Have Micro and Nanoplastics Become Part of Our Diet?

It is a well-known fact that microplastics swimming in our oceans are a huge problem but have they already found their way into our stomachs?

Ocean plastic pollution is a major and growing global problem. Scientists estimate that the Earth’s oceans may already contain more than 150 million metric tonnes of plastic, with eight million metric tonnes more entering the oceans each year. Plastics do not degrade easily. In the marine environment, plastics are usually broken down into smaller pieces by the sun, waves, wind and microbial action. These micro- and nanoplastic particles in the water may be ingested by filter-feeding marine organisms such as barnacles, tube worms and sea squirts.

What happens when plastics end up in the marine environment?

In a study funded under the Marine Science Research and Development Programme of the National Research Foundation Singapore (first published online in the journal ACS Sustainable Chemistry & Engineering in March 2018), a team of scientists from the National University of Singapore (NUS) found that plastic nanoparticles – tiny pieces of plastic less than one micrometre in size–

are easily ingested by marine organisms and accumulate in the organs over time, potentially contaminating food chains, threatening food safety and posing health risks.

The NUS research team, comprising scientists from the Tropical Marine Science Institute (TMSI) and Department of Chemistry, used the acorn barnacle Amphibalanus amphitrite in its tests to demonstrate for the first time that nanoplastics ingested during the larval stage are retained and accumulated inside the bodies of the barnacle larvae until they reached adulthood. “We opted to study acorn barnacles as their short life cycle and transparent bodies made it easy to track and visualise the movement of nanoplastics in their bodies within a short span of time,” said Mr Samarth Bhargava, a PhD student from the Department of Chemistry in the NUS Faculty of Science.

Barnacle larvae were incubated in two solutions containing their regular feed and different amounts of 200-nanometre-wide

plastics marked with green fluorescent tags: ∙ “Acute” treatment: Solution with regular feed and 25 times more nanoplastics than the current estimate of what is present in the oceans on average for three hours

∙ “Chronic”treatment: Solution with regular feed and a low amount of nanoplastics for four days

The larvae were subsequently filtered from the solution and examined under the microscope. The distribution and movement of the nanoplastics were monitored by examining the fluorescence from the particles present within the larvae over time.

The fluorescence markers showed that plastic particles were ingested and distributed throughout their bodies.

“Our results showed that after exposing the barnacle larvae to nanoplastics in both treatments, the larvae had not only ingested the plastic particles, but the tiny particles were found to be distributed throughout the bodies of the larvae,” said Ms Serina Lee from TMSI.

Even though the barnacles’ natural waste removal pathways of moulting and excretion resulted in some removal of the nanoplastics, the team detected the continued presence of nanoplastics inside the barnacles throughout their growth until they reached adulthood.

According to Dr Neo Mei Lin from TMSI, because the barnacles are at the bottom of the food chain, the nanoplastics they consume are transferred to the organisms that eat them. As plastics absorb pollutants and chemicals from the water, these toxins are transferred to the organisms when they consume contaminated plastics and can cause further damage to marine ecosystems and human health.

Martin Wagner, a biologist at the Norwegian University of Science and Technology has cautioned that the study is “small scale and not at all representative”, adding that it wasn’t reviewed by independent scientists and the authors haven’t provided details about the measures taken to prevent samples from becoming contaminated. His concerns were echoed by Mark Browne, an expert on microplastics at the University of New South Wales, who said the study lacked crucial details. While further studies are required to prove that nanoplastics have found their way into our bodies through our food, these findings should encourage and ultimately compel us to urgently make the switch to safer alternative materials and adopt stringent measures to ensure that our plastic waste does not end up in our oceans.

“Nanoplastics ingested during the larval stage are retained and accumulated inside the bodies of the barnacle larvae until they reached adulthood”