A study published in the International Journal of Molecular Sciences has uncovered startling effects of microplastics on mice, revealing significant behavioral changes and immune responses in both young and old subjects. This research expands our understanding of how these environmental pollutants might be affecting mammals — potentially including humans.
Microplastics, tiny plastic particles less than 5 millimeters in diameter, have been a growing concern for environmentalists and health professionals alike. Found in everything from water bodies to human tissues, these particles have become a symbol of modern pollution. Previous studies have primarily focused on the harmful effects of these particles on marine life — shown to cause oxidative stress, inflammation, and decreased cell vitality. However, their impact on mammals, especially on a cognitive and biological level, has remained largely unexplored.
The study, conducted by a team of researchers at the University of Rhode Island, aimed to bridge this gap in knowledge. With microplastics being a constant in the environment and already proven harmful to marine organisms, the team sought to understand if similar detrimental effects could be observed in mammals. They specifically chose to explore how these particles could influence the behavior and immune responses in mice, providing insights that could have wider implications for other mammals, including humans.
To test their hypotheses, the researchers conducted an experiment using female C57BL/6J, or “black 6”, mice, divided into young and old groups of 40 each. These mice were exposed to various concentrations of polystyrene microplastics in their drinking water for three weeks. This method of exposure was selected to closely mimic how humans might encounter these particles in everyday life. The team used a series of behavioral assays, such as open-field and light-dark preference tests, coupled with tissue analyses, to evaluate the impact of microplastics.
Mice exposed to microplastics showed increased movement and rearing activity, particularly more pronounced in older mice. This suggested that the particles had a significant effect on their behavior. Additionally, changes were observed in immune marker expression in the liver and brain. In older mice, these changes were more robust, indicating a stronger immune response. Perhaps most alarmingly, microplastics were detected in various tissues, including the brain — revealing their capability to cross protective barriers like the blood-brain barrier.
In other words, this study showed that mice, after being exposed to tiny plastic particles for a short time, began to act differently, with older mice showing more noticeable changes — hinting at a possible effect on their brain and nervous system. This may suggest that our everyday contact with microplastics might also affect our brain health and immune systems, as humans.
However, the focus on female mice alone in the study may limit the extent to which these findings can be generalized across genders. Also, the study used a specific type of microplastic, which means the results may not apply to all microplastics. Furthermore, the experiment’s timeframe of three weeks does not reflect the potential long-term exposure humans might experience. Lastly, while the behavioral changes in mice were statistically significant, translating these findings to predict similar effects in humans requires caution due to differences in biology between species.
While the study sheds light on the potential impacts of microplastics on mammalian health, further research is needed to fully understand the extent and nature of these effects, especially in humans.
The study, “Acute Exposure to Microplastics Induced Changes in Behavior and Inflammation in Young and Old Mice“, was authored by Lauren Gaspar, Sydney Bartman, Giuseppe Coppotelli, and Jaime Ross — all from the University of Rhode Island.