Five studies published between the end of September and early October 2024 assessed human samples for the presence of microplastics and their association with negative health outcomes, focusing on the nervous system, as well as female and male reproductive organs.
Impacts on the central nervous system
In an article published on October 1, 2024, in the Journal of Hazardous Materials, Jian Xie from the Southeast University, Jiangsu, China, and co-authors assessed whether microplastics made of different polymer types accumulate in the human central nervous system (CNS) and induce an inflammatory response.
The scientists analyzed cerebrospinal fluid samples from 14 patients with CNS infections and 14 without. Patients with CNS infections showed significant disruption of their blood-brain barriers and intracranial inflammation. Upon sample processing and application to pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS), the researchers detected polypropylene (PP) and polystyrene (PS) microplastics in all patients, polyethylene (PE) in 26, and polyvinyl chloride (PVC) in 17 of the 28 samples. Since microplastics of other common polymer types (e.g., PET) were not present, the authors hypothesized the “CNS has a selective barrier restricting the entry of certain micro- and nanoplastics.”
Comparing participants with and without CNS infection showed higher PP and PE levels in those with CNS infection. For PVC and PS there was no difference between the two groups. The scientists used the cerebrospinal fluid albumin index to measure blood-brain barrier permeability and found that an impaired barrier promotes PP and PE to enter the cerebrospinal fluid while this was not the case for PS and PVC. Based on interleukin-6 and -8 levels as indicators for inflammation, the researchers found that the accumulation of plastic particles did not worsen inflammation in the CNS.
Earlier this year, Yanxu Zheng from Xiangya Hospital, Hunan, China, and co-authors, reviewed in vivo and in vitro studies looking at the effects of micro- and nanoplastic on the CNS. In their article, published on April 11, 2024, in Toxicology, the authors concluded current evidence demonstrates that plastic particles disturb neurons, as well as alter the memory and behavior of organisms. As a consequence, this may favor diseases of the CNS such as inflammation and Parkinson’s-like neurodegenerative disorders.
A previous publication reported PE microplastics accumulate in the brain and induce autism spectrum disorder-like symptoms using a mouse model (FPF reported). An in vitro study found microplastics negatively impact human forebrain organoid development (FPF reported).
Presence in reproductive organs
In an article published on September 27, 2024, in the journal Ecotoxicology and Environmental Safety, Chunlin Dong from Affiliated Hospital of Jiangnan University, Wuxi, China, and co-authors investigated microplastic levels in female reproductive organs. They sampled 20 cases each of adenomyosis, ovarian ectopic cysts, and uterine tubes from patients who had undergone removal procedures. After tissue digestion, they assessed microplastics using micro-Raman spectroscopy. The scientists detected plastic particles in 43 out of the 60 samples with an average of 1.4 ± 1.11 particles/g tissue after blank correction. Particles in the size between 4.51 and 32.92 µm were the most prominent as were the polymer types PE and PP. Fiber-shaped plastics (39%) exceeded fragments (24%). Dong and co-authors clarified that their results need validation by a larger sample size.
Chenyao Deng from Peking University First Hospital, Beijing, China, and co-authors focused on the presence of microplastics in the human prostate. In their article published on September 27, 2024, in eBioMedicine, the researchers describe that they examined microplastic levels and properties in para-tumor and tumor tissues of 22 patients. Therefore, they analyzed the processed samples with laser direct infrared spectroscopy, scanning electron microscopy, and Py-GC/MS. Microplastics were detected in 32% of para-tumor and 35% of tumor samples with mean concentrations of 181.0 μg/g and 290.3 μg/g tissue, respectively. Irregular shapes were predominant and several polymer types were detected with PS only being present in the tumor tissue. By asking the patients if they consume take-out foods, the scientists assessed and established a correlation between the frequency of take-out food consumption and PS particle abundance.
The study did not include healthy prostate samples. Accordingly, no connection between microplastic presence and prostate health can be drawn. However, previous studies associated microplastic exposure with liver and ovarian cancer development (FPF reported) and connected the presence of particles with colorectal cancer (FPF reported) and with exacerbated breast cancer metastasis (FPF reported). Based on in vitro assays and mice in vivo experiments, others reported microplastics induce premature testicular aging (FPF reported).
Effects on sperm function
In an article published on September 28, 2024, in the journal eBioMedicine, Chen Zhang from the Obstetrics and Gynecology Hospital of Fudan University, Shanghai, China, and co-authors investigated the presence of microplastics in semen and urine samples of 113 male participants from three regions in China. Using Raman microscopy, the scientists detected microplastics in all samples with PS, PP, and PP being most prevalent. To assess a potential association between microplastic presence and semen quality, sperm count, concentration, mortality, and morphology were also investigated. The presence of polytetrafluoroethylene (PTFE), used as a coating material in non-stick pans, was associated with a reduction in total sperm count, concentration, and progressive mortality. In addition, multi-linear regression analysis outlined reduced semen quality with an increasing number of microplastic types. “Future research is warranted to further elucidate the mechanisms underlying the adverse effects of microplastics on male fertility and cross-generational effects.”
The study by Dong et al. is based on a larger cohort compared to previous studies which demonstrated the presence of microplastics in human semen (FPF reported and here).
References
Deng, C. et al. (2024). “Identification and analysis of microplastics in para-tumor and tumor of human prostate.” eBioMedicine. DOI: 1016/j.ebiom.2024.105360
Dong, C. et al. (2024). “Microplastics detected in three types of female reproductive organs using micro-Raman spectroscopy.” Ecotoxicology and Environmental Safety. DOI: 10.1016/j.ecoenv.2024.117099
Xie, J. et al. (2024). “Blood-brain barrier damage accelerates the accumulation of micro- and nanoplastics in the human central nervous system.” Journal of Hazardous Materials. DOI: 10.1016/j.jhazmat.2024.136028
Zhang, C. et al. (2024). “Association of mixed exposure to microplastics with sperm dysfunction: a multi-site study in China.” eBioMedicine. DOI: 0.1016/j.ebiom.2024. 105369
Zheng, Y. et al. (2024). “The effects of micro- and nanoplastics on the central nervous system: A new threat to humanity?.” Toxicology. DOI: 10.1016/j.tox.2024.153799
Related research
Chen, Y.-C.. et al. (2024). “Impact of seasonal changes and environmental conditions on suspended and inhalable microplastics in urban air.” Environmental Pollution. DOI: 10.1016/j.envpol.2024.124994
Özsoy, S. et al. (2024). “Presence of Microplastics in Human Stomachs.” Forensic Science International. DOI: 10.1016/j.forsciint.2024.112246
Parobková, V. et al. (2024). “Raman microspectroscopy and laser-induced breakdown spectroscopy for the analysis of polyethylene microplastics in human soft tissues.” Heliyon. DOI: 10.1016/j.heliyon.2024.e37844
Wang, Y. et al. (2024). “Exploring alternatives for detecting microplastics in the human body: questionnaire survey.” Scientific Reports. DOI: 10.1038/s41598-024-73982-9
