(to affirm). The plaintiff worked as a tire recapper for defendant Hosking Tire Company from 1964 to 1971 and in the same capacity for defendant Eureka Tire Company from 1971 to 1974. He ceased working for Eureka in 1974 because of a disabling degenerative disc disease for which he is now entitled to and does receive workers’ compensation benefits. The question presented is whether the last employer, Eureka, should bear full responsibility for payment of the benefits due plaintiff or whether that responsibility should be shared by both employers. The hearing referee factually found that the plaintiff’s back condition was caused by the repeated lifting and bending he was required to do in the course of his work for both employers. On the basis of this finding, the referee concluded that an apportionment of liability was required. The Worker’s Compensation Appeal Board accepted and independently verified the referee’s factual findings, but rejected his legal conclusion. The appeal board ruled on the basis of public policy, administrative precedent and statutory interpretation that an apportionment was not permitted in cases involving back conditions such as that suffered by the plaintiff. The Court of Appeals reversed the board and remanded for reinstatement of the referee’s original order apportioning liability. Defendant Hosking now appeals.
I would affirm the Court of Appeals. Given the particular factual findings of the referee and the appeal board in this case, apportionment was proper. If it is better public policy (less issues to be decided by the WCAB) to excise from "occupa*477tional disease” those having to do with the back, the Legislature is the proper forum.
I
The tire recapping process used by both defendants Hosking and Eureka required the plaintiff to engage in extremely repetitious and strenuous physical activity. The plaintiff testified that, in order to recap one tire, he had to lift the tire up and down into and out of various molds and machines a total of approximately 20 times. The lifting distance varied from three to four feet. The tires ranged in weight from 30 pounds to 150 pounds or more. The plaintiff did most of this lifting manually without help from his co-workers.
The plaintiff’s work during his seven years at Hosking was much more demanding than his work during his three years at Eureka. At Hosking he was required to recap 50 to 60 tires per day, while at Eureka he was only required to recap 20 to 35 tires per day.
After several minor back incidents in the course of his work at both Hosking and Eureka, the plaintiff suffered another incident at Eureka in December of 1973. Although he worked the rest of the day of this incident and continued to work thereafter, he remained in constant pain. He worked six more months until June of 1974 when the pain became too great and he was forced to cease work.
Two medical experts examined the plaintiff in connection with this case and both of them concluded that the plaintiff was suffering from "degenerative disc disease”. One of these experts, Dr. Sim, an orthopedic surgeon from Mayo Clinic, described this disease in lay terms as "[b]asically *478* * * a worn-out disc” and responded in the affirmative when asked whether this disease was a "process rather than an occurrence type of injury”. The other expert, Dr. Roberts, stated that the plaintiff’s back condition was of a type that "required prolonged stress, wear and tear, taking years to develop”.
Because the plaintiff had not been examined by these experts during the seven years he had worked at Hosking and because there were no X-rays of the plaintiff’s back dating from that period, neither doctor could state with a reasonable degree of medical certainty whether the degenerative disc disease had begun at Hosking and continued at Eureka or whether it had sprung up solely during the plaintiff’s final three years at Eureka. Based on the data available to them, the doctors could only be certain that the disease had been present since the more serious incident suffered by the plaintiff at Eureka in December of 1973. However, Dr. Sim did testify that it was "quite probable” that the plaintiff’s work at Hosking had either caused, contributed to, or accelerated the disease; and Dr. Roberts reiterated his view that the degenerative changes in the plaintiff’s back, as evidenced by current X-rays, were of "a type and result of rather prolonged wear and tear”.
The hearing referee factually found that the plaintiff’s back condition "was not caused by any single event but was the result of repeated trauma caused by lifting and bending in the course of his employment with the two defendant companies”.1 On the basis of this finding, the referee concluded that an apportionment of liability was required based on the respective lengths of time the plaintiff had worked for Hosking and Eureka.
*479Defendant Hosking appealed the referee’s findings and decision to the Worker’s Compensation Appeal Board (WCAB) arguing, inter alia, that the plaintiff’s back condition resulted solely from the single-event incident suffered by the plaintiff at Eureka in December of 1973 or from that incident plus subsequent aggravation caused by his continued employment at Eureka until June of 1974. Hosking contended that the plaintiff’s condition was compensable by virtue of Chapter Three of the Worker’s Disability Compensation Act.2 Because Chapter Three did not contain any apportionment provisions, there could be no apportionment.
