New Research from the Yale Center for Climate Change and Health Bridges the Gap in Understanding NO₂ Exposure Disparities

We had the opportunity to interview Dr. Lingzhi Chu, a postdoctoral associate at the Yale School of Public Health and lead author on a paper published in One Earth this July. Dr. Chu explained findings on the health impacts of nitrogen dioxide (NO₂) exposure and disparities across different demographic segments, and shared a new research brief for policymakers created by the Yale Center for Climate Change and Health. The project received funding from the Yale Planetary Solutions Grant Program in 2023.

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Nitrogen dioxide (NO₂) is a common pollutant produced mainly from the combustion of fossil fuels in cars, power plants, and industrial facilities. Although NO₂ levels have gone down in the United States, long-term exposure has still been linked to higher risks of respiratory and cardiovascular problems. Critically, there has been a gap in understanding about how exposure to NO₂ affects different people differently. Without this knowledge, air quality and healthcare policies might miss the opportunity to protect those who are most at risk. 

In the new study, the research team, including members from the Yale School of Public Health, evaluated how NO₂-related health impacts vary across US counties based on race, ethnicity, and income. Communities experience different levels of exposure to pollutants like NO₂, and a higher level of exposure can be a driving factor in illness. But people also respond to exposures differently, meaning that two people exposed to the same amount of a contaminant could have different health outcomes. In other words, some people are more susceptible to the pollutant than others. 

“There are many drivers that lead to susceptibility, and one thing is someone’s baseline health condition,” explained Dr. Chu. “If a person has a chronic comorbidity, we would expect them to be more susceptible. Another example is access to health care. If someone has symptoms and health care is more accessible, that person might have better health outcomes than someone without that access.” 

The study is unique in that it evaluated the intersection of both kinds of disparity. Using 34 million death records, the research team found that the increased risk of mortality from NO₂ exposure could last for up to two and a half years, with significant differences in susceptibility and exposure levels across racial and ethnic groups. In addition, previous studies primarily focused on all-cause mortality or diseases that have been considered climate-sensitive, like respiratory or cardiovascular ailments. The new research indicates that the health impacts of NO₂ extend further, causing multi-organ damage due to systemic inflammation and oxidative stress.

In addition to identifying broader health impacts, the team’s findings demonstrate the complex interplay between socio-economic factors and environmental health. The results emphasize that for NO₂, targeted interventions and policies based on location and exposure sources are critical. Key conclusions and recommendations about NO₂ exposure weave together the two population factors and the two types of disparity evaluated.

For example, in high-income counties, non-Hispanic Black individuals face an all-cause mortality rate of 69.67 deaths per 100,000, more than three times that of their non-Hispanic White counterparts. With this knowledge, policymakers are empowered to prioritize solutions like low-emission zones around residential areas or affordable preventative healthcare for these communities.

Another example is that the most affected groups varied by location in high-income counties. Using this insight, environmental agencies can allocate resources efficiently using maps that overlay pollution data, health outcomes, and demographic information to target enforcement around populations that are most impacted. 

“I think the main take home message is that there is not a single solution that fits all the conditions,” said Dr. Chu. “Solutions should be location-specific, cause-specific, and population-specific. We’ll need more refined strategies and actions to address the many adverse impacts.”

Along with Kai Chen, Faculty Director of the Yale Center on Climate Change and Health, Dr. Chu wrote a research brief that provides an overview of the findings. It includes a series of “points for policymakers,” designed to inform non-scientists about the impacts of NO₂ and how to consider both exposure and susceptibility disparities in public health strategies. 

Looking ahead, the team hopes to illuminate short-term health impacts and explore NO₂ pollution at finer spatial resolutions, such as zip code or census tract levels. They also intend to examine additional socio-economic indicators, such as education level, to gain a more comprehensive understanding of the drivers of disparity.

The research highlights the need for NO₂ pollution interventions that consider the unique vulnerabilities of different communities. With the team’s focus on creating accessible information for policymakers and healthcare providers, the insights from this study offer a path for knowledge generated at Yale to increase the quality of life for communities across the country. Yale Planetary Solutions is proud to be a part of research like this that proposes solutions to urgent global challenges, including catalyzing research-informed environmental and public health policy that improves the health of people and the planet.  

Learn more about the Yale Planetary Solutions Grant Program.