Two separate laboratory studies, one involving mice at Peking University in Beijing, and another involving human cadavers at Duke University in North Carolina, investigated the presence of microplastics in the human brain. Researchers at Peking University injected polystyrene micro-spheres intravenously into mice and used fluorescence imaging to track its movement. They found that the polystyrene is able to cross the blood-brain barrier and accumulated in blood vessels around the brain’s cortex. The study at Duke University looked at the brains of deceased individuals and found nanoscale “shards” in brain tissue, with polyethylene being the predominant polymer. They found an approximately 50 percent increase in the total mass of microplastics and nanoplastics detected in brain tissues from patients who died in 2024 compared to patients who died in 2016. The methods used for preparation of the tissue samples may result in residual materials, resulting in potential biased high results. The mass concentration was higher in dementia patients compared to patients with normal cognitive function. Causal links between the amount of microplastics and nanoplastics in the brain and other factors such as age, health, race, etc. continue to be further explored, as well as the potential health effects of microplastic accumulation in the brain.
A recent study quantified the number of anthropogenic particles (APs) in “edible tissue” collected from a variety of marine species that are historically, economically, and culturally significant to the state of Oregon (chinook salmon, pink shrimp, lamprey, lingcod, pacific herring, and black rockfish). APs refer to a broad category of materials that are produced or modified by humans, which include microplastics. In the study, APs were found in 99 percent of the edible tissue sampled. The findings highlight the presence of APs in seafood and need for further research.
A recent study conducted by researchers in Beijing investigated the concentrations of microplastics in composted materials. As composting is a natural way of breaking down organic materials, the same mechanisms can also degrade microplastics in compost. Microplastics can enter the compost stream through animal manure, atmospheric deposition, surface runoff, and sewage irrigation. After composting, microplastics were smaller sizes and have rougher morphologies (folds, cracks, and grooves) which adhere to more mineral colloids, making them difficult to separate from the composted materials. Additionally, microplastics can adsorb environmental contaminants such as heavy metals, organic contaminants, and antibiotics. The most effective way of reducing microplastics in compost was to prevent them from entering the stream from beginning through sorting and screening; this reduced the weight by approximately 30 percent. These results highlight the need for improved waste management practices to mitigate microplastics in composting systems.
An International Joint Commission (IJC) Great Lakes Science Advisory Board (SAB) work group released a report summarizing their findings for the Laurentian Great Lakes Project, which focused on microplastics monitoring and developing frameworks for ecological risk assessment and management. The risk assessment and management framework scope included deriving preliminary ambient water and sediment thresholds following the approach used in Mehinto et al 2022. The preliminary thresholds ranged from 398 to 23,200 particles/liter for water and 62.6 to 6.09 x106 particles per kilogram dry weight for sediment. Some samples from the Great Lakes exceeded these thresholds. As a result, the report recommends that microplastics be assessed under the Great Lakes Water Quality Agreement and designate microplastics as a Chemical of Mutual Concern (CMC). If microplastics are identified as a CMC, Canada and the United States would need to collaborate on a binational strategy to tackle microplastic pollution in the Great Lakes.