Microplastics From Decades Ago Found in Fish 


After researchers examined the guts of fish, they discovered that fishes had swallowed microplastics since the 1950s. Researchers believe that the concentration of microplastics in the guts of fish has increased over the years. Additionally, scientists have discovered microplastics from water, air, soil, and the atmosphere in the recent past. 

Plastic materials take centuries to break down, meaning every plastic ever made still exists today. Tim Hoellein, an associate professor of biology at Loyola University Chicago, noted that, for the past 10-15 years, there had been a problem of plastic in the water. Hoellein also noted that water-living organisms have probably been exposed to plastic since its invention.

How Researchers Conducted the Study

An ichthyologist named Caleb McMahan takes care of more than a million fish specimens in the museum. Most of these specimens are stored in the museum’s Underground Collection Resource Center. According to McMahan, these specimens represent real life on earth. They enable researchers to go back in time and narrow down to specific areas they need to study.

With the help of McMahan, Hoellein and his graduate student named Loren Hou examined the buildup of microplastics in freshwater fish from the Chicagoland region. McMahan helped the team identify four common fish species; the museum had chronological records dating back to 1900. These species include; largemouth bass, channel catfish, round gobies, and sand shiners.

The study involved dissecting out digestive tracts from fish from at least five specimens per decade. Then the researchers treated the guts with hydrogen peroxide, which breaks down all organic matter, but plastic. The unbreakable plastic is too small to see with the naked eye, so one must use a microscope to see them.

During the microscopic examination, the shapes of these unbreakable materials had both frayed and smooth edges. Frayed-edged matter represents organic material, while the smooth-edged materials represent microplastics. This examination technique is known as Raman Spectroscopy, which involves light to examine chemical signatures of samples.

How Microplastics Get into Fish System

According to the researchers, there were no plastic particles before the mid-century. So what happened after plastic manufacturing began, tiny particles from clothing in the water system during cleaning. These microplastics build up over time as the level of plastic production rises. Although it’s not clear how these microplastics affect the fish, there are high chances these plastics are also in our systems from consuming the fish. “The entire purpose of our work is to contribute to solutions,” Hoellein said.