Car tyres a likely source of microplastics in coastal waters

  • Climate
  • Thursday, 20 Feb 2020

Driving is not just an air pollution and climate change problem: Turns out, it just might be the largest contributor of microplastics in coastal waters. — Jorgensen/Bildagentur-online/dpa

Driving is not just an air pollution and climate change problem: turns out, it just might be the largest contributor of microplastics in coastal waters.

That is one of many new findings from the most comprehensive study to date on microplastics in the US state of California.

Rainfall washes more than 7 trillion microplastics, much of it tyre particles left behind on streets, into San Francisco Bay each year – an amount 300 times greater than what comes from microfibres washing off polyester clothes, microbeads from beauty products and the many other plastics washing down our sinks and sewers.

These tiny plastics, invisible to the naked eye, have been vilified for tainting water and wildlife but are notoriously difficult to study. They’re everywhere and seemingly come from everywhere. They wash into the ocean in all different shapes and sizes, many covered with dyes and chemicals. Scientists and labs across the United States and the world haven’t even agreed on how exactly to measure or sample or study them.

So a team of researchers, led by the San Francisco Estuary Institute and 5 Gyres, a nonprofit research group focused on reducing plastic pollution, set off to create an inventory of sorts to identify all the ways these different microplastics were getting into the San Francisco Bay. They analysed hundreds of samples from fish, sediment, surface water, wastewater and stormwater runoff and tried to trace the origins of all these particles.

Mark Gold, who heads the state’s Ocean Protection Council and was recently appointed the state’s deputy secretary for ocean and coastal policy, said he was surprised that car tyre particles were such a large source.

“I’m so used to thinking of the toxics that come from urban runoff and not the actual physical particles from something like tyre dust, ” said Gold, who has worked for 30 years on cleaning up California’s beaches and oceans from toxic chemicals. “But the sheer number of particles... the scope and scale of this problem makes you realise that this is something that’s definitely worth looking at a great deal more seriously.”

Once plastic enters the environment, it breaks down into smaller and smaller pieces but never goes away. The tiny particles make their way into the ocean, into the stomachs of marine animals, and ultimately become part of the food and water people consume.

A recent UC Davis study sampled seafood sold at local markets in Half Moon Bay and found that one-quarter of fish and one-third of shellfish contained plastic debris. A survey comparing 150 tap-water samples from five continents found synthetic microfibres in almost every sample – 94% in the United States.

Microplastics have been found in Lake Tahoe, in the deep, deep ocean – even in the Arctic, one of the most remote regions in the world. A scientific review of 52 studies recently concluded that humans on average consume a credit card’s worth of microplastic each week. The European Union is trying to classify microplastics as a contaminant that is unsafe at any level of discharge.

Eliminating plastic at its source will always be the ultimate, though somewhat unrealistic, solution. While people can stop using plastic straws, states can ban microbeads and companies can redesign their shrink wrap, reducing the world’s dependence on automobiles is a tougher nut to crack.

One creative idea is the use of so-called rain gardens and other nature-based infrastructure that can trap polluted runoff before it reaches the ocean. Designed to remove well-known toxins and metals – as well as bringing more nature back into the city – a local rain garden was found to capture more than 90% of the microplastics.

“The role of greening cities becomes part of the overall solution. It’s all part of a complex dance, ” said Warner Chabot, executive director of the San Francisco Estuary Institute, an independent science think tank.

“Plastic pollutes the air we breathe, the water we drink, the food we eat. Plastics are a big part of the climate change problem.... Since California is the fifth-biggest economy on earth, we have the potential to lead the planet with solutions.” – dpa/tca/Rosanna Xia

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