When an occupational disease is aggravated by any other disease or infirmity not itself compensable, or death or incapacity from any other cause not itself compensable is aggravated, prolonged, accelerated or in any way contributed to by an occupational disease, the compensation payable must be reduced and limited to the proportion only of the compensation that would be payable if the occupational disease were the sole cause of the incapacity or death as the occupational disease, as a causative factor, bears to all the causes of that incapacity or death, the reduction in compensation to be effected by reducing the number of weekly or monthly payments or the amounts of the payments as, under the circumstances of the particular case, may be for the best interest of the claimant or claimants. [PL 1991, c. 885, Pt. A, §8 (NEW); PL 1991, c. 885, Pt. A, §§9-11 (AFF).]