Environ Health Perspect. Dec 2010; 118(12): 1743–1747.
In-Home Coal and Wood Use and Lung Cancer Risk: A Pooled Analysis of the International Lung Cancer Consortium
1 Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland, USA;
2 International Agency for Research on Cancer, Lyon, France;
3 Tisch Cancer Institute, Mount Sinai School of Medicine, New York, New York, USA;
4 International Prevention Research Institute, Lyon, France;
5 Department of Epidemiology, University of California School of Public Health, Los Angeles, California, USA;
6 Samuel Lunenfeld Research Institute, Toronto, Ontario, Canada;
7 National University of Singapore, Singapore;
8 Unit of Nutrition, Environment and Cancer, Cancer Epidemiology Research Programme, Catalan Institute of Oncology, Barcelona, Spain;
9 Norris Cotton Cancer Center, and Department of Community and Family Medicine, Dartmouth Medical School, Lebanon, New Hampshire, USA;
10 Institute of Carcinogenesis, Cancer Research Center, Moscow, Russia;
11 Department of Epidemiology, Nofer Institute of Occupational Medicine, Lodz, Poland;
12 National Institute of Environmental Health, Budapest, Hungary;
13 Cancer Center and Maria Sklodowska-Curie Institute of Oncology, Warsaw, Poland;
14 Department of Occupational Health, Specialized State Health Institute, Banska Bystrica, Slovakia;
15 Institute of Hygiene, Public Health, Health Services, and Management, Bucharest, Romania;
16 Institute of Hygiene and Epidemiology, First Faculty of Medicine, Charles University, Prague, Czech Republic;
17 Department of Cancer Epidemiology and Genetics, Masaryk Cancer Institute, Brno, Czech Republic;
18 Department of Preventive Medicine, Faculty of Medicine, Palacky University, Olomouc, Czech Republic;
19 Departments of Epidemiology and Environmental Health Sciences, School of Public Health, and Comprehensive Cancer Center, University of Michigan, Ann Arbor, Michigan, USA
Received March 26, 2010; Accepted September 15, 2010.
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We found that the cases tended to be older, more educated, and more likely to have smoked more than did the controls (). Predominant solid-fuel users had an increased risk of lung cancer compared with nonsolid-fuel users (). We saw this increased risk among both men and women, in ever- and never-smokers, among whites and Asians, and among studies carried out in Asian and in North American and European countries.
Characteristics of pooled indoor air pollution study population.
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), (more ...)
Given the substantial heterogeneity for the risk of solid-fuel use across continents, we then examined coal and wood use separately and by studies carried out in Asian and North American and European countries. When we compared only predominant coal users and nonsolid-fuel users, we observed an increased risk of lung cancer (). We saw this increased risk in studies in North America and Europe and particularly in studies in Asia. Further stratification showed that predominant coal users in Asia had an increased risk of lung cancer among men, women, and ever-smokers.
Similarly, predominant wood users had an increased risk of lung cancer compared with nonsolid-fuel users (). This association was largely from studies conducted in North American and European countries because the number of exposed cases from Asian countries was small. Further stratification showed that predominant wood users from North American and European countries had an increased risk of lung cancer among men and never-smokers.
Nonsmoking women are of special interest because of their likely high exposure during household work such as cooking and because their results would likely suffer minimal residual confounding by tobacco use. Lung cancer was associated with coal use among never-smoking Asian women (OR = 5.41; 95% CI, 3.65–8.00); however, results for wood use among never-smoking Western women were more ambiguous (OR = 1.15; 95% CI, 0.81–1.64).
When restricting the analyses to only lifetime solid-fuel users (OR = 2.07; 95% CI, 1.80–2.38), lifetime coal users in Asia (OR = 2.85; 95% CI, 1.80–4.51), and lifetime wood users in North American and European countries (OR = 1.43; 95% CI, 0.97–2.11), the results were similar to those based on predominant use. Further, sensitivity analyses found lung cancer to be associated with solid-fuel use regardless of which study we excluded (CEE excluded: OR = 1.54; 95% CI, 1.37–1.73; California excluded: OR = 1.47; 95% CI, 1.34–1.62; Toronto excluded: OR = 1.57; 95% CI, 1.43–1.73; Singapore excluded: OR = 1.62; 95% CI, 1.48–1.77; Xuanwei1 excluded: OR = 1.23; 95% CI, 1.15–1.38; New England excluded: OR = 1.64; 95% CI, 1.50–1.79; Xuanwei2 excluded: OR = 1.55; 95% CI, 1.42–1.69).
For the studies that used population-based controls, lung cancer was associated with solid-fuel use (OR = 2.02; 95% CI, 1.72–2.38) and coal use in Asia (OR = 6.42; 95% CI, 4.24–9.72) but not wood use in North America and Europe (OR = 1.05; 95% CI, 0.78–1.40). Among studies using hospital-based controls, results were similar to the overall findings for the associations with solid-fuel use (OR = 1.12; 95% CI, 0.99–1.28) and wood use in North America and Europe (OR = 1.24; 95% CI, 1.05–1.46). The one study in Asia that used hospital-based controls did not have any cases or controls who were predominant coal users.
We assessed study heterogeneity for the association between lung cancer risk and fuel use. We observed study heterogeneity among predominant coal users (pheterogeneity = 0.001), mainly attributed to the strong association observed in Xuanwei1. When we excluded Xuanwei1 from the analysis, residual heterogeneity was within that expected from random variation (pheterogeneity = 0.31), and the association between coal use and lung cancer risk remained. Study heterogeneity for wood use in Western countries was also within that expected from random variation (pheterogeneity = 0.06).