3 million bottles worth of microplastics falling on Auckland each year

The more scientists hone their techniques when it comes to studying plastic pollution, the more we understand about the way it moves through the environment, and it can often make for some uncomfortable reading. Researchers in Auckland have used advanced chemical analysis to calculate the amount of microplastic particles falling from the sky over the city, equating it to three million plastic bottles each year.

While plastic waste is generally understood to be widespread across the land and seas, scientists have recently started to drill into the ways it can get swept up in the air to travel far and wide. This can be facilitated by winds that collect plastic particles off the surface of the ocean and carry them into the atmosphere, with fragments turning up in Arctic and Antarctic snowfall a sign of the distances they can cover.

The new study, by researchers at the University of Auckland, adds new detail to our understanding of airborne plastic pollution, and suggests the situation is graver than we realized. Studies assessing the concentration of airborne microplastics in European cities have found that the average number of pieces detected per square meter in a day ranges from 100 to 700.

But using sophisticated chemical methods to detect and analyze particles as small as 0.01 mm, the Auckland team has landed on a much higher number – 4,885. The team used funnels and jars to sample the amount of microplastics falling from the sky over a nine-week period, with the majority of them too small to be seen with the naked eye. By applying a colored dye that emits light and a heat treatment to assess their mass, however, the team was able to identify and study them in fine detail.

Particles made of common packaging materials like polyethylene and PET are among the most common, along with polycarbonate used in electronics. According to the team, the findings suggest some 74 metric tonnes of microplastics fall out of the atmosphere and onto Auckland each year, the equivalent of more than three million plastic bottles.

“The smaller the size ranges we looked at, the more microplastics we saw,” said lead author Dr Joel Rindelaub. “This is notable because the smallest sizes are the most toxicologically relevant.”

Scientists are continuing to explore the issue of what microplastic exposure means for human health, but the particles have been found in stool samples, the bloodstream and in living lung tissue.

“Future work needs to quantify exactly how much plastic we are breathing in,” says Dr Rindelaub. “It’s becoming more and more clear that this is an important route of exposure.”

The scientists believe the particles fall onto Auckland as a result of waves crashing into the adjacent Hauraki Gulf, propelling waterborne microplastics into the air, with increased concentrations observed in the presence of stronger winds from that direction.

“The production of airborne microplastics from breaking waves could be a key part of the global transport of microplastics,” says Rindelaub. “And it could help explain how some microplastics get into the atmosphere and are carried to remote places, like here in New Zealand.”

The research was published in the journal Environmental Science & Technology.

Source: University of Auckland

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