A central tenet of toxicology is that “the dose makes the poison.” Every chemical is toxic if enough of it is consumed, and every chemical has some dose – even if miniscule – at which it poses no significant risk. A chemical must be given in sufficient amount – something exceeding the “threshold dose” – before it will cause effects. This has obvious implications for toxic tort litigation, where a plaintiff who alleges injury from exposure to a toxic chemical must prove at minimum that he or she was exposed to enough of the chemical to produce the alleged injury. This poses a problem for plaintiffs who have been exposed only to very small doses of the chemical at issue. What is a plaintiff to do when their exposure falls below the threshold dose? One approach that generally does not work is to reject the very concept of a threshold dose altogether.

In Pinares v. Raytheon Technologies Corporation, 2023 WL 2661521 (11th Cir. Mar. 28, 2023), Plaintiff alleged that she had developed kidney cancer after chemical compounds from the defendant’s facility made their way into the groundwater near her home. Plaintiffs relied on three experts to prove causation – a toxicologist to establish general causation and two physicians to establish specific causation. The district court excluded Plaintiffs’ toxicology expert, holding that the expert had not conducted a reliable dose-response assessment. The district court then also excluded each of Plaintiffs’ specific causation experts, noting that they had not performed an independent dose-response assessment of their own and therefore relied on the toxicology expert’s deficient opinion. Plaintiffs could not establish causation without expert opinion, and the district court therefore granted summary judgment.

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