Background: We conducted a meta-analysis of occupational studies of trichloroethylene-exposed workers to evaluate patterns of associations by study design, exposure assessment methods, and occupational groups.
Methods: Estimates of summary relative risk (RR) were calculated using inverse-variance weighting methods. Cohort studies were classified as group I or group II, depending on quality of the study design and exposure assessment procedures. We conducted sensitivity analyses to examine sources of heterogeneity.
Results: Across all studies meeting our inclusion criteria (n = 23), the summary RR was 1.42 (95% confidence interval = 1.17–1.77), with heterogeneity present (test for heterogeneity: P = 0.001). After removal of 3 outlier studies, the summary RR for the remaining studies was 1.24 (1.06–1.45 (test for heterogeneity: P = 0.616)). The summary RR for studies of workers who were identified as more likely exposed to trichloroethylene (group I studies) was 1.34 (1.06–1.68). With outlier studies removed, the group II summary RR estimates for the cohort studies was 0.88 (0.58–1.33) and for the case-control studies was 1.33 (1.02–1.73). The summary RR for studies that used biomarkers to classify exposure (n = 3) was 1.02 (0.59–1.77) and for studies of aerospace/aircraft workers (n = 7) was 1.14 (0.84–1.57).
Conclusions: Positive associations were observed across various study groups. However, considerations of unmeasured potential confounding, lack of quantitative exposure assessment and lack of exposure-response patterns limit epidemiologic insight into the role of trichloroethylene exposure and its potential causal association with kidney cancer.
From the aHealth Science Practice, Exponent, Inc, Menlo Park, CA; bHealth Science Practice, Exponent, Inc, Chicago, IL; cHealth Science Practice, Exponent, Inc, Washington, DC; dDepartment of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, GA; and eDivision of Environmental Health Sciences, School of Public Health, University of Minnesota, Minneapolis, MN.
Submitted 13 January 2009; accepted 24 June 2009.
Supported by the TCE Issues Group and the Halogenated Solvents Industry Association.
Supplemental digital content is available through direct URL citations in the HTML and PDF versions of this article (www.epidem.com).
Correspondence: Michael A. Kelsh, Exponent, Inc, 149 Commonwealth Dr, Menlo Park, CA 94025. E-mail: firstname.lastname@example.org.