Occupational diseases are a result of repetitive and continuing effects of certain conditions in an area of an occupancy over a period of time. Within a code of Occupational Health and Safety, it is being defined as, "a disease resulting from an exposure to occupational risk factors." There are certain lists being made to reveal occupational diseases with an aim of getting rid of unjust treatments resulted from the conditions that take place during a course of an occupation but that are not being proven to be an occupational disease. Any kind of metal, whose amount is out of certain limits, shows toxic effects on humans' health. In Group A, occupational diseases related to chemical substances take place. Their importance on humans' health comes from their accumulation in tissues and possible synergistic effects. In addition to the particles inhaled from air, an accountable amount of metallic particles is taken into the body through food and drinkable water. Lead, arsenic, nickel, mercury metals and solvents, like benzene etc. are found commonly in the atmosphere and so important due to their negative effects on humans' health. Things that differ occupational diseases from occupational-work accidents are the following: the cause of an occupational disease is continuous, the occupational disease is progressive, and the starting date of the occupational disease cannot be certainly determined. With this study, it is being aimed to approach occupational diseases from a perspective of forensic sciences.