You know that nail salon smell? That sharp hit of chemicals, the strangely sweet scent of polish, the faint tingle in your nose? That’s air pollution, and it’s been linked to a variety of experienced by the workers who breathe it. Nail salon workers commonly experience irritated skin and eyes, headaches, loss of smell and respiratory problems.����

Officials in some cities and states, including Washington, have introduced new regulations designed to better protect nail salon workers — .��

But the mysteries around what, exactly, causes those potent smells make protecting these workers more difficult. Cosmetics manufacturers are rarely required to disclose what specific chemicals they use to scent their products, which has hindered efforts to better understand the air that salon workers breathe. ��

, a 91̽��assistant professor of environmental and occupational health sciences, set out to solve the mystery. In a study published , Ceballos and her co-authors analyzed the air in a group of nail salons around Boston — where Ceballos previously worked at Harvard University — and identified 18 distinct fragrance chemicals. It’s the most comprehensive study to date of the specific fragrance chemical mixtures found in nail salon air, and will allow researchers to further study the potential health risks.

91̽��News sat down with Ceballos to discuss the findings of the study, the mysteries around fragrance chemicals and how to better protect nail salon workers’ health.����

Nail salons are a bit of a research specialty of yours. You’ve published papers on , workers’ exposure to “old” and as well as “” harmful chemicals, and the . How did you come to focus on nail salons and their workers? ��

Diana Ceballos: I started working on nail salons soon after I read a back in 2015. It won all sorts of awards. When that story came out, it created havoc. I was working at the Centers for Disease Control and Prevention at the time, and the New York Health Department asked for technical assistance because they were horrified by the conditions in nail salons. I was put on the team partly because I’m an industrial hygienist, but also because I speak Spanish, and there are a lot of Spanish-speaking workers in these salons.����

Then my life changed, and I went back to academia. I just knew there was more we could be doing. There was just so little research in this area, it was incredible. So, I decided I wanted to focus on nail salons. In the meantime, a lot of other people had the same idea, so lots of different groups around the country and internationally have started working on this.����

What are fragrance chemicals, and what do we know about them? ��

DC: Fragrances are added to nail salon products to create a desired smell — lotion that you want to smell like lavender, for example — but many fragrances are used to mask undesired smells. A lot of nail products have very strong, not-so-good smells, so companies add fragrances to mask those smells. But then you have even more scented chemicals in the air!��

A good number of fragrances are known sensitizers. That doesn’t only cause irritation on the skin, but, for example, some fragrances could trigger an asthma attack if inhaled. Or, if they’re a sensitizer, they could even help cause asthma and other respiratory complications. It’s not just the skin, it’s the entire immune system. And that’s just the effects that we know of.��

There are also some positive effects from fragrances. It’s well-known that some fragrances can be relaxing or affect the ambiance of an environment. But that hasn’t been well-studied. Some of these chemicals are very little-known. They could be toxic, but we don’t know. They’re just used in small amounts to produce fragrance, and for the most part, chemical regulations have been focused on bigger culprits. It’s just in the last decade or so that officials have paid attention to chemicals that show up in smaller quantities, like fragrances.��

For a very long time, fragrances were trade secrets, and specific chemicals weren’t listed as ingredients. Labels just said ‘fragrance.’ In the last 10 years, chemical regulations in Europe and in some states have introduced more discrimination of toxic chemicals that could include fragrances, but there’s a lot of work still to disclose the ingredients. For example, in the new cosmetics bill in Washington, there’s more information required on ingredients lists. That was already the case in California, for example, but it’s just starting. We aren’t the first ones to ever measure them, but to our knowledge we’ve measured the biggest number of fragrances. Also, our analysis suggests that not only nail products are contributing to fragrances, but also other products in the salons such as personal care products and cleaning agents are potential emission sources.��

Many people can identify the strong scent of a nail salon, but I’m not sure we consider that we’re actually smelling air pollution. How does that pollution affect nail salon workers?����

DC: Indoor air quality is important for anyone. The quality of our health depends on the air that we breathe. Even for a customer, nail salons are very fragrant and have many odors. Some people are very sensitive to odors. Even just talking about the odor itself can trigger a lot of health effects. People can get headaches, dizziness, and get nauseated. So, there are people that don’t go to nail salons because they can’t be in there. And that’s a customer. Imagine the workers. ��

There are people who have to do this work because they don’t have training in anything else, and in surveys of the health of people who work in nail salons, it’s fairly prevalent to have headaches, irritation, fussiness — all the typical symptoms of odors, let alone toxic chemicals. It can deteriorate your well-being and quality of life, especially as some of these workers are on 12-hour shifts, seven days a week. So, it’s significant, the amount of time they’re exposed to these fragrances along with many other toxic chemicals.��

You note throughout your research that the air pollution in nail salons is something that can affect the air we all breathe — even if we never visit a salon. How is that possible?��

