Figure 1.
Lung cancer risk (ORs and 95% CIs) in all solid-fuel users (A), predominant wood users in North America and Europe (B), and predominant coal users in Asia (C) by sex and smoking status compared with subjects who used nonsolid fuels (gas, oil, electric), adjusted for age, sex, education, race/ethnicity, and smoking status. The gray squares represent the adjusted ORs, with the size proportional to the number of cases in that subgroup of analyses (i.e., overall, wood in Europe/North America, coal in Asia), and the horizontal lines represent the 95% CIs. p-Value for heterogeneity measures heterogeneity between studies. (A) All solid-fuel users (n = 1,548 unexposed cases and 2,732 unexposed controls). p-Value for heterogeneity between subgroups: men versus women, 0.18; ever- versus never-smokers, 0.14; whites versus Asians, 6.5 × 10−5; studies carried out in Asian versus North American and European countries, 1.9 × 10−7. (B) Predominant wood users in North America and Europe (n = 3,146 unexposed cases and 4,081 unexposed controls): includes only studies from North America and Europe (CEE, California, New England, Toronto), because the number of exposed cases from Asian countries was small (n = 94). The risk of lung cancer associated with wood use among all seven studies was 1.24 (95% CI, 1.10–1.41). Models also include interaction terms between the covariates and study. (C) Predominant coal users in Asia (n = 165 unexposed cases and 511 unexposed controls): includes only studies from Asia (Singapore, Xuanwei1, Xuanwei2). The risk of lung cancer associated with coal use was 1.64 (95% CI, 1.49–1.81) among all seven studies and 1.15 (95% CI, 1.02–1.30) among the four studies in North America and Europe.