Study: Trees Generating PM2.5 Pollutants in Los Angeles

According to a new University of California Berkeley report, trees are a big contributor to PM2.5 particulate pollution in Los Angeles. (Joel Mott via Unsplash)

According to a new report by scientists at the University of California Berkeley, all the electric vehicles in the world won’t make the air crystal clear in the Los Angeles area. Their research shows that trees now account for a substantial portion of the unhealthy particulates in the region’s air.

Measuring 2.5 microns in diameter, these fine particulate matter hydrocarbon emissions (PM2.5) are breathed in by people living in the region, lodging in their lungs and causing cardiovascular and respiratory problems. Further, some of these biogenic volatile compounds released by trees can interact with nitrogen oxides caused by human activity, creating ozone.

Trees are not new to Southern California, so if these PM2.5 particulates have existed since before the advent of industrial emissions in the region, why are they suddenly an issue now?

It’s a bit of a silver lining story.

Regulations have lowered vehicle emissions in California to a point where these organic compounds from the region’s flora and fauna now cause a more significant proportion of aerosol pollution.

Researchers from UC Berkeley claim tailpipe emissions in the L.A. basin in 2012 were half what they were in 1999. This reduction, say scientists, means that vegetation is now responsible for a greater percentage of the PM2.5 particulate matter in the local atmosphere. They estimate that 25% of the aerosols in the LA basin, which is home to about 18 million trees, comes from plants.

Scientific American says some of the biggest offenders include the non-native Mexican fan palms that are emblematic of the L.A. skyline. Black gun and poplar are also high emitters, whereas cedar and birch tend to be low emitters. While no one suggests that cities chop down trees to reduce existing PM2.5 particulate matter in the air, scientists hope that the types of trees that cities choose to plant in the future might be given more careful consideration.

While driving, you can afford yourself a degree of protection from PM2.5 air pollution by choosing a vehicle with a sophisticated air filtration system.

For example, the Volvo Advanced Air Cleaner option equips many Volvos with an ionizer that captures particles as small as 2.5 microns, while Ford Motor Company is offering for select models an optional Auto Air Refresh feature that makes a similar claim. Hyundai’s Smart Air Purification system can monitor air quality, send a report to your smartphone, and activate the filtration technology before you enter the car. Hyundai has yet to announce which vehicles will have this feature.

You can also research aftermarket products that assert their ability to filter PM2.5 particulates from your vehicle’s cabin air. Note, however, that no vehicles sold in the United States can claim to filter out the COVID-19 virus, which ranges in size from 0.06 to 0.125 microns in diameter.

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