
95 Mich. App. 380 (1980)
289 N.W.2d 919
JOHNSON
v.
HARNISCHFEGER CORPORATION.
Docket No. 46342.
Michigan Court of Appeals.
Decided February 6, 1980.
Green, Renner, Weisse, Rettig, Rademacher & Clark, for plaintiff.
Bridges & Collins (by Paul A. Peterson), for Harnischfeger Corporation and Employers Insurance of Wausau.
Frank J. Kelley, Attorney General, Robert A. Derengoski, Solicitor General, and Joseph M. Binno, Assistant Attorney General, for the Second Injury Fund.
Before: V.J. BRENNAN, P.J., and R.B. BURNS and M.J. KELLY, JJ.

ON REMAND
M.J. KELLY, J.
Plaintiff was totally disabled by an injury to his right knee on December 1, 1964, and his employer paid compensation through July 1, 1974, 500 weeks after the date of injury. In August, 1974, plaintiff filed a petition for hearing, alleging loss of industrial use of both legs on May 1, 1974. At the hearing plaintiff testified that he first had pain in his left knee in May, 1974. Dr. James W. Lyons, plaintiff's orthopedic surgeon, testified by deposition that plaintiff did not complain of pain in his left knee when he was examined in April, 1974; it was not until the doctor saw plaintiff on September 17, 1974, that plaintiff complained of pain in his left knee.
Relying primarily on the testimony of Dr. Lyons, *383 the hearing referee found that plaintiff was permanently and totally disabled as of September 17, 1974, because of the loss of industrial use of both legs. Defendants were ordered to pay benefits from July 2, 1974, when plaintiff's previous benefits had ceased, until further order of the Bureau of Workmen's Compensation.
All parties appealed; defendants contested the finding of permanent and total disability, and plaintiff contested the date of total and permanent disability. The Worker's Compensation Appeal Board specifically considered MCL 418.361(2)(g); MSA 17.237(361)(2)(g), which provides:[1]
"(2) Total and permanent disability, compensation for which is provided in section 351 means:

