Fifth Circuit Rejects Specific Dose Requirement for Exposure Claims, Expert’s Testimony Nonetheless Inadmissible

Ruffin v. BP Expl. & Prod., Inc., 137 F.4th 276 (5th Cir. 2025)

By Arthur A. Crais, Adjunct Professor of Law

            Floyd Ruffin filed suit against BP Exploration & Production, Inc. and BP America Production Company as part of the medical benefits class action settlement for alleged injuries that became manifest after the settlement.[1] Mr. Ruffin was employed to clean up oil after the Deepwater Horizon/BP oil spill and claimed exposure to crude oil caused his prostate cancer.[2] He designated Dr. Benjamin Rybicki as his expert who

reported that Ruffin was exposed to ‘polycyclic aromatic hydrocarbons’ (PAHs)—chemical compounds that are ‘ubiquitous in the environment’ and occur ‘in coal, peat, crude oil, and shale oils’—and that at least one of these compounds can cause prostate cancer. Rybicki pointed specifically to a compound called ‘benzo(a)pyrene,’ the ‘most prevalent PAH,’ and reported that it causes cancer in humans.[3]

      Following Dr. Rybicki’s deposition, BP moved to exclude his testimony, asserting he failed to quantify an amount of the chemical exposure to cause prostate cancer[4] and his testimony failed to prove general causation.[5] The district court granted the motion, excluded the proffered expert’s testimony, and granted summary judgment for the BP interests dismissing the case.[6]

On appeal, the panel consisting of Judges Elrod, Higginbotham, and Southwick rejected BP’s quantitative dose standard.[7] “Simply put, our general-causation-standard caselaw is inconsistent with requiring a quantitative dosage for expert testimony to be relevant under Rule 702 or Daubert.”[8]

Nevertheless, the court affirmed the order excluding the expert’s testimony and upheld the dismissal of the claim on the basis that the plaintiff could not prove general causation.[9] Although the plaintiff asserted he was exposed to “polycyclic aromatic hydrocarbons” (PAHs),[10] he testified that only one kind of PAH, benzo(a)pyrene, is a proven carcinogenic.[11] Neither Mr. Ruffin nor Dr. Rybicki claimed he was exposed to it.[12] Moreover, the court noted that exposure to that chemical “lacks a strong association with prostate cancer.”[13]

The testimony was properly excluded without which the plaintiff could not prove general causation.[14] Summary judgment was proper.[15]

[1] The court refers to the “Back-End Litigation Option” (BELO). 137 F.4th at 279.

[2] Id. at 278.

[3] Id. at 279.

[4] Id. at 281.

[5] Id. “The medical-benefits settlement provides that it ‘shall be interpreted in accordance with General Maritime Law’ while excepting disputed issues of ‘law applicable to the underlying claims.’ Ruffin also characterizes his claims as arising under general maritime law. However, assuming arguendo that Ruffin is correct, we have still previously required general and specific causation for toxic-tort claims arising under general maritime law, and we see no reason to depart from that here.” Id. at 280, note 1. The parties agreed that both general and specific causation must be proven. See id.

[6] 137 F.4th at 280.

[7] See id. at 283.

[8] Id.

[9] See id. at 284.

[10] Id. at 279.

[11] 137 F.4th at 284.

[12] Id.

[13] Id. at 285.

[14] Id. at 286.

[15] Id.