Heavy air traffic at LAX is contributing to pollution woes in Los Angeles.

Los Angeles is no stranger to pollution. The city recently topped the list of cities that have the worst ozone pollution in the U.S.

Poor air quality with high levels of tiny particulate matter can lead to cardiovascular diseases. An estimated 9,000 people in California prematurely die due to particulate air pollution.

A new study from Keck School of Medicine and the University of Southern California suspected that at least a part of particle air pollution in the city was from the Los Angeles International Airport (LAX). Previous research has shown that people living near airports are exposed to ultra-fine particles the most. These particles get embedded in the lungs and can cause severe health problems. However, most of these studies measure particle pollution in areas that are close to the airports.

According to the researchers, heavy air traffic at LAX is causing worse damages to the residents' health than previously imagined. LAX is the sixth busiest airport in the world. During peak travel hours as many as 40 to 60 jets take off and land every hour at the airport.

For the study, researchers measured air pollution level 10 miles downwind of the airport for 29 days. Highly populated neighbourhoods flanked by major freeways were among the areas covered by the study team, according to a news release.

Their analysis found that LAX was a major contributor of particulate matter in Los Angeles. Particle number (PN) concentrations over a 23-square-mile area were double than the background concentration. Researchers define background concentration as the levels of particles in the absence of LAX. At two-square-mile area, the PN was ten times greater than background levels.

"Therefore, the LAX should be considered one of the most important sources of PN in Los Angeles," the scientists wrote.

The study was funded by the National Institute of Environmental Health Sciences and the Environmental Protection Agency and is published in the journal Environmental Science & Technology.