| Background: Crystalline silica is one of the main minerals of pottery production.In the production process,a large amount of free silicon dioxide for dust,known as silica dust,floating in the air of the production environment,was produced in the pottery production.The concentration of the silica dust is usually high in the pottery industries,and the pottery dust is the main factor affecting the pottery workers' health.Long-term exposure to pottery dust could cause occupational diseases,potter's pneumoconiosis or potter's silicosis,and is closely related to the incidence and death of chronic obstructive pulmonary disease,respiratory system inflammation,lung cancer and cardiovascular diseases.There are many researches about health damage caused by pottery dust,but there are few reports about health damage and disease burden caused by long-term exposure to pottery dust.In order to evaluate the health damage and disease burden caused by long-term exposure to pottery dust,this study used the pottery workers cohorts to carry out the connection between the dust exposure and mortality,and disease burden.Objective: To analyze the effect of silica dust exposure on the mortality and disease burden of selected diseases of workers in pottery factories,and to provide basis for disease control and prevention among workers exposed to silica dust.Methods: Cohort study was conducted.This study selected 7,373 employees who worked more than one year at four porcelain factories in Jingdezhen,following up until the end of 2003.Silica dust concentration was monitored in different job titles in four pottery factories from 1960 to 2003.Based on the evaluation of the monitoring data accuracy,we established a job-exposure matrix in different industries,and calculated cumulative silica dust exposure(CDE)for each worker by linking work history,which was regarded as the personal level of dust exposure.The diagnosis of silicosis was performed by the diagnostic team of the local occupational disease precaution clinic,according to the national occupational health standards.The cause of death evidence was recorded by local hospitals and enterprises.Smoking information was collected by trained investigators using a unified questionnaire,including the beginning and the end year of smoking and the numbers of cigarettes every day.The smoking amount was calculated based on the smoking index.Hazard ratios(HRs)and 95% confidence interval(CI)for selected causes of death related to different exposure amount(level)of silica dust were calculated using the Cox proportional hazards model.And population attributable risk(PAR)due to silica dust of various diseases was estimated.HR and 95% CI for selected causes of death related to different smoking amount were calculated using the Cox proportional hazards model,compared with never smoked.Then the interaction of silica exposure and smoking in selected diseases was estimated.We used the interaction index such as the relative excess risk due to interaction(RERI),the attributable proportion(AP)due to interaction,and multiplicative model to evaluate the interaction effect for selected causes of death between silica dust and smoking.Years of Life Lost(YLL)were calculated by a standard method according to the death age and standard life expectancy,which were used to quantify the age-specific and cause-specific disease burden.What' more,stratification analysis according to gender,silica exposure and silicosis were conducted.Results: The cohort included 7,373 individuals(5,465 males,74.1%),and included 4,838 workers exposed to silica dust,accounting for 65.6% of the total population.Administrative and support crew were 2,535.Among men exposed to silica dust,78.7% were men.The average age was 28.4 y for individuals entering into the cohort,and the missing rate was 5.6% at the end of follow-up.During an average follow-up period of 35.6 y(262,317.4 person-years),2,448 deaths were reported,and the cumulative mortality was 33.2%.The mortality was 933.22 per 100,000 person-years.The top three cause of death were cerebrovascular diseases,heart diseases and malignant neoplasms in entire cohort,and the top three cause of death in workers exposed to silica dust were also cerebrovascular diseases,heart diseases and malignant neoplasms.Compared with unexposed workers,workers exposed to silica dust had higher cumulative mortality from all diseases,respiratory diseases,malignant neoplasms(including lung cancer),respiratory tuberculosis,pulmonary heart diseases,cerebrovascular diseases and external causes,and the difference was statistically significant(P<0.05).Compared with non-silicosis workers,silicosis