University of Mississippi researchers have linked exposure to high levels of black carbon in the air to an increase in respiratory-related hospital admissions in Mississippi's capital city, according to a study published in Environmental Pollution.
Courtney Roper, assistant professor of environmental toxicology, found in a 2023 study that Jackson's air contains the state's highest concentration of black carbon, commonly referred to as soot. In a new study published this summer , her team found that this pollutant may be contributing to a rise in hospital visits for respiratory issues among older adults.
"We can see that there is a connection between respiratory issues – particularly for women – and these exposures," she said. "The thing that we, as Mississippians, can take right now from this research is that our environment impacts our health."
Black carbon is a component of PM 2.5 air pollution – pollutants whose particles are 2.5 microns or smaller, which is approximately 30 times smaller than the diameter of a human hair. PM 2.5 pollutants have been linked to increased risk of cancer, heart attacks, strokes and lung disease.
Some 4 million deaths worldwide are attributed to long-term exposure to PM 2.5 air pollution.
"There are many studies that show black carbon is associated with health problems," said Hang Nguyen, postdoctoral research associate in the School of Pharmacy. "It is very small in size, so it can go deep into your lungs and actually pass into your bloodstream."
Black carbon pollution is created while producing energy for homes and commercial areas through coal, wood or fossil fuel burning, and by transportation and industrial emissions, according to the Climate and Clean Air Coalition .
By combining air quality data with emergency department visits and hospitalization rates for respiratory-related issues from Medicare between 2014 and 2015, the researchers were able to show a positive correlation between exposure to black carbon and the likelihood of a hospital visit.
"When we saw black carbon increases, we also saw an increasing rate of hospitalizations," Nguyen said. "At 1.42 micrograms per cubic meter of black carbon in the air, there was a 1.3% increase in the rate of respiratory admissions."
This was particularly true for women, who experienced higher rates of respiratory hospital visits associated with increases in black carbon levels, the research found.
"A higher percentage of women were going to the hospital because of this," Roper said. "When we layer in that pollutant data, we can see that effect. It's more likely that a woman is at risk following exposure to a pollutant."
While biology can explain some of this difference – particularly, because women's airways and organs tend to be smaller than men's – the reason black carbon disproportionately affected women remains unclear.
The season and temperature can also play a role in how air pollutants affect hospitalizations, the researchers found. Unlike black carbon, PM 2.5 was not linked to increased hospitalizations year-round, though springtime spikes did coincide with higher asthma-related hospital admissions.
"That could be related to pollen, traffic emissions or a combination of airborne irritants," Roper said. "We were also surprised to find that colder temperatures led to increased hospital visits — not immediately, but 10 to 25 days later.
"That could be tied to winter illnesses or people spending more time indoors with poor ventilation."
The team's next step will be to look at similar black carbon and PM 2.5 exposure data paired with cardiovascular hospitalizations or admissions, Roper said. The new study also will focus on Jackson.
"When I came to the University of Mississippi, I was surprised by how little air quality research was being done here, especially given our health disparities," she said. "So, it's been an intentional choice to focus on this state and this population.
"We do work with other states as well, but a lot of our focus has been here because it's our air, too. We want to understand the air we're breathing."
