Los Angeles, California, is famous for its car culture and, not coincidentally, its air pollution. But hope for a cleaner L.A. is not lost: Researchers suggest that closing streets for cycling and walking events might help clear away some of that smog, at least temporarily.
Air quality in Los Angeles is a lot better than it used to be, and that's led to a decline in lung disease, particularly among children living in the Southland. Still, the air isn't exactly pristine. The city tops the American Lung Association's State of the Air 2015 list for the highest concentrations of ozone, and it comes in at number five for particulate matter, meaning there's still much to be done—particularly, as it turns out, in more disadvantaged neighborhoods.
Downtown and East Los Angeles have some of the most polluted air in the state. What could policymakers do to change that?
"Air quality in [much] of Los Angeles County does not meet national attainment standards," write University of California–Los Angeles postdoctoral researcher Shi Shu, associate professor Yifang Zhu, and their colleagues in Environmental Pollution. And, according to California Office of Environmental Health Hazard Assessment data, Downtown and East Los Angeles have some of the most polluted air in the state. The question is, what could policymakers do to change that?
The short and perhaps obvious answer is to discourage driving. Cars emit a substantial amount of fine particulate matter, the stuff smaller than 2.5 micrometers that's the biggest threat to human health. But in a place like L.A., where cars rule the sprawling landscape, it's not easy to measure how much reducing traffic could impact the air and people's health.
At the same time, Shu, Zhu, and their colleagues realized, the perfect air quality experiment already existed in the form of CicLAvia, a program that closes city streets to cars for a few Sundays every year and opens them instead to pedestrians and cyclists, primarily to foster better health and stronger communities. During one such event covering 16 kilometers of Downtown and East L.A. in October 2014, the researchers deployed pollution monitors, traffic monitors, and other instruments both on the CicLAvia route and, for comparison's sake, in the surrounding community. As an additional control, the team took measurements the Sunday before and after the street closures.
The researchers estimated that the CicLAvia event cut airborne fine particulate matter on the route by 49 percent during the day. And although the effect was less dramatic in surrounding communities, the event still improved air quality, as, overall, fine particulates went down 12 percent that day.
While their study is small and preliminary, the researchers argue their findings point to the health benefits of shutting down streets to cars once in a while.
Quick Studies is an award-winning series that sheds light on new research and discoveries that change the way we look at the world.