Zebrafish are a model organism used to understand our own gut conditions, such as inflammatory bowel disease. Polystyrene is used in food packaging, toys, and electronics. It’s also known as styrofoam. We sip coffees, catch waves on surfboards and live in homes made out of styrofoam. It’s everywhere. Even inside our own bodies.
It’s no surprise polystyrene makes its way into the ocean. Polystyrene is infamously hard to degrade and is resistant to sunlight. It’s also mainstream knowledge that plastics are choking ocean life and forming huge garbage patches in the middle of the ocean.
Microplastics are making their way into the stomachs of fish and other marine wildlife. Microplastics aren’t a specific type of plastic, like polystyrene, but rather small fragments that are smaller than a sesame seed (i.e., less than 5 mm in length). They aren’t a recent problem either – about 50 years ago they started to become in personal care products. Exfoliating products generally contain microbeads of plastic that eventually get washed out into the ocean from our wastewater systems. Although microbeads have been banned from the US, larger plastic waste eventually breaks down into microplastics. And microplastics happen to be a similar size to food for marine life, like plankton.
The two studies both used zebrafish, which are commonly used to study intestinal diseases, especially inflammatory bowel disease. Zebrafish are used as a model organism because they are genetically similar to humans.
One study exposed zebrafish to different concentrations of 5 micrometer polystyrene pellets for three weeks. The concentrations were similar to environmental measurements of microplastics. The researchers observed increased inflammation and oxidative stress in zebrafish exposed to both high and low concentrations of the microplastics. In addition, the polystyrene microplastics induced changes in glycolipid and energy metabolism. Finally, the gut microbiome of the zebrafish were altered and reduced in diversity, meaning there were less variety in the bacterial species populating the gut. Reduced diversity of the gut microbiome is highly correlated with inflammatory bowel disease.
The other study examined different sizes of microplastics: 5 and 50 micrometer pieces. The smaller microplastic pieces entered the bodies of larval zebrafish but the larger pieces cause greater changes in the gut microbiome. After examining metabolites, the researchers found that ingesting polystyrene caused disturbed energy metabolism. This reduces the amount of energy the zebrafish get from feeding, which may further reduce their feeding rates.
Microplastics are consumed by a variety of ocean-dwelling life, which can cause reproductive and neurotoxicity issues. Microplastics also build in concentration as you move up the food chain, which poses a clear threat to human health. Indeed, it was recently discovered that microplastics are found in human stool. The concentrations of microplastics was so high it surprised scientists. They guessed it would be related to the amount of microplastics found in the ocean, but it was much higher, suggesting we are consuming microplastics from food packaged or stored in plastic containers. Further research will be able to determine if there are links between microplastic consumption in humans and conditions like inflammatory bowel disease.
These studies are important for understanding declines in marine wildlife, management of fish populations we eat and human health conditions.
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This article was published on forbes.com and written by Linh Anh Cat.