While a worn out sole is a universal frustration for all shoe-wearers, not many of us stop to think about where the rubber on the bottom of our footwear disappears to.
A mystery to many, PhD student Nicola Forster is shedding light on the permanent marks our footprints are leaving on the environment, and how this is affecting biodiversity and soil health in our outdoor spaces.
“Hiking and trail running are increasingly popular, and the shoes we wear may be a leading source of microplastics in wilderness areas such as national parks, conservation reserves and World Heritage sites,” says Nicola.
“When we visit wilderness areas, we aim to take only photos and leave nothing but footprints, but I encourage you to ask yourself next time you're on a trail, what does your footprint really leave behind?”
Microplastics are defined as small plastic pieces less than five millimetres long, and can appear in a number of environments including cities, farms, and conservation areas.
Nicola says while they might be tiny, every piece adds up. This is something she’s seen first-hand during her research studying trails in conservation areas around Armidale.
So far, in a conservation area near Armidale, I’ve found the trail surfaces can have up to 3000 microplastics per square metre, and the majority were fibres and rubber from clothing and footwear.
“In 2018, there were 60 million visitors to NSW National Parks; if each of those people were to leave only a small amount of microplastics, the total amount being left in our natural environments is significant,” she says.
“So far, in a conservation area near Armidale, I’ve found the trail surfaces can have up to 3000 microplastics per square metre, and the majority were fibres and rubber from clothing and footwear.”
Nicola’s research has seen her recently win the inaugural Society of Environmental Toxicology and Chemistry Asia-Pacific research grant, which is designed to promote the advancement of environmental sciences, education in the field, and the use of science in environmental policy and decision-making.
She says the grant will partially fund a study investigating the impact of weathering on the bioavailability of microplastics in soils of conservation and wilderness areas.
In this study, we’re going to expose microplastics on and below the soil surface to light and heat, and then check what happens to rates of leaching and the types of chemicals that are released, and to what extent leaching is offset by natural soil processes.
“Studies have shown that microplastics can have toxic effects on soil organisms, leach chemicals into the surrounding environment, and impact soil structure, microbial activity and plant growth,” she says.
“When rubber microplastics are left on the trail, they’re prone to degradation due to sunlight and heat.”
She says this can lead to chemical changes on a molecular level, potentially making microplastics more toxic to the environment.
“In this study, we’re going to expose microplastics on and below the soil surface to light and heat, and then check what happens to rates of leaching and the types of chemicals that are released, and to what extent leaching is offset by natural soil processes,” she says.
“This will help us to better understand the risks posed by microplastics to conservation areas, including endemic and vulnerable plant and animal species.”
While the effects of microplastics have received increased media attention in recent years, Nicola says clothing and footwear companies have a long way to go in recognising the impacts of their products have on the environment.
We can all take personal responsibility and reduce, reuse, and recycle – avoid single use plastics, purchase good quality products that will last a long time, and not litter, however, it’s also important that we encourage manufacturing companies to design sustainable products that produce fewer microplastics.
“There’s an increasing awareness that microplastics are released when clothing is washed, but it’s also important to consider how many are shed during normal day to day activities,” she says.
“Footwear and clothing can shed microplastics during hiking and trail running, and there’s the potential for companies to develop more abrasion resistant rubbers and anti-pilling fabrics.
“We can all take personal responsibility and reduce, reuse, and recycle – avoid single use plastics, purchase good quality products that will last a long time, and not litter, however, it’s also important that we encourage manufacturing companies to design sustainable products that produce fewer microplastics.”
