Last Injurious Exposure: What Does “Impossible” Mean?

Oregon Court Says “Impossibility” May be Established by Medical “Probability”

Oregon, like the majority of American jurisdictions, employs the “last injurious exposure” rule to assign liability among multiple employers in occupational disease cases. Under the state’s case law, a presumptively responsible employer may nevertheless shift responsibility to a prior employer by establishing that it was “impossible” for conditions at its workplace to have caused or worsened the disease. Parsing its words carefully, an Oregon appellate court recently reiterated that proof of “literal impossibility” is not what Oregon’s case law requires [Liberty Metal Fabricators, Inc. v. SAIF Corp. (In re Alcorn), 2019 Ore. App. LEXIS 154 (Jan. 30, 2019)]. An employer can show “impossibility” even where there is some question as to medical causation.

Background

Claimant, a sheet metal fabricator, worked for Lynch from 1996 to 2006, for Liberty from 2006 to June 2014, and again for Lynch from June 2014 until his retirement in November 2014. In February 2016, claimant sought treatment for hearing loss and filed an occupational disease claim with Lynch and then with Liberty.

At Lynch’s request, claimant was evaluated by an otolaryngologist who opined that claimant’s life-long occupational exposure to noise in the metal-fabrication industry was the major contributing cause of his hearing loss. Claimant had an audiogram in June 2014, before beginning his second period of employment with Lynch, and a second audiogram in April 2016, when he first saw the otolaryngologist. The doctor opined that there had been no appreciable change in claimant’s hearing loss during the second period of employment with Lynch and that it was impossible for claimant’s second period of employment with Lynch to have caused or contributed to his hearing loss.

Possible Change in Hearing During Subsequent Employment Stint

On cross-examination, the doctor admitted that it was possible that claimant had sustained a one decibel change in his hearing during his second period of employment with Lynch, but that such a loss was not measurable. Additionally, the doctor testified that a change of less than five decibels is disregarded as falling within “test-retest variability.”

Liberty contended that if, as the doctor acknowledged, there was a possibility of a contribution (although non-measurable or insignificant) to claimant’s hearing loss by claimant’s second period of employment with Lynch, then the evidence could not support the conclusion that causation by claimant’s second period of employment with Lynch was impossible. The Board disagreed and assigned liability to Liberty under the last injurious exposure rule. It acknowledged that employment conditions at the second Lynch employment were similar to claimant’s previous workplace exposures but found, based on the medical evidence, “that it was not possible that claimant’s last period of employment with Lynch caused or contributed to the hearing loss.”

Can “Impossibility” Be Established by Medical “Probability”

Liberty contended that the error was apparent in the Board’s phrasing of its conclusion that, to a reasonable degree of medical probability, it was impossible for claimant’s latter period of employment with Lynch to have contributed to his hearing loss. Liberty asserted that “impossibility” could not be established by medical evidence stated in terms of “probability.” The appellate court disagreed.

According to the Court, “Reasonable medical probability” described the level of proof required to establish medical causation by a preponderance of the evidence. Just as evidence, offered in terms of reasonable medical probability, would suffice to establish that claimant’s hearing loss was caused by his employment, evidence offered in terms of reasonable medical probability would suffice to establish that it was not possible for the second period of employment at Lynch to have caused claimant’s hearing loss. The board did not, therefore, err in describing the medical evidence in terms of reasonable medical probability.

Literal “Impossibility” Was Not Required

The Court stressed that proof of literal impossibility was not what the case law required [see Roseburg Forest Products v. Long, 325 Ore. 305, 937 P2d 517 (1997)]. The Court concluded that the Board could reasonably interpret the doctor’s opinion, read as a whole, to support the finding that, to a reasonable medical probability, claimant’s hearing loss was caused solely by employment conditions other than the second period of employment with Lynch.

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