DC: It’s very important to lower chemical concentrations indoors because they eventually go outside and contribute to overall air pollution. It’s hard to control that in small businesses, but one thing that was clear when Boston was building a ventilation policy was that it was important to make sure businesses filtered out chemicals before they went out the window. Now we know that fragrances make up a considerable part of overall chemicals in nail salons and they’re adding to the mix. And since you have fragrances in a bunch of products, it all adds up. We must consider the accumulated burden that fragrances can have in the indoor environment and put more purposeful thought into how we produce products that contain those things — not just during the life cycle of the products, but also how they interact with the environment. ��

There are policies right now that are trying to work on fragrances, but we need to learn more. It’s going to be a while before we can control or guide manufacturers better. It’s very early, but I think there’s a lot we can learn about fragrances in the future.��

Other authors on the June 19 paper are Chunrong Jia and Xianqiang Fu of the University of Memphis and Thomas Webster of Boston University.����

For more information or to reach Ceballos, contact Alden Woods at acwoods@uw.edu.��

A team led by researchers at the 91̽�� has discovered a major cause for a drop in nighttime pollinator activity — and people are largely to blame.

The researchers found that nitrate radicals (NO3) in the air degrade the scent chemicals released by a common wildflower, drastically reducing the scent-based cues that nighttime pollinators rely on to locate the flower. In the atmosphere, NO3 is produced by chemical reactions among other nitrogen oxides, which are themselves released by the combustion of gas and coal from cars, power plants and other sources. The findings, Feb. 9 in the journal Science, are the first to show how nighttime pollution creates a chain of chemical reactions that degrades scent cues, leaving flowers undetectable by smell. The researchers also determined that pollution likely has worldwide impacts on pollination.

The team — co-led by , a 91̽��professor of biology, and , a 91̽��professor of atmospheric sciences — studied the (Oenothera pallida). This wildflower grows in arid environments across the western U.S. They chose this species because its white flowers emit a scent that attracts a diverse group of pollinators, including nocturnal moths, which are one of its most important pollinators.

At field sites in eastern Washington, the researchers collected scent samples from pale evening primrose flowers. Back in the laboratory, they used chemical analysis techniques to identify the dozens of individual chemicals that make up the wildflower’s scent.

“When you smell a rose, you’re smelling a diverse bouquet composed of different types of chemicals,” said Riffell. “The same is true for almost any flower. Each has its own scent made up of a specific chemical recipe.”

Once they had identified the individual chemicals that make up the wildflower’s scent, the team used a more advanced technique called mass spectrometry to observe how each chemical within the scent reacted to NO3. They found that reacting with NO3 nearly eliminated certain scent chemicals. In particular, the pollutant decimated levels of monoterpene scent compounds, which in separate experiments moths found most attractive.

Moths, which smell through their antennae, have a scent-detection ability that is roughly equivalent to dogs — and several thousand times more sensitive than the human sense of smell. Research suggests that several moth species can detect scents from miles away, according to Riffell.

Using a wind tunnel and computer-controlled odor-stimulus system, the team investigated how well two moth species — the (Hyles lineata) and the (Manduca sexta) — could locate and fly toward scents. When the researchers introduced the pale evening primrose’s normal scent, both species would readily fly toward the scent source. But when the researchers introduced the scent and NO3 at levels typical for a nighttime urban setting, Manduca’s accuracy dropped by 50% and Hyles — one of the chief nocturnal pollinators of this flower — could not locate the source at all.

Experiments in a natural setting backed up these findings. In field experiments, the team showed that moths visited a fake flower emitting unaltered scent as often as they visited a real one. But, if they treated the scent first with NO3, moth visitation levels dropped by as much as 70%.

“The NO3 is really reducing a flower’s ‘reach’ — how far its scent can travel and attract a pollinator before it gets broken down and is undetectable,” said Riffell.

The team also compared how daytime and nighttime pollution conditions impacted the wildflower’s scent chemicals. Nighttime pollution had a much more destructive effect on the scent’s chemical makeup than daytime pollution. The researchers believe this is largely due to sunlight degrading NO3.

The team used a computer model that simulates both global weather patterns and atmospheric chemistry to locate areas most likely to have significant problems with plant-pollinator communication. The areas identified include western North America, much of Europe, the Middle East, Central and South Asia, and southern Africa.

“Outside of human activity, some regions accumulate more NO3 because of natural sources, geography and atmospheric circulation,” said Thornton, who added that natural sources of NO3 include wildfires and lightning. “But human activity is producing more NO3 everywhere. We wanted to understand how those two sources — natural and human — combine and where levels could be so high that they could interfere with the ability of pollinators to find flowers.”

The researchers hope their study is just the first of many to help uncover the full scope of pollinator failure.

“Our approach could serve as a roadmap for others to investigate how pollutants impact plant-pollinator interactions, and to really get at the underlying mechanisms,” said Thornton. “You need this kind of holistic approach, especially if you want to understand how widespread the breakdown in plant-pollinator interactions is and what the consequences will be.”

The study highlights the dangers of human-fueled pollution and its implications for all pollinators as well as the future of agriculture.

