There are numerous studies and publications on smoking and cancer risks.
Su-jok can point to several unpleasant moments about modern lifestyle:
--- cancer is related to Dryness energy growing from epithelium and
connective tissue
--- Dryness controls lungs and colon among inner organs, respiratory and
immune system
--- Dryness relates to negative emotions of grief, frustration, depression
So everything which weakens respiratory system directly harms everything related to
Dryness energy.