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Domestic use of bituminous coal linked to lung cancer risk
The domestic use of smoky coal in the Yunnan province of China is associated with a significant increase in the lifetime risk for developing lung cancer, according to study results.
The use of less carcinogenic types of coal could result in a substantial reduction of lung cancer risk in this area, according to Francesco Barone-Adesi, MD, PhD, of the NCI’s epidemiology and biostatistics program, and colleagues.
Although China is urbanizing rapidly, most of the population remains rural. Many households use biomass fuel — including wood, crop residues and coal — in stoves that often are unvented and produce substantial indoor air pollution.
“Lung cancer rates in Xuanwei County, Yunnan province, southwestern China, are among the country’s highest,” Barone-Adesi and colleagues wrote. “In contrast, lung cancer rates in Yunnan province as a whole are low, even in relation to the Chinese national average rate. Rates in Xuanwei are similar for men and women, even though almost all women are non-smokers.”
Xuanwei residents have traditionally used at least one of three different types of fuel for household cooking and heating: bituminous coal, anthracite coal and wood. In a prior case-control study of lung cancer in Xuanwei, lung cancer risk was observed to be increased 30-fold among users of bituminous coal than among users of anthracite coal and wood; however, the relationship between bituminous coal use and lung cancer is not fully understood.
To estimate the absolute risk for lung cancer among users of different types of coal, Barone-Adesi and colleagues retrospectively reviewed 27,310 participants who used bituminous coal and 9,962 participants who used anthracite coal during their entire lives.
Primary outcomes were absolute and RR for death from lung cancer among users of different types of coal. Unadjusted survival analysis was used to estimate the absolute risk for lung cancer, whereas Cox regression models compared mortality hazards for lung cancer between bituminous and anthracite coal users.
According to results of the review, lung cancer mortality was observed to be substantially higher among users of bituminous coal than users of anthracite coal. For those who used bituminous coal, the absolute risks for lung cancer death before 70 years of age were 18% among men and 20% among women vs. less than 0.5% among anthracite coal users of both sexes.
Lung cancer alone accounted for about 40% of all deaths before age 60 years among those using bituminous coal. Compared with anthracite coal, use of bituminous coal was associated with an increased risk for lung cancer death (men, HR=36; 95% CI, 20-65; women, HR=99; 95% CI, 37-266).
“The results of the present study provide additional evidence that different coal types are associated with different carcinogenicity,” the researchers wrote. “Carcinogenic polycyclic aromatic hydrocarbons (PAHs), methylated PAHs, and nitrogen-containing heterocyclic aromatic compounds were found in abundance in the particles emitted from smoky coal combustion. During combustion, these contaminants are potentially released into the air in their original or oxidized forms. The quality of coal that is used in households around the world varies markedly because of differences in local coal deposits. The results of our study underline the importance of evaluating the carcinogenic potential of the different types of coal and taking actions to minimize exposure to the most hazardous ones.”