Multiple employers or insurers can be liable for a cumulative trauma (CT) injury, and it's common for employers or insurers to dispute whether and how much liability they have for such an injury. Pursuant to Labor Code 5500.5(a), liability for a CT injury is limited to employers who employed the worker during the one-year period immediately preceding the date of injury (LC 5412), or the last date of injurious exposure, whichever occurs first.
So there's no single point from which the liability period is determined. It could be based on either the date of injury under LC 5412 or the last date of injurious exposure. Furthermore, the date of injury under LC 5412 requires the concurrence of: (1) compensable disability; and (2) knowledge of industrial causation. The liability period for a CT injury is a frequent source of contention.