patients had higher mortality from all diseases,respiratory diseases,malignant neoplasms(including lung cancer),respiratory tuberculosis and pulmonary heart diseases,and the difference was statistically significant(P< 0.05).Further analysis of relationship between the exposure to silica dust and the risk of death was conducted.Compared with unexposed workers,workers exposed to silica dust had higher risk of death from all diseases,lung cancer(HR:1.54,95% CI:1.00-2.37),respiratory tuberculosis(1.50,1.16-1.95)and respiratory diseases(2.54,1.92-3.36),and the difference was statistically significant(P<0.05).We observed significant positive exposure-response relationships between CDE and mortality from lung cancer,certain infectious and parasitic diseases(including respiratory tuberculosis),pulmonary heart diseases and respiratory diseases(including pneumoconiosis).The results of PAR showed that 5.0% of all death,26.2% of lung cancer death,14.6% of pulmonary heart diseases death and 50.3% of respiratory diseases death among entire workers were attributable to silica dust exposure.Smoking rate(including ever-smokers)among entire workers was 58.3%,and smoking rate among male workers exposed to silica dust was even 62.3%.Compared with unexposed workers,workers exposed to silica dust had higher risk of death from all diseases(HR:1.57,95% CI:1.42-1.73),lung cancer(4.93,2.66-9.15),respiratory tuberculosis(1.36,1.04-1.78),cerebrovascular diseases(1.61,1.29-2.01)and respiratory diseases(1.69,1.29-2.22),and the difference was statistically significant(P < 0.05).We observed significant positive exposure-response relationships between smoke and mortality from all causes,malignant neoplasms(including lung cancer),respiratory tuberculosis,heart diseases(including pulmonary heart diseases),cerebrovascular diseases and respiratory diseases.The total YLL of cohort workers was 43,164.92 y,and the total YLL rate was 16,455.22 per 100,000 person-years.The YLL rate of malignant neoplasms was the highest(3,606.55/100,000 person-years),followed by cerebrovascular disease(3,053.09/100,000 person-years)and heart diseases(2,862.21/100,000 person-years).Compared with unexposed workers,workers exposed to silica dust had higher YLL rate from malignant neoplasms(including lung cancer),respiratory tuberculosis,pulmonary heart diseases,cerebrovascular diseases,respiratory diseases,and external causes,and the difference was statistically significant(P<0.05).Compared with non-silicosis workers,silicosis patients had higher YLL rate from malignant neoplasms(including lung cancer),respiratory tuberculosis,pulmonary heart diseases and respiratory diseases,and the difference was statistically significant(P<0.05).The 60-69 age group in entire cohort had the most number of deaths(826)and the most YLL(14,588.32 years).The 60-69 age group in workers exposed to silica dust had the most number of deaths(614)and the most YLL(11,005.55 years).Compared with unexposed workers,workers exposed to silica dust in 50-50 age group and 60-69 age group had higher age-specific YLL rate,and the difference was statistically significant(P<0.05).Compared with non-silicosis,silicosis patients over 50 years old had higher age-specific YLL rate,and the difference was statistically significant(P< 0.05).Conclusion: Long-term silica dust exposure was associated with significantly increased mortality from lung cancer,certain infectious and parasitic diseases(including respiratory tuberculosis),pulmonary heart diseases and respiratory diseases(including pneumoconiosis)among workers in Chinese pottery factories.Significant positive exposure-response relationships between CDE and mortality from lung cancer,certain infectious and parasitic diseases(including respiratory tuberculosis),pulmonary heart diseases and respiratory diseases(including pneumoconiosis)among pottery workers were observed.This study further confirmed that smoking was associated with significantly increased mortality from lung cancer,respiratory tuberculosis,cerebrovascular diseases,and respiratory diseases in workers.Smoking has the greatest impact on increased mortality from lung cancer.Compared with unexposed workers,workers exposed to silica dust had higher disease burden of all causes,and workers exposed to silica dust in 50-59 age group and 60-69 age group had higher disease burden.Compared with non-silicosis,silicosis patients over 50 years old had higher disease burden of respiratory diseases,certain infectious and parasitic diseases and malignant neoplasms,and silicosis patients over 50 years old had higher disease burden. |
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