Pierce Greenberg is making the invisible visible, mapping air quality across rural counties in South Carolina. The data can help policymakers and health care providers spot patterns — and protect communities from potential risk.
On a hot midsummer day, Pierce Greenberg stands in a watermelon field in Blackville, South Carolina, surveying the landscape. He has come here to affix an air quality sensor — no bigger than a coffee mug — to a tree pole 8 feet high. As he sets the pole, connects the power source and secures the sensor, he stops to consider how the device looks almost insignificant against the vast backdrop. Small but mighty, he thinks.
An assistant professor in Clemson University’s Department of Sociology, Anthropology and Criminal Justice, Greenberg spent the months leading up to this moment traveling the state, conducting spatial analyses and assessing air-quality uncertainty in rural communities across South Carolina. This installation marks the first step toward change.
Air may be invisible to the human eye, but these small sensors bring the unseen to life, translating air quality into a discernible, evolving color-coded map. From green to maroon, varying hues detail the quality of the air people breathe every day.
Soon, data will begin to stream in, and patterns will emerge; seasonal trends will take shape, and invisible pollutants will become visible. Each reliable data point will fill a gap in knowledge that could influence community planning and public health efforts in rural South Carolina.
With guidance from environmental engineering Associate Professor Andrew Metcalf and the Clemson Air Quality Lab, Greenberg worked to install eight more sensors across the state last summer. Attached to fence posts, satellite poles and gutters at six Clemson Extension sites, two Clemson Rural Health locations, and one Research and Education Center, the mug-sized sensors have been collecting vital environmental data for rural communities.
A mighty job indeed.
Rural Communities, Colors Fade
Across urban America, air quality sensors are the norm for monitoring pollution in real time. Data is collected by commercial-grade sensors in densely populated areas and translated into color-coded maps to inform citizens and government agencies about harmful pollutants, such as ground-level ozone pollution and atmospheric particulate matter (PM2.5) — or smog, dust, soot and smoke.
The color codes align with the Air Quality Index guidelines set by the U.S. Environmental Protection Agency (EPA). Data points with satisfactory air quality are green, and air quality decreases as the colors change from green to yellow, then orange, red, purple and finally maroon.
“In South Carolina, we have a good sense of what real-time air quality looks like near Greenville, Columbia and Charleston, but beyond the city limits, the picture begins to fade,” says Greenberg.
Across the state, only one nonmetropolitan county has a government-sponsored air quality sensor, so air quality and pollution in rural areas are calculated based on the distances between urban air sensors. Limited monitoring infrastructure means fewer sensors and fewer localized readings. On an air quality map, this absence appears as empty space — wide stretches without color or accurate data.
According to Greenberg, the implications of invisibility can be misleading.
“Empty space on the map does not necessarily indicate clean air; it often indicates a lack of resources,” he explains.
Data maps are powerful communication tools, and this lack of visual representation has practical consequences. Maps translate complex measurements into accessible visuals, allowing citizens, health care providers and policymakers to quickly interpret patterns and risks.
“When rural areas are missing from the visual landscape of environmental data, they are also missing from the broader public conversation about air quality and health,” says Greenberg.
Small Sensors Fill Large Gaps
By placing sensors in rural communities, Greenberg provides the communities with accurate data to determine seasonal patterns, occupational exposures, and human and animal health risks. The data from these sensors allows community members to accurately assess, understand and respond to the air they breathe.
Manufactured by PurpleAir, Greenberg’s sensors use two laser counters to measure air pollution, temperature, humidity and barometric pressure. Metcalf and students in the Clemson Air Quality lab calibrate each sensor to ensure its accuracy and comparability with other public data sources.
Through his research, Greenberg focuses on the geographic distribution of environmental risks and benefits. He identifies geographical disparities to address environmental and human health challenges.
Greenberg’s air quality project was funded by the Clemson Faculty Succeeds (CU SUCCEEDS) program, a competitive internal funding initiative that positions faculty to succeed at various stages of the research process. He and Metcalf were awarded seed funding to collect pilot data for a project that integrates place-based environmental data with other data sources to improve exposure estimates at the community and individual level. The project aims to advance the knowledge and understanding of environmental exposures on health outcomes and to inform intervention and prevention strategies across South Carolina and the nation.
But it is the lived experiences of individuals in rural communities that provide the foundation for Greenberg’s work. Conversations with residents and local leaders are what shape the trajectory of his research endeavors. Along with the data, their stories fuel his determination to advance knowledge, inform policy, guide health care decisions and ultimately strengthen the environmental health of communities nationwide.
“When Clemson University research can partner with county Extension offices to invest in rural communities, it creates meaningful impact by generating valuable data — such as air quality insights — that protect public health, support agriculture and strengthen local livelihoods through more informed, sustainable decision-making,” says Karissa Ulmer, district Extension director for the Savannah Valley.
Visibility Promotes Safety
While Greenberg’s current work focuses on measuring and mapping air quality specifically in rural communities, an earlier research study examined a different but related question: Are environmental crimes more or less likely to be prosecuted in communities with higher pollution levels?
The study did not find a clear relationship between higher pollution levels and prosecution, but it did reveal that prosecutions occur unevenly across communities based on socioeconomic status. The findings suggested that many communities — particularly those with fewer health resources, as is common in rural areas — remain more vulnerable to environmental harm, not necessarily because violations are more frequent but because enforcement depends on both detection and response.
Both studies underscore the importance of access to information. If air pollution is not measured and mapped, it is far more difficult for communities and agencies to mitigate and respond to harms. Also, if environmental crimes are not documented and mapped, it is more difficult for regulatory agencies to allocate resources and prosecute offenders.
Together, the two studies point to the same challenge: visibility.
“Some environmental violations do not affect a single place,” says Greenberg. “Crimes may span multiple counties, occur offshore or happen digitally, as environmental tax violations. Without detailed maps to depict crime rates and locations, it is difficult to understand where environmental accountability is being applied.”
To fill the information gap, Greenberg worked with a team of undergraduate researchers in the Clemson University Center for Public Safety Research to review case summaries of crimes prosecuted by the EPA between 2011 and 2020. For each of the nearly 1,000 cases, the team identified the crime’s location and unique characteristics.
The result was one of the first efforts to place environmental prosecutions on a national map.
Environmental Mapping Reflects Clemson’s Mission
The air quality project addresses gaps in environmental monitoring, particularly in rural areas where sensors and data have historically been sparse. The environmental prosecution project fills gaps in understanding where environmental crimes occur and how laws are enforced across communities.
Ultimately, both projects are built on the same foundation: The relationship among people, communities and the environment begins with access to reliable information. Through the visualization of data, Greenberg and his collaborators are equipping citizens, researchers and public officials with information to better understand the places where environmental protection is strongest — and where more attention may still be needed.
In that way, the work reflects Clemson’s land-grant mission. By combining research, community engagement and practical tools for decision-making, Greenberg’s work ensures that knowledge does not remain confined to academic journals. Instead, it flows outward — into South Carolina communities — where it can inform policy, strengthen environmental and public health, and provide individuals with reliable data to “see” the air they breathe.
Shelley Gordon ’10 is the public information director for the College of Behavioral, Social and Health Sciences.
