In 2008, China needed to improve the air around Beijing before the Olympics, so they did something that was considered Draconian - they banned cars for everyone except the rich and the government.

It worked. A new study from UCLA says forcing cars off the roads works in California as well.  In study findings announced today, researchers report that they measured air pollutants during last year's Carmageddon (July 15th, 2011) and found that when 10 miles of the 405 closed, air quality near the shuttered portion improved within minutes, reaching levels 83 percent better than on comparable weekends. Because traffic dipped all over Southern California that weekend, air quality also improved 75 percent in parts of West Los Angeles and Santa Monica and an average of 25 percent regionally — from Ventura to Yucaipa, and Long Beach to Santa Clarita. 

The study was led by two professors at UCLA's Institute of the Environment and Sustainability: Yifang Zhu, who is also an associate professor of environmental health sciences at the UCLA Fielding School of Public Health, and Suzanne Paulson, who is also a professor of atmospheric and oceanic sciences.  The researchers gushed at the possibilities.

"The air was amazingly clean that weekend," Paulson said. "Our measurements in Santa Monica were almost below what our instruments could detect, and the regional effect was significant. It was a really eye-opening glimpse of what the future could be like if we can move away from combustion engines."

The research gives a peek at what the air would look like in Los Angeles with more battery-powered cars and they say it confirms how quickly less driving can improve key measures of air quality.
Advocates have not been so irrationally convinced of a benefit since the glory days of ethanol campaigning by environmentalists. 

But to get a regional effect, the researchers said, you need a regional drop in traffic, like what Los Angeles saw during the first Carmageddon — it doesn't last if traffic returns. "The effect was gone by the next week," Paulson said. "We measured fresh emissions: pollutants that come directly from cars. It's a very short-term effect." 

The researchers measured ultrafine particles (PM1.0, less than 0.1 microns in diameter), which are key indicators of real-time traffic levels, and also fine particulate matter known as PM2.5 (less than 2.5 microns in diameter), which includes tailpipe emissions and new particles created when the emissions interact with the atmosphere. PM2.5 can spread farther from the freeway and last longer than ultrafine particles, but both are pollutants with health risks. Exposure to near-roadway pollutants has been linked to increases in asthma, heart attacks, strokes, diabetes, low birth weight, pre-term births and other ailments, the researchers noted. 

Zhu and Paulson found that when traffic dropped more than 90 percent on the closed 405, with only construction vehicles still on the move, ultrafine particles dropped by 83 percent. PM2.5 concentrations dropped 36 percent.

More broadly, ultrafine particles and PM2.5 levels dropped 75 percent across a swath of West Los Angeles near the I-405/I-10 interchange stretching from Santa Monica to Westwood. Elsewhere, they measured PM2.5 and found the air 31 percent cleaner in Ventura, 19 percent cleaner in Yucaipa, 30 percent cleaner in Long Beach, 23.2 percent cleaner in Santa Clarita and 19.9 percent cleaner in Northridge.

"There is no safe level of PM2.5 concentrations, where you would no longer observe health impacts, so any reduction is an improvement," Zhu said. "This study shows that with such dramatic traffic reductions, there are specific air-quality improvements. It gives policymakers and the public incentives to put more effort into reducing traffic emissions."

So why mess with cars at all then?   Other studies showed a single hamburger patty in a restaurant is equivalent to 143 miles of driving a diesel truck, so making every restaurant cook 10 fewer hamburgers should mitigate all of the cars in the county.   If only actual air quality worked that way in the real world.  It only does in studies like this but PM 2.5 is not the end all of actual pollution. In reality, composting and dust each produce more particulate matter than hamburgers and diesel trucks combined.

Paulson's team drove instruments around in their "mobile measurement platform" — a late-1990s electric Toyota Rav-4 equipped with a fast mobility particle sizer to detect ultrafine particle levels and a dusttrack to measure PM2.5 concentrations. The team has used the same route since 2008 and can compare measurements over the years, from Santa Monica's Sunset Park neighborhood to the Santa Monica Airport, and from north of the 10 freeway, across the 405, and into Rancho Park and Westwood.  For measurements across the Southern California basin, Zhu and Paulson used South Coast Air Quality Management District measures of PM2.5 levels and CalTrans measures of traffic. 

Though the pair will not duplicate their research for Carmageddon II this weekend, if there's less traffic again, the basin will get a brief reprieve from pollution - unless they stay home and grill hamburgers.