Exposure to micro- and nanoplastics and human reproductive outcomes: a systematic review

Background: Micro- and nanoplastics are novel pollutants which have been detected in human tissues including placenta and fetal meconium. However, their association with adverse fertility or pregnancy outcomes in humans is not known. Objectives: To synthesise evidence for the presence of micro- and nanoplastics in human reproductive tissue and their associations with environmental exposures and reproductive outcomes. Search Strategy: Medline, Embase, Emcare, CINAHL, ClinicalTrials.gov and ICTRP were searched from inception to 03/02/2023. Selection Criteria: Studies of human participants, assessing presence of micro- and nanoplastics in reproductive tissues, environmental exposures to micro- and nanoplastics, and fertility or pregnancy-related outcomes. Data Collection and Analysis: Two independent reviewers selected studies and extracted data on study characteristics, microplastics detected, environmental exposures, reproductive outcomes, and risk of bias. Narrative synthesis was performed due to methodological heterogeneity. Main Results: Of 1094 citations, seven studies were included, covering 96 participants. Microplastics were detected in 68 out of 96 placentas examined across all studies, and in all 14 meconium samples. Two studies reported associations between lifestyle factors (daily water intake, use of scrub cleanser or toothpaste, bottled water and takeaway food) and placental microplastics. One study reported associations between meconium microplastics and microbiota diversity and composition. One reported placental microplastics levels correlated with reduced birth weights and 1-minute Apgar scores. All studies had a very high risk of bias. Conclusions: There is a need for high-quality observational studies to assess the effects of microplastics on human reproductive health. Funding: None received Keywords: microplastics, nanoplastics, pregnancy, fertility, environmental pollution