Measuring Houston’s environmental injustice from space


Juan Flores is a longtime resident of Galena Park, an eastern suburb of Houston, who “smelled all kinds of chemicals” in the air of nearby industrial facilities.

“I’m probably going to get cancer as I get older just because I live here,” Flores, manager of the nonprofit organization’s community air monitoring program, Houston Airline Alliance, told EHN. “If it’s not refineries, if it’s not traffic, it’s something else.”

Earlier this month, the Houston Health Department reported that high levels of formaldehyde, a known carcinogen, were prevalent in Galena Park and other predominantly black and Latino neighborhoods.

“Air pollution is… an invisible killer,” Bakeyah Nelson, executive director of Air Alliance Houston told EHN, “And communities of color and working-class neighborhoods have really been the dumping ground for [high-polluting] facilities. “

But tracking exactly which areas of Houston face the highest pollution loads is nearly impossible using America’s air monitoring system. Even in a city like Houston, which has a unique network of air quality monitors, pollution hot spots can easily be missed due to constraints on how many monitors are present and where they are allowed. to be installed.

And this disproportionately affects marginalized communities, which are much more likely live near sources of pollution. Thus, a team of researchers used satellite data to measure these disparities. They found that nitrogen dioxide (NO2) levels –related to higher rates of childhood asthma, increased hospitalizations and development of cardiovascular disease – were 32% higher for Latino residents, 19% higher for black residents and between 15 and 28% higher for living residents below the poverty line.

Additionally, those who are marginalized by both race and income experienced the worst air quality and saw 37% higher NO2 pollution, on average. But “in some cases we’ve seen inequalities of up to 85%,” Sally Pusede, assistant professor of environmental science at the University of Virginia and lead author of the study, told EHN.

The research highlights the limitations of our nation’s air monitoring network and the persistent racial divide in pollution exposure, but also suggests that measuring air quality from space may help identify environmental injustices and create policies specifically targeting high pollution areas.

Ineffective air pollution monitoring

“In some cases we’ve seen inequalities of up to 85%,” said lead author Sally Pusede, pictured here in 2016 (Credit: Dan Addison /

The Texas Commission on Environmental Quality (TCEQ) monitors Houston’s air and operates one of the most robust surveillance networks in the countryside. According to the agency’s website, it includes “more than double” the number of monitors typically required by the Environmental Protection Agency.

But “even cities that have a lot of these monitors don’t have enough coverage,” Tracey Holloway, professor of environmental studies at the University of Wisconsin-Madison, told EHN. They are expensive, costing around $ 100,000 to install and $ 25,000 per year to maintain, so “there is a limit to how many they can fund in a particular state or city,” she said. .

In Houston’s case, that means just 3% of its residents live within 1.25 miles of an air monitor, Pusede calculates. She also points out that this equipment may not always be found in areas with the highest pollution.

There are a lot of criteria that dictate where these monitors are placed: is there enough power for it to work? Is the site easy to access? Do you want to know the average air quality in the city or how a pollutant can change when it moves downwind?

Unfortunately, balancing all of these requirements, cities like Galena Park often end up with just one air monitor, even though its nearly 11,000 residents live right next to the heavily polluted Houston Ship Channel, one of the most heavily polluted waterways. busiest in the world.

This is why “there is a huge interest in using satellite data to understand these disparities,” Holloway said. Because not only can this data fill in the gaps between monitors, but it can potentially help link it to issues surrounding health and justice.

Measuring air pollution disparities from space

If you’re in Houston at 1:30 p.m., look up and say hello. At that time, the European Union’s satellite, Sentinel-5P, will fly overhead carrying the TROPOspherical monitoring instrument (TROPOMI). Since the end of 2017, TROPOMI has been measuring the variation in NO2 concentrations on our planet. “They measure almost everywhere, every day,” Pusede said.

“For free,” added Holloway, who was not involved in this study.

Plus, unlike its ground cousins, its measurements span a much larger area with far fewer data gaps. It was because of these characteristics that Pusede and the study’s first author, Mary Angelique Demetillo, thought it would be interesting to test whether TROPOMI could see how NO2 was changing between neighborhoods in Houston.

They first compared the spatial measurements with air quality data collected a few years earlier by plane. After confirming that the two measurements matched well, they then used TROPOMI to determine where the highest concentrations of NO2 were in the Houston area. Between June 2018 and May 2019, they identified hot spots of this pollutant in central Houston and the Houston Ship Channel to the east, both areas primarily home to working-class people of color.

“This is another study that shows blacks and brunettes are disproportionately exposed to air pollution,” said Nelson, of Air Alliance Houston.

The future of space measurements

Other cities are often in a worse air watch position than Houston. “Most areas don’t have any monitoring data, and even if they do, it can be an entire city,” Holloway said. That is why she thinks the study by Pusede and Demetillo is promising. “Instruments like TROPOMI can really play a role in characterizing the differences between neighborhoods … and a better understanding of those disparities.”

Pusede agrees, which is why she and her team have already used TROPOMI data to measure pollution disparities in 52 other U.S. cities. The results of this new study are currently under peer review.

In addition, technology will improve. TEMPO, which stands for “Tropospheric Emissions: Monitoring Pollution”, is another satellite instrument that will measure NO2 pollution, just like TROPOMI, but can do so hourly, for all of North America. “With the launch of TEMPO in a few years, we are really going to have quite powerful observation constraints on [how pollution can vary across cities]”said Pusède.

However, these spatial instruments are not perfect because their data can be difficult to use and interpret. “It’s not like everyone needs a PhD to analyze the data,” Holloway said, but there is still a long way to go before it can be easily used for regulatory purposes by agencies. environmental, like TCEQ, or by defense organizations, like Houston Air Alliance.

Work on ground air pollution remains

Holloway, who also runs the NASA Applied Health Sciences and Air Quality Team, tries to solve this problem by making his team become an accessible point of contact for organizations – “from large to small, technical or non-technical” – who wish to learn how to use satellite data.

“We are really trying to make the data more useful and relevant,” she said. And when that happens, Air Alliance Houston will likely be one of the first groups to use it.

“We have everything to gain from having more data in order to continue to argue that this is a serious problem impacting the lives of people every day,” said Nelson of Air Alliance Houston.

In the meantime, however, the organization is doing its best on the ground. “We are working with community leaders and community organizations to install [low-cost] air monitors to expand the city’s surveillance network, ”she said.

While this particular type of air monitor is generally considered to be less accurate than those used by TCEQ, it can still give local residents an idea of ​​how much pollution is present near their homes.

Flores, who is overseeing this initiative, has already installed three of these monitors in Pasadena, an eastern suburb of Houston much larger than Galena Park which also has only one regulatory monitor.

“It’s up to us to have our own defense,” said Flores, “We’re trying to capture data so that we can show them ‘Hey, this is what’s going on.'”

Banner photo: 2014 aerial view of the Houston Ship Channel and surrounding energy facilities in Houston, Texas. (Credit: GPA / flickr photo archive)

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