Air pollution raises mortality risk, worsens lung function in fibrotic ILD

In patients with fibrotic interstitial lung disease, exposure to small particulate matter was linked to increased mortality, poor lung function and faster disease progression, according to a study in JAMA Internal Medicine.

Further, sulfate, ammonium and nitrate elements in the air — which researchers called byproducts of industrial and transportation activities — had the worst harm on this patient population, according to researchers.

Gillian C. Goobie

“The majority of studies of [particulate matter 2.5 m or less in diameter (PM_2.5)] health effects have not evaluated the impact of PM_2.5 composition on outcomes,” Gillian C. Goobie, MD, PhD, FRCPC, who just completed her PhD in the department of human genetics at the University of Pittsburgh School of Public Health, told Healio. “This work indicates that composition matters to a substantial degree in this vulnerable population of patients with fibrotic interstitial lung disease, highlighting the need to investigate compositional associations in other chronic disease and general populations. These findings may influence future policy and regulatory interventions to mitigate the harmful impacts of human-derived sources of pollution.”

In a multicenter, international, prospective cohort study, Goobie and colleagues evaluated 6,683 adults (55% men; median age, 66 years; range, 58-73; 84% white; 6.5% Asian; 3.1% Black) with fibrotic ILD from three registries — Simmons Center for Interstitial Lung Disease Registry at the University of Pittsburgh, the Pulmonary Fibrosis Foundation Registry and the Canadian Registry for Pulmonary Fibrosis — between June 1, 2021, and Aug. 2, 2022. Researchers aimed to observe how PM_2.5 exposure was related to mortality and lung function. In order to observe associations of PM_2.5 exposures of 8 m/m³ or greater in the 5 years prior to censoring (ie, before death, lung transplant or cessation of follow-up), researchers used multivariable Cox models for mortality and linear mixed models for lung function.

Median follow-up was 2.9 years, during which 28% of the population died and 10% underwent lung transplant.

According to researchers, increased mortality with a PM_2.5 exposure of 8 m/m³ or higher was observed in all three cohorts but varied in each location. Specifically, for those in the Simmons cohort, the hazard ratio for mortality was 4.4 (95% CI, 3.51-5.51); in the Pulmonary Fibrosis Foundation cohort, the hazard ratio was 1.71 (95% CI, 1.32-2.21); and in the Canadian Registry for Pulmonary Fibrosis cohort, the hazard ratio was 1.45 (95% CI, 1.18-1.79).

Goobie told Healio this was initially a surprising finding before they found that differences in patient exposures to human-derived sources of PM_2.5 explained the variability.

“We found that patients in our Simmons cohort, who are primarily recruited from Western Pennsylvania, exposed to high PM_2.5 (above the 8 g/m³ American Thoracic Society annual recommended threshold for exposure) had approximately 440% increased risk of death as compared to their counterparts with annual exposures less than 8 g/m³,” Goobie said. “In contrast, the mortality risk was only approximately 45% higher for the high-exposure group in our Canadian cohort as compared to the low-exposure group. Our Western Pennsylvania patients were exposed to much higher levels of these anthropogenic PM_2.5 pollutants, and these pollutants seemed to be driving the greater mortality impact.”

In every cohort, researchers found that higher exposure to sulfate, ammonium and nitrate PM_2.5 elements in particular were linked to worse baseline lung function and a higher risk for mortality, with ammonium (HR = 50.99; 95% CI, 2.46-1,056.64) and nitrate (HR = 3.78; 95% CI, 2.3-6.2) showing increased risk for mortality by meta-analysis.

Meta-analysis also showed sulfate, ammonium and nitrate to be linked to worsening lung function as demonstrated by decreasing rates of both FVC and diffusion capacity of carbon monoxide.

According to Goobie, these results indicate that clinicians need to talk about the significance of air quality with their patients.

“It is important to know about what levels of exposures an individual may have accumulated throughout their lifetime and what their exposure risk is now,” Goobie said. “Clinicians should be helping to provide their patients with the tools and resources they need to monitor air quality where they live. We should be teaching our patients about how to modify their behavior during poor air quality days (ie, exercising indoors rather than outdoors, keeping windows closed). We should also be acting as partners to our patients in advocating for cleaner air and better environmental policies that protect the health and well-being of all people.”

“Without [the contributions of the patients from each of the registry studies], we would not be on this path to finding a cure for pulmonary fibrosis or making the quality of the air safer for everyone to breathe,” Goobie added.

For more information:

Gillian Goobie, MD, PhD, FRCPC, can be reached at goobiegc@upmc.edu or gcgoobie@alumni.ubc.ca.

Reference:

Air pollution from factories and vehicles linked to worse outcomes for patients with lung disease. https://www.eurekalert.org/news-releases/967859. Published Oct. 17, 2022. Accessed Oct. 20, 2022.