Editor's note: This article has been updated with more data on how the pollution levels have changed.

Research shows the Greater Houston area’s air quality improved amid the coronavirus pandemic, but a Houston-area organization said air quality in communities located near major industrial sectors still needs attention.

Houston Advanced Research Center, an environmental research organization, published a report in late April showing that several common pollutants in Harris County decreased from March 11-April 13 compared to historical data. The pollutants were ground-level ozone, nitrogen oxides, or NOx, and a group of volatile organic compounds, or VOCs, comprised of benzene, toluene, ethylbenzene and xylenes, or BTEX.

Data for the pollutants were collected from monitoring stations maintained by either the Texas Commission on Environmental Quality or the Environmental Protection Agency, depending on the pollutant.

What the levels mean

Mustapha Beydoun, chief operating officer and vice president of HARC, said the lowering of these three pollutants was partially due to stay-at-home orders limiting people’s mobility as well as reduced industrial production across the Houston region.

"It's better with respect to NOx, it's better with respect to VOC, and it's definitely better with respect to ozone, which in our region is really the most important air pollutant," he said. "That improvement we're primarily seeing because of the reduction in emissions from the transportation sector, mainly because of the stay-at-home orders."

Harris, Montgomery and Brazoria counties saw more than 30% reductions in average distance traveled during the outbreak, according to HARC's mobility analysis report. Meanwhile, Fort Bend and Galveston counties saw at least a 40% reduction in distance traveled during the same time, per the data.

Data showed that ground-level ozone concentrations decreased an average of 16% on weekdays and 17.5% on weekends from March 11-April 13 compared to a historic six-year trend over the same time period. Saturdays experienced the most drastic reduction with 34% on average. The 20 ozone monitoring stations were located mostly within Harris County, with four of them in Brazoria, Montgomery and Galveston counties. BTEX emmissions saw a 39% drop and nitrogen oxides saw a 46% drop in the same time period.

“It’s kind of a double victory for us because a significant portion of our VOC emissions also come from transportation, so you’re removing the NOx, [and] you’re removing the VOC," he said.

Why it matters

Prior to the pandemic, the Greater Houston area's air quality—specifically for ground-level ozone concentration—was given a nonattainment designation per National Ambient Air Quality Standards, Beydoun said.

“Houston does have an air quality problem, specifically with respect to ozone,” he said. “With air quality, ... the lower the concentration, the better, because that means it’s less of that pollution in the air. The less pollution it is and the less exposure, the less problematic it is from a public health perspective."

However, he said the Houston region has made great strides toward better air quality in recent decades.

Bakeyah Nelson, executive director of nonprofit Air Alliance Houston, which advocates for cleaner air, said despite pollutants decreasing across the region during the pandemic, there are still specific Houston-area neighborhoods that are dealing with chronic air quality issues. Communities of color and low-income neighborhoods that are adjacent to large industrial facilities are particularly vulnerable to high levels of pollutants, she said.

"Regional improvements for air quality don't necessarily translate to neighborhood-level improvements in air quality—particularly for communities that are directly adjacent to industrial facilities," she said.

While HARC's report used data from six of the EPA's BTEX monitoring stations near the Houston Ship Channel, Nelson said regulatory agencies need to install more air monitoring stations across the Houston area to get a better idea of air quality standards on a local level.

According to HARC's report, BTEX emissions primarily come from refineries, petrochemical plants, vehicle emissions and evaporative losses from fuel storage tanks.

"We have many air monitors, comparatively speaking, in the Houston region, but we have such a density of industrial facilities throughout our region that we don't have near the amount of air monitors that we need," she said. "We don't really have a sense of whether air quality has improved at a neighborhood level."