Particulate matter collected in the homes of current and former smokers indicate the houses of these individuals are a potential environment for bacterial growth and biofilm formation, according to recent research presented at the American Thoracic Society meeting in Dallas.

“The pulmonary health effects of air pollution particulate matter (PM) are well documented in epidemiological studies; however, the health effects of indoor air pollution remain less understood, especially in susceptible populations such as those with COPD,” Emma Stapleton, PhD, from the Internal Medicine/Pulmonary and Department of Occupational and Environmental Health at the University of Iowa in Iowa City, IA, and colleagues wrote in their study abstract.

Meeting presentation. Source: Getty

The researchers conducted a pilot study of particulate matter collected from 21 homes of individuals who are current or former smokers and had either a history or no history of respiratory exacerbations. They studied bacterial growth and biofilm formation in vitro with the PM samples.

Dr. Stapleton and colleagues found enhanced bacterial growth from PM (120% to 203%) and biofilm formation (414% to 1,597%) across all houses regardless of smoking or exacerbation status when compared with a field blank control. The researchers found 48% of samples contained bacterial colonies, and there were 13 identified and 18 unidentified pathogens in the samples.

Regardless of exacerbator status, there was no differential effect of bacterial growth or biofilm formation between groups. Individuals with no pulmonary exacerbations were more likely to own pets or cats (P ≤ .05), smoked fewer packs per year (P = .07) and used fewer aluminum pans (P = .11) than individuals with pulmonary exacerbations, researchers said. In 12 PM samples, there was impaired bacterial killing from airway surface liquid (ASL), while 2 samples had enhanced impaired bacterial killing from ASL, and researchers noted a trend towards impaired ASL bacterial killing in homes of individuals with respiratory exacerbation.

“The results of our pilot study demonstrate that exposures to indoor PM enhance bacterial growth and biofilm formation, and potentially affect airway innate immunity,” the researchers said.

When testing the metals in the PM samples, the researchers discovered copper, aluminum and magnesium at low doses were responsible for impaired ASL bacterial killing, while copper at doses of > 10-5 mol were responsible for dose-dependent bacterial killing. “When metals were combined to proportions typical in the house-dust samples, bacterial killing profiles were different, indicating individual metals cannot explain results,” Dr. Stapleton and colleagues concluded.