Utah Code § 34A-3-105: Last employer liable -- Exception.

(1) Except as provided in Subsection 34A-3-113(5), the extent compensation is payable under this chapter for an occupational disease which arises out of and in the course of an employee's employment for more than one employer, the only employer liable shall be the employer in whose employment the employee was last injuriously exposed to the hazards of the disease if:

(a) the employee's exposure in the course of employment with that employer was a substantial contributing medical cause of the alleged occupational disease; and

(b) the employee was employed by that employer for at least 12 consecutive months.

(2) Should the conditions of Subsection (1) not be met, liability for disability, death, and medical benefits shall be apportioned between employers based on the involved employers' causal contribution to the occupational disease.