Workers’ Compensation · Primary-source case analysis

Martinez: The Carrier Must Prove a Claimed Period of Cumulative Exposure Was Not Injurious

By Aneeta Mishra and Timothy Chan

Published September 14, 2026

Alejandro Martinez developed silicosis after years of porcelain fabrication. The decision separates proof of industrial disease from allocation of liability within the final year of injurious exposure and also applies the distinct section 5412 date-of-injury test.

The worker proved an occupational disease

The medical record supported industrial lung injury from workplace silica exposure. Zurich insured only the final portion of the employment and argued that the worker had not separately proved exposure during the carrier’s own coverage window caused the disease.

Section 5500.5 allocates liability to the final injurious period

The Board explained that an employer or carrier may escape the statutory liability period when substantial medical evidence establishes that a discrete period was not injurious. But once industrial disease from the employment is shown, the carrier seeking that exclusion bears the burden of proving the particular period was noninjurious. Zurich offered no medical evidence establishing that the earlier exposure alone caused the disease.

Section 5412 required disability and knowledge

A cumulative-injury date arises only when disability and actual or constructive knowledge of industrial causation coincide. Symptoms and a suggestion that work could be responsible did not compel an earlier date where the worker did not receive a definitive diagnosis and medical advice connecting the condition to work until September 2022.

Temporary disability required a narrower award

The Board affirmed the liability period and section 5412 findings but amended temporary disability to the supported period from August 10, 2022 through February 1, 2024. It deferred alleged earlier and later periods because the present medical record did not support an open-ended award.

Key takeaways

• Separate proof of industrial disease from allocation among coverage periods.
• A carrier seeking to exclude part of the final exposure period needs substantial medical evidence that the period was noninjurious.
• Section 5412 requires the concurrence of disability and knowledge of industrial causation.
• Temporary-disability dates must track the periods actually supported by the medical record.