Microplastics

Written By Tony Thorpe

Plastic can be found in every aspect of our modern lives. Humans have become so entangled with plastic that it’s difficult to imagine what life was like before it was invented. Some scientists have even proposed calling our current geological age The Plasticene (1).

Plastic is a term used to describe a group of synthetic polymers formed by linking chains of carbon-based monomers (2). Microplastics are plastic particles ranging in size from 5 millimeters to 1 nanometer. That’s a wide range of sizes; from a pencil eraser to 1/80,000 the width of a human hair (3) or less than half the diameter of a strand of human DNA. Particles at the smaller end of the scale, from 1 nanometer to 1 micrometer, are now typically called nanoplastics. For the sake of this article, the term microplastics will include nanoplastics.

Microplastics are now ubiquitous worldwide, having been found in both the Arctic and in Antarctica, at the top of Mount Everest and within the Mariana Trench (4). Because of their small size, microplastics are in the air, soil, and water. They are also in our food (5, 6).

While some microplastics are intentionally manufactured, we call these "primary microplastics", many are unintentionally formed when larger plastic items break down into what are known as "secondary microplastics". Whether it’s a disposable drinking water bottle, the weed barrier in your lawn, or your polyester sweater, eventually the plastic will start to degrade and create microplastic particles.

Human Health

It’s safe to say that most of us, and likely all of us, have microplastic particles in our bodies. We eat, drink, and breathe them into our bodies, and we absorb them through our skin. Large particles likely “pass” through us to the wastewater system, but smaller particles can be taken up by the body and enter our bloodstream. They have been found throughout the human body, including in breast milk, placentas, kidneys, livers, and the brain (7). The human health effects are currently under examination by researchers, and the evidence does not suggest good news (8).

In addition to the direct effects on human health, plastic frequently has other chemicals added to improve its intended function (e.g., flexibility; lubrication; resistance to light, mold, heat, etc.). Many of those additives have well-documented adverse effects to human health. Additionally, microplastics may pick up toxic substances, like heavy metals, while in the environment (9).

Microplastic in our lakes

Microplastic can enter lakes through many pathways, like wastewater treatment discharge, air deposition, soil runoff, litter. Urban lakes and large lakes are particularly vulnerable. Compared to rural lakes, urban lakes receive higher rates of stormwater runoff, plastic litter, road dust, clothing fibers, etc. All of these pollutant sources can be significant contributors of microplastics. Large lakes tend to have a greater residence time, meaning the water and its plastic particles remain in large lakes longer than in small lakes. Large lakes also have a larger watershed and thus more land surface area contributing runoff and potentially microplastics (10).

Main sources of microplastics (MPs) in lakes. (a) suburban and remote lakes and (b) urban lakes). source

Once in a lake, microplastics cause a variety of problems, particularly as they work their way through the food web. For phytoplankton (cyanobacteria, aka bluegreen algae, and algae) at the base of the food web, microplastics can adhere to cells potentially blocking sunlight and inhibiting growth. Zooplankton, which feed on phytoplankton and are a primary food source for some fish, (11) may consume microplastics either directly, mistaking them for a food item, or indirectly if the plastic is adhered to a phytoplankton cell. In one Daphnia species, microplastics were found accumulate in their bodies and reduce feeding and reproductive capacity (12). 

Exposure to microplastics has been linked with tissue damage and problems with reproduction, growth, locomotion, and/or neural activity in a variety of aquatic organisms. If microplastics enter an organism at a faster rate than they leave it, the concentration within that organism will increase over time, a process called bioaccumulation (13). Similarly, the effect can be magnified in predators if their prey consistently contains microplastics.

What can we do?

One way we can help is to reduce our consumption of single use plastics. This includes disposable bottles, disposable food containers, and plastic grocery bags. For example, 481.6 billion plastic bottles were purchased globally in a single year, according to Reuters (14). Considering that there are 240,000 plastic particles per liter in a disposable plastic bottle (15), by drinking tap water, we put less plastic into both the environment and ourselves. Synthetic clothing is reported to be the largest source of microplastics in the oceans (16). Switching to natural fibers can help. Microwaving food or water in plastic can release billions of particles in just 3 minutes of heating (17), so using glass for food storage and microwaving makes sense.

Ultimately, the best way to curtail plastic consumption will be to reduce its production. That is unlikely to happen without external forces applying pressure to switch to recyclable, reusable, or compostable alternatives. Our small part in that can be to reduce demand by choosing alternatives when available. With that said, I’m writing this article while wearing an acrylic sweater, drinking a cup of tea (18), and listening to music via plastic earbuds. Moving away from unnecessary plastic is hard, but being more mindful and intentional with our consumption is a good place to start. I’m working on it.

Stream Teams United has some fantastic information, including ways you can take action.

Tony Thorpe
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