* * *
"(g) Permanent and total loss of industrial use of both legs or both hands or both arms or 1 leg and 1 arm; for the purpose of this subdivision such permanency shall be determined not less than 30 days before the expiration of 500 weeks from the date of injury."
The board then employed the test set down by the *384 Supreme Court in Burke v Ontonagon County Road Comm, 391 Mich 103; 214 NW2d 797 (1974),[2] and after reviewing plaintiff's testimony, concluded that it contained insufficient evidence that plaintiff had lost the industrial use of both legs. Relying on Dr. Lyons' testimony, the board also concluded that plaintiff had failed to prove permanent and total disability "within the period provided by Subsection (2)(g)". It therefore reversed the referee and denied further benefits. This Court granted leave to appeal that order and in an unpublished per curiam opinion [Docket No. 77-521, January 4, 1979] found no error in the appeal board's conclusion that plaintiff had failed to meet his burden of proof under the Burke test.
Plaintiff asserted that the distinction drawn by the Legislature between the first six classes of total and permanent disability, § 361(2) (a)-(f), which are not subject to any statute of limitations, and the seventh, loss of industrial use of two limbs, § 361(2)(g), violates equal protection. Because we affirmed the factual findings of the WCAB, we did not address this constitutional question. This cause is now remanded here, on order of the Supreme Court, for "consideration of the constructional and constitutional issues raised by plaintiff". 406 Mich 1002 (1979). We assume that our affirmance of the factual determination of the appeal board is overruled sub silentio. We had *385 concluded that the "[p]laintiff's proofs, which were taken at face value by the appeal board, merely establish that ambulation has been made more difficult for plaintiff as a result of his accident. They do not indicate that his present condition is functionally equivalent to physical loss of use of his legs." The Supreme Court must have found that conclusion incorrect and intended to overrule it, else why would it issue its order requiring consideration of the constitutional issue if the disability issue already foreclosed the plaintiff from any possibility of prevailing?
Subsection (2)(g), supra, establishes the time frame for a determination of permanency when an injured employee claims permanent and total loss of industrial use of the specified limbs: "* * * such permanency shall be determined not less than 30 days before the expiration of 500 weeks from the date of injury." Plaintiff submits that construed as a statute of limitations, i.e., that permanency must be determined within 500 weeks less 30 days, the provision constitutes a denial of equal protection under even the minimal rationality standard of review.
The Supreme Court, in O'Donnell v State Farm Mutual Automobile Ins Co, 404 Mich 524, 540; 273 NW2d 829 (1979), recently reaffirmed the position taken in Shavers v Attorney General, 402 Mich 554; 267 NW2d 72 (1978), regarding the proper judicial approach when confronted with an equal protection or due process challenge to socioeconomic legislation:
"`[I]n the face of a due process or equal protection challenge, "where the legislative judgment is drawn in question", a court's inquiry "must be restricted to the issue whether any state of facts either known or which could reasonably be assumed affords support for it." *386 United States v Carolene Products Co, 304 US 144, 154; 58 S Ct 788; 82 L Ed 1234 (1938). * * * [W]here the legislative judgment is supported by "any state of facts either known or which could reasonably be assumed", although such facts may be "debatable", the legislative judgment must be accepted. Carolene Products Co v Thomson, 276 Mich 172, 178; 267 NW 608 (1936).'"
Various sections of the Worker's Disability Compensation Act, included within this socioeconomic legislative category, have previously been analyzed under the "rational basis" test. Kunde v Teesdale Lumber Co, 55 Mich App 546; 223 NW2d 67 (1974), Verberg v Simplicity Pattern Co, 357 Mich 636; 99 NW2d 508 (1959).
The legislation in question comes clothed in a presumption of constitutionality; plaintiff assumes the burden of proving that the distinctions embodied in § 361(2) (a)-(g) lack a reasonable relation to a legitimate government interest. Cruz v Chevrolet Grey Iron Div of General Motors Corp, 398 Mich 117; 247 NW2d 764 (1976), Kunde, supra.
The preliminary question is whether the statute is clear and unambiguous, since judicial construction is inappropriate when the language clearly reflects the legislative intent. Oakland Prosecutor v 46th District Judge, 76 Mich App 318; 256 NW2d 776 (1977), Adrian Mobile Home Park v City of Adrian, 94 Mich App 194; 288 NW2d 402 (1979). Both parties here present equal protection arguments based upon an interpretation of the challenged language as a statute of limitations. We agree that the language is certain; therefore, we must sustain the different treatment accorded § 361(2)(g) claimants or sever that provision creating a statute of limitations if deemed constitutionally offensive. Eastwood Park Amusement Co v Mayor of East Detroit, 325 Mich 60; 38 NW2d 77 (1949).
*387 The only basis suggested by defendants for the special § 361(2)(g) statutory requirement is that it permits employers and insurance carriers to avoid stale claims. Defendants argue that the other categories of total and permanent disability are more readily apparent than loss of industrial use and thus have built-in statutes of limitation. An examination of the other listed § 361 categories, however, reveals inclusion of several other medical conditions potentially involving long-term development: total and permanent loss of sight of both eyes,[3] permanent and complete paralysis of both legs or both arms or of one leg and one arm,[4] incurable insanity or imbecility.[5] In light of other *388 potential long-term developing total and permanent disabilities we are not persuaded by defendants' argument that the first six categories of total and permanent disability are more clearly apparent sooner after the industrial injury, event or disease occurs, thereby providing the employer with notice of possible total and permanent consequences to follow. In the absence of a rational basis for the different treatment accorded claimants whose disability is defined under subsection (g), we find that imposition of a statute of limitations on that class, when employees in categories (a)-(f) are not so restricted, constitutes a denial of equal protection.
Plaintiff's single challenge to § 361(2)(g) is grounded on equal protection analysis, but we believe the statute of limitations included therein is constitutionally infirm on due process grounds as well. To deprive employees whose industrial loss of use does not arise until after 500 weeks minus 30 days of both their statutory and common law remedies before the right to bring suit is discovered would violate due process of law. Dyke v Richard, 390 Mich 739, 746-747; 213 NW2d 185 (1973). A statute which abolishes the right to sue before the cause of action arises is sustainable only if intended as an abrogation of a common law cause of action. Oole v Oosting, 82 Mich App 291; 266 NW2d 795 (1978). Such analysis is unreasonable in the instant case, as § 361(2)(g) was enacted for the purpose of defining a formerly unrecognized class of claimants. It is highly likely that when the Legislature added § 361(2)(g) to the act, *389 defining a formerly unrecognized class of claimants, it included the statute of limitations as a means of confining the class to claimants with injuries that occurred within the last 500 weeks less 30 days and those injured in the future, thereby precluding resurrection of ancient claims by giving only prospective application to that section of the act. See Clark v Chrysler Corp, 377 Mich 140, 148; 139 NW2d 714 (1966), and Sanders v General Motors Corp, 80 Mich App 190, 194 fn 5; 263 NW2d 329 (1977). If the language was intended as a time limitation for the specific purpose of denying retroactivity,[6] its continued presence is unnecessary. Directed by the Supreme Court to resolve the constitutional issue presented, we find the statute of limitations imposed upon § 361(2)(g) claimants violative of both due process and equal protection guarantees.
In the instant case the WCAB found that plaintiff had failed to demonstrate total and permanent disability within the statutory period. We therefore remand this case to the WCAB for a determination consistent with this opinion and the standards set forth in Burke, supra, and Martin v Ford Motor Co, 401 Mich 607; 258 NW2d 465 (1977). To avoid the possibility of any confusion as to whether or not the appeal board considered all of plaintiff's proofs, including the testimony of Dr. Lyons on the question of permanent and total loss of industrial use of both legs, we instruct the board to do so anew.
Reversed and remanded.
NOTES
[1]  MCL 418.361(2); MSA 17.237(361)(2) states:

