Researchers at the University of Auckland have discovered about 74 million metric tons of microplastics rain down over Auckland, New Zealand every year.

these microplastics weigh approximately equal to 3 million plastic water bottles.  

The study was conducted by capturing microplastics falling from the sky in wooden boxes using funnels placed in jars. 

Two boxes were used in the experiment: 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) away from the city.

To determine the total mass of materials, scientists used heat treatment after collecting them. 

Polyethylene (PE) was identified as the most prevalent material, followed by polycarbonate (PC) and polyethylene terephthalate (PET).

Materials such as these are commonly found in packaging, electronics, and construction.

“The smaller the size ranges we looked at, the more microplastics we saw,” Joel Rindelaub, the study’s lead author said in a press release. “This is notable because the smallest sizes are the most toxicologically relevant.”

Particles captured during the experiment were mostly between 10 and 50 micrometers in size and the majority of them were plastic fragments. 

only 3 percent of the materials were larger than 100 micrometers.

The smallest particles are determined as microplastic and they can be inhaled by humans.

Based on various studies, researchers have hypothesized that human exposure to microplastics could lead to oxidative stress, DNA damage and inflammation, among other health problems.