I have low fev1 spirometry results; 68% predicted level. I am a 47 year old South East Asian male. Chest X-ray are normal. No shortness of breath, no coughing and I’m a non - smoker. I work in the mines so a very dusty environment. 5 years ago my fev1 spirometry results was 75% of predicted levels. So within 5 years, it’s gone down. What might be the possible causes of this? Lung infections, living in a polluted environment or etc? Thank you.