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What Is California Labor Code §5500.5 (CT Last-Injurious-Exposure Rule)?
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By Eman Yazdchi, Esq. · Certified Specialist in Workers' Compensation Law, State Bar of California Board of Legal Specialization · Cal Bar #285231
(a) Except as otherwise provided in Section 5500.6, liability for occupational disease or cumulative injury claims filed or asserted on or after January 1, 1978, shall be limited to those employers who employed the employee during a period of four years immediately preceding either the date of injury, as determined pursuant to Section 5412, or the last date on which the employee was employed in an occupation exposing him or her to the hazards of the occupational disease or cumulative injury, whichever occurs first.
What does California Labor Code §5500.5 actually establish?
Section 5500.5 places cumulative-trauma liability on the employer where the worker last had injurious exposure during the final year before the date of injury.
Section 5500.5 is California's last-injurious-exposure rule, it assigns cumulative-trauma liability to the employer where the worker was last injured during the final year before the date of injury, so one carrier pays the entire claim rather than every prior employer splitting it. Liability in a multi-employer CT case turns entirely on this rule. Certified Specialist Eman Yazdchi (California Board of Legal Specialization, State Bar of California) handles multi-employer CT allocation files.
California Labor Code §5500.5 establishes the "last-injurious-exposure" rule for California cumulative-trauma claims. The §5500.5 California rule places liability for a CT injury under California Labor Code §3208.1, California's specific-versus-cumulative injury definition, on the employer or employers during the last year of injurious exposure preceding the California Labor Code §5412, the discovery-rule date when the worker first knew the disability was work-related, date of injury, not on every employer the worker had during the cumulative exposure period. The §5500.5 California rule is the practical mechanism for assigning CT claim liability when a worker was repetitively exposed at multiple employers over years or decades.
How does §5500.5 California liability actually work in a multi-employer CT case?
The last-injurious-exposure rule means one carrier pays the full CT claim, the most recent employer's insurer cannot apportion backwards to prior employers.
Under California Labor Code §5500.5, a California worker who developed a cumulative-trauma shoulder injury across three employers over 10 years generally files a CT claim against the final employer (or employers) during the year preceding the California Labor Code §5412 date of injury, not against all three. The §5500.5 California rule simplifies CT liability by concentrating it on the last year of exposure. If multiple employers operated during that final year, the §5500.5 California liability is allocated among them.
How does §5500.5 interact with the §5412 California date of injury?
Section 5500.5 interacts with the section 5412 discovery rule: the one-year exposure window is measured back from the section 5412 date of injury, not the hire date.
Under California Labor Code §5412 (date of injury) and California Labor Code §5500.5 (employer liability), the §5412 date triggers the §5500.5 lookback. The §5412 California date of injury for a CT claim is the date the worker first suffered disability AND knew (or with reasonable diligence should have known) the disability was work-related. The §5500.5 California one-year lookback runs from that §5412 date, capturing the employer(s) during the year immediately preceding disability-plus-knowledge.
What types of California injuries does §5500.5 actually cover?
CT injuries covered by section 5500.5 include carpal tunnel, lumbar disc, shoulder impingement, hearing loss, respiratory disease, and any other gradual-onset condition.
Under California Labor Code §5500.5 and California Labor Code §3208.1, California cumulative-trauma claims cover slow-developing injuries from repetitive exposure, repetitive-motion injuries (back, shoulder, wrist, knee from lifting, bending, computer use), occupational-disease claims (silicosis, asbestos exposure, chemical sensitization, hearing loss), and stress-induced injuries developing over time. The §5500.5 California rule applies to any CT injury that meets the §3208.1 definition. Traumatic single-event injuries are not §5500.5 California cases, they have a clear injury date and one employer at the time.
How does §5500.5 connect to the §5405 California statute of limitations?
Section 5500.5 interacts with the section 5405 filing deadline: the claim must be filed within one year of the section 5412 discovery date, not the last day worked.
Under California Labor Code §5405 (one-year filing statute of limitations) and California Labor Code §5412 (CT date of injury), the §5500.5 California liability framework only matters if the worker timely files a claim under California Labor Code §5405. The §5405 California one-year clock starts running from the §5412 date of injury, and the §5500.5 employer is the defendant. A California worker who waits too long after the §5412 date can lose the right to recover even when a §5500.5 employer would clearly have been liable.
Related on yazdchilaw.com: California workers' compensation lawyer pillar · California Labor Code §5500.5 explained · California Labor Code §5400.30 explained · What counts as a cumulative trauma injury in california workers comp.
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What does California Labor Code §5500.5 actually establish for CT claims?
California Labor Code §5500.5 establishes the "last-injurious-exposure" rule for California cumulative-trauma claims. The §5500.5 California rule places liability for a CT injury under California Labor Code §3208.1 on the employer or employers during the last year of injurious exposure preceding the California Labor Code §5412 date of injury, not on every employer the California worker had during the cumulative exposure period. The §5500.5 rule is the practical mechanism for assigning CT claim liability when a worker was repetitively exposed at multiple California employers over years or decades.
How does §5500.5 California liability actually work in a multi-employer CT case?
Under California Labor Code §5500.5, a California worker who developed a cumulative-trauma shoulder injury across three employers over 10 years generally files a CT claim against the final employer (or employers) during the year preceding the California Labor Code §5412 date of injury, not against all three. The §5500.5 California rule simplifies CT liability by concentrating it on the last year of exposure. If multiple California employers operated during that final year of injurious exposure, the §5500.5 liability is allocated among them by the WCAB judge.
How does §5500.5 interact with the California §5412 date of injury?
Under California Labor Code §5412 (date of injury) and California Labor Code §5500.5 (employer liability), the §5412 California date triggers the §5500.5 lookback. The §5412 date of injury for a CT claim is the date the California worker first suffered disability AND knew (or with reasonable diligence should have known) the disability was work-related. The §5500.5 California one-year lookback runs from that §5412 date, capturing the California employer or employers during the year immediately preceding disability-plus-knowledge.
What types of California injuries does §5500.5 actually cover?
Under California Labor Code §5500.5 and California Labor Code §3208.1, California cumulative-trauma claims cover slow-developing injuries from repetitive exposure, repetitive-motion injuries (back, shoulder, wrist, knee from lifting, bending, computer use), occupational-disease claims (silicosis, asbestos exposure, chemical sensitization, hearing loss), and stress-induced injuries developing over time. The §5500.5 California rule applies to any CT injury meeting the §3208.1 definition. Traumatic single-event injuries are not §5500.5 California cases, they have a clear injury date and one employer at the time.
How does §5500.5 connect to the California §5405 statute of limitations?
Under California Labor Code §5405 (one-year California filing statute of limitations) and California Labor Code §5412 (CT date of injury), the §5500.5 California liability framework only matters if the worker timely files a claim under §5405. The §5405 California one-year clock starts running from the §5412 date of injury, and the §5500.5 employer is the defendant. A California worker who waits too long after the §5412 date can lose the right to recover even when a §5500.5 employer would clearly have been liable for the CT injury.
Last reviewed by Eman Yazdchi, Esq., June 2026.
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