Air pollution comes from many sources, from factories, to cars, to cigarette smoke. But when we think about air pollution, we generally think of the smog in major cities caused by heavy traffic and proximity to industrial factories. It’s not often that we consider the contributions of the day-to-day products we use.
But now, a new study led by the National Oceanic and Atmospheric Administration (NOAA) has found that chemical products that contain certain compounds refined from petroleum – such as pesticides, paints, perfumes, and household cleaners, now rival motor vehicle emissions as the biggest source of urban air pollution.
Although people use about 15 times more fuel by weight than they do petroleum-based compounds in chemical products, these products contribute about as much air pollution as the transportation sector does. In particular, particle-forming emissions from chemical products – which contain tiny particles than can damage people’s lungs – are roughly twice as high as those from the transportation sector.
“As transportation gets cleaner, those other sources become more and more important,” says Brian McDonald, a scientist at the Cooperative Institute for Research in Environmental Sciences (CIRES) working in the NOAA’s Chemical Sciences Division, and lead author of the study. “The stuff we use in our everyday lives can impact air pollution.”
In this new assessment, researchers zeroed in on volatile organic compounds (VOCs), which can move into the atmosphere and react to produce either ozone or particulate matter. Both products of these reactions are regulated in the U.S. and other countries due to their health hazards.
The researchers assessed recent chemical production statistics gathered by industries and regulatory agencies, and made atmospheric chemistry measurements of the air in Los Angeles. They found that in the U.S., the amount of VOCs emitted by consumer and industrial products is actually two to three times greater than previously estimated by current air pollution inventories.
They also determined that these same inventories overestimate vehicular sources of air pollution. The Environmental Protection Agency estimates that about 75 percent of VOC emissions come from vehicular sources, with the remaining 25 percent coming from chemical products. These new findings have the split closer to 50/50.
So why does this disproportionate air quality impact of chemical product emissions occur? It’s due in part to a fundamental difference between these products and fuels.
“Gasoline is stored in closed, hopefully airtight, containers and the VOCs in gasoline are burned for energy,” explains Jessica Gilman, an atmospheric scientist at the NOAA and co-author of the paper. “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.”
Part of the reason that consumer and industrial chemical products have now been found to have this larger contribution is that, in recent years, cars have gotten cleaner. This means that we now have to focus our efforts on reducing emissions from these products in much the same way we did with cars.
“It’s worked so well that to make further progress on air quality, regulatory efforts would need to become more diverse,” says Joost de Gouw, a CIRES chemist and co-author of the paper. “It’s not just vehicles any more.”