(CN) – Household cleaners, paints, perfumes and other chemical products that feature compounds refined from petroleum now contribute about as much to urban air pollution as vehicle emissions, a new study finds.
By weight, people use about 15 times more fuel in their vehicles than petroleum-based products. However, the household products contribute about as much to air pollution as vehicles do, said lead author Brian McDonald, a research scientist with the Colorado-based Cooperative Institute for Research in Environmental Sciences (CIRES).
One type of particle-forming emissions from chemical products is even about twice as high as those from the transportation sector, according to the report, published Thursday in the journal Science.
“As transportation gets cleaner, those other sources become more and more important,” McDonald said. “The stuff we use in our everyday lives can impact air pollution.”
For the report, the team focused on volatile organic compounds (VOCs), which can waft into the atmosphere and react to create either ozone or particulate matter – both of which are regulated by many nations due to health impacts such as lung damage.
City dwellers assume that much of the pollution they breathe comes from vehicle emissions or leaky gas pumps. While true in the past, regulators and car manufacturers have made emissions-limiting changes to fuels, engines and pollution-control systems.
The team evaluated air-pollution sources by examining recent chemical production statistics released by regulatory agencies and industries. They also made detailed atmospheric-chemistry measurements in Los Angeles air and analyzed indoor air quality measurements made by others.
The researchers concluded that, in the United States, the volume of VOCs emitted by industrial and consumer products is actually two or three times larger than estimated by existing air-pollution inventories, which also overestimate transportation-sector sources. For example, the U.S. Environmental Protection Agency estimates that, by weight, roughly 75 percent of VOC emissions come from vehicles, while about 25 percent stem from chemical products.
The report, which considers previously unavailable atmospheric data and up-to-date chemical-use statistics, suggests the split is closer to 50-50.
The disproportionate air-quality impact of emissions from chemical products partially stems from a basic difference between those products and fuel, according to co-author Jessica Gilman, an atmospheric scientist with the National Oceanic and Atmospheric Administration.
“Gasoline is stored in closed, hopefully airtight, containers and the VOCs in gasoline are burned for energy,” Gilman said. “But volatile chemical products used in common solvents and personal care products are literally designed to evaporate.
“You wear perfume or use scented products so that you or your neighbor can enjoy the aroma. You don't do this with gasoline.”
The researchers were particularly curious about how those VOCs end up contributing to particulate pollution. A comprehensive assessment published last year in the journal The Lancet determined air pollution is one of the five greatest global mortality threats. The report ranked “ambient particulate matter pollution” as the largest air pollution risk.
The new study suggests that as cars have gotten cleaner, the VOCs forming those pollution particles are coming increasingly from consumer products.
“We've reached that transition point already in Los Angeles,” McDonald said.
The team determined that they could not recreate the levels of ozone or particles measured in the atmosphere unless they added emissions from volatile chemical products. They also found that people are exposed to very high levels of volatile compounds indoors, which are more concentrated inside than out, said co-author Allen Goldstein, an atmospheric chemist at the University of California, Berkeley.
“Indoor concentrations are often 10 times higher indoors than outdoors, and that's consistent with a scenario in which petroleum-based products used indoors provide a significant source to outdoor air in urban environments,” he said.
The report also finds that U.S. regulatory efforts on vehicle emissions have been very effective, according to co-author Joost de Gouw, a CIRES chemist.
“It's worked so well that to make further progress on air quality, regulatory efforts would need to become more diverse,” he said.
“It's not just vehicles anymore.”
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