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WASHINGTON -- Indoor nitrogen dioxide (NO₂) concentrations in homes with gas stoves were more than double those in homes with electric stoves in an analysis of U.S. environmental cohort studies.

Across seven such studies conducted largely in Baltimore from 2009 through 2022, gas stoves were also found to be a stronger predictor of higher indoor NO₂ levels than was gas heat, Hewlett Pham, BS, a post doc research assistant at Johns Hopkins Allergy and Asthma Center in Baltimore, reported here at the annual meeting of the American Thoracic Society.

The poster discussion session on the impact of environmental exposures on respiratory disease also highlighted new research on links to interstitial lung disease (ILD) and sarcoidosis.

Gas Stoves

In the environmental cohort studies included in Pham's analysis, indoor NO₂ was measured with passive Ogawa badge samplers left in the homes for approximately 1 week. The researchers used two-sided t-tests to quantify differences in mean indoor NO₂ concentrations between homes with gas and electric stoves.

A total of 64% (449 of 702) of participants reported having gas stoves. Weekly indoor NO₂ levels averaged 15.79 parts per billion (ppb) across all homes, but 20.89 ppb in homes with gas stoves compared with 6.74 ppb in homes with electric stoves (P<0.01).

Just over two-thirds (70%) of homes with gas stoves also had gas heat, but the analysis showed gas stoves to be strongly linked to NO₂ levels even in colder months when heating systems were on.

NO₂ is a reactive nitrogen species that is regulated as a pollutant in outdoor settings but not indoors. Some evidence points to indoor levels as impactful for human health as well, with studies linking elevated indoor NO₂ concentrations to increased respiratory morbidity, Pham's group noted.

"We found that across the board, gas stoves were associated with higher indoor NO₂ compared to electric stoves," said Pham. His group concluded, "Future studies are needed to define the impact of gas stove replacement on respiratory health and to assess [the] most feasible intervention strategies."

Interstitial Lung Disease Link

Sudarshan Bala, MD, of the University of British Columbia in Vancouver, presented a systematic review of 20 studies that examined the impact of air pollution exposure on ILD incidence and outcomes.

The studies were identified through a literature search of the databases Medline, EMBASE and the Cochrane Review.

"To our knowledge this is only the second-ever systematic review examining this topic," Bala said, adding that the newly reported analysis included more than twice as many studies as .

His group's review showed an increase in ILD incidence with greater levels of particulate matter exposure, while several studies showed harmful associations between gaseous pollutants and fine particle pollution (PM_2.5) and baseline and future lung function declines.

ILD exacerbation frequency was also elevated with greater gaseous and particulate pollutant exposures. Mortality, too, was increased with greater particulate pollutant exposure.

Since the studies included in the review were largely conducted in the U.S. and Canada, Bala said broader global studies are needed to further explore the impact of pollution exposure on ILD incidence and outcomes.

"We need more global data, as well as data exploring the interactions between various constituents of air pollution, specifically those that are human derived versus those that are environmental pollutants," Bala said.

Race and Sarcoidosis

Ali M. Mustafa, MD, and colleagues at Johns Hopkins School of Medicine in Baltimore, explored racial differences in exposure to ambient particulate matter and NO₂ among people with sarcoidosis.

In his poster presentation, Mustafa noted that Black patients with sarcoidosis experience higher rates of severe disease, hospitalization, and steroid use compared with white patients.

"We know that there are health disparities in sarcoidosis," Mustafa said. "We know that Black individuals do worse than white individuals with sarcoidosis, and we wanted to examine why this is and specifically investigate the possible role of air pollution on outcomes."

The retrospective study included 452 sarcoidosis patients with pulmonary function data. Multivariable linear regression was used to evaluate the association between pollution levels in patients' neighborhood of residence and their pulmonary function outcomes.

Compared with white patients with sarcoidosis, Black patients were exposed to higher median levels of air pollution (6.4 vs 4.6 ppb NO₂ and 11.5 vs 10.3 μg/m³ PM_2.5).

This higher exposure was associated with lower lung function on spirometry after adjustment for a wide range of potential confounders, including race, sex, tobacco use, duration of disease, Charlson Comorbidity Index, and Area Deprivation Index. The beta coefficient for diffusing capacity of the lungs for carbon monoxide percent predicted was 3.36 lower per interquartile range increase in PM_2.5 and 2.40 lower per interquartile range increase in NO₂, both of which were statistically significant.

"Given the number of things we looked into as possible covariants, I am fairly confident that air pollution contributed at least in some way to the disparities in pulmonary function outcomes in these patients," Mustafa said.