They're the tiny particles causing big problems, and while microplastics may be out of sight, they're front of mind for scientists across the globe,
"We find plastics in almost every trawl that we do," said Khay Fong, a senior lecturer at Monash University's School of Chemistry.
"That's the most shocking part. We have microplastics everywhere we go — the Whitsundays, the Pacific, everywhere."
What are microplastics?
They're tiny plastic fragments — measuring less than five millimetres — that as a result of the breakdown of larger plastic products and industrial pollution
Evidence suggests humans are ingesting microplastics , but that's not the only way they can enter the human body.
As well as oceans, they've infiltrated soil, the air we breathe, some tap water and bottled beverages.
Scientists have found microplastics in our blood and even the placenta.
Trawling Australia's iconic Sydney Harbour
Fong and a team of scientists are trawling Sydney Harbour to determine the scale of pollution in one of the world's most iconic waterways.
"We are trying to look for microplastics all the way down to the size of the width of the hair," she said.
In a haul from a recent outing, she detected what she believed to be tiny plastic particles in just seconds.
Khay Fong and her team found microplastics in every sample collected from the Sydney Harbour
"There are plastics in every single sample, and a lot of them," she said.
"It's a concentration that's akin to the Mediterranean which is one of the most polluted places in the world, mainly because it's one of the most populated."
Three Olympic-size swimming pools worth of microplastics
Further north, a different mission is underway. But it's yielded a similar discovery.
University of Queensland researchers have collected surface sediment samples from 50 sites across Brisbane's Moreton Bay.
"We found plastics at all of these sites," lead researcher Elvis Okoffo from the University of Queensland's Alliance for Environmental Health Sciences said.
Marine plastic pollution
"There are about 7,000 metric tonnes of microplastics in the bay," Okoffo said.
That's equivalent to 1.5 million plastic bags or three Olympic-sized swimming pools worth of plastic.
"This was surprising, looking at the fact that the bay is very protected and we were not expecting to see this much plastic."
The main types of plastic detected were polyethylene, found in single-use items like plastic bags, bottles and food wrapping, and polyvinyl chloride, used in pipes, building materials, electronics, and clothing.
"That actually tells us there is a direct link between the amount of plastics we consume in Australia and the amount that's being washed into the environment."
What are the risks of microplastics?
Despite the ubiquity of microplastics in the environment, scientists don't fully understand the direct and long-term impacts on our health.
"We definitely know we're exposed every day. We know that we are breathing in plastics every day, and we know that we're ingesting them through food and water," Cassandra Rauert, a senior research fellow also based at the University of Queensland's Alliance for Environmental Health Sciences, said.
Brisbane's Forest Lake last year ranked high on a global list of freshwater lakes with microplastic pollution problems. Source: AAP / David Hamilton
"We're still at the very early stages yet, so we can't really draw any conclusions at this point," she said. "[But] we're developing new instrumental methods that can really help to fill this knowledge gap and answer these questions."
Can we reduce our exposure?
We can, Rauert said.
, found in some clothing, are one of the two biggest sources of microplastics, she said. And if small fibres come off garments, we can breathe them in.
"So where it's appropriate to change over to, say, a cotton shirt instead of a polyester shirt," she said.
Ways to limit exposure to microplastics
"Reducing the number of cars on the roads helps the environment in many different ways," she said. "So I'd say catch the bus where you can, or ride your bike."
Avoiding single-use plastic can also limit exposure.
Rauert said her current research suggests that such plastics, like takeaway containers, shed a lot of particles.
"So try and avoid those plastics by using stainless steel (containers) if you can," she said.
"That will also reduce the amount of plastic that's ending up in your food that you're eating.
"Use a reusable water bottle instead of buying bottled water, try and avoid single-use plastics. All those small things can make a big difference."