“Pollution from human activity is altering the chemical composition of critical scent cues, and altering it to such an extent that the pollinators can no longer recognize it and respond to it,” said Riffell.

Approximately three-quarters of the more than 240,000 species of flowering plants rely on pollinators, Riffell said. And more than��70 species of pollinators are endangered or threatened.

Lead author on the paper is Jeremy Chan, a postdoctoral researcher at the University of Copenhagen who conducted this study as a 91̽��doctoral student in biology. Co-authors are Sriram Parasurama in the 91̽��Department of Biology; Rachel Atlas, a postdoctoral researcher at the Pierre Simon Laplace Institute in France who participated in this study as a 91̽��doctoral student in atmospheric sciences; , a 91̽��doctoral students in atmospheric sciences; Ruochong Xu, a doctoral student at Tsinghua University in China; , a 91̽��professor of atmospheric sciences; and , a professor of chemistry at Seattle University. The research was funded by the Air Force Office of Scientific Research, the National Science Foundation, the National Institutes of Health, the Human Frontiers in Science Program, and the 91̽��.

For more information, contact Riffell at 206-348-0789 or jriffell@uw.edu and Thornton at 206-543-4010 or joelt@uw.edu.

For more than a century, American cities have been sliced and diced by high-traffic roadways. Interstate highways and��wide arterials are now a defining feature of most metropolitan areas,��their constant flow of cars spewing pollution into nearby neighborhoods. ��

Researchers have only just begun to understand the health risks posed by all that pollution. Long-term exposure to traffic-related air pollution — a complex mixture of exhaust from tailpipes, brake and tire wear, and road dust — has been linked to increased rates of , , and . ��

New research from the 91̽�� suggests those health risks are also seen in people traveling busy roads. found that unfiltered air from rush-hour traffic significantly increased passengers’ blood pressure, both while in the car and up to 24 hours later.��

“The body has a complex set of systems to try to keep blood pressure to your brain the same all the time. It’s a very complex, tightly regulated system, and it appears that somewhere, in one of those mechanisms, traffic-related air pollution interferes with blood pressure,” said , a 91̽��physician and professor of environmental and occupational health sciences who led the study.����

An by Kaufman’s lab found that exposure to diesel exhaust fumes increased blood pressure in a controlled environment. The roadway traffic study was designed to test that finding in a real-world setting by isolating the effects of traffic-related air pollution.��

Researchers drove healthy participants between the ages of 22 and 45 through rush-hour Seattle traffic while monitoring their blood pressure. On two of the drives, unfiltered road air was allowed to enter the car, mirroring how many of us drive. On the third, the car was equipped with high-quality HEPA filters that blocked out 86% of particulate pollution. Participants did not know whether they were on a clean air drive or a roadway air drive.��

Breathing unfiltered air resulted in net blood pressure increases of more than 4.50 mm Hg (millimeters of mercury) when compared to drives with filtered air. The increase occurred rapidly, peaking about an hour into the drive and holding steady for at least 24 hours. Researchers did not test past the 24-hour mark.����

The size of the increase is comparable to the effect of a high-sodium diet.��

“We know that modest increases in blood pressure like this, on a population level, are associated with a significant increase in cardiovascular disease,” Kaufman said. “There is a growing understanding that air pollution contributes to heart problems. The idea that roadway air pollution at relatively low levels can affect blood pressure this much is an important piece of the puzzle we’re trying to solve.”��

The findings also raise questions about ultrafine particles, an unregulated and little-understood pollutant that has become a source of growing concern among public health experts. Ultrafine particles are less than 100 nanometers in diameter, much too small to be seen. Traffic-related air pollution contains high concentrations of ultrafine particles. In the study, unfiltered air contained high levels of ultrafine particles, though the overall level of pollution as measured by fine particle concentration (PM 2.5) was relatively low, equivalent to an AQI of 36.����

“Ultrafine particles are the pollutant that were most effectively filtered in our experiment – in other words, where the levels are most dramatically high on the road and low in the filtered environment,” Kaufman said. “So, the hint is that ultrafines may be especially important [for blood pressure]. To actually prove that requires further research, but this study provides a very strong clue as to what’s going on.”��

Traffic-related air pollution is the main cause of air quality variation from community to community in most U.S. metropolitan areas.��

“This study is exciting because it takes the gold-standard design for laboratory studies and applies it in an on-roadway setting, answering an important question about the health effects of real-world exposures. Studies on this topic often have a challenging time separating the effects of pollution from other roadway exposures like stress and noise, but with our approach the only difference between drive days was air pollution concentration,” said , a former 91̽��postdoctoral fellow in the Department of Environmental and Occupational Health Sciences and lead author of the new study. “The findings are valuable because they can reproduce situations that millions of people actually experience every day.”��

This research was funded by the U.S. Environmental Protection Agency and the National Institutes of Health.����

Other authors are , , , and of the 91̽��Department of Environmental and Occupational Health Sciences; of the 91̽��Department of Civil and Environmental Engineering; and of the Department of Biostatistics.��

For more information or to reach the researchers, contact Alden Woods at acwoods@uw.edu.