With millions of people applying these products in close proximity, the particles greatly add to ozone pollution – even more than traffic. In New York City, for example, air samples collected during a 2018 field mission found that these fragrant personal care products were responsible for about half of the volatile organic compounds (VOCs) that were generated by people.
VOCs are a primary ingredient in the formation of ground-level ozone and are mostly found in man-made chemicals used in paints, pharmaceuticals and personal products. They are emitted as gases, which can trigger health issues in people of all ages who suffer from lung diseases like asthma.
Smog, also known as ozone, forms on warm, sunny days and is typically made worse by the chemicals that exit vehicle tailpipes and power plant and industrial smokestacks. Ozone is more likely to form in warmer temperatures. It can be "good" or "bad," depending on where it is. (Related: Wildfire plumes worldwide are contributing to ozone pollution and harming air quality.)
The ozone layer high up in the atmosphere is the good one because it acts like a sunscreen, blocking potentially harmful ultraviolet energy from reaching our planet's surface. Without it, humans and animals can experience increased rates of skin cancer and other ailments, such as cataracts.
On the other hand, the bad ozone is near the surface and can cause respiratory problems. Pollutants emitted by cars, power plants, industrial boilers, refineries, chemical plants and other sources are often cited as the chief cause of the bad ozone.
Cooperative Institute for Research in Environmental Sciences (CIRES) scientist and study co-author Georgios Gkatzelis said he was initially skeptical that consumer products could play such a big role in ozone pollution.
"Seeing all those cars when biking to work in Boulder, Colorado convinced me they had to be the dominant VOC source," Gkatzelis said in a statement. "But after driving our NOAA van though New York City and watching our instrument displays, Matt [Coggon, the study's lead author] and I were often shouting at each other in amazement at what we were seeing."
The study was published Monday, August 2, in the peer-reviewed multidisciplinary scientific journal Proceedings of the National Academy of Sciences. It used the New York City case as basis to look at other urban areas, such as Los Angeles and Las Vegas.
The team has been driving around cities in the U.S. Southwest, conducting mobile laboratory and ground-site measurements to know how much personal care products account for VOCs.
"The big takeaway is how much VOC emissions from consumer products increase as urban population density increases, and how much these chemicals actually matter for producing ozone," said Coggon, a CIRES scientist working at NOAA.
He and his team previously found products with volatile chemicals – paints, cleaners and personal care products – were responsible for 78 percent of the Manhattan VOCs. Transportation accounted for the remaining 22 percent.
Similar measurements were also taken in Boulder, Colorado to see if a less dense city would have the same results. The researchers found that volatile consumer products were still responsible for 42 percent of human-caused VOCs in the area, but traffic contributed the most with 58 percent.
Coggon said the current generation of air quality models do not accurately simulate both the emissions and atmospheric chemistry of these consumer products and must be updated in order to capture their full impact on urban air quality.
In areas where ozone pollution is a problem, new strategies to control VOC sources may need to be devised.
"We know now that these products are making ozone pollution worse," Coggon explained. "We can't control what the trees are emitting, but what we can do is look for ways to make these common everyday products less polluting."
Another group of researchers published a study in February 2021 that detailed even more about the effects of air pollution, finding it can increase the risk of heart and lung disease. A team of Harvard University researchers used the addresses of 63 million American adults aged 65 and older to assess their exposure to particulate matter, nitrogen dioxide and ozone.
"Long-term exposure to air pollution was associated with an increased risk of hospital admissions with cardiovascular and respiratory outcomes on an additive scale among the elderly population of the United States," the researchers wrote. (Related: Air pollution increases risk of heart disease and stroke, study says.)
"Each unit increase in levels of particulate matter, nitrogen dioxide and ozone were associated with thousands of additional admissions each year. Air pollution should be considered as a risk factor for cardiovascular and respiratory disease. The risk persists even at levels below current national and international guidelines."
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