December 3, 2020Published Article

Benson authors article, “The Dose Makes the Poison”: Incorporating the Concepts of Exposure and Dose into Your Witness Questioning Strategy


You will often hear the phrase used in toxic tort cases, “The dose makes the poison.” It is attributed to Paracelsus (1493–1541), known as the father of toxicology. Paracelsus actually stated (translated from German), “All substances are poisons, there is none which is not a poison. The right dose differentiates a poison from a remedy.” A classic example of this is water. Drinking several glasses in a day will hydrate the body and is part of a healthy lifestyle. Drinking multiple gallons in a day can be lethal.

Another phrase that should be a focus in toxic tort cases is “intensity, frequency, and duration.” These concepts are critical to a proper understanding of exposure and dose. In legal matters, exposure scientists, who include industrial hygienists, occupational medicine physicians, and toxicologists (among others), rely on attorneys’ lines of questioning to characterize and conceptualize an alleged exposure to an occupational or environmental toxicant, and its corresponding dose, for the trier of fact. A retained defense expert exposure scientist is often asked to calculate a hypothetical dose for a toxicant associated with plaintiffs’ use, or work proximal to, a specific product. In order to do this, the defense attorney must have a clear understanding of the parameters of the exposure that is needed to calculate a dose, so that the expert has a valid basis for dose calculations. This is the product of exposure intensity (or concentration), exposure frequency, and exposure duration.

A well-developed line of questions of fact witnesses will provide an exposure scientist with the necessary insights into a plaintiff’s exposure intensity, frequency, and duration to occupational or environmental toxicants. This article is intended to assist attorneys in formulating lines of questioning for a fact witness that can assist an exposure scientist in developing an accurate dose determination to assess the question of cause in toxic tort cases.

A Hypothetical Toxicant Exposure Context

Let us assume a toxic tort claim has been filed in which the plaintiff’s pathologically confirmed leukemia is claimed to be causally associated with exposure to benzene. The exposure scientist has been retained on behalf of the defendant, who manufactured a consumer product in the late 1960s which contained Stoddard solvent. It is known that Stoddard solvent may have contained approximately 0.5 percent benzene by volume during the same time frame. It is important to consider that Stoddard solvent is a generic term, and one can only determine the precise benzene content if the formulation is available. Regardless, the plaintiff was an auto mechanic hobbyist who claims he utilized the defendant’s consumer product during mechanical work (engine rebuilding) on his personal vehicles at his home.

The defense exposure scientist has been asked to calculate a lifetime dose of benzene from the plaintiff’s use of this product and opine on the probability or risk of the potential for adverse health effects. In this example, the dose will be measured in ppm-years of benzene, which is the product of the intensity, duration, and frequency of benzene exposure in years and the airborne concentration of benzene in parts-per-million (as air volume).

Establishing Product Identification

The first parameter for establishing dose is confirmation of the plaintiff’s exposure to the defendant’s product. This is referred to as “product identification.” For obvious reasons, this parameter must be established before the exposure scientist can provide an expert opinion. If the defendant’s product is not identified, the exposure scientist cannot calculate the dose necessary to be a potential cause of harm.

Questions on this topic will probe whether the witness can identify the correct product, the product’s formulation, and the time frame in which the product was produced by the defendant using Stoddard solvent. Can the witness identify the defendant’s product labels and markings, and does he recall any information about the product’s labeling, container, consistency, color, and odor? Indeed, defense counsel must determine if the defendant’s product could be confused with a different product made by a different manufacturer. Do not allow the plaintiff or witness to use common monikers such as, “Kleenex” in lieu of “facial tissue” or similar tradenames for identifying the defendant’s product. It is common for witnesses to identify groups of similar products with similar use profiles as a trade name component. Were alternative brands used in a similar fashion? For example, did the plaintiff use multiple brands of a similar product with the same use profile? If so, delineate the percentage use of each product and their associated timeframes of use. Additionally, were alternative products from a different class used occasionally in lieu of the defendant’s product? For example, if the hypothetical defendant’s product was spray applied to bolts to loosen them during disassembly, when the bolts were unable to be removed using the defendant’s product, how were they removed? Were other products used? If so, how frequently did this situation occur?

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