An evidence mapping approach to support hazard identification for polychlorinated biphenyl (PCB) mixture exposure and female reproductive endpoints

BACKGROUND AND AIM: Evidence mapping can facilitate the organization and review of complex databases. Here, we utilize evidence mapping to survey and explore human and animal studies of female reproductive effects of PCB mixture exposures and to identify whether the database is sufficient to support human health hazard identification. METHODS: We developed a Population, Exposures, Comparators, and Outcomes (PECO) statement to direct screening and categorization. Study information was extracted into literature inventory tables and organized by outcome. To identify outcomes promising for human health hazard identification and explore the strength of the database, we considered the following: size of outcome-specific database, study design, biological significance of the outcome, and exposure biomarker. RESULTS:We identified over 200 human and animal studies that evaluated PCB mixture exposures and reproductive effects in females over a variety of life stages and exposure scenarios. Most human studies quantified PCB exposure using blood, which integrates exposure over all routes. The most commonly measured outcomes in human studies were endometriosis, reproductive hormones, and gestational length; most of these were evaluated in cohort or case-control studies. All of these outcomes are biologically significant and clearly measurable. In animals, the most commonly measured outcome was impacts on female fertility; these studies utilized a dam-only exposure scenario, which eliminates potential confounding by male exposure status that could exist in human studies of similar outcomes. Many outcomes were measured in both humans and animals (e.g., hormonal status, pubertal development, gestation length), which can facilitate hazard identification and assessment of coherence across these lines of evidence. CONCLUSIONS:Through evidence mapping, we have identified numerous female reproductive outcomes that have been evaluated in studies of PCB-exposed humans and animals. The database of PCBs and female reproductive effects in both humans and animals is sufficient to support future hazard identification. KEYWORDS: Reproductive Outcomes, Female, Chemical exposures, Mixtures