Alarming figures show how much plastic is falling on Auckland, motorists stuck in a sticky situation and how New Zealand’s stepping up its message to the regime in Iran in the latest New Zealand Herald headlines. Video / NZ Herald
Scientists are concerned Aucklanders may be exposed to high levels of broken-down plastics floating in the air, after revealing the equivalent of three million bottles are dropping out of the atmosphere and into the city every year.
In a just-published study, scientists have calculated that 74 metric tonnes of airborne microplastics are annually flowing into our largest city, with wind and waves helping send them from ocean to atmosphere.
Invisible to the naked eye, microplastics are a macro problem - they’re now found in our rainwater, food chain and oceans, where some 15 to 51 trillion particles are estimated to drift near the surface.
For the first time, a team have assessed the total mass of airborne microplastics within Auckland’s own environment - and the large numbers they recorded posed concerning questions about the potential for these to be inhaled and accumulate within peoples’ bodies.
“Future work needs to quantify exactly how much plastic we are breathing in,” said study leader Dr Joel Rindelaub, an aerosol chemist at the University of Auckland.
“It’s becoming more and more clear that this is an important route of exposure.”
The results - recorded using sophisticated chemical methods that could detect and analyse particles as small as 0.01 of a millimetre - also suggested that observations in other global centres may have dramatically under-counted levels.
In Auckland, the average number of airborne microplastics detected in a square metre in a day was 4885 - much higher than the 771 per square metre measured in London and reported in a 2020 study, along with 275 and 110 in Hamburg and Paris, respectively, in previous papers.
This effect was seen when the team – also including PhD student Wenxia Fan and Professor Jennifer Salmond – observed increased levels when winds from the gulf picked up speed, likely leading to bigger waves and more spread.
“The production of airborne microplastics from breaking waves could be a key part of the global transport of microplastics,” Rindelaub said.
“And it could help explain how some microplastics get into the atmosphere and are carried to remote places, like here in New Zealand.”
Particle sizes also changed with wind direction.
When winds passed over the Auckland city centre, the microplastics downwind were larger, indicating the plastics had gone through less environmental aging and came from a closer source.
Polyethylene (PE) was the major substance detected, followed by polycarbonate (PC) and polyethylene terephthalate (PET) - all of which are used in the construction industry.
Polyethylene and PET are typically packaging materials, while PC is used in electrical and electronic applications.
In the research, microplastics falling from the air were captured by a funnel and jar in a wooden box on a rooftop at the central city university campus. The same set-up was in a residential garden in Remuera.
One of the study sites in central Auckland. Photo / Supplied
The researchers identified the very smallest ones by using a coloured dye that emitted light under certain conditions, while a heat treatment was used to analyse mass.
“The smaller the size ranges we looked at, the more microplastics we saw,” Rindelaub said.
“This is notable because the smallest sizes are the most toxicologically relevant.”
Nanoplastics, the very smallest particles, could potentially enter cells, cross the blood-brain barrier, and may build up in organs such as the testicles, liver and brain, the study found.
“Microplastics have also been detected in human lungs and in the lung tissue of cancer patients, indicating that the inhalation of atmospheric microplastics is an exposure risk to humans.”
The plastics had also been detected in the placenta.
“This is a new area of study, so we’re very much at the information-gathering stage right now,” Rindelaub said.
The paper, co-authored by Professor Kim Dirks, Dr Patricia Cabedo Sanz and Associate Professor Gordon Miskelly, called for standardisation of reporting metrics so studies of airborne microplastics could be better compared.
The paper’s introduction said: “Over the last 70 years, 8.3 billion metric tons of plastic have been produced globally. Only nine per cent have been recycled, with the rest either incinerated or released into the environment.”
Fibres dispersed by washing synthetic clothes, fragments shed by car tyres and washed by rain into the ocean, and bottles floating down rivers are just some of the ways plastic is added to the environment.
Weathering and ageing broke plastic down into ever smaller particles.
The researchers identified the smallest microplastic particles by using a coloured dye that emitted light under under certain conditions. Photo / Supplied
“This is a useful study, and we always welcome new research,” Auckland Council’s chief sustainability officer, Matthew Blaikie, said of the findings.
“From an air quality perspective, we would like to see further studies measuring smaller particles, particularly those less than 10µm or 2.5µm, which are considered to have greater health impacts as they travel deeper into the lungs and typically contain higher proportions of toxic particles, such as exhaust fumes.
“The council is required to monitor particles less than 10µm against the National Environmental Standards for Air Quality.”
Over recent years, scientists have also been investigating the health impacts of microplastics in drinking water.
In 2019, a World Health Organisation evidence review found microplastics larger than 150 micrometres were not likely to be absorbed in the human body, uptake of smaller particles was expected to be limited.
Absorption and distribution of very small microplastic particles including in the nano-size range may, however, could higher – and more research was needed.
Wastewater treatment could strip out more than 90 per cent of microplastics from wastewater, with the highest removal coming from tertiary treatment such as filtration, while conventional drinking-water treatment could remove particles smaller than a micrometre.
But here in New Zealand, where groundwater and surface water are the major sources of drinking water, authorities didn’t have good information on the burden of microplastics in our environments, or how they were getting there.
The latest study comes as a separate team, led by the University of Canterbury’s Dr Laura Revell, have received a $959,000 grant through the Marsden Fund to further investigate how microplastics are contributing climate change, through scattering light and seeding cloud formation.
