Mich. Comp. Laws § 418.535
If an employee's disability is caused by a combination of silicosis or other dust disease, or arose in the course of employment in the logging industry, and other compensable causes, a worker's compensation magistrate shall apportion the amount of disability between that due to silicosis or other dust disease, or to employment in the logging industry, and other compensable causes. The trustees of the silicosis, dust disease, and logging industry compensation fund shall reimburse the employer liable for compensation for that portion of compensation paid in excess of $12,500.00 for personal injury dates before July 1, 1985, and for all compensation paid in excess of $25,000.00 or 104 weeks of weekly compensation, whichever is greater, for personal injury dates after June 30, 1985, that the silicosis or other dust disease disability, or disability arising out of and in the course of employment in the logging industry, bears to the total disability.
MCL 418.535