Opinion by
Judge RULAND.This case is before us pursuant to a mandate from our supreme court in Subsequent Injury Fund v. Electron Gory., 817 P.2d 533 (Colo.1991). There, the court vacated our decision in Electron Corp. v. Industrial Claim Appeals Office, 817 P.2d 576 (Colo.App.1991) and directed us to reconsider our analysis in light of its decision in Climax Molybdenum Co. v. Walter, 812 P.2d 1168 (Colo.1991). In accordance with that latter holding, we affirm the order of the Industrial Claim Appeals Panel.
Claimant was exposed to significant amounts of silica dust and asbestos fibers during twenty-one and one-half years of employment as a foundry worker at Electron Corporation. In 1977, at age 38, claimant filed a workers’ compensation claim for the occupational disease of silicosis. He was found to be fifty per cent permanently partially disabled and was awarded maximum permanent partial disability benefits of $26,292. The award was upheld by this court. Electron Corp. v. Industrial Commission, (Colo.App. No. 81CA1275, July 15, 1982) (not selected for official publication).
Claimant continued to work for Electron and suffered further injurious exposures to silica dust and asbestos fibers. He filed a second claim for workers’ compensation benefits in February 1987, and became totally and permanently disabled from silicosis in May of 1987.
Claimant’s sole exposure to silica dust occurred during his employment for Electron.
*823Both the Administrative Law Judge (AU) and the Panel ruled that the allocation of liability for permanent total disability benefits was controlled by § 8-51-112(1), C.R.S. (1986 Repl.Vol. 3B) (now codified at § 8-41-304(1), C.R.S. (1991 Cum. Supp.)), which imposes liability upon the last employer in occupational disease disability cases, rather than by § 8-51-106(l)(a), C.R.S. (1986 Repl.Vol. 3B) (now codified at § 8-46-101(l)(a), C.R.S. (1991 Cum.Supp.)), which allocates liability between the employer and the Subsequent Injury Fund (SIF) when a worker who previously sustained a permanent partial industrial disability becomes permanently and totally disabled as a result of a subsequent injury.
I.
Electron contends that the Panel erred in finding it solely liable for claimant’s permanent total disability under § 8-51-112(1). We disagree.
In Climax Molybdenum Co. v. Walter, supra, our supreme court addressed the relationship between § 8-51-106(l)(a) and § 8-51-112(1). Section 8-51-106(l)(a) apportions liability between the employer and the SIF in cases in which an employee is rendered totally and permanently disabled by the combined effect of two or more permanent partial disabilities. In contrast, § 8-51-112(1), establishes the “last injurious exposure” rule for disabilities attributable to occupational diseases. The court concluded that this latter rule is an exception to the general apportionment rule set forth in § 8-51-106(l)(a).
It ruled specifically that:
[T]he statutory provisions of section 8-51-112(1) are controlling on the liability of an employer or the employer’s insurer for that portion of a worker’s permanent total disability attributable to an occupational disease which, in combination with other industrial disabilities, contributes to the worker’s permanent total disability.
Conversely, the court ruled that the SIF is liable under § 8-51-106(l)(a) only for “that part of the worker’s permanent total disability attributable to those other prior industrial injuries not involving an occupational disease.” (emphasis added)
Thus, since claimant’s permanent total disability in this case is solely attributable to the occupational disease of silicosis, the Panel correctly applied § 8-51-112(1) in assessing Electron with full liability for claimant’s disability benefits. See Climax Molybdenum Co. v. Walter, supra.
II.
Alternatively, Electron challenges the constitutionality of the apportionment scheme established by § 8-51-106 and § 8-51-112. We perceive no constitutional defect.
The SIF is financed by assessments imposed uniformly on all Colorado employers and carriers. Section 8 — 51—106(l)(b), C.R.S. (1986 Repl.Vol. 3B) (subsequently amended and now codified at § 8-46-102, C.R.S. (1991 Cum.Supp.)). However, Electron argues that if a worker is totally and permanently disabled by multiple disabilities which include an occupational disease, the employer or its insurer will be liable for either a percentage of the permanent total disability benefits awarded, 100% of the benefits, or only $10,000 of the benefits depending on whether the employer’s liability is assessed under § 8-51-106(l)(a), § 8-51-112(1), or § 8-51-112(2). Thus, Electron argues that the statutory scheme discriminates against employers of workers disabled by occupational diseases and violates the guarantees of equal protection under the United States and the Colorado constitutions. We disagree.
Since the equal protection challenge here involves neither a suspect classification nor an infringement of a fundamental right, the rational basis test applies in determining the classification’s constitutionality. People v. Rosburg, 805 P.2d 432 (Colo.1991).
Under this test, the party challenging the classification must prove beyond a reasonable doubt that the classification is not rationally based on legitimate differences and is not reasonably related to a *824permissible state interest. If any state of facts can be conceived that would sustain the challenged classification, that state of facts will be presumed to exist in the absence of legitimate proof to the contrary. Orsinger Outdoor Advertising, Inc. v. Department of Highways, 752 P.2d 55 (Colo.1988).
In this ease, the classification is not affirmatively drawn but, rather, results from the overall statutory scheme for assessing and apportioning liability among different classes of employers. See Bath v. Department of Revenue, 758 P.2d 1381 (Colo.1988).
Further, both § 8-51-106 and § 8-51-112 embody legitimate governmental interests. The purpose of the general apportionment rule under § 8-51-106(l)(a) is to encourage the employment of partially disabled persons. It does this by relieving employers who employ partially disabled persons from the full responsibility for permanent total disability resulting from a subsequent disabling injury. Climax Molybdenum v. Walter, supra.
The purpose of the last injurious exposure rule under § 8-51-112 is to provide a certain and expedient method of compensating workers disabled by occupational diseases.
Moreover, the statute has previously been upheld from constitutional challenge on equal protection grounds. Union Carbide Corp. v. Industrial Commission, 196 Colo. 56, 581 P.2d 734 (1978).
Accordingly, we find the statutory classification bears a rational relationship to legitimate state objectives and does not violate equal protection.
The order is affirmed.
PIERCE, J., concurs. MARQUEZ, J., dissents.