Study shows air quality from ultrafine particles extends further than demonstrated by previous research
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The study, published May 29, 2014, in the journal Environmental Science and Technology (ES&T) and conducted with University of Washington (UW) researchers, found a doubling of ultrafine particle number concentrations extended east more than 10 miles downwind from the airport boundary over a 20-square mile area, encompassing communities including Lennox, Westmont, parts of South L.A., Hawthorne and Inglewood, and, in certain wind conditions, areas south of LAX.
“Our research shows that airport impacts extend more than 5 times further than previously assumed,” said Scott Fruin, D. Env., lead researcher and assistant professor of preventive medicine at the Keck School of Medicine of USC. “Effects from planes that are landing appear to play a major role in this large area of impact.”
To put this large area of impact into perspective, the researchers calculated that one-quarter to one-half of the entire L.A. County freeway system produces an equivalent increase in ultrafine particle numbers on a concentration-weighted basis.
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| Graphic depicting ultrafine particle increase downwind of LAX relative to urban background air quality |
“LAX may be as important to L.A.’s air quality as the freeway system,” said Fruin. “The impact area is large, and the airport is busy most hours of the day. That makes it uniquely hard for people to avoid the effects of air pollution in affected areas.”
Most previous research on the air quality impacts of airports focused on measuring air quality near where jet takeoffs occur. Takeoffs produce immense plumes of exhaust but only intermittently, and pollution concentrations downwind have been observed to fall off rapidly with distance. The assumption has been that total airport impacts also fall off rapidly with distance. The new research finds that this assumption is wrong.
The study found that concentrations of ultrafine particles were more than double over 20 square miles compared to background concentrations in nearby areas outside the area of LAX impact. Also, ultrafine particle number concentrations four times higher than background extended a distance of six miles.
“Given the existing concern about the possible health effects of urban ultrafine particle levels, living in an area with two to four times the average L.A. levels of ultrafine particles is of high public health concern,” said first author Neelakshi Hudda, Ph.D., research associate in preventive medicine at the Keck School.
Ultrafine particles are currently unregulated, but are of concern because they appear to be more toxic than larger particles on an equal mass basis in animal and cellular studies, and because they appear able to enter the bloodstream, unlike large particles that lodge in the lungs.
The research team used vehicles equipped with special measurement devices to capture data not available using traditional fixed monitors. The team was able to take moving measurements for more than 5 hours under consistent wind conditions to fully capture the extent of the impact boundaries.
“Other airports generally have less steady wind directions, which would make these measurements more difficult,” said Hudda. “Similar impacts are probably happening, but their location likely shifts more rapidly than in Los Angeles.”
“The on-shore westerly winds cause this impact regularly in communities east of LAX, because the impact’s location corresponds to the wind direction,” Hudda added. “In the winter months, when the winds were different, impacts were measured south of the airport during northerly winds.”
The research was funded by the National Institute of Environmental Health Sciences.
UW researchers included Tim Larson, Ph.D. and Tim Gould, Ph.D. in the Department of Civil Engineering, and Kris Hartin, Ph.D. in the Department of Environmental and Occupational Health Sciences.
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Hudda, N., Gould, T., Hartin, K. Larson, T.V., and Fruin, S. A. (2014). Environmental Science and Technology, Published online May 29, 2014; dx.doi.org/10.1021/es5001566
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