[Molecular epidemiology study in Xuanwei: the relationship among 
coal type, genotype and lung cancer risk].

backgroundIt has been proven that the lung cancer mortality rate in Xuanwei County, China was among the highest in the country and has been associated with exposure to indoor smoky coal emissions that contain high levels of polycyclic aromatic hydrocarbons. This risk may be modified by variation in genetic polymorphisms and coal subtypes. Our objective was to use molecular epidemiological techniques to investigate the relationship among genetic polymorphisms, coal subtype and lung cancer risk in Xuanwei County.

methodsOn the basis of two population-based case-control studies in residents of Xuanwei County, China, questionnaires covering demographic information, smoking history, family and personal medical history, and information on other variables were administered and buccal cells and sputum samples were collected separately from each subject enrolled to extract DNA. GST superfamily, AKR1C3 superfamily, OGG1 superfamily and other genotype were scanned by useing PCR method. ORs and 95%CIs were used to estimate the association between genotypes, coal subtypes and lung cancer risk factors by conditional Logistic regression using Statistical Analysis Software.

resultsCompared with subjects who using smokeless coal or wood, smoky coal use was statistically significantly associated with lung cancer risk (OR=7.7, 95%CI: 4.5-13.3). There was marked heterogeneity in risk estimates for specific subtypes of smoky coal. Estimates were highest for coal from the Laibin (OR=24.8), Longtan (OR=11.6) and Baoshan (OR=6.0) coal types, and lower for coal from other types; the risk within the same subtype of coal in male and female were similar. The GSTM1-null genotype, the AKR1C3 (Ex1-70C>G), OGG1 (Ex6-315C>G) genotypes were closely associated with increased risk of lung cancer in Xuanwei County, and their odds ratios (95%CI) were 2.3 (1.3-4.2), 1.8 (1.0-3.5) and 1.9 (1.1-3.3), respectively. Compared to subjects who with GSTM1-positive and used less than 130 tons of smoky coal during their lifetime, higher risks were closely associated with GSTM1-null and heavier users (≥130 tons), with the OR was 4.9 (95%CI: 1.3-18.2) and 2.7 (95%CI: 1.0-7.4) for female and male, respectively. However, higher risks were only found within female for AKR1C3 (Ex1-70C>G) and OGG1 (Ex6-315C>G), with OR (95%CI)=12.9 (2.2-107.8) and 5.7 (1.1-34.2), respectively.

conclusionsLung cancer risks varied among coal subtypes; however, risks were similar between men and women exposed to the same type of coal. The GSTM1-null genotype may enhance susceptibility to air pollution from indoor smoky coal combustion emissions. AKR1C3 and OGG1 genotypes were significantly associated with higher risk of lung cancer, especially among heavily exposed women.