Your shampoo, along with other common household products, produces almost as much air pollution in the U.S. as the millions of cars, trucks and other vehicles belching fumes into the atmosphere.
According to a recent paper published in the journal Science, so-called volatile organic compounds, or VOCs, contained in consumer products and industrial sources like shampoo, perfume, paint and cleaning supplies emit two to three times as many pollutants as scientists previously believed.
That is surprising, in part, because people use roughly 15 times more fuel by weight compared with petroleum-based compounds in products. Previous data from the Environmental Protection Agency had suggested that 75 percent of fossil VOC emissions (by weight) came from fuel-related sources, with about 25 percent derived from chemical products.
The latest research is based on previously unavailable atmospheric data and more up-to-date chemical production statistics.
"Gasoline is stored in closed, hopefully airtight, containers, and the VOCs in gasoline are burned for energy," National Oceanic and Atmospheric Administration scientist Jessica Gilman, a co-author of the new paper, said in a statement. "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 gas."
The findings come at an awkward time for the EPA. Under Administrator Scott Pruitt, the agency has focused on reducing environmental regulations, including the Clean Power Plan, passed under the Obama administration. Pruitt and President Trump also have expressed doubts that climate change is a man-made phenomenon.
Steven Milloy, an attorney who was a member of Mr. Trump's EPA transition team, dismissed the study, which involved some 20 researchers affiliated with universities and research facilities in the U.S., Canada and Korea.
"It's a nonsense study," he said in an interview. "Do consumer products with scents emit VOCs? They always have. This is just playing on people's paranoia."
An EPA spokesman said the agency is reviewing the study.
"EPA continuously reviews the latest scientific developments to inform its approaches to calculating air pollution amounts and sources," he said. "As new methods and information become available and proved reliable, EPA updates its approaches."
The EPA estimates that VOC pollution fell 42 percent between 1990 and 2016 thanks to the Clean Air Act. Ground-level ozone, created by the reaction of VOC and nitrogen oxide along with sunlight, has plummeted 31 percent between 1980 and 2016.
Ozone has been linked to global warming. VOCs also have been linked to particulate matter or soot, which causes asthma and other health problems.
One reason air pollution from consumer products is drawing the attention of scientists is that emissions from motor vehicles have fallen in recent years thanks to cleaner-burning gasoline and the emergence of vehicles powered by electricity and other alternative energy sources.
"As transportation gets cleaner, those other sources become more and more important," said Brian McDonald, a scientist in the Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, working in NOAA's Chemical Sciences Division, in a statement.