Mass of Microplastics Raining on Auckland Weighs as Much as 3 Million Plastic Bottles Yearly, Study Finds

A new study from researchers at the University of Auckland has found about 74 million metric tons of microplastics rain down over Auckland, New Zealand each year. This amount of microplastics weighs around the same as over 3 million plastic water bottles.

The study, published in the journal Environmental Science & Technology, analyzed over nine weeks’ worth of samples, collected in September through November 2020, in two sites in Auckland. The results showed an average of about 4,885 airborne microplastics in one square meter in just one day. Comparatively, London had about 771 as of 2020, Hamburg had around 275 in 2019, and Paris had an average of 110 in 2016.

According to the researchers, waves in the Hauraki Gulf could be moving more water-borne microplastics into the air. Researchers noted higher numbers of airborne microplastics as gulf winds increased in speed.

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

The team captured microplastics falling from the sky with funnels in jars, which were placed in wooden boxes. The boxes were placed in two locations: one on a rooftop at the university campus in the center of the city, and one in a residential garden in Remuera, a suburb about 4 kilometers (2.49 miles) from the city center.

After collecting the microplastics, the scientists used a heat treatment to analyze the total mass of the microplastics. The team identified polyethylene (PE) as the most present material, followed by polycarbonate (PC)  and polyethylene terephthalate (PET). These materials are commonly found in packaging, electronics, and construction materials.

The Plastic Health Coalition, which was not involved in the study, noted that previous studies suggest microplastics may lead to DNA damage, oxidative stress and other health issues, but more research is needed on the impacts of microplastics on human health and the environment. 

The University of Auckland study authors said that the smallest nanoparticles could potentially enter human blood cells and could build up in human organs. Other studies have found microplastics in human lungs and blood. A 2021 study said that microplastics at concentrations found in the environment could kill human cells. 

The new study is the first to measure the total mass of airborne microplastics in a city, and Rindelaub said that many researchers globally have likely undercounted these microplastics in the air.

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