NEW RESEARCH: Estimating asthma incidence if air pollution levels had remained high and if the levels were lowered

Building off a recent study, our team of researchers had a study published this week in PNAS (Proceedings of the National Academy of Sciences of the United States of America). The study, looking at data from the Children’s Health Study 9 communities can be found here.

The research published earlier this year (Garcia et al. JAMA 2019) found strong associations between new-onset asthma in children and exposure to air pollutants, specifically NO2 and PM2.5. “We wanted to take these results a step further by estimating answers to ‘What-if’ scenarios, such as ‘What if the observed air quality improvements in the 1990s and early 2000s never happened?’ or ‘What if no one was exposed to more than 20 ppb NO2?’ This approach would provide us with an estimate of what would happen to asthma incidence rates in children given different shift in air pollution exposure,” said Erika Garcia, lead study author and researcher in the department of Preventive Medicine in the Keck School of Medicine.

9 southern California communities from the Children’s Health Study featured in this research paper. Map background layer: Google Maps.
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NEW RESEARCH: Improved air quality leads to fewer kids developing asthma in nation’s most-polluted region

By LEIGH HOPPER, USC

PRESS COVERAGE: National Public Radio, Reuters,

Improved air quality in the Los Angeles region is linked to roughly 20 percent fewer new asthma cases in children, according to a USC study that tracked Southern California children over a 20-year period.

The findings appear in the May 21 issue of the Journal of the American Medical Association.

The research expands on the landmark USC Children’s Health Study, which found that children’s lungs had grown stronger in the previous two decades and rates of bronchitic symptoms decreased as pollution declined throughout the region.

“While the findings show a clear benefit of lower air pollution levels, there must be continued efforts to reduce pollution in our region,” said first author Erika Garcia, a postdoctoral scholar in the Department of Preventive Medicine at the Keck School of Medicine of USC. “We’re not in a place where we can stop and say, ‘Hey, we’ve arrived’.”

USC Infographic: Lower air pollution = less asthma
Graphic by Wendy Gutschow
Full study related infographic and printable PDF can be found here.

Los Angeles remains the nation’s most-polluted region, but air quality improvements between 1993 and 2006 cut nitrogen dioxide pollution by 22 percent and fine particulate matter by 36 percent.

Nitrogen dioxide can cause airway inflammation and airway hyper-responsiveness. Particulate matter — tiny particles of soot, smoke dust, etc. — can penetrate deep into the lungs and cause serious health problems.

To assess new-onset cases of asthma, USC scientists used data from 4,140 children in nine California communities: Alpine, Lake Elsinore, Lake Gregory, Long Beach, Mira Loma, Riverside, San Dimas, Santa Maria and Upland. Parents or guardians completed questionnaires regarding their children’s health. New-onset asthma was defined as a newly reported, physician-diagnosed case of asthma on an annual questionnaire during follow-up.

Researchers looked at rates of new-onset asthma alongside air pollution data collected from monitoring stations in each of those communities during three different periods: 1993-2001, 1996-2004 and 2006-2014. Using statistical methods, they separately examined four air pollutants and found that two were associated with reductions in new-onset asthma. They estimated that the nitrogen dioxide reductions achieved between 1993 and 2006 led to a 20 percent lower rate of asthma, while fine particulate matter reductions led to a 19 percent lower rate.

The findings add to the increasing scientific evidence supporting the role of air pollution in the development of new cases of asthma. Asthma is the most common chronic disease in children, affecting about 14 percent of children around the world, and a major contributing factor to missed time from school and work.

“This is encouraging news as it shows the number of new cases of asthma in children can be reduced through improvements in air quality,” said Kiros Berhane, a professor of preventive medicine at the Keck School of Medicine of USC and one of the study’s authors. “This is very likely a direct result of the science-based environmental policies that have been put in place.”

In addition to Garcia and Berhane, the study’s other authors are Talat Islam, Rob McConnell, Robert Urman, Zhanghua Chen and Frank Gilliland, all of the Department of Preventive Medicine at the Keck School of Medicine.

The research was supported by the National Institute of Environmental Health Sciences (grants P30ES007048, P01ES009581, R01ES021801, and R01ES025786), the National Heart, Lung and Blood Institute (grant R01HL118455), the United States Environmental Protection Agency (grants R826708 and RD831861), and the Hastings Foundation.

Airport pollution linked to acute health effects among people with asthma in Los Angeles

by Wendy Gutschow

A recent research study by Dr. Rima Habre took a detailed look at the short-term health impacts caused by breathing in ultrafine particulate (UFP) matter that is emitted from aircraft activity at the Los Angeles International Airport (LAX). Several years ago, USC researchers identified a clear pattern of UFP emissions from takeoff and landing aircraft activities at LAX. Levels of the dangerous UFPs were found to be 4 to 5 times greater than background levels in downwind communities.  “Ultrafine particulate matter is known to contribute to reduced lung function, and airway inflammation in individuals with asthma. We wanted to take a close look at short term effects on health when individuals breathe air that contains UFPs from airplanes,” said Habre. The study participants were made up of adults with doctor diagnosed asthma.

