specially concurring.
In determining which of two successive employers is responsible for compensation for claimant’s present back condition, the lead opinion concludes the dispositive analysis is whether the cause of the disability is an injury or an occupational disease. The opinion states that there was an injury and that Early is responsible. I disagree with the conclusion that claimant’s disability is the result of an injury rather than an occupational disease. I, however, agree that Early is responsible for the claim.
The distinction between industrial injury and occupational disease has become blurred under the Workers’ Compensation Act but it still is important, at least for the purpose of time limitations for claim filing and for application of the last injurious exposure rule. See, e.g., Boise Cascade Corp. v. Starbuck, 61 Or App 631, 659 P2d 424, rev allowed 294 Or 792 (1983). The distinction also assumes some importance in determining the cause of the disability, i.e., whether the disability is related to the work environment. The definition of occupational disease devised by the courts is based, in part, on the necessities of applying the dictates of the Act and is not necessarily consonant with the medical definition of disease. In some measure the definition is an attempt to contrast occupational disease with accidental injury.
The key case for the appropriate definition of occupational disease under the Act is O’Neal v. Sisters of Providence, 22 Or App 9, 537 P2d 580 (1975). In that case we adopted the substance of the definition from IB Larson’s Workmen’s Compensation Law § 41:31:
«* * * what set[s] occupational disease apart from accidental injuries [is] both the fact that they [can] not honestly be said to be unexpected, since they [are] recognized as inherent hazard of continued exposure to conditions of the particular employment, and the fact that they [are] gradual rather than sudden in onset. * * *”
The facts of O’Neal put the definition in context. The claimant worked as a hospital maid which required her to push a heavy cleaning cart over the carpeted hallways. As a result, she developed strain and muscle spasms in her legs causing her disability. We held that she was suffering from an occupational disease because the results were gradual in onset, as they *268occurred over a period of time and could not honestly be said to be unexpected, i.e., it could be expected that pushing a heavy cart would cause strain and muscle spasms in the worker’s legs. One of the principal bases for the distinction between the two types of disability we noted in O’Neal is that an accidental injury results from a distinct identifiable event such as a trauma that a worker can point to as the precipitating cause of the disability.
As we indicated in Valtinson v. SAIF, 56 Or App 184, 641 P2d 598 (1982), the identifiable event distinguishing an injury from an occupational disease need not be an instantaneous happening. In Valtinson the claimant, who had been free from back pain for some period of time, drove a van from Grants Pass to Portland and experienced back pain during the trip. We held that he suffered an accidental injury because the trauma producing the disability occurred over a short discrete period of time.
The lead opinion takes a lead from Valtinson and utilizes the analysis there by stretching the time period of Valtinson — a one day trip — to include a six-week exposure to the jolting and jarring associated with the front end loader driven by claimant. Because claimant here had no back problems prior to starting his duties for Early, the lead opinion concludes the results of driving the front end loader were unexpected and were related to a discrete period of time, i.e., six weeks.
Claimant identified the jerking and jolting of a particular front end loader as the cause of his back problem. The machine he drove for approximately six weeks was generally rough riding and had a faulty transmission that caused a substantial jolt each time a gear change was made. He changed gears from forward to reverse approximately 200 to 300 times each shift. Such work conditions over a substantial period of time could reasonably be expected to cause a back strain. Although the jolting may have been more intense than the exertion needed to push the cleaning cart described in O’Neal, it is conceptionally the same for determining if the resulting disability is an occupational disease. The work condition experienced by claimant and the resulting disability more nearly fit the description of an occupational disease set out in O’Neal *269than the accidental injury described in Valtinson. I would conclude that claimant’s disability is an occupational disease.
In situations where there are successive employers or successive periods of employment covered by different compensation carriers it is necessary to assign responsibility for the compensation due. The allocation of responsibility is determined by application of the last injurious exposure rule. See Bracke v. Baza’r, 293 Or 239, 646 P2d 1330 (1982); Boise Cascade Corp. v. Starbuck, supra. In Starbuck, we concluded that the last injurious exposure rule applied particularly to occupational disease rather than accidental injury. In essence, the rule of substantive responsibility places sole responsibility on the last employer or insurer if the conditions of employment during that period could have caused the disability. Because I conclude that claimant suffers from an occupational disease, the critical inquiry is whether the working conditions at Drake could have caused claimant’s present back problems. As indicated, claimant identified that the particular idiosyncrasies of the front end loader he used at Early as the cause of the back condition. The machine he drove for two days at Drake did not have a faulty transmission and was much smoother operating than the loader at Early. When viewed as a cause of the disability, the conditions at Early are not the same as the work conditions at Drake. It oversimplifies the analysis to compare only the type of machinery operated as Early does in its brief. I conclude that the working conditions could not be said to be the same at Drake and, therefore, that an important part of the last injurious exposure analysis has not been established. Early is responsible for the claim.