Additional file 10. Medical examination of the welders. Medical examination of the welders with lower airway symptoms during the previous month, including skin prick test positivity for a standard panel of aeroallergens, methacholine test (MCH) positivity, and lung function (FVC and FEV1 as % of predicted) at the baseline examination before the study. MMP9 concentration (fmol/ÂľL) and lung function (FVC and FEV1 as % of predicted) before and after exposure to welding fume particles (A) or filtered air (B). N/A: no data could be obtained due to missing samples.