The appeal board did not accept the factual propositions urged by defendant Hosking. The board stated:
"First, we proceed to our fact finding. We accept the referee’s factual conclusion and independently find that plaintiff’s disability is the result of his heavy lifting duties at both employers.”3
The board then stated the legal question presented:
"Having made that finding, which directs that plaintiff’s disablement is compensable by virtue of the provisions of Chapter 4 * * * are we required to apportion liability by application of Section 435?”4
The pertinent portion of § 4355 to which the board referred states:
"The hearing referee shall apportion liability for *480compensation among the several employers in proportion to the time that the employee was employed in the service of each employer in the employment to the nature of which the disease was due and in which it was contracted * * (Emphasis added.)
The board concluded that this statute should not be read to require apportionment in cases involving degenerative disc disease caused by repeated lifting duties at two or more employers. The board candidly admitted that this conclusion was based on a "conscious policy determination” by the board and its predecessors not to treat back conditions as diseases for purposes of apportionment under § 435.6
The primary reason given by the board for this policy determination was the possibility of an increase in litigation and a concomitant increase in the length of time a claimant must wait for benefits if the statute were to be read so as to include back conditions. In closing, the board added:
"Should our decision here be subject to Court review, and should the Court find insufficient the argument of policy and administrative precedent urged here (which we deem more than sufficient), we urge the consideration of a statutory rationale arising out of definitional differences in Sections 401 and 435. In Section 401, * * * [the term 'personal injury’ is defined to] 'include a disease or disability’. Section 435 provides for apportionment among prior employers only for 'disease’. Notwithstanding the medical term 'degenerative disc disease’, occupationally-weakened backs could more appropriately be described by the term 'disability’ than by the term 'disease’ as the latter word is treated in common usage, and thus be excluded from the provisions of Section 435.”7
*481Defendant Eureka appealed the board’s decision to the Court of Appeals. That Court reversed the board and remanded the case for reinstatement of the referee’s original order apportioning liability. 79 Mich App 750; 263 NW2d 30 (1977). In its opinion, the Court first explained the purpose of the apportionment provision:
"Apportionment of financial liability for an employee’s disease-caused disability is designed to reflect the relative contribution of similar employment conditions at each employer to the occurrence of the disability. In other words, the fortuitous event of a disability, which is but the culmination of a prolonged exposure of the employee to deleterious employment conditions at multiple employers, should not result in the imposition of a financial burden only upon the last in the series of employers.” Id., 754.
The Court then interpreted the term "disease” in § 435 in light of this purpose:
"A disease is present for purposes of the apportionment statute whenever the evidence establishes that the compensable disability derives from the effects of continued and protracted exposure to the inherent elements of the employee’s employment.”
Finally, the Court compared the factual findings of the appeal board to this interpretation and concluded that the plaintiffs back condition did constitute a disease for purposes of § 435.
Defendant Hosking has now appealed the Court of Appeals decision to this Court.
II
The appeal board’s findings of fact are conclusive in the absence of fraud. MCL 418.861; MSA *48217.237(861). Thus, we are bound to accept the WCAB’s factual finding (which has support in the record) that the plaintiffs back condition was not the result of the incident he suffered at Eureka in December of 1973 or the result of that incident plus subsequent aggravation at Eureka, but was instead the result of his heavy lifting duties for both employers.
The legal issue generated by this finding of fact is whether a medically recognized back disease caused by repeated duties in the normal course of an employee’s daily routine constitutes a "disease” within the meaning of § 435.
Ill
The appeal board does not have any authority to alter or modify a provision of the Worker’s Disability Compensation Act, by interpretation or otherwise, in order to square that provision with the board’s perception of good public policy. That is solely the Legislature’s prerogative.
The language used by the Legislature in § 435 is clear and straightforward. It requires an apportionment of liability according to the length of time the employee has worked for each employer "in the employment to the nature of which the disease was due and in which it was contracted”. Thus, the employee must be suffering from a "disease” which is "due” to the "nature” of his or her employment in order for the statute to apply.
The plaintiffs back condition falls within the ordinary meaning of the language used by the •Legislature in § 435. The American Heritage Dictionary of the English Language, New College Edition (1975), defines the word "disease” as:
*483"An abnormal condition of an organism or part, especially as a consequence of infection, inherent weakness, or environmental stress, that impairs normal physiological functioning.”
Other dictionaries contain a similar definition.8 The plaintiffs condition is certainly "abnormal”, it was found to be a "consequence of * * * environmental stress” and it "impairs” his "normal physiological functioning”. In addition, the condition is considered a disease — "degenerative disc disease” —by the medical profession. And the appeal board found it was caused by the nature of his employment at both employers — his "heavy lifting duties”.9
The board would have us reject the ordinary meaning of the words used by the Legislature in § 435 by reference to § 401(c)10 of the act which states:
"Whenever used in this act:
"(c) 'Personal injury’ shall include a disease or disability which is due to causes and conditions which are characteristic of and peculiar to the business of the employer * * *.” (Emphasis added.)
