Notwithstanding subsection (a), benefit payments under this section to a miner or his widow, child, parent, brother, or sister shall be reduced, on a monthly or other appropriate basis, by an amount equal to any payment received by such miner or his widow, child, parent, brother, or sister under the workmen’s compensation, unemployment compensation, or disability insurance laws of his State on account of the disability of such miner due to pneumoconiosis, and the amount by which such payment would be reduced on account of excess earnings of such miner under section 203(b) through (l) of the Social Security Act [42 U.S.C. 403(b) to (l)] if the amount paid were a benefit payable under section 202 of such Act [42 U.S.C. 402]. This part shall not be considered a workmen’s compensation law or plan for purposes of section 224 of such Act [42 U.S.C. 424a].
Benefits payable under this part shall be deemed not to be income for purposes of the Internal Revenue Code of 1986.