Occupational exposures to various dusts can cause disease of the lung of varying symptoms and severity. All such problems are increased in smokers and in malnourishment. Thus vitamins and antioxidants can help but most important is to avoid other smoke besides the occupational dust or chemicals. The best preventive at work would be a space outfit such as is used by technicians in the computer chip industry, or using well fitted masks/respirators of better quality. Otherwise miners of coal need to test the lungs every so often since different workers have quite different tolerances and only if one is shown to be deteriorating can one be sure that there is a problem and major correction is needed such as quitting that job. But the main advice is to avoid smoking.