A Study On Application Of Five Risk Assessment Methods For Occupational Health

Background:Risk assessment refers to a quantitative evaluation of the possible effects caused by events or things, and an objective understanding of the risk factors. Through which, people can judge the possibility of harm occurring and the severity of the result. Also, appropriate measures can be taken to reduce the risk probability. According to the Code of Occupational Disease Prevention of PRC revised in2011, occupational health risk assessment has become one of the main functions of the department of health in our country. However, there is no corresponding guide or specification for occupational health risk assessment. In1983, the American National Research Council (NRC) proposed a management theory for risk assessment. Since then, guides or specifications for the occupational hazards risk assessment were set successively by Occident and other international organizations successively. By contrast, the occupational diseases still seriously endanger our people’s health. In order to prevent the occupational hazards and protect the occupational health, our state health department needs to set standards for occupational health risk assessment as soon as possible.Objective:This study aimed to evaluate the applicability of five occupational health risk assessment methods in risk assessment for coal-fired power plants and gas-fired power plants. The five assessment methods were set by the United States Environmental Protection Agency (EPA), the Singapore Ministry of Manpower(MOM), the University of Queensland (UQ), the Romania Labor and Social Protection Department(MLSP) and the International Council on Mining and Metals(ICMM) respectively. Through comparative analysis, we expected to find out the best among the five methods to assess the occupational health risk in thermal power plants, which may provide a basis for setting standards in relevant occupational health risk assessment.Methods:We investigated on the key positions in a new coal-fired power plant and a new gas-fired power plant.Field investigation:We studied on the production process, the time and space distribution of occupational-disease-inductive factors, the risk factors contact situation in key positions, the occupational-disease-prevention facilities, personal protective equipment, exposure time and occupational health examination, etc,.Field test:According to the standard " Specifications of air sampling for hazardous substances monitoring in the workplace"(GBZ159-2004), we continuously sampled for3days in each monitoring point.Risk assessment methods:We applied the five occupational health risk assessment methods made by EPA, MOM, UQ, MLSP and ICMM in occupational health risk assessment in key positions in coal-fired power plant and gas-fired power plant, respectively.Results:1.Field investigationThe main hazard factors in coal-fired power plant include noise, power frequency electronic field, coal dust, silica dust, ammonia, carbon monoxide, sulfur dioxide, nitrogen dioxide, nitric oxide, hydrochloric acid, sodium hydroxide and chlorine. In field investigation, the percent of pass for the factor of dust was25.0%, for the factor of noise was83.3%, and for the factor of toxic chemicals was100%. The percentage of key position with noise above80dB(A) was50.0%. There are9workers found with abnormal hearings, and no other contraindications or suspected occupational diseases were found.Compared with coal-fired power plant, the main hazard factors in gas-fired power plants are consisted of noise, power frequency electric field, methane, nitrous oxide, carbon monoxide, nitrogen dioxide, ammonia, hydrazine, sodium hydroxide, hydrogen chloride and hydrochloric acid. In our field investigation, the percent of pass for the factor of noise was66.7%, and for the factor of toxic chemicals waf100%. The percentage of key position with noise above80dB(A) was66.7%. There are7workers found with abnormal hearings, and no other contraindications or suspected occupational diseases were found.2.risk assessmentApplying EPA in risk assessment in the coal-fired plant and the gas-fired power plant, we found that the exposure to ammonia and treated water is a low-risk, as same as the exposure to ammonia and hydrochloric acid. Upon the boiler and treated water inspection in the gas-fired power plant, hydrazine turned out to be a larger risk of cancer.According to MOM, we inspected the water treatment system of the coal-fired power plant, and found a medium risk of exposure to chlorine. Similarly, exposure to hydrazine in boiler and treated water inspection in the gas-fired power plant was also a medium risk. The exposure risks to other toxic chemicals were low.According to UQ、MLSP、ICMM, the risk factors were evaluated with their impacts on health-common or serious. In accordance with UQ, the silica dust in boiler inspection and ash-sulfur inspection, the coal dust in coal transportation inspection, and the noise in boiler inspection, turbine inspection and ash-sulfur inspection were found to be common health-risk factors in the coal-fired power plant. However, based on the UQ, the ammonia exposure risk in boiler inspection for the gas-fired power plant was considered as a major risk to health, which was rated at medium risk by matrix method using MLSP and ICMM, and intolerable risk employing quantitative method in ICMM. In all the three ways, there was high risk in serious health impact of exposure to noise, silica dust and coal dust in the above jobs. The noise in coal transportation of the coal-fired power plant was considered to be with low risk in common health impact, and medium risk in serious health impact. All the other chemical factors and the occupational-disease-inductive factors in the rest of the positions were judged to be low risks.5. The advantages and disadvantages(1) The EPA could quantitatively and qualitatively evaluate the carcinogenic and non-carcinogenic effects of chemicals, while its evaluation results depend on the field investigation and test, which could avoid subjective bias. However, the EPA can only evaluate chemicals with existing risk assessment parameters.(2) The MOM could objectively assess the chemical poison based on the field investigation and test result with a semi-quantitative assessment method, and the co-exposure could be calculated among factors with similar health impacts. However, the MOM can’t evaluate risks of dust and physical factors.(3) Compared with the other assessment methods, the UQ is easier to use. It can qualitatively evaluate toxic chemicals, physical factors and dust pollution in workplaces independent of test results. However, the assessment of consequences, exposure frequency, and the probability of occurrence are mainly given with subjective judgment, which could bring with subjective bias.(4) The classic assessment model of MLSP can evaluate chemicals, physical factors, and dust in workplaces, and can qualitatively assess the risk level by combining the seriousness and the possibilities of the risk factors. However, there is also subjective bias in judging the occurrence probability.(5) The ICMM can be applied to assess the risks brought by chemical poison, physical factors and dust in workplaces. The quantitative method and the matrix method can be used in assessment with or without site test results, respectively. However, due to the heavy subjective judgment in exposure level, the result of this assessment method would come with subjective bias; In addition, the quantitative method can’t be applied in assessment of risk with wide span level.Conclusion:1. UQ, MLSP and the matrix method of ICMM can be qualitatively and comprehensively assess the chemical toxins, physical factors, dust and other occupation hazards risks in thermal power plant.2. EPA and MOM can quantitatively or semi-quantitatively and objectively assess the chemical poisons risk level in thermal power plant.