Cooking Emissions Rival Fossil Fuels as an Ozone Pollution Source in Los Angeles

As the adoption of cleaner-burning engines and electric vehicles drives fossil fuel emissions lower, scientists have discovered that a surprising pollution source is playing a significant role in cooking up ozone in the air over Los Angeles.

According to new research from NOAA, the potent and often pungent volatile organic compounds (VOCs) given off from cooking food are now responsible for over a quarter of the ozone production from VOCs generated by human activity in the LA basin. This is roughly equal to the amount of ozone produced by VOCs from on-road and off-road motor vehicles.

The new study, published in Atmospheric Chemistry & Physics, takes a more complete look at the mix of VOCs in urban air by adding chemical compounds specific to cooking emissions to an air quality model set up to replicate the conditions in and around Los Angeles.

“We knew from our research that chemical compounds from cooking can make up an important fraction of VOCs present in urban air, but they were not well represented in inventories or included in air quality models,” said lead author Chelsea Stockwell, a research chemist at NOAA’s Chemical Sciences Laboratory (CSL). “Given the known chemical reactivity of these compounds, their omission from air quality models may be a blind spot when it comes to urban ozone production.”

VOCs are one of the two ingredients necessary for creating ground-level ozone, an EPA-regulated air pollutant that in high concentrations is toxic to humans, animals and plants. Ozone is formed in the atmosphere when VOCs undergo a series of photochemical reactions with nitrogen oxides or NOx, which is primarily generated by vehicle exhaust.

Over the past several decades, efforts to reduce ozone pollution by controlling emissions from the transportation sector substantially improved air quality across the country.