Morbidity And Mortality Among Workers Exposed To Occupational Hazards At An Automobile Foundry In Hubei, China

ObjectivePurpose of this study was to evaluate occupational hazards and their effects on health in automobile foundry workers, with implementation of new technology, new production process and comprehensive measures for dust and toxicant control.MethodsData of work environmental monitoring for varied occupational hazards at an automobile foundry in Hubei, China during the past about 30 years were collected and some additional occupational hazards were measured, as well as levels of dust cumulative exposure for foundry workers were estimated, to elaborate characteristics of occupational hazards there, and observe end-point outcomes affected their health (disease occurrence and causes of death) among them. Logistic regression model was fitted for analyzing related factors for adverse health effects to predict incidence of pneumoconiosis among foundry workers with cumulative dust exposure and length of employment.1 Study designCohort study design was used in the study, with a foundry factory of a state-owned large-scale automobile company in Shiyan City, Hubei province as study site, to follow-up workers exposed to occupational hazards for another 12 years based on an original cohort for 17 years of follow-up, including all those employed for more than one year during January 1,1980 to December 31,2008. In total,1 300 of 2 009 workers at eight worksites of sand preparation, cast shakeout and finishing, melting, moulding, core-making, overhead crane operation and pouring in foundry were defined as exposed group, and another 709 at auxiliary work of the factory such as electricians, inspectors, fitters, and so on as control group.2 Statistical analysisData were input with EpiData version 3.1 software and Office Excel 2003 software for Windows and compiled and cleaned with SAS version 8.1 software. Person-year incidence and relative risk (RR) or odds ratio (OR) and its 95% confidence intervals for pneumoconiosis and other work-related diseases in the workers stratified by varied variables were estimated, and relevant factors were analyzed for their correlation to pneumoconiosis and work-related diseases with logistic regression model using SPSS version 15.0 software.Results1 OverviewTotally,2 009 cohort members were followed-up for 37 151 person-years, with morbidity of 4 468.25 per 100 000 person-years (1 660 disease cases or events) and mortality of 238.91 per 100 000 person-years (102 deaths).In total, data of environmental air dust concentrations at work sites of 2978 samples from 2424 sampling spot-times were collected, including silica dust, grinding wheel dust, coal dust, respirable dust, asbestos dust, welding fume, during 1978 to 2008. Additionally,8 air dust samples were collected from 8 sampling spot-times for measuring concentrations of respirable dust at major worksites. Meanwhile, free silicon dioxide content and dispersion of dusts were measured and composition of dust was analyzed with scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDS). Data of air concentrations of ammonia, phenol, phenol formaldehyde resin, formaldehyde, benzene, toluene and xylene in another 451 samples from 385 sampling spot-times were collected, and air concentrations of polycyclic aromatic hydrocarbons (PAHs), lead and lead fume, cadmium and its inorganic compound, manganese and its inorganic compound, nickel and its inorganic compounds, chromium and its inorganic compound, hydrogen sulfide, phosphine, sulfur dioxide, carbon monoxide were measured in 96 samples from 42 sampling spot-times. Data of intensity of physical occupational hazards such as heat stress, heat radiation and noise were collected for 179 measurements at 173 sampling spots. 2 Characteristics of occupational hazards in foundryOccupational hazards in automobile foundry are complex and diversified, whose air concentrations exceed allowable occupational exposure limits stipulated by the national occupational hygienic standards, and coexist with variety of occupational hazards such as high concentrations of dust, metals and their compounds, low-concentrations of variety of chemicals, high intensity of noise, vibration, heat stress, compulsory posture, as well as other heavy metals, asbestos, carbon monoxide, PAHs and dioxin, which may all exist in environmental air in foundry and whose hazards have not been fully recognized in the country, yet.3 Characteristics of adverse health effects in foundry workers3.1 Major diseasesThere were 12 kinds of diseases significantly affected health of foundry workers, including hypertension, liver disorders, chronic lower respiratory diseases, arthritis, diseases of the esophagus, stomach and duodenum, low back pain, pulmonary tuberculosis, disorders of the gallbladder, biliary tract and