OSHA has amended one of the rules interpreting the anti-retaliation provision of the Occupational Safety and Health Act of 1970.

According to a final interpretive rule published in the Sept. 3 Federal Register, the change was made to clarify the causal connection “between protected activity and adverse action is ‘but-for’ causation.”

The rule first appeared in the Department of Labor’s semiannual regulatory agenda for Fall 2020. That entry states that the change was necessitated by the Supreme Court’s opinion in University of Texas Southwestern Medical Center v. Nassar issued in 2013. In the case, the court held that plaintiffs in anti-retaliation cases must prove retaliation was the sole motivating factor for an adverse action such as a firing, instead of one of multiple motivating factors, including poor work performance. This also is known as “but-for” causation: The employee wouldn’t have been fired but for blowing the whistle on their employer.

Previously, section 1977.6(b) in the OSH Act gave two ways to establish a causal connection between whistleblowing or other protected activities and an “adverse action” such as a dismissal. One was the “but-for” causation, and the other was the “protected activity was a substantial reason for the adverse action.”

OSHA concludes: “Ultimately, the issue as to whether a discharge or other adverse action was because of protected activity will have to be determined on the basis of the facts in the particular case.”