[Descriptive study on the epidemiology of lung cancer in coal-producing area in eastern Yunnan, China]

Background and objective: Xuanwei county is located at Late Permian coal-accumulating area in eastern Yunnan and western Guizhou, China. The lung cancer mortality rate in Xuanwei county is among the highest in China and has been attributed to exposure to indoor smoky coal emissions that contain very high levels of polycyclic aromatic hydrocarbons (PAHs). Recent years, the pollution and the higher mortality rate of lung cancer has been watched in the area around Xuanwei, and there is no report about whether the epidemic levels and the pathogen of lung cancer in other area of eastern Yunnan is similar to that in xuanwei. The aim of this study is to epidemic levels and cause of lung cancer in coal-producing area in the east of Yunnan province.

Methods: 382 study units (nature villages) were selected by stratified cluster random sampling from coalproducing area in eastern Yunnan province, China. The villagers who were aged 30-79 years with no history of lung cancer were enrolled. All the participants received an initial single-view posterior-anterior chest radiograph and administered a questionnaire survey (which involves the information of demography, household and fuel use, lifestyle, tobacco and occupational exposure history, family and personal medical history, etc. The subjects with a positive screen by chest x-ray underwent to have a computed tomography scan of the chest and biopsy examination. The confidence interval of the standardized rate ratio were adopted to evaluate the statistical significance of differences in different regions.

Results: 52,833 villagers were surveyed and screened with X-ray. 604 of them were suspicious lung cancer with an initial chest radiograph, 541 underwent CT scan (362 were diagnosed by CT and 109 were diagnosed by histology). The adjusted positive rates for lung cancer screening with CT is 763.08 per 100,000, the age-standardized rate (ASR) with the world standard population is 426.28 per 100,000 (95% confidence interval=381.51/10 per 100,000 to 471.05 per 100,000), 482.78 per 100,000 for man, 387.98 per 100,000 for woman, male-to-female (M:F) rate ratios is 1.24. The intensity of lung cancer had significant difference between different study units. The ASR for lung cancer screening from A, B, C to D areas decreased in turn, and the area A was the highest of all, which was 6.97 times higher than the lowest area D, and the ratio between male and female was increased gradually. The positive rate for lung cancer was related to the distribution of coal and in direct proportion to the amount of smoky coal burning, but not associated with smokeless coal combustion. There are above 80% residents who burned "smoky" coal in indoor firepits which generated very high levels of air pollution. Lung cancer mortality of family members has the same distribution to positive rates of lung cancer screening, and they are in proportion to each other. 85% men smoke 16.12 cigarettes per day, averagely. About 50% of them did the job like coking, mining coal and so forth. Smoking rate of woman is 1.37%, they always did housework such as cooking, raising pigs and so on. Though the smoking and occupational hazard factors were not the major reasons for women to get lung cancer, they were possible reasons for men.

Conclusions: In coal-producing area in eastern Yunnan, China, [corrected] lung cancer was associated with exposure to smoky coal emissions and family susceptibility. Smoking, coking and mining were not the major risk factors lead to lung cancer for women.