In any case where compensation is payable for an occupational disease, the employer in whose employment the employee was last injuriously exposed to the hazards of such disease, and the insurance carrier, if any, which was on the risk when the employee was so last exposed under such employer, shall be liable.
For the purpose of this section when an employee has been exposed to the hazards of asbestosis or silicosis for as much as 30 working days, or parts thereof, within seven consecutive calendar months, such exposure shall be deemed injurious but any less exposure shall not be deemed injurious; provided, however, that in the event an insurance carrier has been on the risk for a period of time during which an employee has been injuriously exposed to the hazards of asbestosis or silicosis, and if after insurance carrier goes off the risk said employee is further exposed to the hazards of asbestosis or silicosis, although not so exposed for a period of 30 days or parts thereof so as to constitute a further injurious exposure, such carrier shall, nevertheless, be liable.