Efficiency of automotive cabin air filters to reduce acute health effects of diesel exhaust in human subjects

Objectives-To evaluate the efficiency of different automotive cabin air fil ters to prevent penetration of components of diesel exhaust and thereby red uce biomedical effects in human subjects. Filtered air and unfiltered dilut ed diesel exhaust (DDE) were used as negative and positive controls, respec tively, and were compared with exposure to DDE filtered with four different filter systems. Methods-32 Healthy non-smoking subjects (age 21-53) participated in the stu dy. Each subject was exposed six times for I hour in a specially designed e xposure chamber: once to air,once to unfiltered DDE, and once to DDE filter ed with the four different cabin air filters. Particle concentrations durin g exposure to unfiltered DDE were kept at 300 mu g/m(3). Two of the filters were particle filters. The other two were particle filters combined with a ctive charcoal filters that might reduce certain gaseous components. Subjec tive symptoms were recorded and nasal airway lavage (NAL), acoustic rhinome try, and lung function measurements were performed. Results-The two particle filters decreased the concentrations of diesel exh aust particles by about half, but did not reduce the intensity of symptoms induced by exhaust. The combination of active charcoal filters and a partic le filter significantly reduced the symptoms and discomfort caused by the d iesel exhaust. The most noticable differences in efficacy between the filte rs were found in the reduction of detection of an unpleasant smell from the diesel exhaust. in this respect even the two charcoal filter combinations differed significantly. The efficacy to reduce symptoms may depend on the a bilities of the filters investigated to reduce certain hydrocarbons. No acu te effects on NAL, rhinometry, and lung function variables were found. Conclusions-This study has shown that the use of active charcoal filters, a nd a particle filter, clearly reduced the intensity of symptoms induced by diesel exhaust. Complementary studies on vehicle cabin air filters may resu lt in further diminishing the biomedical effects of diesel exhaust in subje cts exposed in traffic and workplaces.