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Background: Increased susceptibility of smokers to ambient PM may potentially promote development of COPD and accelerate already present disease.

Objectives: To characterize the acute and subacute lung function response and inflammatory effects of controlled chamber exposure to concentrated ambient fine particles (CAFP) with MMAD <= 2.5 microns in ex-smokers and lifetime smokers.

Methods: Eleven subjects, aged 35-74 years, came to the laboratory 5 times; a training day and two exposure days separated by at least 3 weeks, each with a post-exposure visit 22 h later. Double-blind and counterbalanced exposures to "clean air" (mean 1.5 +/- 0.6 mu g/m(3)) or CAFP (mean 108.7 +/- 24.8 mu g/m(3)) lasted 2 h with subjects at rest.

Results: At 3 h post-exposure subjects' DTPA clearance half-time significantly increased by 6.3 min per 100 mu g/m(3) of CAFP relative to "clean air". At 22 h post-exposure they showed significant reduction of 4.3% per 100 mu g/m(3) in FEV1 and a significant DLCO decrease by 11.1% per 100 mu g/m(3) of CAFP relative to "clean air". At both 3 h and 22 h the HDL cholesterol level significantly decreased by 4.5% and 4.1%, respectively. Other blood chemistries and markers of lung injury, inflammation and procoagulant activity were within the normal range of values at any condition.

Conclusions: The results suggest that an acute 2 h resting exposure of smokers and ex-smokers to fine ambient particulate matter may transiently affect pulmonary function (spirometry and DLCO) and increase DTPA clearance half-time. Except for a post exposure decrease in HDL no other markers of pulmonary inflammation, prothrombotic activity and lung injury were significantly affected under the conditions of exposure.