Abstract
We conducted a meta-analysis focusing on studies with high potential for trichloroethylene (TCE) exposure to provide quantitative evaluations of the evidence for associations between TCE exposure and kidney, liver, and non-Hodgkin lymphoma (NHL) cancers. A systematic review documenting essential design features, exposure assessment approaches, statistical analyses, and potential sources of confounding and bias identified twenty-four cohort and case-control studies on TCE and the three cancers of interest with high potential for exposure, including five recently published case-control studies of kidney cancer or NHL. Fixed- and random-effects models were fitted to the data on overall exposure and on the highest exposure group. Sensitivity analyses examined the influence of individual studies and of alternative risk estimate selections. For overall TCE exposure and kidney cancer, the summary relative risk (RRm) estimate from the random effects model was 1.27 (95% CI: 1.13, 1.43), with a higher RRm for the highest exposure groups (1.58, 95% CI: 1.28, 1.96). The RRm estimates were not overly sensitive to alternative risk estimate selections or to removal of an individual study. There was no apparent heterogeneity or publication bias. For NHL, RRm estimates for overall exposure and for the highest exposure group, respectively, were 1.23 (95% CI: 1.07, 1.42) and 1.43 (95% CI: 1.13, 1.82) and, for liver cancer, 1.29 (95% CI: 1.07, 1.56) and 1.28 (95% CI: 0.93, 1.77). Our findings provide strong support for a causal association between TCE exposure and kidney cancer. The support is strong but less robust for NHL, where issues of study heterogeneity, potential publication bias, and weaker exposure-response results contribute uncertainty, and more limited for liver cancer, where only cohort studies with small numbers of cases were available.
Highlights
The interpretation of the epidemiologic studies on cancer and trichloroethylene (TCE) continues to be an area of considerable interest despite numerous reviews, including those of multidisciplinary expert panels whose conclusions have ranged widely due, in part, to differences in the qualitative evaluation of the epidemiologic data as well as in the studies available at the time [1,2,3,4,5]
Two advisory panels reviewing the epidemiologic evidence on cancer and TCE recommended meta-analysis as an approach to synthesize the data, noting individual studies had limited statistical power for relatively uncommon cancers such as kidney, liver, and non-Hodgkin lymphoma (NHL) [6,7]
Studies selected for inclusion in the meta-analysis met the following criteria: (1) cohort or case-control design; (2) exposed and control groups in cohort studies and cases and controls in case-control studies are comparable and drawn from the same base population; (3) TCE exposure potential and some estimate of TCE exposure assessed for each subject by reference to industrial hygiene records, individual biomarkers, job-exposure matrices, expert assessment, water distribution models, or questionnaire responses; and (4) relative risk (RR) estimates for kidney cancer, liver cancer, or NHL
Summary
The interpretation of the epidemiologic studies on cancer and trichloroethylene (TCE) continues to be an area of considerable interest despite numerous reviews, including those of multidisciplinary expert panels whose conclusions have ranged widely due, in part, to differences in the qualitative evaluation of the epidemiologic data as well as in the studies available at the time [1,2,3,4,5]. We focus on three specific cancers of a priori interest from rodent bioassays of TCE exposure [11,12,13] and a broader qualitative review of the epidemiologic data—kidney cancer, liver cancer, and NHL. Our meta-analysis updates the literature covered by previous meta-analyses of TCE exposure and cancer [14,15,16,17,18,19], adding four case-control studies on NHL [20,21,22,23], one case-control study on renal cell carcinoma [24], two studies in a cohort of aerospace workers [25,26], and an updated mortality follow-up of a cohort of aircraft maintenance workers [27]. The incorporation of clear a priori guidelines for identifying studies with moderate-to-high probability of TCE exposure, inclusion of both cohort and case-control studies, supplemental examination of the highest exposure group in each study to reduce the impact of exposure misclassification, and assessments of heterogeneity and sensitivity provide insight for the evaluation of a causal link between
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: International Journal of Environmental Research and Public Health
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