The board argues that because § 435 only authorizes apportionment for a "disease” and not for a "disease or disability”, apportionment was not meant to apply to a "disability”. Furthermore, the *484board urges that because the plaintiffs back condition could be described by the term "disability” rather than by the term "disease”, there should be no apportionment in this case. Ergo, if the policy argument should fail, we could simply give the disease another name.
This argument by the board is not a conclusive finding of fact that the plaintiffs back condition is a "disability” and not a "disease”. To the contrary, the argument is couched in a legal conclusion as to the meaning of the words used by the Legislature in §§ 401(c) and 435, thus bringing it within the proper scope of judicial review.
IV
The first flaw in the board’s legal argument is that it does not appear from a reading of the act that the Legislature, by using the phrase "disease or disability” in § 401(c), intended thereby to create two distinct classes of personal injuries. Section 401(a)11 defines the term "disability” in a manner at odds with the meaning which the board urges us to adopt. That section states:
"Whenever used in this act:
"(a) 'Disability’ means the state of being disabled from earning full wages at the work in which the employee was last subject to the conditions resulting in disability. ” (Emphasis added.)
As so defined, the term "disability” represents a shorthand expression for the end result of a personal injury. It does not connote a class of personal injuries distinct from diseases. Many sections of the act, including § 435 itself, use the term *485"disability” in the same sense as defined by the Legislature in § 401(a).12
Despite the Legislature’s express definition of the term "disability” in § 401(a), the board would have us infer that the Legislature additionally intended that this term should designate a class of personal injuries distinct from diseases.
If we accepted this interpretation and the board’s conclusion that the plaintiff’s back condition could more appropriately be described by the term "disability” than by the term "disease”, no benefits could be awarded in this case. Based on its factual findings, the board properly concluded that Chapter Four and not Chapter Three controlled. Section 41513 of Chapter Four, which delineates the circumstances under which benefits can be awarded, only authorizes the payment of benefits when the claimant’s condition is "caused by a disease”. The phrase "disease or disability” is not used. Thus, under the board’s interpretation, § 415 would not apply to a "disability”.
I do not believe that the Legislature intended such a result. Nor do I believe that in addition to the express definition of the term "disability” in § 401(a), the Legislature also intended that this term should have some other meaning when used in another section.
Assuming arguendo that the Legislature did intend to distinguish between a "disease” and a "disability” for purposes of apportionment under § 435, the board is also incorrect in its conclusion that the plaintiff’s back condition could more appropriately be described by the term "disability” *486than by the term "disease” as the latter word is treated in common usage.
As noted above, the dictionary meaning of the word "disease” includes abnormal physiological conditions such as that suffered by the plaintiff and caused (the board found) by environmental stress. Also, both of the medical experts who examined the plaintiff diagnosed his condition as "degenerative disc disease” — in lay terms, "a worn-out disc”. The board found that this condition was the result of the plaintiff’s heavy lifting duties at both employers. Those duties required the plaintiff to lift hundreds of thousands of tires each year for ten successive years.14 Professor Larson, speaking about "occupational diseases” in his treatise on workers’ compensation law, states that "repeated strains associated with the employment may supply the distinctive element necessary to make a back injury occupational”.15
These factors in toto are too clear to permit obfuscation in order to avoid Eureka’s claim under §435.
V
This conclusion is consistent with a long series of cases in which this Court, in the course of interpreting other sections of the act, has treated back conditions caused by repeated heavy lifting duties as constituting or possibly constituting occu*487pational diseases (whether or not degenerative disc disease was involved). See Underwood v National Motor Castings Division, Campbell, Wyant & Cannon Foundry Co, 329 Mich 273; 45 NW2d 286 (1951), Fields v G M Brass & Aluminum Foundry Co, 332 Mich 113; 50 NW2d 738 (1952), Gibbs v Motor Wheel Corp, 333 Mich 617; 53 NW2d 573 (1952),16 and Braxton v Chevrolet Grey Iron Foundry Division of General Motors Corp, 396 Mich 685; 242 NW2d 420 (1976). It is also consistent with Kalee v Dewey Products Co, 296 Mich 540; 296 NW 826 (1941), in which the plaintiff developed bursitis in her shoulder from repeated twisting motions required as a normal part of her work. This Court affirmed an award of benefits for an occupational disease. A worn-out shoulder is little different from a worn-out back.
