Odds for COVID-19 increase with long-term air pollution exposure

Key takeaways:

• As 5-year exposure levels to nitrogen dioxide and PM_2.5 increased, so did the likelihood for COVID-19.
• In patients with COVID-19, higher nitrogen dioxide exposure was linked to elevated antibody titers.

Elevated exposure levels to nitrogen dioxide and fine particulate matter over 5 years raised the odds for COVID-19, according to results published in Respiratory Medicine.

“While we were not able to address mechanisms directly, the finding of an association with long-term pollutant exposures suggests that susceptibility to SARS-CoV-2 viral infection is increased through chronic effects on some or all of the following: local respiratory immune modulation, epithelial permeability, airway remodeling, potentially together with systemic immune dysfunction, including immune senescence,” Hajar Hajmohammadi, MSc, PhD, senior data analyst at Queen Mary University of London, and colleagues wrote.

Using serological data from the large, population-based COVIDENCE UK cohort, Hajmohammadi and colleagues assessed 10,489 individuals (median age, 62.3 years; 70.3% women; 95.6% white) to determine how 5-year exposure to nitrogen dioxide and fine particulate matter with an aerodynamic diameter of 2.5 μm (PM_2.5) or less are each linked to odds for a SARS-CoV-2 infection and COVID-19 symptom severity.

Researchers collected every individual’s postcode to estimate yearly average exposures to each pollutant and adjusted for several potential confounders (age, ethnicity, educational attainment, urban living, etc) during logistic regression analysis.

Notably, 84.8% of individuals lived in a city or a town, whereas fewer individuals lived in a rural area (6.9%) or a conurbation (8.36%).

A small proportion of the total cohort received a positive test for SARS-CoV-2 antibodies (n = 1,621; 15.5%).

As exposure to 5-year nitrogen dioxide went up, so did the odds for seropositivity for SARS-CoV-2 (adjusted OR = 1.092 per 10 μg/m³ increase in nitrogen dioxide; 95% CI, 1.02-1.17; P = .012). Researchers also observed heightened odds for seropositivity with each 10 μg/m³ rise in 5-year PM_2.5 (aOR = 1.65; 95% CI, 1.015-2.68; P = .049).

Based on quintiles of nitrogen dioxide exposure, researchers noted significantly higher adjusted odds for seropositivity among those with levels between 15.8 μg/m³ and 19.5 μg/m³ (aOR = 1.31; 95% CI, 1.09-1.58), between 19.6 μg/m³ and 25.8 μg/m³ (aOR = 1.28; 95% CI, 1.07-1.54) and between 25.9 μg/m³ and 87.8 μg/m³ (aOR = 1.31; 95% CI, 1.08-1.59) vs. those with levels between 1.8 μg/m³ and 12 μg/m³.

The lowest quintile of PM_2.5 exposure was between 3.1 μg/m³ and 8.5 μg/m³, and the only quintile with significantly heightened odds for seropositivity was the highest one with levels between 10.3 μg/m³ and 15.7 μg/m³ (aOR = 1.35; 95% CI, 1.11-1.63).

Similar to the single pollutant models, researchers found that each increase in nitrogen dioxide and PM_2.5 by 10 μg/m³ raised the odds for seropositivity in a bi-pollutant model (nitrogen dioxide, aOR = 1.074; 95% CI, 0.984-1.172; PM_2.5, aOR = 1.214; 95% CI, 0.984-1.172).

When evaluating the adjusted odds for heightened COVID-19 symptom severity in relation to increases in each air pollutant, no significant link was found between these two factors.

As an additional outcome, researchers evaluated the link between 5-year exposure to each pollutant and antibody response in those who contracted COVID-19. PM_2.5 exposure was not linked to antibody titers, but there was a significant relationship between increased nitrogen dioxide exposure by 10 μg/m³ and elevated antibody titers (P = .011).

“These findings highlight the importance of reducing air pollution for mitigating the transmission and severity of COVID-19, as well as other respiratory infections and noncommunicable disease,” Hajmohammadi and colleagues wrote.