An investigation into microplastic pollution in Auckland's waterways has suggested it's not broken-down litter, but tiny fibres from our washing that are likely causing the biggest problems.
So small that they're typically invisible to the naked eye, microplastics nonetheless pose a goliath threat to our oceans.
These particles of broken-down plastic products are now being found within rainwater, sea salt, air and even us, having entered the food chain through species like tuna and mackerel.
Just-published findings from a collaborative survey, focused on nearly 40 sites across Auckland, showed the bulk of these particles were fibres that may likely be traced back to the washing of clothing.
The study, involving researchers from Scion, University of Canterbury, Auckland Council and Watercare, also suggested the problem was no better – or worse – in New Zealand than any other part of the world.
"We wanted to establish a sense of the scale of the plastic microparticle issue in New Zealand, and evidential data looking at the sources," said Dr Florian Graichen, Scion's science leader for biopolymers and chemicals.
"These are crucial first steps to design enduring solutions which successfully reduce and remove plastic pollution from New Zealand's environment."
While plastic microparticles have been documented on our coast since the 1970s, it wasn't until this new study that we had data about the scale of the problem.
The research team chose Auckland because it was New Zealand's most populous city and had a wide range of industries, parks and residential suburbs close to the marine environment.
After being analysed at Scion's laboratory in Rotorua, they found 88 per cent of the microparticles were fibres, small amounts of fragments and films.
The majority of fibres were identified as the common plastics polyethylene, polyethylene terephthalate and polypropylene.
The remaining third was not plastic, but plant-based cellulose or regenerated cellulose such as rayon.
"These findings indicate a major source of microparticle pollution could be the washing of clothing and textiles," Graichen said.
The team was surprised at how similar the data was to other results reported at Christchurch and elsewhere in the world – and that much of nuisance stemmed from fibres.
"This work is the foundation needed for us to have a fact-based discussion on the next steps," Graichen said.
"The options for reducing and removing plastic pollution from our environment could include reducing its use, removing major sources of plastic microparticles before they enter the environment, and the introduction of alternative options such as marine degradable plastics."
If a big cause was the washing of clothing, there might also be a need for improved filter systems for washing machines, and in wastewater treatment plants.
The study, funded through the Ministry for the Environment's Waste Minimisation Fund and Packaging New Zealand, was one of several new projects looking at the issue.
Another major study awarded a five-year, $12.5 million Government grant aimed to take a rigorous assessment, using Auckland and Nelson as test sites.
While New Zealand has moved to ban microbeads, the wider problem of microplastics couldn't be tackled in the same way.
Current legislation encouraged product stewardship and environmental responsibility at the beginning of a product's life cycle.
Globally, microplastic pollution has become so invasive and ubiquitous – it's estimated eight million tonnes of plastics now enter the sea each year – that the United Nations has likened its impacts to climate change.