Could it be asbestos related on the inhaled substance?
The description seems consistent with an insult on the lung interstitium. The interstitium is the supporting structure of the lung - it does not participate in air exchange. The insult could be infection, immune-mediated inflammation, an inhaled irritant. If you are not feeling anything now - you probably had a previous infection.
General advice would include: If you are a smoker - best to quit. If you have an occupation which involves an inhaled substance that may irritate the lung- best to take some precautions.