Home to some of the busiest runways in the world, the Los Angeles International Airport can have 40 to 60 planes taking off and landing each hour during peak traffic times. But that heavy air traffic produces serious smog that could pose health risks for residents who live nearby. Researchers analyzing the level of pollutants in the area found that within 14 kilometers of the airport, the number of particles in the air was five times higher than regions further out. And within 3 kilometers east of the facility, particle levels were nearly 10 times higher. The findings, published online today in Environmental Science & Technology, also include the discovery of ultrafine particles, which can block arteries and lead to asthma if inhaled.