Microplastics

ISTC studies microplastics’ chemical makeup as well as how they move through the environment, interact with other contaminants, and affect health and ecosystems. We have examined microplastics in groundwater, surface water, and landfills, as well as their effects on aquatic environments and co-contaminants.

About Microplastics

Microplastics and how they form

Microplastics are small plastic fragments, beads, or fibers that are less than five millimeters in at least one dimension. Many materials in the environment are slowly decomposed by a variety of bacteria and other organisms. However, most plastics do not break down in this way. Plastics break down through physical or chemical processes, or through ultraviolet light. These processes break large macroplastics (> 5 mm) into smaller and smaller pieces, forming microplastics that eventually mineralize to CO2 (Bohdan, 2022). In addition, humans have engineered microplastics in the form of microbeads for personal care products (now banned in the U.S. and UK), as microfibers from synthetic textiles, and for use in nanotechnologies (some are 5 million times smaller than the largest microplastic).

How plastics get into lakes, rivers, and oceans

Plastic pollution has been observed in lakes and rivers (Carbery et al., 2018), oceans, beaches (Imhof et al., 2018), and even in sea ice in the Arctic and Antarctic (Waller et al., 2017). Plastics serve numerous indispensable purposes, such as lightweight, inexpensive, durable packaging, but these properties and their prevalent usage also make it easy for plastics to enter the environment. Plastic production has increased markedly over the past 60 years (Thompson et al., 2009), increasing plastic waste. In 2015, global plastic production reached 380 Megatons (Chamas et al., 2020).

Plastics end up in water bodies mainly because of improper disposal and human littering. An estimated 10 million tons of plastic leak into the marine environment every year (Boucher and Friot, 2017). Yet plastics enter the environment in another, sneakier way—through sewers to wastewater treatment plants and through proper disposal in landfills. Examples include broken macroplastics in the trash, small fibers from synthetic clothing that end up in wastewater, and dryer lint that ends up in landfills. Many of these plastic fragments and fibers are too small for filtration systems in wastewater treatment plants to catch. They are now being found in many different aquatic environments (Mason et al. 2016). This can be caused by improper landfill lining.

How plastics affect the aquatic ecosystem

Some of the most obvious impacts of plastics on animals occur when animals become tangled up in plastic netting or rings and suffer physical impairments that may lead to death. Animals can also mistake plastics for food. For example, thin film plastics and plastic bags can look like jellyfish or free-floating kelp. Small microplastics can look like plankton, which many fish and other aquatic life feed on. Plastics are hard for digestive systems to pass and usually end up sitting in the gut, giving the animal a false sense of fullness and can lead to starvation and death. In addition, small bits of plastic can have sharp edges that cause significant internal damage.

All levels of the marine food web can be affected, including bacteria, algae, crustaceans, and bivalves (Goncalves et al., 2021). Certain types of nanoplastics can inhibit the ability of bacteria to form biofilms and their overall growth rate (Okshevsky et al., 2020). Algae are very important for producing oxygen and other nutrients at the base of many food webs (Mao et al., 2020), and any disruption to their normal growth and behavior can be detrimental to a variety of species. Exposure to nanoplastics for as little as 96 hours has been shown to have significant impacts on growth rates of some species of microalgae (Venancio et al., 2019). In crustaceans, accumulation of nanoplastics in the gut (Bergami et al., 2017), lower swimming speed (Gambardella et al., 2017), and interruption in embryo development were observed as a consequence of nanoplastic exposure.

In addition, the micro plastics could harbor persistent organic pollutants (POPs) that are resistant to environmental degradation. Microplastics accumulate POPs on their surfaces that can negatively affect development, nervous, and reproductive systems. They can bioaccumulate in animals and other aquatic organisms and may move up the food chain (Roland, 2000; Rochman et al,. 2015). Toxic heavy metals such as lead, arsenic, and copper are commonly found on the surface of microplastics (Vo and Pham, 2021). Other foreign substances on or in the plastics can weaken immune systems and cause animals to be more susceptible to disease (Rochman et al., 2013).

Microplastics in humans

There is growing concern about the ubiquity of microplastics in our world and in our bodies. Microplastics have been found in seafood (Li et al., 2015) and in processed food including sugar (Liebezeit and Liebezeit, 2013), beer (Liebezeit and Liebezeit, 2014), salt (Yang et al., 2015), bottled water, milk, honey, and plastic teabags (Hernandez et al., 2019). As a result, microplastics have also been found in a growing list of tissues and human fluids. Blood, placenta, breastmilk (Ragusa et al., 2022), lungs (Amato-Lourenço et al., 2021), and stool (Schwabl et al., 2019). Virtually all body sites are represented. Some studies suggest that exposure to these particles is “inevitable” (Ragusa et al., 2022).

Regarding the potential human health risks of microplastic ingestion, many questions remain. What are the overall exposure concentrations from dietary and airborne sources? Can microplastics accumulate in the body? What is the toxicological response to bio-persistent microplastics? Current analytical techniques may have limitations in accurately quantifying concentrations in humans. Better understanding of exposure levels will provide a clearer picture of toxicological and potential health effects. (Wright and Kelly, 2017)

The type of plastic, as well as potential additive chemicals, affects toxicity. Polyvinyl chloride has been identified as the most carcinogenic substance in plastics (Patil et al., 2022) and is one of the most highly produced plastics in the world. Bisphenol A and phthalates, among others, have been associated with harmful effects on fertility and the endocrine system (Xing et al., 2022), and induced asthma in children (Lumio et al., 2021), respectively. These two additives have largely been phased out of baby products because of these health effects, but thousands of other additives in plastics remain largely unstudied.

Solutions

The world has started to take notice of this vast problem. Several countries (for example, the Sri Lankan government) have banned single-use plastic items and are working to improve waste management. Countries such as the U.S. and the United Kingdom (UK) have banned the production and sale of products with plastic microbeads. Also, many non-government organizations such as the Ocean Conservancy, the 5 Gyres Institute, and the Alliance for the Great Lakes, to name a few, are conducting research, education, and advocacy to prevent plastic pollution and help clean up oceans, lakes, and other water bodies.

Resources

• These tiny plastics make their way up the food chain and into your diet – Rachel Smith, Indy Star
• We’re Drowning In Plastic Trash. Jenna Jambeck Wants To Save Us – Christopher Joyce, NPR
• ISTC produced seminars on microplastics