Systematic review of perchloroethylene and non-Hodgkin's lymphoma.

We conducted a systematic review of epidemiology studies that evaluated the association between perchloroethylene (PCE) and non-Hodgkin's lymphoma (NHL). This included an independent detailed assessment of a few critical aspects of study quality (i.e., study design, exposure measurement, exposure levels, and potential confounding), and a consideration of other aspects of quality less formally. Of the identified 18 cohort studies of 15 unique cohorts, 17 case-control studies of 14 unique population groups, and 3 ecological studies, none was high quality for all four critical quality elements and each study also had other major methodological study limitations. Reported risk estimates were mostly null, ranged widely from below to above 1, and often had extremely wide confidence intervals (CIs), indicating unstable risk estimates. In addition, there was no consistent evidence of dose-response. Overall, given the low quality of the available epidemiology studies, the evidence does not support an association between PCE exposure and NHL.