The 8th Circuit has upheld the trial court’s decision that a plaintiff who alleged she was injured by drinking water from a bottle filled with freon did not have adequate and valid expert evidence of causation. Bland v. Verizon Wireless, 2008 WL 3474178 (8th Cir. August 14, 2008).
Plaintiff alleged that she inadvertently left her water bottle behind in a store, and an employee of defendant sprayed compressed air into her water bottle “as a joke,” believing the water bottle belonged to a fellow employee. At home, plaintiff opened the bottle which “made a-kind of pressurized noise.” She took a drink, then decided to smell the contents, taking a big whiff which made her cough. She then allegedly took another drink.
Plaintiff later reported to her doctor that after drinking from the bottle she coughed, which persisted for nearly an hour. She also described a “sore sensation in her throat” and for the next few days a “raspy sensation in her lungs.” Plaintiff alleged she developed a headache which persisted for about two weeks. Later testing at the University of Iowa Lab determined the bottle contained 820 parts per million (ppm) (.08%) of difluoroethane, a freon compound.
Plaintiff was later seen by a Dr. Sprince, complaining of shortness of breath when running. Her lung function test results were basically normal. Dr. Sprince eventually diagnosed her as having “exercise-induced asthma.” Dr. Sprince later theorized that “[b]ased on the initial clinical findings, [a] strong temporal relationship between the inhalation of freon and the occurrence of respiratory symptoms, and the subsequent response to pre-exercise treatment with inhaled bronchodilator” that plaintiff’s exercise-induced asthma was caused by the inhalation of freon.
Plaintiff sought to use the testimony of this treating physician, Dr. Sprince, to establish a causal link between inhalation of freon and the alleged exercise-induced asthma. The district court excluded Dr. Sprince’s testimony because Dr. Sprince’s proffered testimony as to causation did not satisfy the standards for admission of expert scientific testimony under Daubert.
The 8th Circuit affirmed, noting first that a treating physician’s expert opinion on causation is subject to the same standards of scientific reliability that govern the expert opinions of physicians hired solely for purposes of litigation.
The first problem with Dr. Sprince’s causation testimony was that she failed scientifically to eliminate other possible causes as part of her differential diagnosis. In particular, her own testimony acknowledged the cause of exercise-induced asthma in the majority of cases is unknown. Where the cause of the condition is unknown in the majority of cases, an expert cannot properly conclude, based upon a simple differential diagnosis, that exposure, here to freon, was the most probable cause of the injury. As a practical matter, Dr. Sprince’s causation opinion could not possibly be based upon a reasonable degree of medical certainty. Where the majority of cases of exercise-induced asthma have no known cause, and where Dr. Sprince failed to do an investigation and analysis of plaintiff’s home or other environments in search of other possible causes, the district court did not abuse its discretion in determining Dr. Sprince’s differential diagnosis did not satisfy Daubert.
Second, plaintiff’s expert did not know what amount of exposure to freon causes, or involves an appreciable risk of causing, asthma, and had no good grounds for determining whether plaintiff was exposed to a sufficient dose to have caused her asthma. Dr. Sprince could not determine or estimate the amount of freon plaintiff was actually or probably exposed to. The expert could not extrapolate from the existing data because the gap between the data identified (exposure facts) and Dr. Sprince’s proffered opinion was simply too great an analytical gap to support admissibility. Critical to a determination of causation is characterizing exposure. In a toxic tort case, the magnitude or concentration of an exposure should be estimated and the temporal aspects of the exposure should be determined –whether the exposure was short-term and lasted a few minutes, days, weeks, or months, or was long-term and lasted for years. Dr. Sprince lacked knowledge regarding what level of exposure to freon constitutes an appreciable risk of causing asthma and the specific concentration and degree of exposure to the freon. Similarly, plaintiff’s expert did not offer as evidence any personal experience with treating other patients following a similar exposure, admitting she had no such experience.
Finally, the expert’s heavy reliance on temporal proximity, without more, was insufficient to establish causation. In the absence of an established scientific connection between exposure and illness, or compelling circumstances, the temporal connection between exposure to chemicals and an onset of symptoms, standing alone, is entitled to little weight in determining causation. See Moore v. Ashland Chem., Inc., 151 F.3d 269, 278 (5th Cir.1998). It is not always irrelevant, said the court. The temporal relationship often will be one of several factors, and the weight to be given to the temporal relationship will differ depending on the strength of that relationship. But in this case, the district court properly discounted all the other factors supporting Dr. Sprince’s opinion leaving only temporal proximity to support Dr. Sprince’s causation opinion. And that was not enough, especially when plaintiff did not make an appointment with a doctor until two to three weeks after the incident.