A. When an employee has an occupational disease that is covered by this title, the employer in whose employment he was last injuriously exposed to the hazards of the disease and the employer’s insurance carrier, if any, at the time of the exposure, shall alone be liable therefor, without right to contribution from any prior employer or insurance carrier.
B. For the purposes of this section, “injurious exposure” means an exposure to the causative hazard of such disease which is reasonably calculated to bring on the disease in question. Exposure to the causative hazard of pneumoconiosis for ninety work shifts shall be conclusively presumed to constitute injurious exposure.
C. The operator of a coal mining business covered by this title who acquires the business or substantially all of the assets thereof is liable for, and must secure the payment of, all benefits which would have been payable by the prior operator under this section with respect to persons previously employed by such business if the acquisition had not occurred and the prior operator had continued to operate the business; and the prior operator of the business is not relieved of any liability under this section.