Rima Habre holds an ultrafine particle monitor monitor while a plane flies overhead. Photo courtesy of Something in the Air documentary.

Dr. Rima Habre has been with USC for five years. Dr. Habre’s expertise lies in air pollution exposure assessment, analyzing patterns of how people get exposed to air pollution across time and space and studying how specific pollutants impact their health.  

Recently Dr. Habre’s work reached the international stage through a documentary, produced by the Canadian Broadcasting Company, called Something in the Air.  “The producers were very interested in learning more about our latest work around air pollution and asthma – specifically around the latest technologies we are using to better understand the impacts of small particles on a personal level – in children and adults with asthma, and in pregnant women.” Dr. Habre was interviewed about her work around ultrafine particle exposures downwind of major airports and its effects on asthma, as well as her work to understand how children’s personal exposure to air pollution predict their risk of experiencing an asthma attack. Something in the Air will be released this week in Canada, with an international release to be announced.

Airport-related ultrafines affect health differently than traffic-related ultrafine particles

Habre and her team designed this study to test the short-term effects of breathing ultrafine particles by asking study participants to walk in a Los Angeles park located within the known higher levels of UFPs emitted from airplanes and near heavily trafficked roads, and another park farther away from the airport and busy roads with lower levels of UFPs.

The map above shows the two parks where the study took place. The grey shaded area shows the approximate location of the plume of ultrafine particles created by air traffic around LAX, that usually occurs when the winds are blowing steadily from the West.

“In our study, we found that inhaling UFPs led to higher inflammation in the blood in adults with asthma shortly after exposure. However, different inflammation markers responded to aircraft-related versus traffic-related UFPs – both of which are major ultrafine particle sources in dense urban areas. We were able to see these different signals because we managed to overcome the challenge of separating the air pollution mixture into its major sources using sophisticated measurements and modeling techniques,” said Habre.  The pollutants measured by the study included UFP particle number, particle size, black carbon, carbon dioxide, particle-bound polyaromatic hydrocarbons, and ozone.

The significance of Habre’s study is that in such a short time, following regular walking exposure and a higher exposure, they were able to see significant elevation in inflammation systemically, not just in the lungs but in the overall blood circulation. Inflammation is tied to a lot of disease processes; cardiovascular, respiratory, and metabolic. “We don’t know specifically what this inflammation will lead to down the line, but we know that inflammation is generally a bad thing, and will complicate or exacerbate existing conditions. Ideally, we would have liked to have been able to monitor people long-term to see if that inflammation persists or if it goes down after a while but we were not able to do that in this specific study, that’s a future direction of this research I’d like to look at,” said Habre.

When asked what this research means to the overall population, Habre described the current body of research that has found ultrafine particles to be much more toxic than the larger sizes of particulate matter, UFPs are not regulated, and UFPs impact large numbers of people who live in communities surrounding airports.

Ultrafine particulate matter research: future directions

Dr. Habre also leads environmental exposure assessment efforts in multiple research studies being conducted at USC, including the MADRES study of pregnant women and babies and the LA DREAMERs study of children’s health across the life course, and in partnership with other research groups such as the Los Angeles PRISMS Center, a UCLA/USC partnership.  Her work in the Los Angeles PRISMS Center is taking a deeper dive into the different sources of air pollution asthmatic children encounter in their day to day lives in Los Angeles and how it impacts their health.  This study focuses on personal experiences, using Bluetooth-enabled wearable sensors to monitor environmental exposures, location, activity, medications and symptoms, to ultimately generate new information to help predict and prevent asthma attacks. To learn more about the Los Angeles PRISMS Center, watch this video: https://www.youtube.com/watch?v=-m72NkwolgU&feature=youtu.be

As she moves forward with her research on the health effects of ultrafine particulate matter in urban areas, Dr. Habre plans to build on her current work by studying how people with asthma are affected, as well as those who are obese, have diabetes, or cardiovascular issues. “I would like to be able to capture a wider variety of sources of ultrafines in urban areas and also be able to monitor individuals for a longer period of time to really understand what happens next. In this study we saw very quick and acute effects, but do people tend to recover after a day? I think the ultimate goal would be to really understand if people living in these high exposure locations, for extended periods of time, and breathing this mixture in regularly are at a significantly higher risk or not,” she said.


For more information on the “Something in the Air” documentary that Dr. Habre’s work is featured in, on the documentary’s website: www.somethingintheair.ca. Once the documentary is released in the United States, USC Environmental Health Centers will publish the release date and viewing information.

Rima Habre, Hui Zhou, Sandrah P. Eckel, Temuulen Enebish, Scott Fruin, Theresa M. Bastain, Edward B. Rappaport, and Frank D Gilliland, 2018. Short-term effects of airport-associated ultrafine particle exposure on lung function and inflammation in adults with asthma. Environment International. https://doi.org/10.1016/j.envint.2018.05.031

Funding: This study was funded by the Southern California Environmental Health Sciences Center (National Institute of Environmental Health Sciences, P30ES007048) pilot program, NIEHS grants 1R01ES023262, 1K22ES022987, 1R01ES027860, and the Hastings Foundation.