Background exposure to polychlorobiphenyls and mortality: A systematic review and meta-analysis

Abstract

Abstract Polychlorinated biphenyls (PCBs) are a family of 209 congeners known to be highly persistent in the environment and with long-range transport leading to a ubiquitous pollution. This group of persistent organic pollutants is known to be carcinogenic and to have endocrine-disrupting properties. Due to bioaccumulation along the food chain, the main route of exposure in general population is through diet. High level toxicity was well characterized with mass poisoning episodes and occupational cohort but the association with PCBs exposure at low doses with mortality in general population is uncertain. We conducted a systematic review and meta-analysis to assess whether background exposure levels of PCBs increase all-cause and cancer- and cardiovascular-specific mortality risk in the general population, following the National Toxicology Program/Office of Health Assessment and Translation framework. Studies were identified by searching PubMed, Embase and Web of Science up to 1st of January, 2021. Random-effects meta-analysis was used to estimate summary relative risks (SRRs). Eight prospective cohort studies met our inclusion criteria, leading to 72,852 participants including 17,805 deaths. Overall exposure to PCBs was not statistically significantly associated with all-cause mortality (SRR=1.13, 95% CI = 0.90-1.41, n = 7 studies, low certainty); however, dietary exposure to PCBs was associated with an increased risk of cardiovascular-specific mortality (SRR=1.38, 95% CI = 1.14-1.66, n = 3 studies, moderate certainty), while no association was found with cancer-specific mortality. Bayesian meta-analysis and subgroup analyses confirmed these findings. Our meta-analysis suggests that background exposure to PCBs is associated with an increased risk of cardiovascular-specific mortality in the general population with a “moderate” level of evidence. This should be interpreted with caution given the small number of studies on mortality in the general population. Key messages This meta-analysis fails to highlight any clear association between background level of PCB exposure and all-cause and cancer-specific mortality, probably due to the limited number of studies. This study brings new evidence of an increased risk of cardiovascular-specific mortality associated with a higher exposure to PCBs in the general population, with a moderate level of certainty.