Household products are a significant source of city air pollution

"The main message is that the important sources of air pollution in urban areas are changing. Historically, it was dominated by motor vehicles and over time there has been major success in controlling that source. As a result, other sources are more prominent now as a fraction of the overall problem."

What's new: Air pollution measurements have long focused on gasoline-related hydrocarbons. It can be difficult to measure chemical compounds in coatings, paints and other products because they are volatile by nature, and can convert into hundreds of different intermediate species before eventually creating carbon dioxide and water. But "measurement capabilities have advanced, not in just detecting ultra-low concentrations but also non-traditional compounds," says Harley, an author on the study.

What they did: A multi-year, multi-institute study identified the chemical fingerprints left behind by various consumer products, then looked for their presence in both indoor and outdoor air in Los Angeles.

What they found: Despite automobile use increasing, particulates from gas were much lower than previous estimates, likely due to strict emissions controls. Compounds like ethanol and acetone, however, were present in much higher amounts than predicted.

• The authors believe the likely source is household and consumer products like scented hygiene products and cleaners.
• Most of the volatile particles from those products get washed down the drain, but the authors estimate roughly 40% end up in the air.
• Even though these consumer goods make up only 5% of petroleum products, they're responsible for up to half of the volatile organic compound (VOC) emissions from fossil fuels. That's because "many of the volatile chemical products we use each day are intended to evaporate," said one of the study authors Jessica Gilman, a research scientist at NOAA, in a press conference. Think of waiting for nailpolish or glue to dry, she said.

Yes, but: "Every city is different," says Caltech's Paul Wennberg, who wasn't involved in the research. Trees also emit volatile organic compounds and in the wooded Southeast may be bigger contributors than these compounds from consumer products. And in Houston, for example, the petrochemical industry is an outsized source compared to other cities. The study underscores the need for local measurements, says Wennberg.

The health impact: Emissions — whether from gasoline or chemical products — contribute to the amount of fine particulate matter in the air, which has been linked to health issues and premature death and is capped by the Environmental Protection Agency. “Health data suggest we could still get benefit by going lower and if we are going to go lower, we need to address these sources," says Allen Robinson, a professor of mechanical engineering at Carnegie Mellon University who wasn't involved in the study. “Air quality is degrading people’s health and if we’re going to improve air quality, it’s not cars anymore, there are other sources.”

And, unlike car emissions, people encounter these chemicals inside. "A lot of the products that are now the major source of air pollution are products we use inside our homes and as result we can be highly exposed to the organic chemicals in the air we breathe inside our homes," says Harley.

The big picture: The authors caution that more research needs to be done before any regulations can be passed because it's still not clear what specific products are the largest polluters, or if any one pollutant stands out. In the past, regulations successfully limited the amount of ozone-depleting chlorofluorocarbons, or CFCs, allowed in household products.

For now, said Gillman, this research is a reminder that "the choices we make every day in our daily lives are changing the composition of the atmosphere," and the very air we breathe.