title: Chromium VI and stomach cancer: a meta-analysis of the current epidemiological evidence.
abstract: OBJECTIVE
  Chromium VI (hexavalent chromium, Cr(VI)) is an established cause of lung cancer, but its association with gastrointestinal cancer is less clear. The goal of this study was to examine whether the current human epidemiological research on occupationally inhaled Cr(VI) supports the hypothesis that Cr(VI) is associated with human stomach cancer.
  
  
  METHODS
  Following a thorough literature search and review of individual studies, we used meta-analysis to summarise the current epidemiological literature on inhaled Cr(VI) and stomach cancer, explore major sources of heterogeneity, and assess other elements of causal inference.
  
  
  RESULTS
  We identified 56 cohort and case-control studies and 74 individual relative risk (RR) estimates on stomach cancer and Cr(VI) exposure or work in an occupation associated with high Cr(VI) exposure including chromium production, chrome plating, leather work and work with Portland cement. The summary RR for all studies combined was 1.27 (95% CI 1.18 to 1.38). In analyses limited to only those studies identifying increased risks of lung cancer, the summary RR for stomach cancer was higher (RR=1.41, 95% CI 1.18 to 1.69).
  
  
  CONCLUSIONS
  Overall, these results suggest that Cr(VI) is a stomach carcinogen in humans, which is consistent with the tumour results reported in rodent studies.
authors.affiliation: Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, California, USA.
authors.forename: Roberta
authors.initials: R
authors.lastname: Welling
authors.affiliation: Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Sacramento, California, USA.
authors.forename: James J
authors.initials: JJ
authors.lastname: Beaumont
authors.affiliation: Occupational Medicine, Kaiser Permanente, Oakland, California, USA.
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Petersen
authors.affiliation: Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Sacramento, California, USA.
authors.forename: George V
authors.initials: GV
authors.lastname: Alexeeff
authors.affiliation: Office of Environmental Health Hazard Assessment, California Environmental Protection Agency, Oakland, California, USA.
authors.forename: Craig
authors.initials: C
authors.lastname: Steinmaus
mesh_terms: D002274:Carcinogens, Environmental / Q000009:adverse effects*; D002857:Chromium / Q000009:adverse effects*; D006801:Humans; D007221:Industry; D009784:Occupational Diseases / Q000209:etiology*; D016273:Occupational Exposure / Q000009:adverse effects*; D013274:Stomach Neoplasms / Q000209:etiology*
chemical_list: D002274:Carcinogens, Environmental; D002857:Chromium; C074702:chromium hexavalent ion