pancreas, ischemic heart disease, cerebrovascular diseases, renal disease and malignant neoplasm. Risk of Chronic lower respiratory disease, Arthritis, Low back pain, Hypertension were significantly higher in exposed group than that in control one.3.2 PneumoconiosisPerson-year incidence of pneumoconiosis was 2.02 per thousand in high-and moderate-dust exposure groups and 0.15 per thousand in low-dust exposure group (control), respectively. Its case-fatality rate was 20.83 percent, with immediate leading causes of death of lung cancer, liver cancer and ischemic heart disease. Their length of employment at onset of pneumoconiosis averaged 25.94 years and its incidence increased with length of employment. Smoking and pulmonary tuberculosis in the workers could increase their risk of pneumoconiosis.Results of logistic analysis showed that risk of pneumoconiosis increased 2 folds with an increase in cumulative dust exposure of 1 mg/m3·year in exposed group. Results of multiple logistic analysis showed that risk of pneumoconiosis increased by 4.38 folds and 3.79 folds with increase cumulative dust exposure of 1 mg/m3·year, on level of smoking, respectively, adjusted for alcohol drinking and age. According to logistic predictive model, if incidence of pneumoconiosis is expected to be controlled less than 1 per thousand, daily exposure to dust should be controlled below 0.2 mg/m3 for the workers with 20 years of employment, or below 0.1 mg/m3 for the workers with 30 or 40 years of dust exposure.3.3 Chronic lower respiratory diseaseRisk for chronic lower respiratory disease increased significantly in workers exposed to pouring, cast shakeout and finishing, moulding, sand preparation, core-making, melting in foundry, respectively, and their risk increased with length of employment, significantly higher in exposed men than that in women. Smoking could significantly increase the risk in exposed group. Results of multiple logistic regression analysis showed that incidence of chronic lower respiratory disease increased by 2.60 folds and 1.14 folds with increase cumulative dust exposure of 1 mg/m3·year, on level of smoking, respectively, adjusted for alcohol drinking and age.3.4 Pulmonary tuberculosisResults of multiple logistic regression analysis showed that incidence of pulmonary tuberculosis increased by 3.74 folds and 2.68 folds with increase cumulative dust exposure of 1 mg/m3·year, on level of smoking, respectively, adjusted for alcohol drinking and age.3.5 Liver diseasesRisk of liver disease increased significantly in high dust exposure group, and in those exposed to coexisted chemical hazards of benzene, toluene and xylene, particularly in those exposed to cast shakeout and finishing, sand preparation and moulding in foundry and significantly higher in men than that in women. Results of multiple logistic regression analysis showed that risk of liver diseases increased by 3.76 folds and 1.85 folds with increase cumulative dust exposure of 1 mg/m3·year, on level of smoking, respectively, adjusted for alcohol drinking and age.3.6 Ischemic heart diseasesRisk of ischemic heart disease (IHD) increased significantly in exposed men than that in control men and was also higher in men than that in women, particularly in those exposed to pouring and cast shakeout and finishing in foundry. Incidence of IHD was 3.08 folds high in those with 21 to 30 years of employment in exposed group as that in control one. Smoking could increase risk of IHD. Results of multiple logistic regression analysis showed that risk of IHD increased by 1.11 folds and 1.35 folds with increase cumulative dust exposure of 1 mg/m3·year, on level of smoking, respectively, adjusted for alcohol drinking and age.3.7 Low back painRisk of low back pain was higher in workers exposed to pouring, cast shakeout and finishing, and sand preparation in foundry, and higher in exposed men than that in control men. Results of multiple logistic regression analysis showed that risk of low back pain increased by 2.72 folds and 2.72 folds with increase cumulative dust exposure of 1 mg/m3·year, on level of smoking, respectively, adjusted for alcohol drinking and age.3.8 ArthritisRisk of arthritis was significantly higher in exposed group than that in control one, particularly in those exposed to cast shakeout and finishing, pouring, sand preparation and moulding in foundry, and higher in exposed men than that in control men. Smoking could increase the risk. Results of multiple logistic regression analysis showed that risk of arthritis increased by 2.21 folds with an increase in cumulative dust exposure of 1 mg/m3·year in exposed group, adjusted for smoking, alcohol drinking and age.3.9 Malignant neoplasmLeading malignant neoplasm in foundry workers included lung cancer and liver cancer. Patients with pneumoconiosis had a risk for lung cancer 13.01 