Racheal Bland (Bland) brings this action claiming she ingested freon after a Verizon Wireless, (VAW) L.L.C. (Verizon) employee sprayed canned air containing freon into her water bottle. Bland contends ingesting the freon caused her to suffer exercise-induced asthma. The district court 1 excluded evidence from Dr. Nancy Sprince (Dr. Sprince), Bland’s treating physician, opining the freon caused Bland’s exercise-induced asthma. The district court then granted defendants’ motion for summary judgment because, without Dr. Sprince’s testimony, Bland was unable to set forth sufficient evidence of causation. Bland appeals. We affirm.
I. BACKGROUND
On June 8, 2005, Bland and her friend J.J. Roetlin (Roetlin) entered a Verizon store in Coralville, Iowa, so Roetlin could have his phone updated. When they left *895 the store, Bland inadvertently left her water bottle behind. After Bland and Roetlin left, Verizon employee Christopher Reid (Reid) sprayed compressed air into Bland’s water bottle “as a joke,” believing the water bottle belonged to a fellow Verizon employee. The compressed air would freeze the top of the water in the water bottle, which supposedly was funny. Reid previously performed this same “joke” with his own water bottle and the water bottles of fellow employees. Once Reid drank the water in a bottle after such a “joke” and experienced no ill effects. No one else reported any adverse effects from drinking the water frozen in the bottles.
Shortly after Reid sprayed the compressed air into Bland’s water bottle, Roet-lin returned and retrieved Bland’s water bottle from a Verizon employee. Several Verizon employees were laughing as Roet-lin took the bottle, causing Roetlin to ask, “Is something funny? Did you piss in [the bottle] or something?” None of the Verizon employees responded and Roetlin left saying, “Take it easy.” Though the Verizon employees never acknowledged taking any action, Roetlin jokingly reported to Bland, “I wouldn’t drink that [because when I retrieved the bottle] they were laughing pretty hard.... Maybe they peed in it.”
Neither Bland nor Roetlin attempted to open the water bottle or drink from it until after they drove to Roetlin’s home to make dinner, a drive of 30 to 45 minutes. At Roetlin’s home, Bland opened the bottle which “made a — kind of pressurized noise.” Bland thought this sound was weird but figured it may have been caused by the heat. Bland took a drink, then decided to smell the contents “because [she] thought it was odd that [the bottle] was pressurized,” even though she “didn’t know if it was going to stink from being in the heat or what.” Bland took a big whiff and the bottle “had a really potent smell that made me cough.” Bland “took another drink and kind of swished it around [her] mouth ... trying to figure out if there was something in there or if [she]' was just being crazy.” In total, Bland had “two or three drinks at most.” Bland then passed the bottle to Roetlin saying, “Smell this, it smells like plastic.”
Bland later reported to her doctor, “Immediately after drinking from the bottle she coughed a few times, and this coughing persisted for nearly an hour.” Bland also described a “sore sensation in her throat” and for the next few days a “raspy sensation in her lungs.” Bland developed a headache which persisted for about two weéks.
Roetlin also took a drink from the bottle but did not swallow. Both Bland and Roetlin reported not feeling well. They called the police. The police spoke to Reid, who admitted spraying compressed air 2 in Bland’s water bottle. Roetlin and Bland delivered the bottle to the University of Iowa Hygienic Lab (Lab) for testing. The Lab determined the bottle contained 820 parts per million (ppm) (.08%) of difluoroethane, a freon compound. The Lab then contacted the Iowa Poison Control Center (Poison Control) to determine what the Lab should tell Roetlin and Bland. After consulting Poison Control, the Lab contacted Roetlin and referred Bland and Roetlin “to a physician if experiencing symptoms.”
*896 On July 13, 2005, Bland was seen by Dr. Sprince for the first time, complaining of shortness of breath when running. Bland’s lung function test results were normal. Dr. Sprince initially thought Bland’s shortness of breath might be due to lack of physical conditioning, change in her exercise routine or the July weather. Dr. Sprince eventually diagnosed Bland as having “exercise-induced asthma.” Dr. Sprince theorized that “[biased 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 bron-chodilator” that Bland’s exercise-induced asthma was caused by the inhalation of freon.
Bland filed this action in the Iowa District Court for Johnson County on January 5, 2006. Verizon removed this action to federal court on January 26, 2006. Bland was granted leave to amend to add Célico Partnership and Reid as defendants. All defendants moved for summary judgment on May 21, 2007.
Bland sought to have the testimony of her treating physician, Dr. Sprince, admitted to establish a causal link between Bland’s inhalation of freon and Bland’s 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, 3
II. DISCUSSION
“We review for abuse of discretion rulings concerning the admissibility of testimony that is offered as expert opinion.”
