Health effects of a subway environment in mild asthmatic volunteers.

Particle exposure is known to have negative health effects. In Stockholm the environment in the subway has been reported to have higher particle exposure levels, measured as PM(2.5) and PM(10), than roads with intense traffic in the inner city area. We have recently shown that healthy volunteers exposed to subway environment had statistically significant increase of fibrinogen and CD4 cells expressing regulatory T-cell marker CD25(bright)/FOXP3 in blood. The aim of the present study was to find out whether a more vulnerable population, asthmatics, would demonstrate similar or other changes in the lungs or in the peripheral blood. Sixteen mild asthmatics were exposed to a subway and a control environment for 2 h while being monitored by measurements of lung function, and inflammatory response in the lower airways evaluated by bronchoscopy and in peripheral blood. An attempt to standardize the exposures was done, by letting the volunteers alternate 15 min intervals of moderate exercise on a bicycle ergometer with 15 min of rest. We found a statistically significant increased frequency of CD4 cells expressing T-cell activation marker CD25 in bronchoalveolar lavage fluid, but no significant increase of regulatory T-cells in blood as was found in healthy volunteers. Our study shows that airway inflammatory responses after exposure in subway environment differ between asthmatic and healthy humans.