title: Household coal use and lung cancer: systematic review and meta-analysis of case-control studies, with an emphasis on geographic variation.
abstract: BACKGROUND
  Emissions from household coal combustion associated with cooking and heating are an important public health issue, particularly in China where hundreds of millions of people are exposed. Although coal emissions are a known human carcinogen, there is still uncertainty about the level of risk for lung and other cancers.
  
  
  METHODS
  We performed a meta-analysis on 25 case-control studies (10,142 cases and 13,416 controls) to summarize the association between household coal use and lung cancer risk, and to explore the effect modification of this association by geographical location.
  
  
  RESULTS
  Using random-effects models, household coal use was found to be associated with lung cancer risk among all studies throughout the world [odds ratio (OR) = 2.15; 95% confidence interval (CI) = 1.61-2.89, N(studies) = 25], and particularly among those studies carried out in mainland China and Taiwan (OR = 2.27; 95% CI = 1.65-3.12, N(studies) = 20). Stratification by regions of mainland China and Taiwan found a variation in effects across the regions, with south/southeastern (OR = 3.27; 95% CI = 1.27-8.42, N(studies) = 3) and southwestern China (OR = 2.98; 95% CI = 1.18-7.53, N(studies) = 3) experiencing the highest risk. The elevated risk associated with coal use throughout Asia was also observed when stratifying studies by gender, smoking status, sample size, design (population vs hospital case-control) and publication language. No significant publication bias was found (p(Begg's) = 0.15).
  
  
  CONCLUSIONS
  Our results provide evidence that although the carcinogenic effect of coal use varies by location, coals from many locations exhibit elevated lung cancer risks.
authors.affiliation: Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD, USA. hosgoodd@mail.nih.gov
authors.forename: H Dean
authors.initials: HD
authors.lastname: Hosgood
authors.forename: Hu
authors.initials: H
authors.lastname: Wei
authors.forename: Amir
authors.initials: A
authors.lastname: Sapkota
authors.forename: Imran
authors.initials: I
authors.lastname: Choudhury
authors.forename: Nigel
authors.initials: N
authors.lastname: Bruce
authors.forename: Kirk R
authors.initials: KR
authors.lastname: Smith
authors.forename: Nathaniel
authors.initials: N
authors.lastname: Rothman
authors.forename: Qing
authors.initials: Q
authors.lastname: Lan
mesh_terms: D016902:Air Pollution, Indoor / Q000009:adverse effects*; D001208:Asia / Q000453:epidemiology; D016022:Case-Control Studies; D002681:China / Q000453:epidemiology; D003031:Coal / Q000009:adverse effects*; D016001:Confidence Intervals; D003296:Cooking; D003906:Developing Countries; D005191:Family Characteristics; D005260:Female; D006361:Heating; D006801:Humans; D008175:Lung Neoplasms / Q000453:epidemiology* / Q000209:etiology*; D008297:Male; D020380:Needs Assessment; D016017:Odds Ratio; D015995:Prevalence; D011634:Public Health; D018570:Risk Assessment; D013624:Taiwan / Q000453:epidemiology
chemical_list: D003031:Coal