A new study by Harvard and Esri researchers has determined that air quality has generally improved across the US since 2000. But it has not improved equally for everyone – namely Black, Asian, Latinx, and low-income populations.
The results show that diminished air quality is common in low-income and ethnically diverse ZIP codes suggesting environmental injustice could be a key reason for air quality disparities. Areas where people have fewer tools and money to fight injustice result in a lack of enforcement, regulation, and remediation.
The maps above show air quality levels for primarily Black ZIP codes (right) and primarily white ZIP codes (left). The top maps show PM2.5 levels in the year 2000, while the bottom maps show PM2.5 levels in the year 2016. Notice how, between the years 2000 and 2016, majority-Black ZIP codes saw air quality improve from less healthy red levels to acceptable lime green levels. Meanwhile, majority-white ZIP codes saw air quality improve from red to the optimal dark green levels, marking the most significant air quality improvement. In 2016, the average PM2.5 concentration for the Black population was 13.7% higher than that of the white population. These maps show that while air quality is improving overall across the US, the rate of improvement is not equal and varies based on the racial makeup of an area.
Similar disparities were observed when comparing income-level. The maps above show PM2.5 levels for low-income communities (right) and high-income communities (left). The tops maps show PM 2.5 levels for the year 2000 and the bottom maps show PM2.5 levels for the year 2016. Notice that, between the years 2000 and 2016, air quality in low-income communities improved from being in the dangerous red range to the acceptable lime green range. Meanwhile, air quality in high-income communities improved from the dangerous red range to the optimal dark green range, making the amount of improvement much greater for high-income communities. While air quality did improve for both communities, these maps suggest that the income of a ZIP code plays a strong role in the amount of air-quality remediation an area receives.
Even as air quality is improving, it is not improving equally for all people.
Most notably, the results also show that as the Black population increased within a ZIP code, the amount of PM 2.5 particles also increased. This was especially true in ZIP codes where more than 85 percent of the population was Black, with a similar trend observed for Latinx populations. However, the opposite trend was observed for predominantly white ZIP codes. As the white population increased in a ZIP code, the amount of PM2.5 in the air decreased.
Dominici said seeing the disparities on maps was key to helping readers of the study understand the dire situation, pointing to the partnership with Esri as being particularly helpful.
“By working with Esri, not only have we kept this paper at a very high level of scientific rigor, which is important, we have also taken many steps forward by being able to communicate and visualize our results,” she said.
Anyone can capture the disparity pattern easily from our maps and animations.
The study was created to be easy to understand for all people, rather than being statistically complicated, Dominici explained.
“The more accessible we make our results, the higher the impact they’re going to have. It’s not about pointing fingers or agreeing and disagreeing. It’s about being able to visualize and see. Look at the data,” she said, throwing up her hands in emphasis.
Dominici urged people with a GIS and statistics background to download the data and look at the code, which will allow them to see step-by-step what was done and potentially apply the team’s methodology to other situations, “not only in the context of air pollution but also in the context of weather, pesticides, climate change, and more.” In addition to open access to the team’s code, supplemental videos are available that show how the team created each map. The study’s code and data can be found here.
“People that live in both clean-air areas and dirty-air areas, now have the visualization of maps combined with a peer-reviewed paper in Nature to advocate for change,” said Dominici. “By keeping the study simple, everyday people can engage with the figures and use them to push for targeted legislation in their area.”
The data can also be downloaded, and individuals can look up their ZIP code to see the disparities in their own community.
“It’s really about mobilizing the entire community to advocate for change,” said Dominici.