Another special category is occupational diseases. At first no diseases were covered by the Act. Then only listed diseases were covered. Then all occupational diseases were covered but certain special conditions were laid down for the payment of compensation benefits in occupational disease cases. Most of those have been gradually taken out of the law.

Section 431 of the Act provides that if a worker "wilfully and falsely represents in writing that he has not previously suffered from the disease which is the cause of the disability or death," the employer is not responsible for workers' compensation benefits. There is no similar provision relating to specific injuries.

There are certain occupational diseases (and now injuries in certain industries) that are treated specially. Silicosis was a very frequent disease among foundry workers. When occupational diseases began to be covered by the law, there was concern that the foundry industry would go out of business if they had to pay full compensation. Accordingly the law was changed to provide special protection under those circumstances.

Under the present law, if a worker suffers from certain dust diseases or receives an injury while performing certain work in the logging industry, he or she receives exactly the same benefits as if the injury had occurred in some other way, but the employer receives special protection. After the first 104 weeks or the first $25,000, whichever is greater, weekly benefits are paid by the employer but the employer is reimbursed from a special fund to which all Michigan employers contribute.