“Symptom Threshold Methodology” Rejected by Court of Appeals of New York Pursuant to Frye

In an opinion decided February 11, 2016, the Court of Appeals of New York precluded two causation experts put forth by a plaintiff in a toxic tort case. The case involved allegations that a minor was born with severe mental and physical disabilities caused by in utero exposure to unleaded gasoline vapor. The vapor was allegedly emitted into the car from a defective fuel hose. The automobile manufacturer subsequently recalled the vehicle at issue due to defects in the feed fuel hoses.

In support of his claims, the plaintiff put forth numerous expert witnesses, including Linda Frazier, M.D., M.P.H. and Shira Kramer, M.H.S., Ph.D. Applying what the court termed a “symptom threshold methodology” those experts reached the conclusion that the in utero exposure to gasoline vapor proximately caused the birth defects. The “symptom threshold methodology” employed by the experts involved started with the conclusion that people experience certain symptoms at a threshold level of exposure, in this case 1,000 parts per million (ppm). The doctors then employed the Bradford Hill criteria and weight of the evidence approach, respectively to conclude that based on the symptoms the mother experienced she was exposed to 1,000 ppm of gasoline vapor, because symptoms occur at that level. The court found that the only evidence the experts relied upon to establish the mother was exposed to a sufficient amount of gasoline vapor to cause the birth defects were the reports by the plaintiff’s mother and grandmother that the smell of gasoline occasionally caused them nausea, dizziness, headaches, and throat irritation. The Court of Appeals found that there was no scientific evidence cited by the experts to establish consensus in the scientific community that such a method was reliable.

The court drew an important distinction between the methodology employed in this case and the “odor threshold” analysis that has survived Frye scrutiny and been admitted in other cases. The odor threshold is the level at which a substance is capable of olfactory detection and concentrations below it are not detectable by smell. The odor threshold analysis is often employed by experts in cases involving occupational exposures because the expert can opine that a plaintiff was exposed to a certain level of a substance where the substance was necessarily present at a certain level if it was smelled. When the odor threshold exceeds safe levels causation experts have been allowed to rely upon it in court. However, in the case at issue, the Court of Appeals found that the plaintiff’s experts made an unreliable leap when they determined that there is a minimum threshold of gasoline vapor beneath which individuals do not experience headache, nausea or dizziness. The court did not find any other cases or support in the scientific literature that such a “symptom threshold methodology” was generally accepted.

Quantifying past exposure to a substance is often difficult, if not impossible, nonetheless, there are generally accepted methods that causation experts can follow to establish that a plaintiff was exposed to toxic levels of a substance. In New York, and other states that apply Frye, this case provides important precedent and insight into challenging causation in toxic tort cases.

Read the full, uncorrected opinion here.

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