This appeal concerns a dispute between two workers' compensation insurance carriers as to which is liable for the payment of disability compensation to Arthur Smith, Jr., a worker who suffered successive injuries while working for different employers. Alaska Pacific Insurance Company was the carrier for M-K Rivers, Smith's employer at the time he was initially injured. Industrial Indemnity Company of Alaska was the carrier for United Asphalt Paving, Smith's employer at the time of his most recent injury.
After a hearing on Smith's application for disability benefits, the Alaska Worker's Compensation Board filed a decision concluding that United Asphalt, Industrial Indemnity's insured, was liable for the disability compensation here in dispute. That decision was affirmed in superior court. The Board's findings of fact and conclusions of law are set forth here, for they present a factual background and demonstrate the necessity of a remand.
It is apparent that the Board's decision was based solely on a finding that Smith's previous disc rupture had been aggravated by an injury occurring while he was employed by United Asphalt. This was an insufficient basis for holding United Asphalt liable.
In Ketchikan Gateway Borough v. Saling, 604 P.2d 590 (Alaska 1979), we adopted the "last injurious exposure rule," which "imposes full liability on the employer at the time of the most recent injury that bears a causal relation to the disability." 604 P.2d at 595 (citing 4 A. Larson, The Law of Workmen's Compensation § 95.12 (1979)). Under this rule there are two distinct determinations which must be made: (1) whether employment with the subsequent employer "aggravated, accelerated, or combined with" a pre-existing condition; and, if so, (2) whether the aggravation, acceleration or combination was a "legal cause" of the disability, i.e., "a substantial factor in bringing about the harm." 604 P.2d at 597, 598; see also Fluor Alaska, Inc. v. Peter Kiewit Sons' Co., 614 P.2d 310, 312-13 (Alaska 1980). Unless both of the above questions are answered in the affirmative, the subsequent employer is not responsible for the employee's disability compensation.
Here the Board failed to answer the question as to causation. It is entirely possible that Smith's employment with United Asphalt aggravated his pre-existing back injury but was not a substantial factor in bringing about his disability. We must therefore remand this case to superior court with directions to remand to the Board for additional findings in accordance with this opinion. The Board shall reopen the evidence if it deems it necessary.
REVERSED and REMANDED.