Children's lungs are growing substantially stronger as air pollution in Southern California decreases.

The Los Angeles area had struggled with air pollution for decades. But, according to new research published this month in the New England Journal of Medicine, recent local air quality improvements appear to have led to a positive shift in children's respiratory health. All told, researchers observed a 10% increase in lung growth in children between the ages of 11 to 15 compared to previous groups in their ongoing Children's Health Study (CHS).

Perhaps most interestingly is that the improvement was independent of other factors including race/ethnicity, gender, and other air pollution source factors (for example, the presence of a smoker in the child's home). In other words, the 10% lung development improvement appear to be solely the result of decreased nitrogen dioxide (NO2) and fine particulate matter (PM2.5) air pollution levels in the area.

In turn, this research has revealed an interesting example of how reducing air pollution from transportation and industry can have a significant, positive impact on public health in a relatively short time frame.

Air pollution in Los Angeles as viewed from the Hollywood Hills by Diliff.

Outdoor Air Quality and Energy in Los Angeles

Southern California is famous for high levels of outdoor air pollution due to the large motor vehicle fleet, numerous industrial facilities, and large seaport combined with a topography that helps trap pollution in the Los Angeles basin. According to the U.S. Environmental Protection Agency:

"The [Los Angeles area] is home to many diverse industries. In spite of emission controls that are among the most stringent in the country, power generation and petroleum refining continue to be among the basin's largest stationary sources of air pollution."


"The significant expansion of trade with Asia has increased the importance of the shipping industry as a major economic engine [in Los Angeles], resulting in higher emissions. One of EPA's highest priorities is to support the reduction of diesel emissions from ships, trucks, locomotives, and other diesel engines. We also are working with state and local partners to decrease emissions from port operations and to improve the efficient transportation of goods through the region."

According to the American Lung Association's State of the Air 2014, Los Angeles has the worst smog and the 3rd worst particulate matter pollution in the state. However, the Association notes that improvements are being realized as state and local programs help to decrease air pollution from, in particular, diesel vehicles and industry.

The Children's Health Study (CHS)

The CHS appears to confirm the statements made by the State of the Air 2014, which is not a surprise given the plethora of existing evidence linking air pollution from transportation and other sources to negative public health impacts.

But, this research substantially adds to the community's understanding of the degree to which this pollution can harm the nation's children by inhibiting healthy lung development. In the words of the study's leader, Professor W. James Gauderman:

"Lungs develop very rapidly from age 11 to 15 and when children are done growing - which is toward the end of their teen years - that is really the most lung function that they will have for the rest of their lives. An important criteria that is used by physicians to diagnose respiratory disease is whether or not lung function is below 80% of what is should be. And when we looked at that outcome, we saw that half as many children fell below that criteria if they were breathing cleaner air in the 2000s, compared to their cohorts who were breathing more polluted air back in the in the 1990s."

Conducted by researchers at the University of Southern California, the ongoing study's latest batch of results document large gains in lung development in children between the ages of 11 and 15 from 2007 to 2011 compared to children of the same age in the same communities from 1994-98 and 1997-2001. At the same time, researchers observed significant air quality improvements in terms of both NOx and PM2.5 levels.

The study itself has been on-going for more than 20 years, with an initial cohort of children being recruited in 1992. To date, the study has included three cohorts of children (1994-1998, 1997-2001, and 2007-2011) with 2,120 children in each group. The project's goal is to help to improve our understanding of the long-term effects of air pollution on repiratory health in children. Researchers have collected data on the health, exposure to air pollution, and other factors that affected their physical response to air pollution levels from school-aged children living in 16 communities across the Los Angeles basin.

Photo credit:

1. Photo of air pollution in Los Angeles and the Griffith Observatory, as viewed from the Hollywood Hills by Diliff.

2. Graphic and map from the University of Southern California