An occupational disease is an illness which is caused by work-related conditions. It covers diseases which are medically proven to be associated with certain jobs. A chronic condition is identified as an occupational disease when it has been established to occur in a certain working population as compared to the general population.
For instance, hearing loss has been known to be associated with working in loud environments such as construction sites, airports, and nightclubs. Other examples include lung diseases among miners, skin allergies among health care workers, and PTSD among soldiers.