Oct. 6, 2021
In the hottest parts of the city, how polluted is the air?
Researchers, including VCU’s Stephen Fong, will add local air pollution measurements to climate maps of Richmond.
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Extreme heat is unpleasant and unhealthy. So is polluted air. How — and where — are these two problems connected in Richmond, Virginia?
Stephen S. Fong, Ph.D., a chemical and life science engineering professor at Virginia Commonwealth University who helped develop the first ground-based heat vulnerability map of Richmond, has a new target: air pollution hot spots.
Fong and collaborators, including those at the Science Museum of Virginia, the University of Richmond and volunteers from various Richmond-based organizations, are working to expand and update that map by adding measurements of two forms of air pollution: particulate matter — tiny pieces of soot and other contamination — and ozone.
The groundbreaking efforts to develop the award-winning heat map, which demonstrated the urban heat island effect with details down to the neighborhood and street level, gained national attention in discussions about the hottest parts of cities in modern times and the legacy of redlining policies.
Redlining refers to 1930s federal policies of identifying specific neighborhoods as undesirable and, therefore, too risky an investment for mortgage lenders. The risk level was largely determined by the number of Black or immigrant households. To this day, redlined neighborhoods continue to struggle with higher concentrations of poverty and lower rates of home ownership. In addition, urban areas where nonwhite residents are in the majority tend to be hotter.
To better understand what, in addition to extreme heat, could be impacting the health of residents in various neighborhoods, VCU and others have begun measuring air quality.
Ground-level ozone, or smog, is formed when sunlight interacts with other pollutants (nitrogen oxides and volatile organic compounds) that are released into the air from industrial plants and motor vehicles. A lung irritant, ozone is associated with respiratory problems.
On a recent sweltering day, Fong was among the many volunteers who fanned out across the city at 6 a.m., 3 and 7 p.m. to collect readings for temperature, particulate matter and ozone. They used two devices, one for ozone and one for particulates. Both devices use a light or laser, plus a sensor, for detection and measurement.
The ozone sensor took measurements every 10 seconds during each of the hourlong sampling routes, providing 360 data points per route. “This was done three times a day, so a single route logged 1,080 data points,” Fong said. “We then had particulate matter sensors doing the same thing, and we had 12 different routes. We're easily talking about tens of thousands of data points collected during the data campaign.”
Each of the data sets can be viewed individually on a map, but the actual data analysis is much more involved, Fong said. “Even though we have the different data collection routes covering as much of the city as possible, we are not directly measuring every square inch of the city,” he explained. For this reason, Fong also uses statistical modeling based on measured data to predict values for areas that were not measured directly.
“This is the way we're able to get a broader idea of what the entire city looks like and the effect of specific features such as buildings, trees, etc.,” he said.
Final analyses from this study are still in progress. Fong expects that “we'll find a good number of areas where poorer air quality matches areas with elevated surface temperatures. He is also curious to find out if there are areas where the two don't match. In that case, the researchers will investigate whether those areas might have other features that improve airflow.
Fong said he would expect areas such as busy roadways with diesel trucks to have higher levels of ozone. “Neighborhood to neighborhood variation is so important,” he said. “We don’t really know for certain how much variation there is — is it actually affecting people’s health from one location to another?”
The effects of seemingly minor increases in air pollution are multiplied because of their cumulative effect. In addition, he said, elevated temperatures can directly affect ozone concentrations because of the chemistry involved.
The resulting impacts on air quality could be particularly dangerous to brain health. Scientists have seen an increase in cognitive decline in people who live in areas where they have prolonged exposure to particulate matter, Fong said.
“There's growing evidence that long-term exposure to elevated levels of air pollutants can lead to noticeable cognitive impairment.”
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