Study Downgrades Cars’ Contribution to VOC Pollution

New research finds motor vehicles are not the dominant contributors to health-threatening volatile organic compounds (VOC).

A research team led by the National Oceanic and Atmospheric Admin. says the amount of VOCs emitted by consumer and industrial products is two or three times greater than estimated by current air-pollution inventories, which also overestimate vehicular sources.

The EPA estimates about 75% of VOC emissions by weight come from vehicular sources, with 25% from chemical products.

The NOAA study, published in the journal Science, with its detailed assessment of up-to-date chemical use statistics and previously unavailable atmospheric data, puts the split closer to 50-50.

Since adoption of the Clean Air Act in 1970, air-quality programs have focused on controlling transportation-related pollution emitted by everything from cars and trucks to oil and gas refineries.

But team leader Brian McDonald, a scientist in the Cooperative Institute for Research in Environmental Sciences at the University of Colorado-Boulder, and his colleagues couldn’t reconcile atmospheric measurements made over Los Angeles in 2010 with estimates of transportation emissions.

Co-author Christopher Cappa, a professor of civil and environmental engineering at the University of California-Davis, says the team found it simply could not reproduce the levels of particles or ozone they measured in the Los Angeles area without including emissions from volatile chemical products.

The disproportionate air-quality impact of chemical product emissions including shampoo, cleaning products and paint is partly because of a fundamental difference between those products and fuels.

NOAA atmospheric scientist Jessica Gilman says gasoline is stored in closed, airtight containers and the VOCs in gasoline are burned for energy.

“But volatile chemical products used in common solvents and personal-care products are designed to evaporate,” Gilman says in a statement. “You wear perfume or use scented products so that you or your neighbor can enjoy the aroma. You don’t do this with gasoline.”

People use a lot more fuel than they do petroleum-based compounds in chemical products – about 15 times more by weight. But the researchers found lotions, paints and other products contribute about as much to air pollution as does the transportation sector.

“As transportation gets cleaner, those other sources become more and more important,” McDonald says.