In an article published on September 24, 2023, in the American Journal of Industrial Medicine, Gregory M. Zarus and co-authors from the Office of Innovation and Analytics, Atlanta, USA, reviewed 34 studies on the occupational health effects of microplastic exposure and found a relationship between polyvinyl chloride (PVC) particle exposure and liver toxicity.
The authors screened the literature for publications focusing on worker exposure to microplastics that also reported health outcomes. Of the 34 included studies, 17 concerned PVC and 17 more included five other plastic types. Separating the reported effects by plastic type, Zarus et al. found “an increased risk of lung cancer associated with exposure to high concentrations of PVC microplastic “dust” particles.” Besides effects on the respiratory system, exposure to PVC was further associated with liver damage including lung cancers. These human outcomes were confirmed by the animal exposure studies the authors also had a look at.
Unlike PVC, the available data did not permit conclusions on the carcinogenic effect of other microplastic types, such as polystyrene (PS). One problem particularly highlighted for PS (but also the case for PVC and its monomer vinyl chloride) was that the effects of PS were difficult to separate from those of styrene. While worker exposure to PS particles still needs to be further researched, animal data indicates a hepatoxic effect.
Guangquan Chen from Tongji University, Shanghai, China, and co-authors performed an in vitro and mice study to investigate the potential of PS nanoplastics to induce epithelial ovarian cancer. In an article published on October 5, 2023, in the journal Science of the Total Environment, the authors described that they used spherical 100 nm-sized PS particles to expose the human ovarian cancer HEY cell line to concentrations between 1 and 40 mg/L for 48h to up to 16 days. Furthermore, eight Balb/C nude female mice received 10 mg/L microplastics over 27 days and were compared to unexposed control mice.
Concerning the in vitro tests, the scientists found the particles reduced cell viability in a dose-dependent manner, and changed gene expression and the metabolic pathway. The two latter effects were also observed in microplastic-exposed mice. Concentrations of 10 mg/L further accelerated the growth of epithelial ovarian tumors. The authors concluded that exposure to PS nanoplastics “caused a significant acceleration of epithelial ovarian cancer tumor growth in mice and a dose-dependent decrease in the relative viability of epithelial ovarian cancer cells by altering the tumor growth microenvironment.”
Previously, researchers have reported microplastics to be potentially connected to colorectal cancer and to exacerbate breast cancer metastasis.
Chen, G. et al. (2023). “Polystyrene nanoparticle exposure accelerates ovarian cancer development in mice by altering the tumor microenvironment.” Science of the Total Environment. DOI: 10.1016/j.scitotenv.2023.167592
Zarus, D. et al. (2023). “Worker studies suggest unique liver carcinogenicity potential of polyvinyl chloride microplastic.” American Journal of Industrial Medicine. DOI: 10.1002/ajim.23540