Dust (250-300µg/m3), Ozone (0,1ppm ozone),Dust+ozone (250-300µg/m3 + 0,1 ppm ozone), Filtered air (<20µg/m3). with at least 2 weeks between each exposure session to eliminate hang‐over effects. The filtered air and dust and ozone contaminated sessions will be identical except for the air quality. The exposures are unknown to the participants and staff to keep the study double blinded. The blinding will be continued until the basic statistical analyses have been conducted.