Ahlberg v. Chrysler Corp.,
Federal Rule of Evidence 702 provides: If scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise, if (1) the testimony is based upon sufficient facts’ or data, (2) the testimony is the product of reliable principles and methods, and (3) the witness has applied the principles and methods reliably to the facts of the case.
“A trial judge must make a preliminary assessment of whether the proffered expert’s methodology is both scientifically valid and applicable to the case.”
Ahlberg,
*897
Bland sought to have the testimony of her treating physician, Dr. Sprince, admitted to establish a causal link between Bland’s inhalation of freon and Bland’s exercise-induced asthma. “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.”
Turner v. Iowa Fire Equip. Co.,
Bland asserts the district court abused its discretion in holding Dr. Sprince’s causation opinion was scientifically unsupported because the opinion was the product of reliable methods and principles. Further, Bland asserts the district court “abused [its] discretion by imposing a burden of proof tantamount to scientific certainty rather than the preponderance of evidence standard required by law.”
1. Differential Diagnosis
Bland asserts Dr. Sprince conducted a differential diagnosis which supports Dr. Sprince’s causation opinion. We have held, “a medical opinion about causation, based upon a proper differential diagnosis is sufficiently reliable to satisfy
Daubert.” Turner,
The district court further concluded Dr. Sprince failed to eliminate scientifically other possible causes as part of her differential diagnosis. Even if Dr. Sprince were able to link exercise-induced asthma to freon inhalation or ingestion, Dr. Sprince must also rule out other possible causes.
Id.
at 1209 (recognizing “an expert must ‘rule in’ the suspected cause as well as ‘rule out’ other possible causes” (citing
*898
Nat’l Bank of Commerce of El Dorado v. Associated Milk Producers, Inc.,
2. Lack of Data
The district court’s decision to exclude Dr. Sprince’s causation opinion is also supported by Dr. Sprince’s lack of knowledge as to (1) “what amount of exposure to [the] difluoroethane-containing Freon causes, or involves an appreciable risk of causing, asthma”; and (2) what amount of difluoroethane-containing freon “Bland was actually or probably exposed [to] when she smelled the water in her water bottle.” “Critical to a determination of causation is characterizing exposure.” Federal Judicial Center,
The Reference Manual on Scientific Evidence
472 (2d ed.2000). “The magnitude or concentration of an exposure should be estimated” and “[t]he temporal aspects of the exposure should be determined — whether the exposure was short-term and lasting a few minutes, days, weeks, or months, or was long-term and lasted for years.”
Id.
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 Bland’s exposure to the freon. Without knowledge of these data points, Dr. Sprince could not extrapolate from the existing data because, as the district court reasoned, the gap between the data identified and Dr. Sprince’s proffered opinion was “ 'simply too great an analytical gap’ ... to support admissibility.” (quoting
General Elec., Co.,
Lacking data regarding (1) what exposure levels would involve an appreciable risk of asthma, and (2) Bland’s actual exposure level, the district court then looked for other evidence which would support Dr. Sprince’s causation opinion. The court suggested one way in which Dr. Sprince may have been able to buttress her opinion would be offering as evidence any personal experience with treating other patients following a similar exposure to difluoroe-thane, freon, or freon with difluoroethane. When asked about her personal experience treating other patients with similar exposure, Dr. Sprince admitted she had no such experience.
See Kumho Tire,
The only remaining basis for Dr. Sprince’s causation opinion is temporal proximity, that is, Bland’s inhalation or ingestion of the contents of the water bottle occurred shortly before Bland was diagnosed with exercise-induced asthma. “In the absence of an established scientific connection between exposure and illness, or compelling circumstances ... the tern-
*899
poral connection between exposure to chemicals and an onset of symptoms, standing alone, is entitled to little weight in determining causation.”
Moore v. Ashland Chem., Inc.,
III. CONCLUSION
Having determined the district court’s decision to exclude the causation testimony of Dr. Sprince was not an abuse of discretion, we conclude, under a de novo review,
see Green v. Franklin Nat’l Bank of Minneapolis,
Notes
. The Honorable Celeste F. Bremer, United States Magistrate Judge for the Southern District of Iowa, to whom the case was referred for final disposition by consent of the parties pursuant to 28 U.S.C. § 636(c).
. The compressed air at Verizon was called "Dust Blaster” and contained tetrafluoroe-thane. The compound detected in the Bland water bottle contents was difluoroethane. The mass spectrum analysis of tetrafluoroe-thane and the mass spectrum analysis of difluoroethane are not the same (four fluoro’ molecules vs. two fluoro molecules). The testing Lab had no explanation for why the water in Bland's bottle would contain difluo-roethane if the canned air contained tetrafluo-roethane and not difluoroethane.
.
Daubert v. Merrell Dow Pharm., Inc.,
