What Do We Know About Long-Term Effects of Air Pollution on Health?

Researcher Chris Lim, M.S., investigates the health impacts of long-term exposure to air pollution and extreme temperatures, how diet could help and the future burdens of climate change on human health. 

In 2014, Chris Lim, M.S. set out to understand long-term effects of climate change—specifically, temperature variability and air pollution—on health. At the time, short-term effects had been studied extensively, but not much was known about long-term exposure and adverse health outcomes. As a lung health dissertation fellow at New York University School of Medicine, Lim needed financial support for his doctoral dissertation on this topic. The American Lung Association funded his research, which not only supported his dissertation but also helped open the door for Lim to broaden his work in this area.

Lim is now a postdoctoral associate at the Yale School of Forestry and Environmental Studies and has recently been published in two medical journals. Circulation, by the American Heart Association (AHA), published his study "Mediterranean Diet and the Association Between Air Pollution and Cardiovascular Disease Mortality Risk ." And the American Thoracic Society's (ATS) American Journal of Respiratory and Critical Care Medicine published another of Lim's studies, "Long-term Exposure to Ozone and Cause-Specific Mortality Risk in the U.S."

The first study concluded that a diet rich in antioxidants could help counteract the adverse cardiovascular health effects of long-term air pollution. The findings of the second study showed a significant association of long-term exposure to ozone and increased risk of death from heart and respiratory diseases.

We talked with Lim to learn more about his two recent studies and where his research is headed next.

Q: Tell us about your grant with the American Lung Association and how it helped support your work and ultimately the findings recently published in the AHA and ATS Journals?
A: I was a lung health dissertation fellow in 2014-2016, and the grant supported my doctoral dissertation on long-term temperature exposures and mortality risk.

It was my first grant ever and writing it was very helpful in organizing my ideas. It also allowed me to have some freedom and expand the scope of my research, which led to the findings published in AHA and ATS journals.

Q: How did you come to study the effects of diet and air pollution? Why the Mediterranean diet? Can you explain your conclusions?
A: I saw several news articles and studies that found that dietary interventions were helpful in mitigating adverse effects of short-term air pollution exposures. I decided to investigate the hypothesis that healthy dietary habits would also be protective against long-term air pollution exposures. The Mediterranean diet is enriched in foods full of antioxidants and anti-inflammatory compounds, and since air pollution causes adverse health impacts through oxidative stress and inflammatory pathways, I thought that a Mediterranean diet could provide protection.

In this study, a Mediterranean diet reduced the risk of heart disease death related to long-term exposure to air pollutants in a large prospective U.S. cohort. We concluded that eating more foods rich in antioxidant compounds (such as fruits, vegetables, and wholegrains) may help reduce the considerable disease burden associated with outdoor air pollution.

Q: Is that study linked to your study on ozone?
A: Yes, our study on ozone looked at the same cohort, the NIH-AARP Diet and Health Study [a large prospective cohort of more than half a million U.S. adults with 17 years of follow-up from 1995 to 2011.]

Q: What is ozone and what should people know about long-term effects on health?
A: Ozone (O3) is an outdoor air pollutant (sometimes called smog ) that is linked with various adverse health effects. For example, breathing ozone can trigger asthma, reduce lung function, and harm lung tissue. While there have been many studies that found links between short-term ozone exposure and various health effects (such as asthma, hospitalizations, death), studies looking at long-term effects on health have been very limited.

Long-term ozone exposure was significantly associated with an increased rate of cardiovascular and respiratory disease deaths in our study. This outcome suggests that we need federal standards for long-term ozone pollution to protect public health. While there are federal standards on daily ozone concentration levels, seasonal and annual standards do not currently exist.

Q: What role does climate change play in all this?
A; Since ozone concentration levels are driven by higher temperatures, ozone-related health impacts are projected to increase in the future due to climate change. In line with this, our study also found that respiratory disease mortality risk associated with long-term ozone exposure was elevated at higher temperatures.

Q: What are you working on now and what's next?
A: I am preparing a paper on long-term temperature exposure and mortality risk. I recently started as a postdoctoral researcher at the School of Forestry and Environmental Sciences at Yale University. I will research the potential health effects of exposure to greenspace (trees and parks)—whether it can lower the risks of mortality and cancer in adults and improve school performance and physical activity levels in children.

Want to learn more about the American Lung Association Research Team? Read about the pioneering researchers and studies we're currently funding.