Plastics are ubiquitous, with more than 350 million tons produced worldwide every year. The far-reaching effects of synthetic materials are also in the news, from the pile of garbage circulating in the Pacific to elephants dying from consuming nondegradable plastic waste. Now, a new study from an international team of researchers found tiny plastic particles high in the Alps.
Since plastics do not have a permanent environmental sink, they continue to degrade, becoming smaller until they are considered nanoplastics, which are 100 times thinner than a human hair. These fragments of plastic are tiny enough to be carried aloft and distributed by the wind. However, data on the distribution and concentration of nanoplastics are rarely reported.
Dušan Materić, a researcher at Utrecht University in the Netherlands, and colleagues were interested to see if nanoplastics were present in high-altitude, remote places, like the Alps. So they gathered 38 samples at Sonnblick Observatory from February to March in 2017. The observatory sits on a remote peak in the Austrian Central Alps, more than 3,100 meters above sea level. They focused on four commonly used plastics: polypropylene (PP), polyethylene terephthalate (PET), polyethylene (PE), and polystyrene (PS). The team used thermal-desorption proton-transfer-reaction mass spectrometry to measure and identify the tiny particles in the samples they collected. After analyses, the results were compared to 40 unique ions identified from new plastic exemplars.
“We only recently developed a method that is sensitive and selective enough to track and measure plastics within the aerosol,” said Materić.
Although all four types of plastics were detected in the samples, the researchers discovered that two were dominant: PET and PP, which are most commonly used in everyday products, including single-use packaging, clothing, and rope. PET concentrations reached 15.1 nanograms per millimeter of melted snow and spiked on days without precipitation. Materić believes this type of plastic was delivered by wind (dry deposition). PP was also high, averaging 29.5 nanograms per millimeter of melted snow. The concentration of PP peaked during precipitation events, suggesting distribution by wet deposition. Materić was surprised by how much nanoplastic the team measured but noted that the transport and deposition processes of these plastics require further study.
“These are totally new particles, now pollutants, and no proxy from traditional environmental studies can adequately describe their behavior,” said Materić. “This is like a fresh daily ‘dusting’ on the snow surface.”
According to outside expert Alice Horton, an anthropogenic contaminants scientist at the National Oceanography Centre in the United Kingdom, this study “is one of very few that have yet managed to detect nanoplastics within environmental samples.” She added that this work “enhances and develops our understanding of plastic distribution and degradation within the environment.”
Tracking Nanoplastic Movement
To trace the movement of the plastic pollutants to the observatory, the team “rewound” atmospheric models for the region more than 90 hours before the samples were collected. They identified major European cities as the hot spots for the plastics, from London to Munich. But it is possible that the source was even farther west, possibly originating in the Atlantic Ocean. (Previous studies have suggested that ocean plastic could be a source for microplastics in the atmosphere.)
Using the data from the study, Materić and his colleagues calculated an annual deposition rate of 43.7 kilograms of nanoplastics per square kilometer for the region. This finding raises concerns because nanoplastics can be harmful to human health. Particles smaller than 1 micrometer can penetrate the lungs, enter the bloodstream, and be toxic to the body.
“We need to prioritize this field of research, considering that nanosize particles are toxicologically much more active than bigger particles,” said Materić.
—Stacy Kish (@StacyWKish), Science Writer