By Cate Twining-Ward and Colin A. Chapman

Scientists call the most recent period of Earth’s history the Anthropocene Epoch. This unit of geologic time—our unit—traditionally defined by human activity, is now chillingly being defined by the ubiquitous presence of plastics.

The invention of plastic has transformed human life. Plastics are incredibly convenient: not only do they weigh less than alternative materials, but they are also far more affordable. However, the downsides to plastic are overwhelming. 

The problem with plastics in marine environments and urban cities is largely known, a familiarity that may have diminished its deadly consequences. However, what people may not know is how much plastics are continuing to infiltrate every corner of life on Earth, including the bodies of humans. People may also not be aware that transitioning away from plastics supports the growth of renewable energy and the battle against climate change. 

Plastic is quite literally everywhere. In fact,  the first evidence of microplastics in human placentas has been identified in this year’s January issue of the Journal Environmental International.

It is abundantly clear that plastic is one of our planet’s key environmental challenges. It is thus imperative to understand its scope and complexity. We are well aware of the harm that plastics cause to coral reefs and marine animals, but less known are the potential threats plastics pose for terrestrial wildlife and ecosystems as well as for human health—you may be breathing in particles of plastic at this very moment.

It’s time we get serious about microplastics because this is far more than a marine issue.

We know our oceans and landfills are hotspots of plastic pollution, however, plastic pollution happens globally, and the transfer of plastic to terrestrial life has gone largely unexamined.

New data show that microplastics are capable of entering terrestrial food webs. Microplastic and nanoplastic transfer from soil to chickens through earthworms was identified in a study published by the Journal Scientific Reports, leaving questions and concerns about the human consumption further down the line.

Recent studies on the atmospheric transport and depositing of microplastics suggest they are capable of travelling through the atmosphere over a distance of 95km (59 miles), as reported in a 2019 article in Nature Geoscience. This means that soon, plastics will reach all of the remaining remote and sparsely inhabited areas on Earth: they’ve just reached the glaciers of the Tibetan Plateau.

In a five-month study done in the remote Pyrenees mountains in the southwest of France, microplastic fragments, fibers, and films were found at relatively large levels, illustrating just how plentiful microplastics are in even the most remote locations. The Pyrenees area is sparsely populated, with no industrial, commercial, or large agricultural activities. More alarming still, is the increasing trend in the number of finer fragments, as smaller and less traceable plastics will have far reaching consequences that can easily go unnoticed.

Microplastics also have significant ecological effects. Not only do they cause harm to the individuals that ingest them, but these physiological effects then alter animal behavior which becomes a chain reaction on the entire ecosystem. So far, microplastics and nanoplastics have been found to inhibit the absorption of nutrients from food, reduce body weight, and negatively impact growth and reproduction.

All animals are at risk from the dangers of microplastics — including humans. Humans inhale airborne microfibers and also consume them through common foods such as seafood, sugar, and through drinking water. The effects of such plastic consumption and inhalation are poorly understood; research in this field is still in its early phases. A 2020 article published in PLOS One journal indicates that microplastic fibers accumulate in the lungs and trigger inflammation. Most plastics leach compounds that are estrogenic, and thus, likely suppress reproduction. With more time, the chemical leaching from plastic particles (for example, BPA) are thought to also depress the immune system, create cancerous growths, be neurotoxic, and disrupt the microbiome in the gut.

Because of the hydrophobic nature of plastics, microplastics act as accumulators. This means that as organisms ingest microplastics, they can also be ingesting a number of highly carcinogenic environmental pollutants including those most commonly known by their acronyms — PBCs (polychlorinated biphenyls), PAHs (polycyclic aromatic hydrocarbons), and DDT (dichlorodiphenyltrichloroethane).

The effects of microplastics on the gut microbiome is a growing area for concern. The gut microbiome refers to all the microorganisms that live in the gastrointestinal tract; it’s essential for the function of mammals. The gut microbiome affects metabolism, immune function,  and behavior. Consumption of microplastics increases phagocytic activity of immune cells, and triggers inflammation in gut bacteria, but “research connecting microplastics with the gut microbiome is in its absolute infancy.”

It’s clear that a better understanding of the consequences of ingesting microplastics on the gut microbiome is needed. We strongly suggest more research in this topic. We need research that first quantifies the magnitude of the exposure of wildlife to plastics, and then determines the sublethal consequences of this exposure.

This research will help sound the alarm to an ever increasingly important issue; one that will no doubt negatively impact mammal populations, their conservation, and human health. In doing so, this would add further credibility to calls to curb the use of plastics, and ban some uses altogether, such as single-use plastics. Research targeting primates will be particularly important to minimize plastic production as they are often flagship species in conservation projects (for example, the mountain gorillas of East Africa and the golden monkey of China), and given their phylogenetic similarity to humans, people view threats to primates as threats also to themselves.

One of the complexities underlying plastics is the dependency of plastic producers on cheap fossil fuel feedstock and energy. The natural gas boom in the U.S. made plastic feedstock very cheap and almost all conventional plastics are made from fossil fuels; the two product chains are very intimately linked.

Since the amount of plastic produced is influenced by the demand for and the production of oil and gas, supporting the transition away from fossil fuels (and instead towards renewables) is another way to disincentivize plastic production.

It is, as an individual, disheartening to hear about the deadly consequences of an industry that we do not have ownership of. However, there is, and needs to continue to be, a demand for change. Reason for change is amplified by scientific credibility. Only if we fund research into the impacts of microplastics on our terrestrial ecosystems and on our health will we have the ammunition needed to create meaningful and lasting policy and industry change. We can also create change through our consumer choices. Choosing wind or solar power if available through your utility company, opting for an electric vehicle, and even avoiding single use plastics are indeed small steps, but nevertheless, they are steps in the right direction. 

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About the authors:

Colin Chapman, Ph.D., has worked in the tropics on conservation issues for almost 40 years. He has published over 500 scientific papers, developed new conservation strategies for Uganda, and pioneered efforts to create a union between health care and conservation; the latter resulted in him being given a humanitarian award. He is an adjunct professor in the George Washington University Department of Anthropology.

Cate Twining-Ward is a senior correspondent at Planet Forward, a grand-prize winner of Storyfest 2020, and a student at the George Washington University.