Micro- and nanoplastics (MNPs) are ubiquitous environmental pollutants that may impact human health. MNPs have previously been detected in various reproductive organs, including human placentas, testes, and amniotic fluid (FPF reported, here, and here). However, their pathways to reproductive organs and their impacts on the reproductive system are still poorly understood (FPF reported, and here). Four recent studies investigated the presence and impacts of MNPs on human reproductive health and pregnancy.
A recent study published in Environmental Science & Technology, examined the presence of MNPs in human endometrium samples, the inner lining of the uterus. Xunsi Qin from the Peking University Third Hospital, China, and collaborators also investigated how MNPs enter the uterus and impact fertility in mice.
The authors analyzed human endometrium samples from 22 patients with recurrent spontaneous abortions, using Raman microspectroscopy for particles between 0.2 to 20 μm and FTIR for larger particles. All patients had MNPs in their endometrium.
To explore how MNPs can enter the uterus and the endometrium, the researchers administered fluorescent PS-MNPs to mice by different routes. Small particles (0.2-10 μm) could pass through the gut epithelium and reach the uterus via the bloodstream. Larger particles (50 μm) could enter the uterus from the vagina via the cervical canal.
The authors also studied how MNPs affect fertility using human endometrial organoids in-vitro and mice. High-dose PS-MNP exposure (50 μg/mL) of the endometrial organoids resulted in increased cell death (apoptosis), abnormal organoid structure, and even collapse. Mice exposed to MNPs intravenously had fewer offspring, with a significant increase in the male-to-female ratio. This reduction in offspring was linked to a lower implantation rate, as demonstrated in a separate experiment. Dietary exposure to realistic PS-MNP concentrations led to fewer embryos successfully implanting in the uterus in mice. The exposed mice also showed signs of endometrial inflammation.
Qin et al. conclude that “[c]ollectively, our results demonstrate that [MNPs] essentially cause reproduction toxicity and disrupt the endometrial receptivity, highlighting the potential effects on pregnancy”.
Jiyan Xue from Tongji University, China, and colleagues found MNPs in amniotic fluid from Shanghai residents having emergency C-sections. The study, published in Science of The Total Environment, used Laser Direct Infrared Imaging (LDIR) to detect plastic particles as small as 10 µm. 32 out of 40 amniotic fluid samples contained MNPs, mostly between 20-100 µm. The authors explain that “smaller-sized [MNPs] have a higher likelihood of crossing the uterine membrane and/or placental barrier”. The more seafood and bottled water the pregnant participants consumed, the more MNPs were found in the amniotic fluid. The presence of MNPs also correlated negatively with gestational age at birth, even when controlling for cofounders, suggesting an association with preterm birth. The authors emphasize “the need for the implementation of policies aimed at safeguarding maternal and fetal health”.
Xiang Yun from Qingdao University, China, and coauthors investigated MNPs in the placenta. They used a Raman microspectroscopy system with a detection threshold of 0.25 µm to examine 50 placentas post-delivery. Over 60% of placentas contained MNPs between 1.03 to 6.84 µm. PTFE, PS, and a (ABS) were the most common, while different polymers dominated in other studies (FPF reported). The authors did not find a link between MNP presence and demographic variables, gestational age, neonatal length, birth weight, or pathological alterations.
A study in Environmental Health Insights looked at how pregnant people in Indonesia are exposed to large microplastics. Uswatun Hasanah from Hasanuddin University, Indonesia, and colleagues quantified MNPs in feces samples using microscopy and FTIR. 25g of stool contained up to 21 plastic particles between 0.2 to 4.9 mm. These consisted mostly of polyethylene terephthalate (PET), high-density polyethylene (HDPE), and polyamide (PA). Only particles larger than 0.2 mm could be detected due to the resolution of the microscope. Individuals who ate more seafood had more particles in their stool, something that has previously been linked to MNP uptake in Southeast Asia (FPF reported).
These studies elucidate some of the open questions regarding MNP exposure and early-life health. Researchers from the AURORA project recently presented a roadmap to advance robust MNP risk assessment and to support the selection of suitable methods for detecting MNPs in complex matrices. AURORA is an EU Horizon 2020 research project working on MNPs’ effects on early life health (FPF reported).
References
Qin, X., et al. (2024). ‘Features, Potential Invasion Pathways, and Reproductive Health Risks of Microplastics Detected in Human Uterus.’ Environmental Science & Technology. DOI: 10.1021/acs.est.4c01541
Xue, J., et al. (2024). ‘Microplastics in maternal amniotic fluid and their associations with gestational age.’ Science of The Total Environment. DOI: 10.1016/j.scitotenv.2024.171044
Yun, X., et al. (2024) ‘Raman-guided exploration of placental microplastic exposure: Unraveling the polymeric tapestry and assessing developmental implications.’ Journal of Hazardous Materials. DOI: 10.1016/j.jhazmat.2024.135271
Hasanah, U. et al. (2024) ‘Plasticizing Pregnancy: Microplastics Identified in Expectant Mothers’ Feces’. Environmental Health Insights. DOI: 10.1177/11786302241235810
Other recent research
Paul, I. et al. (2024) ‘Beyond the cradle – Amidst microplastics and the ongoing peril during pregnancy and neonatal stages: A holistic review.’ Journal of Hazardous Materials. DOI: 10.1016/j.jhazmat.2024.133963
Sharma, R., et al. (2024) ‘Impact of Microplastics on Pregnancy and Fetal Development: A Systematic Review.’ Cureus. DOI: 10.7759/cureus.60712
Tian, L. et al. (2024) ‘Effects of nanoplastic exposure during pregnancy and lactation on neurodevelopment of rat offspring.’ Journal of Hazardous Materials. DOI: 10.1016/j.jhazmat.2024.134800
Wang, M. et al. (2024) ‘The hidden threat: Unraveling the impact of microplastics on reproductive health.’ Science of The Total Environment. DOI: 10.1016/j.scitotenv.2024.173177
Zhang, R. et al. (2024) ‘Polystyrene microplastics disturb maternal glucose homeostasis and induce adverse pregnancy outcomes.’ Ecotoxicology and Environmental Safety. DOI: 10.1016/j.ecoenv.2024.116492
Zurub, R.E. et al. (2024) ‘Particulate contamination of human placenta: Plastic and non-plastic.’ Environmental Advances. DOI: 10.1016/j.envadv.2024.100555
Read more
AURORA News (July 3rd, 2024). AURORA scientists propose a roadmap towards risk assessment of MNPs.
Katherine McMahon and Sarah Howard (July 3rd, 2024). Environmental Health News. Microplastics continue to be found throughout human reproductive system, including the uterus.
