of the two grading and classification methods were compared.

Results The occupational hazards that were evaluated in three enterprises in this study were benzene, toluene, xylene, gasoline, hydrogen sulfide, and noise. The exposure levels of benzene, toluene, xylene, and gasoline were all below 10% OEL (occupational exposure limit), and hydrogen sulfide and noise were disqualified. Occupational hazards such as benzene and hydrogen sulfide were serious occupational hazards in the three enterprises, and the number of workers exposed was 461, 912, and 224, respectively; the HRs (hazard ratings) of benzene, toluene, xylene, gasoline, hydrogen sulfide, and noise were level 5, 3, 2, 3, 5, and 3 respectively. The occupational health management status of the three enterprises was graded as B, A, and B, respectively by the occupational disease hazards comprehensive risk assessment method. The occupational health management index of the three enterprises was graded as B, A, and A, respectively by the occupational health grading and classification method. The comprehensive risk assessment results showed that two enterprises classified into as the highest class C and one into class B by the occupational disease hazards comprehensive risk assessment method, while all three enterprises were classified into class B by the occupational health grading and classification method.

Conclusion The two grading and classification methods are not consistent in the evaluation results of petroleum refining enterprises, and there are differences in the evaluation scope, indicators to be collected, and professionalism. It is recommended that occupational health regulators should fully consider the advantages and disadvantages of the two methods and choose the appropriate assessment method according to the actual regulatory purpose.