title: A meta-analysis of occupational trichloroethylene exposure and liver cancer.
abstract: OBJECTIVE
  Findings from epidemiologic studies of trichloroethylene (TCE) exposure and liver cancer have been inconsistent. To quantitatively evaluate this association and to examine sources of heterogeneity, we conducted a meta-analysis of occupational studies of TCE exposure and liver/biliary tract cancer.
  
  
  METHODS
  We identified 14 occupational cohort studies of TCE exposed workers and one case-control study that met our inclusion criteria. Nine studies specifically identified TCE as a workplace exposure, and were classified as Group I cohort studies. Subcohorts of workers, identified within eight of these studies as more likely exposed to TCE than the total cohort, were analyzed separately.
  
  
  RESULTS
  The combined liver/biliary cancer summary relative risk estimate (SRRE) for all studies was 1.08 (95% CI 0.91-1.29; heterogeneity (H)-P-value=0.12). For the total study populations in the Group I cohorts, the SRRE was 1.14 (95% CI 0.93-1.39; H-P-value=0.05) and for the subcohorts, the SRRE was 1.30 (95% CI 1.09-1.55). Within this subcohort analysis, the association for the European studies of workers from various industries (SRRE=1.38; based on four studies) was higher than the association for the US studies of aerospace and aircraft workers (SRRE=0.97, based on four studies).
  
  
  CONCLUSIONS
  Although positive associations were observed for some analyses, results were inconsistent across occupational groups (aerospace/aircraft vs. other industries combined), study location, and incidence versus mortality endpoints. In addition, exposure-response trends were not observed consistently across studies. Interpretation is also limited by the potential impact of uncontrolled confounding by other occupational or lifestyle exposures such as smoking or alcohol consumption. Given these limitations, the currently available epidemiologic data are not sufficient to support a causal relation between occupational TCE exposure and liver/biliary cancer.
authors.affiliation: Exponent Health Sciences, 185 Hansen Ct, Suite 100, Wood Dale, IL 60191, USA. dalexander@exponent.com
authors.forename: Dominik D
authors.initials: DD
authors.lastname: Alexander
authors.forename: Michael A
authors.initials: MA
authors.lastname: Kelsh
authors.forename: Pamela J
authors.initials: PJ
authors.lastname: Mink
authors.forename: Jeffrey H
authors.initials: JH
authors.lastname: Mandel
authors.forename: Rupa
authors.initials: R
authors.lastname: Basu
authors.forename: Michal
authors.initials: M
authors.lastname: Weingart
mesh_terms: D016022:Case-Control Studies; D015331:Cohort Studies; D006801:Humans; D008113:Liver Neoplasms / Q000139:chemically induced*; D016273:Occupational Exposure / Q000009:adverse effects*; D014241:Trichloroethylene / Q000494:pharmacology / Q000506:poisoning*
chemical_list: D014241:Trichloroethylene