Exposure to diesel exhaust harmful to former smokers with COPD

Former smokers with COPD may be more susceptible to inflammatory responses to short-term exposure to moderate concentrations of diesel exhaust than former smokers without COPD or healthy never smokers, researchers reported.

“To date, it is unclear whether or not short-term exposure to traffic-related air pollution, as is typically found in congested urban areas, elicits a distinct inflammatory response in the lower respiratory tract of COPD patients; no study has directly samples bronchoalveolar lavage in those with COPD in this context nor whether such responses are different from those of healthy individuals,” Min Hyung Ryu, MD, postdoctoral research fellow in the Channing Division of Network Medicine at Brigham and Women’s Hospital and Harvard Medical School, and colleagues wrote in the American Journal of Respiratory and Critical Care Medicine.

Min and colleagues conducted a double-blind, controlled human crossover exposure study that enrolled 30 participants (mean age, 60 years; 45.4% women). Ten participants were former smokers with mild to moderate COPD, nine were former smokers and healthy, and 11 were never smokers and healthy. All participants were exposed to filtered air as a control and diesel exhaust in washout-separated 2-hour periods.

Researchers collected bronchoalveolar lavage via bronchoscopy performed 24 hours after exposure, performed cell counts on blood and airway samples as well as enzyme-linked immunosorbent assays to measure acute inflammatory proteins, matrix proteinases and anti-proteases.

Former smokers with COPD had increased serum amyloid A and matrix metalloproteinase-10 in bronchoalveolar lavage when exposed to diesel exhaust (P = .04 for both). The same increases were not seen in former smokers without COPD or never smokers.

In addition, exposure to diesel exhaust increased circulating lymphocytes, irrespective of COPD status (P = .03), according to the researchers.

“Our data suggest that exposure to short-term moderate concentrations of diesel exhaust may be more harmful to former smokers with COPD compared with those without COPD, given the differential response in relevant markers as detailed in our results,” the researchers wrote.

The researchers noted several limitations of the study, including its small sample size.

“In the global fight against pollution, human exposure studies are critical in providing key mechanistic insights to support legislation for public health protection and to shed light on future prevention and therapeutic approaches to protect those who are more susceptible from the harmful effects of air pollution,” the researchers wrote.