"Lung cancer mortality rates in Xuan Wei are among the highest in China in both nonsmoking women and men who smoke, and are associated with exposure to indoor emissions from the burning of smoky coal," said Phouthone Keohavong, Ph.D., study author and associate professor, department of environmental and occupational health, University of Pittsburgh Graduate School of Public Health (GSPH). "In order to account for the high rates of disease within this region, we tested for mutations generally associated with lung cancer in people who had no evidence of disease. We found that a good number of these individuals had mutations that indicated they were at higher risk for developing lung cancer in the future."
The study analyzed sputum samples from the bronchial tract of 92 individuals who had no evidence of lung cancer and screened them for p53 and K-ras mutations. Damage to both p53, a tumor suppressor gene that prevents normal cells from turning into tumor cells, and K-ras, an oncogene, is fundamental to the development of a vast majority of cancers. Mutations to both p53 and K-ras are thought to be primarily caused by chemicals called polycyclic aromatic hydrocarbons that are emitted during the burning of smoky coal. The study found that 15 individuals, or 16.3 percent, tested positive for genetic mutations – 13 individuals tested positive for p53 mutations, one tested positive for K-ras mutation and one tested positive for both p53 and K-ras mutations.
According to Dr. Keohavong, also a faculty member at the University of Pittsburgh Cancer Institute, these findings are similar to other studies in which he and colleagues found that the frequencies and types of K-ras and p53 mutations in women from Xuan Wei who were nonsmokers were similar to the mutations found in men from Xuan Wei who smoked.
"Tobacco smoking is rare in women from Xuan Wei, yet the female population has an abnormally high lung cancer death rate," said Dr. Keohavong. "Women in this region traditionally start the fires and cook, spending more time inside homes that lack ventilation. As a result, they are more likely to be exposed to potentially dangerous emissions."
The lung cancer mortality rate in some communities in Xuan Wei County is among the highest in China, and more than 20 times that country's national average. The levels of polycyclic aromatic hydrocarbons generated during cooking with smoky coal are comparable to exposure levels experienced by coke oven workers.
Co-authors of the study include Qing Lan, Ph.D., division of cancer epidemiology and genetics, National Cancer Institute; Wei-Min Gaol, Ph.D., department of internal medicine, University of Michigan, Ann Arbor; Kui-Cheng Zheng, Ph.D., department of environmental and occupational health, University of Pittsburgh Graduate School of Public Health; Hussam H. Mady, M.D., and Mona F. Melhem, M.D., department of pathology, University of Pittsburgh School of Medicine; and Judy L. Mumford, Ph.D., National Health and Environmental Effects Laboratory, U.S. Environmental Protection Agency. The study was funded by a grant from the American Cancer Society.
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