title: Association of inorganic arsenic exposure with liver cancer mortality: A meta-analysis.
abstract: BACKGROUND
  The association of long-term inorganic arsenic (iAs) exposure through drinking water with risk of liver cancer mortality remains controversial. Therefore, we reviewed and quantitatively summarized the evidence from observational studies with a meta-analysis.
  
  
  METHODS
  Pertinent studies were identified by searching PubMed and China National Knowledge Infrastructure through May 2014 and by reviewing the reference lists of retrieved articles. Studies that reported standardized mortality ratios (SMRs) with 95% confidence interval (95% CIs) for the association of iAs in drinking water with liver cancer were eligible. The random effect model was adopted as the pooling method to generate summary effect estimates (meta-SMRs).
  
  
  RESULTS
  Of the 4851 articles identified through searching databases, 7 articles including 12 studies were included in the meta-analysis. The meta-SMR with 95% CI of liver cancer for the highest versus lowest category of iAs exposure level in drinking water was 1.80 (1.61 to 2.02). Furthermore, an increased risk of liver cancer mortality was found in both females [1.80 (1.45 to 2.24)] and males [1.84 (1.56 to 2.16)]. In subgroup analysis, the meta-SMRs were 1.93 (1.72 to 2.15) for cohort studies, 1.60 (1.22 to 2.10) for ecological studies, 1.93 (1.72 to 2.15) for studies conducted in Asia, and 1.60 (1.22 to 2.10) for studies conducted in South America, respectively. After removing the 3 studies conducted by Smith et al. (having two studies separately for males and females) and Chen et al. that had a strong effect on heterogeneity, a significant association was also found [1.85 (1.72 to 1.99)].
  
  
  CONCLUSIONS
  This meta-analysis indicates that long-term iAs exposure through drinking water increases the risk of liver cancer mortality.
authors.affiliation: Department of Epidemiology and Health Statistics, The Medical College of Qingdao University, 38 Dengzhou Road, Shandong Province, Qingdao 266021, People׳s Republic of China.
authors.forename: Weijing
authors.initials: W
authors.lastname: Wang
authors.affiliation: Department of Epidemiology and Health Statistics, The Medical College of Qingdao University, 38 Dengzhou Road, Shandong Province, Qingdao 266021, People׳s Republic of China.
authors.forename: Shuo
authors.initials: S
authors.lastname: Cheng
authors.affiliation: Department of Epidemiology and Health Statistics, The Medical College of Qingdao University, 38 Dengzhou Road, Shandong Province, Qingdao 266021, People׳s Republic of China. Electronic address: zhangdf1961@126.com.
authors.forename: Dongfeng
authors.initials: D
authors.lastname: Zhang
mesh_terms: D001151:Arsenic / Q000032:analysis / Q000633:toxicity*; D002681:China / Q000453:epidemiology; D060766:Drinking Water / Q000009:adverse effects / Q000737:chemistry*; D004781:Environmental Exposure / Q000009:adverse effects / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008113:Liver Neoplasms / Q000139:chemically induced* / Q000401:mortality*; D008297:Male; D012307:Risk Factors; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity*
chemical_list: D060766:Drinking Water; D014874:Water Pollutants, Chemical; D001151:Arsenic
keywords: Drinking water; Inorganic arsenic; Liver cancer; Meta-analysis; Mortality