Air pollution and lung cancer risks in China—a meta-analysis Yu Zhao a , Shuxiao Wang a,⁎ , Kristin Aunan b , Hans Martin Seip b,c , Jiming Hao a a Department of Environmental Science and Engineering, Tsinghua University, Beijing 100084, PR China b Center for International Climate and Environmental Research, PO Box 1129 Blindern, 0318 Oslo, Norway c Department of Chemistry, University of Oslo, PO Box 1033 Blindern, 0315 Oslo, Norway Received 24 June 2005; received in revised form 7 October 2005; accepted 7 October 2005 Available online 10 January 2006 Abstract Lung cancer is a serious health problem in China, as in the rest of the world. Many studies have already proved that air pollution as well as other environmental factors can increase the risk of lung cancer. Based on epidemiological studies carried out in China, this paper proposes odds ratios (OR) to evaluate the risk of lung cancer from indoor air pollution for the Chinese population by applying the method of meta-analysis. For domestic coal use for heating and cooking, the pooled OR values are 1.83 (95% CI: 0.62–5.41) and 2.66 (1.39–5.07) for women and both sexes, respectively. For indoor exposure to coal dust, the OR values are 2.52 (95% CI: 1.94–3.28) and 2.42 (1.62–3.63) for women and both sexes, respectively. Cooking oil vapor is another factor increasing lung cancer risk. The OR values are 2.12 (95%CI: 1.81–2.47), 1.78 (1.50–2.12) and 6.20 (2.88–13.32) for nonsmoking women, women, and both sexes, respectively. Regarding environmental tobacco smoke, the pooled OR values are 1.70 (95% CI: 1.32– 2.18) and 1.64 (1.29–2.07) for nonsmoking women and both sexes, respectively. Funnel plots with statistical test have been applied to examine the publication bias, and the results implied that the analysis of coal consumption and cooking oil pollution might be affected by publication bias. The meta-analysis results confirm the association between lung cancer and indoor air pollution for the Chinese population. © 2005 Elsevier B.V. All rights reserved. Keywords: Lung cancer; Indoor air pollution; Meta-analysis; Odds ratio; China 1. Introduction Lung cancer is a serious health problem. According to the World Health Organization (WHO), each year more than 1 million people throughout the world die from lung cancer (WHO, 2002). In China, lung cancer takes the highest death toll of all cancer types in the cities, and the mortality and morbidity have increased significantly in both cities and rural areas. In the early 1970s, lung cancer mortality was 7 per 100,000 people (12.61 for urban areas), and it increased to 20.7 per 100,000 in 1998 (Li et al., 1997; Zhou et al., 2002). In 2000, it reached 40 per 100 000 (Yang, 2004), almost 5 times higher than three decades ago, and it is estimated that lung cancer morbidity in China increased by 26.9% from 2000 to 2005. In Xuanwei County, Yunnan Pro- vince, which has the highest prevalence of lung cancer in China, lung cancer mortality was reported to be 151.8 per 100,000 in some townships (Peng et al., 1998). Many studies have already proved that smoking has a significant association with lung cancer (Ezzati and Lopez, 2003; Alberg and Samet, 2003), but smoking cannot explain the relatively high rates of lung cancer observed among Chinese nonsmoking women (Lam et al., 2004). Environmental factors–including outdoor Science of the Total Environment 366 (2006) 500 – 513 www.elsevier.com/locate/scitotenv ⁎ Corresponding author. Tel.: +86 10 62782030. E-mail address: shxwang@tsinghua.edu.cn (S. Wang). 0048-9697/$ - see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.scitotenv.2005.10.010