DAILY SCIENCE

As cars get cleaner, air pollution sources shift indoors
Half of fossil fuel-based volatile organic compounds (VOCs) in the air of industrialized cities now come from industrial and household products, reflecting the success of efforts to address motor vehicle emissions and the need to take a closer look at everyday products.
February 27, 2018

Household and industrial products such as pesticides, cleaners, and lotions are responsible for a surprisingly large proportion of urban air pollution, according to a new study.

The analysis, published February 16 in Science, suggests that half of fossil fuel-based volatile organic compounds (VOCs) in the air of industrialized cities come from petroleum-based chemical products ranging from adhesives, printing inks, paints, and coatings to personal care products and even perfume.

The findings contrast with air pollution inventories such as one by the U.S. Environmental Protection Agency, which estimated that about three-quarters of VOCs come from the transportation industry, and only about one-quarter from chemical products.

VOCs are important because they can react in the atmosphere to produce ozone or fine particulate matter, two forms of air pollution that can damage the lungs and cause other health effects. An analysis last year found that air pollution is one of the top five threats to health worldwide, and there’s evidence that it can be harmful even at levels below current air quality standards. So there’s an urgent need to get a better handle on where this pollution is coming from.

The results reflect the success of efforts in recent decades to curtail emissions from motor vehicle exhaust and fumes from gas pumps – but they also indicate it’s time to look more closely at emissions from household products.

“As transportation gets cleaner, those other sources become more and more important,” Brian McDonald, lead author of the study and a researcher with the Cooperative Institute for Research in Environmental Sciences, said in a press release. “The stuff we use in our everyday lives can impact air pollution.”

McDonald and his collaborators gathered statistics on fuel and chemical production from industry sources and regulatory agencies. They combined these data with laboratory measurements of emissions from various types of products to determine the level of VOCs entering the atmosphere.

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“Volatile chemical products used in common solvents and personal care products are literally designed to evaporate,” study coauthor and National Oceanic and Atmospheric Administration atmospheric scientist Jessica Gilman said in the release. “You wear perfume or use scented products so that you or your neighbor can enjoy the aroma. You don’t do this with gasoline.”

So, even though about 15 times as much petroleum goes to producing fuel as goes into chemical feedstocks, chemical products are responsible for almost as much air pollution as motor vehicle emissions.

The researchers also made measurements of air quality both near and away from roads in the Los Angeles California area. They found that they couldn’t explain the actual pollution in the air – neither the amount nor the specific chemical fingerprint – without taking into account pollution from chemical products.

Previous studies mainly measured the types of VOCs present in fossil fuels, not the ones in chemical products. This may be why they have tended to underestimate the proportion of pollution from chemical products and overestimate motor vehicle emissions.

Finally, the researchers looked at indoor air quality measurements, again using the Los Angeles area as a test case. This analysis revealed that people are exposed to higher concentrations of VOCs indoors than outdoors, and that products used indoors are increasingly a source of outdoor air pollution.

Even though they also contain many VOCs that can contribute to air pollution, household products are not regulated as tightly as motor vehicle fuel. To decrease air pollution further, we’ll have to look beyond transportation and industry and consider the role of everyday household products, the researchers say.

Source: McDonald B.C. et al. “Volatile chemical products emerging as largest petrochemical source of urban organic emissions.” Science2018.
Image: Jessica Lucia via Flickr.

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