Dressier v Grand Rapids Die Casting Corp, 402 Mich 243; 262 NW2d 629 (1978), is inapposite to the case at bar. In Dressier the appeal board factually found that the plaintiff’s back problem was the result of a single-event injury (a fall at work) and subsequent aggravations thereof. On the basis of this finding, the board concludéd that Chapter Three controlled. There was no question about apportionment under § 435. The cases holding that certain back disabilities constituted occupational diseases were distinguished by Justice Williams in Dressier on the grounds that those "cases involve situations where the plaintiff’s back condition arose gradually because of long and repeated bending, twisting, or lifting, even though there might also have been an incidental trauma”. Id. at 257. (Emphasis added.)
In the case at bar, the board rejected the conten*488tion that the plaintiffs back condition was caused by a single-event injury at Eureka in December of 1973 or by that injury plus subsequent aggravations thereof. Instead, the board found that it was caused by the plaintiffs repetitive heavy lifting duties for both employers. On the basis of this finding, the board properly concluded that Chapter Four controlled. Thus, the fact-facting in Dressier is essentially the opposite of the situation presently before us and the language of the opinion is supportive of this opinion. The cases distinguished by the majority in Dressier are particularly applicable to this case because of the fact-findings by the WCAB.
VI
The appeal board in the case at bar failed even to mention that the purpose of § 435 is to distribute equitably the liability for a disease caused by similar employment conditions among the employers who were responsible for those conditions. We agree with the Court of Appeals that § 435 should be interpreted with this purpose in mind. Indeed, the position advocated by the appeal board and Justice Williams insulates the employer (Hosking) whose operation placed the most stress on plaintiff.
Unfortunately, the board also failed to discuss the very real possibility that if back conditions such as that suffered by the plaintiff were not apportionable, employers can be expected to refuse to hire persons who have worked previously in occupations which require repeated heavy lifting duties.
Although the policy considerations toward the reduction of issues in the crowded WCAB docket are understandable, it is not the function of the *489judiciary to override legislatively expressed public policy in order to implement its own views.
The drafters of the Worker’s Disability Compensation Act clearly intended that similar multiple employments, through which an occupational disease finally progressed to a compensable disability, should share proportionately in the payment of benefits. In this case, Mr. Derwinski was found by both the referee and the WCAB to have a degenerative disc disease caused by work in the two employments. That finding is conclusive and requires apportionment of liability. It is not appropriate for this Court to excise back diseases from the statute governing occupational diseases for purposes of easier administration.
The argument that employees might have to wait for benefits while carriers appealed the sole question of apportionment is without merit. Even as in this case, in which the employee has been receiving full benefits, the WCAB can fashion an order directing payment to the worker, with the issue of apportionment to continue to an orderly conclusion.17
I would therefore adopt the Court of Appeals interpretation of § 435 as it applies to the facts of this case and would affirm the reversal of the appeal board and the remand for reinstatement of the hearing referee’s original order apportioning liability.
Kavanagh, Levin, Fitzgerald, and Ryan, JJ., concurred with Coleman, C.J.Hearing Referee’s Opinion, p 1.
MCL 418.301 et seq.; MSA 17.237(301) et seq.
Appeal Board Opinion, p 2.
Ibid.
MCL 418.435; MSA 17.237(435).
Appeal Board Opinion, p 3.
Ibid.
See, for example, Webster’s Third New International Dictionary of the English Language, Unabridged (1966 ed), p 648.
It is questionable that the disease is "caused by” rather than "aggravated by” the hard labor but the WCAB fact-finding is final. Degenerative disc disease is not uncommon and is found in those who perform no hard labor — or any labor — as well as in those who perform arduous tasks.
MCL 418.401(c); MSA 17.237(401)(c).
MCL 418.401(a); MSA 17.237(401)(a).
In addition to § 435, see § 415 (MCL 418.415; MSA 17.237[415]), § 431 (MCL 418.431; MSA 17.237[431]), and § 441 (MCL 418.441; MSA 17.237[441]).
MCL 418.415; MSA 17.237(415).
Assuming, as plaintiff testified, that to recap one tire he had to lift it 20 times and that he was required to recap 50 to 60 tires per day during his seven years at Hosking and 20 to 35 tires per day during his three years at Eureka, the average number of lifts per year at Hosking would be 264,000 (20 lifts X 55 tires x 240 working days) and the average at Eureka would be 132,000 (20 lifts X 27.5 tires X 240 working days).
IB Larson, Workmen’s Compensation Law (1979 rev), § 41.33, pp 7-377 — 7-378.
The appeal board’s opinion in Gibbs makes it clear that the plaintiff was awarded benefits for an occupational disease. See 1950-1951 WCABO (Docket No. 11505, July 20, 1951).
At a minimum, MCL 418.862; MSA 17.237(862) could be employed.