Scented chemicals do more than perfume bodies. They often show up in sundry places such as soaps and other cleaning products to add a pleasant scent or mask unwelcome odors. A new study finds that these fragrant molecules can catch a ride on the wind to pile up in the ice of high, remote places.
Scientists have analyzed an ice core from Mount Elbrus in Russia for fragrances that settled on its snow during the 71 years from 1934 to 2005. Concentrations of fragrances in the later years were about 10 times higher than in the earliest years analyzed, according to research published in Scientific Reports. Trends in these scent molecules also carried a whiff of economic trends and crises.
The study makes a shift from “just checking if some place is polluted…to reconstructing the story of this pollution,” said Marco Vecchiato, an analytical chemist at the Institute of Polar Sciences in Venice, Italy. Vecchiato and his team analyzed the ice core for 17 fragrances and 17 polycyclic aromatic hydrocarbons, called PAHs for short. Released by combustion and industrial manufacturing, PAHs can provide an indication of human activity. Over the 7 decades analyzed, total concentrations of both PAHs and fragrances followed roughly the same pattern.
In the samples from the 1930s and 1940s, fragrance concentrations hovered around the lowest detected levels, which the scientists interpreted as background levels. Although this time period corresponds to World War II (a time when fragrance use may have dropped in Europe), these low levels may occur naturally, as flowers and plants make some of these fragrance molecules. Starting in the 1950s, the fragrance concentrations in samples began to grow and increased drastically starting around the year 2000.
That’s “clearly the Great Acceleration,” Vecchiato said, referring to the drastic increase in human impacts across Earth beginning in 1950.
Mount Elbrus, Europe’s highest peak, receives regular deposits from not only nearby central Europe and Russia but also the Middle East and the Mediterranean, Vecchiato said. The perfume haul may reflect the Anthropocene, a term that describes our current geologic era, dominated by human activity, the authors suggested.
As the Wind Blows
The scientists extracted the fragrances and PAHs from the ice core using a method that separates chemicals on the basis of their tendency to vaporize.
In all the samples, upward of 80% of the perfume belonged to one of three salicylates, chemicals that provide sweet, floral aromas. Humans use a lot of these chemicals for products such as soaps, shampoos, and fabric softeners. They’re fairly inexpensive to produce, Vecchiato noted. He said his team chose to analyze fragrances with a strong smell that can last for weeks or months.
But environmental chemist Staci Simonich, who was not involved with the work, suggests there were fragrances that last longer in the environment the team could have monitored. “There were some fragrance materials I’m surprised they didn’t look for,” she said, pointing to polycyclic musks, a class of fragrances used in personal care products, air fresheners, and detergents that would persist longer in the environment. Simonich works at Oregon State University in Corvallis and was not involved with the study.
The fragrances used in the study have relatively short lifetimes in the atmosphere, Simonich said. If you look at the trajectories of air masses around Elbrus, these fragrances likely come more from regional than global sources, she noted.
Taking the Pulse of Pollution
Still, the Elbrus ice core may present a decades-long diary of fragrance use for the region, mirroring the ups and downs of what was once the Soviet Union.
“It’s unusual to see such a clear indication of human output,” said Kimberley Miner, a climate scientist who has studied pollutants and chemicals in the Arctic and in snow. Miner, a scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., and a professor at the University of Maine in Orono, was not part of this study.
Between 1964 and 1982, the Union of Soviet Socialist Republics (USSR) experienced what was called the Era of Stagnation. Economic growth didn’t stall entirely but was very slow. Perfume concentrations increased slightly from the 1930s baseline, but levels dipped during the economic slowdown.
Later, between 1989 and 1991, the Soviet Union collapsed, sending many into poverty. Lean times continued through the 1990s in former Soviet republics, including Russia. Both fragrance and PAH levels in the Elbrus ice core mirror these hard years before taking off in the 2000s. “You see this abrupt development…after the fall of the USSR,” Miner said, “so it provides a really beautiful case study.”
Miner wondered whether other contaminants, such as microplastics and certain flame retardants, follow this pattern in the region. This study provides yet another example, she said, “that everything that we use in our daily lives, everything that we use in our industrial processes, finds its way into the wider environment.”
—Carolyn Wilke (@CarolynMWilke), Science Writer