"(2) Total and permanent disability, compensation for which is provided in section 351 means:
"(a) Total and permament loss of sight of both eyes.
"(b) Loss of both legs or both feet at or above the ankle.
"(c) Loss of both arms or both hands at or above the wrist.
"(d) Loss of any 2 of the members or faculties enumerated in (a), (b) or (c).
"(e) Permanent and complete paralysis of both legs or both arms or of 1 leg and 1 arm.
"(f) Incurable insanity or imbecility.
"(g) Permanent and total loss of industrial use of both legs or both hands or both arms or 1 leg and 1 arm; for the purpose of this subdivision such permanency shall be determined not less than 30 days before the expiration of 500 weeks from the date of injury. (Emphasis added.)
[2]  In reaching its conclusion the board relied upon the test enunciated in Burke v Ontonagon, supra, at 114, which states:

"There is permanent and total loss of industrial use of both legs where, inter alia,
"1. An employment-related injury in one or both legs causes pain or other condition that prevents use of both legs in industry.
"2. The use of one or both legs, whether or not injured, triggers an employment-related injury or malady in any part of the body, including one or both legs, that causes pain or other condition that prevents use of both legs in industry."
[3]  Total and permanent loss of sight of both eyes may result from injury or disease that progresses gradually, as in the case of cataracts and lens removal. Heat-ray cataracts, for example, are caused by long continued exposure to high temperatures. In the case of electric cataracts, the latent period from the date of the electrical injury to formation of cataracts has been reported to be as long as 11 years. System of Ophthalmology, Vol. 14, pp 828-835. The Michigan Supreme Court, considering the relationship of this specific type of injury to the Workmen's Compensation Act, stated: "the surgical removal of the natural lens made necessary by an injury arising out of and in the course of claimant's employment is loss of an eye within the meaning of the amended statute." Lindsay v Glennie Industries, Inc, 379 Mich 573; 578; 153 NW2d 642 (1967).
[4]  Paralysis could also develop over a long period of time following a specific injury or contraction of an occupational disease. Lead paralysis, caused by lead poisoning, obviously entails a potentially lengthy progression, depending upon the degree and frequency of exposure. Medical literature documents, through case histories, that severe muscle atrophy may first appear as late as 16 years after occupational exposure to lead. Medical treatment with calcium often halts further deterioration, but the existing paralysis is generally irreversible. Campbell, Williams & Barltrop, Motor Neurone Disease and Exposure to Lead, 33 J Neurol Neurosurg Psychiat 877-885 (1970).

Manganese poisoning is an occupational disease which affects the central nervous sytem. Medical studies of this disease reveal that symptoms may first appear as late as 25 years after the onset of exposure. Chronic manganese poisoning results in permanent disabilities most frequently involving use of the lower limbs. Naby & Hassanein, Neuropsychiatric Manifestations of Chronic Manganese Poisoning, 28 J Neurol Neurosurg Psychiat 282 (1965).
[5]  It is also common knowledge that mental disease may become totally and permanently disabling as a result of progressive deterioration. Manganese poisoning is sometimes referred to as "manganic madness", due to commonly reported compulsive behavior including singing, dancing and fighting. Miners inflicted with the disease often have "persisting neurological deficit despite removal from the mine." Lauria, Joselow & Browder, The Human Toxicity of Certain Trace Elements, 76 Annals of Internal Medicine 307-319 (1972).
[6]  In Clark, supra, the Supreme Court did not determine the constitutionality of this construction.