folds as those without it, and those with liver disease had a risk for liver cancer 5.94 folds as those without it.Results of multiple logistic regression analysis showed that risk of malignant neoplasm increased by 69 percent with an increase in cumulative dust exposure of 1 mg/m3·year in exposed group, adjusted for smoking, alcohol drinking and age.3.10 Mortality and causes of deathCause-specific mortality in foundry workers was 94.2 per 100 000 person-years for malignant neoplasm,61.9 per 100 000 for injury and poisoning,24.2 per 100 000 for cerebrovascular disease,18.8 per 100 000 for ischemic heart disease and 13.5 per 100 000 for liver disease, respectively.Results of multiple logistic regression analysis showed that all-cause mortality increased by 64 percent with an increase in cumulative dust exposure of 1 mg/m3·year in exposed group, adjusted for smoking, alcohol drinking and age. Results of multiple logistic regression analysis showed that death caused by liver cancer increased by 1.20 folds and 6.44 folds with increase cumulative dust exposure of 1 mg/m3·year and liver disease, respectively, adjusted for smoking, alcohol drinking and age.3.11 Other diseases3.11.1 HypertensionRisk of hypertension increased significantly in exposed group, higher in exposed men than that in control men and highest in those exposed to moulding, and cast shakeout and finishing in foundry. Smoking could increase risk of hypertension significantly. Results of multiple logistic regression analysis showed that risk of hypertension increased by 1.13 folds and 94 percent with increase cumulative dust exposure of 1 mg/m3·year, on level of smoking, respectively, adjusted for alcohol drinking and age.3.11.2 Cerebrovascular diseasesRisk of cerebrovascular disease was highest in workers exposed to cast shakeout and finishing in foundry. Results of multiple logistic regression analysis showed that incidence of cerebrovascular disease increased by 62 percent with an increase in cumulative dust exposure of 1 mg/m3·year in exposed group, adjusted for smoking, alcohol drinking and age.3.11.3 Diseases of the esophagus, stomach and duodenumRisk of diseases of the esophagus, stomach and duodenum was higher in workers exposed to pouring in foundry, and higher in men than that in women. Results of multiple logistic regression analysis showed that incidence of diseases of the esophagus, stomach and duodenum increased by 4.60 folds with an increase in cumulative dust exposure of 1 mg/m3·year in exposed group, adjusted for smoking, alcohol drinking and age.3.11.4 Disorders of the gallbladder, biliary tract and pancreasPerson-year incidence of disorders of the gallbladder, biliary tract and pancreas was higher in foundry workers exposed to cast shakeout and finishing, sand preparation and moulding. Results of multiple logistic regression analysis showed that incidence of disorders of the gallbladder, biliary tract and pancreas increased by 1.30 folds with an increase in cumulative dust exposure of 1 mg/m3·year in exposed group, adjusted for smoking, alcohol drinking and age.3.11.5 Renal diseasesResults of multiple logistic regression analysis showed that incidence of renal disease increased by 2.06 folds with an increase in cumulative dust exposure of 1 mg/m3 year in exposed group, adjusted for smoking, alcohol drinking and age.Conclusions1 Occupational hazards in automobile foundry are complex and diversified, whose air concentrations exceed allowable occupational exposure limits stipulated by the national occupational hygienic standards, and coexist with variety of occupational hazards such as high concentrations of dust, metals and their compounds, low-concentrations of variety of chemicals, high intensity of noise, vibration, heat stress, compulsory posture, as well as other heavy metals, asbestos, carbon monoxide, PAHs and dioxin, which may all exist in environmental air in foundry and whose hazards have not been fully recognized in the country, yet.2 Workers in foundry exposed to higher risk for occupational hazards, which can lead to varied work-related diseases including pneumoconiosis, ischemic heart diseases, hypertension, low back pain, arthritis, neoplasm, and so on. Risk of occupational hazards varies by job, which is higher in men workers than that in women ones.3 Estimated by the model predicting incidence of pneumoconiosis based on correlation between cumulative dust exposure with incidence of pneumoconiosis, risk of pneumoconiosis is 44.6 per thousand for workers with 30 years exposure to current air dust concentration, and if the risk is expected to be kept less than 1 per thousand, air dust concentration at worksite should be controlled below 0.1 mg/m3 for workers with 30 years of exposure. This demonstrates that current occupational exposure limits for dust in China seem to be necessary to be adjusted.