Exposure, Epidemiology, and External Validity under Rule 702

Sometimes legal counsel take positions in court determined solely by the expediency of what expert witnesses are available, and what opinions are held by those witnesses.

Back in the early days of the asbestos litigation in Philadelphia, a hotbed of early asbestos litigation, plaintiffs and defendants each identified a pool of available expert witnesses on lung diseases.  Each side found witnesses who held views on important issues, such as whether asbestos caused lung cancer, with or without pre-existing asbestosis, whether all types of asbestos caused mesothelioma, whether asbestos caused gastrointestinal cancers, and whether “each and every exposure was a substantial factor” in producing an asbestos-related disease.  Some expert witnesses adopted opinions as a matter of convenience and malleability, but most witnesses expressed sincerely held opinions.  Either way, each expert witness active in the asbestos litigation, came to be seen as a partisan of one side.  Because of the volume of cases, there was the opportunity to be engaged in a large number of cases, and to earn sizable fees as an expert witness.  Both side’s expert witnesses struggled to avoid being labeled hired guns.

A few expert witnesses, eager to avoid being locked in as either a “plaintiff’s” or a “defendant’s” expert witness, with perhaps some damage to their professional reputations, balanced their views in a way to avoid being classified as working exclusively for one side or the other.  The late Paul Epstein, MD, adopted this strategy to great effect.  Dr. Epstein had excellent credentials, and he was an excellent physician.  He was on the faculty at the University of Pennsylvania, and he was a leader in the American College of Physicians, where he was the deputy editor of the Annals of Internal Medicine.  Dr. Epstein exemplified gravitas and learning.  He was not, however, above adopting views in such a way as to balance out his commitments to both the plaintiffs’ and defense bars.  By doing so, Dr. Epstein made himself invaluable to both sides, and he made aggressive cross-examination difficult, if not impossible, when he testified.  I suspect his positions had this strategic goal.

In his first testimonies, in the late 1970’s and early 1980’s, Dr. Epstein expressed the view that asbestos exposure caused parietal pleural plaques, but these plaques rarely interfered with respiration.  Pleural plaques did not cause impairment or disability, and thus they were not an “injury.”  Dr. Epstein’s views were very helpful in obtaining defense verdicts in cases of disputed pleural thickening or plaques, and they led to his being much sought after by defense counsel for their independent medical examinations.  Dr. Epstein also strongly believed, based upon the epidemiologic evidence, that asbestos did not cause gastrointestinal or laryngeal cancer.

Dr. Epstein was wary of being labeled a “defendants’ expert” in the asbestos litigation, especially given the social opprobrium that attached to working for the “asbestos industry.”  And so, by the mid-1980’s, Dr. Epstein surprised the defense bar by showing up in a plaintiff’s lung cancer case, without underlying asbestosis.  Dr. Epstein took the position that if the plaintiff worked around asbestos, and later developed lung cancer, then asbestos caused his lung cancer, and “each and every exposure to asbestos” contributed substantially to the outcome.  Risk was causation; ipse dixit.  Dr. Epstein recited the Selikoff multiplicative “synergy” theory, with relative risks of 5 (for non-smoking asbestos workers), 10 (for smoking non-asbestos workers), and 50 (for smoking asbestos-exposed workers).  Every worker was described with the same set of risk ratios.  Remarkably, and unscientifically, Dr. Epstein gave the same risk figures in every plaintiff’s lung cancer case, regardless of the duration or level of exposure.  In mesothelioma cases, Dr. Epstein took the unscientific position that all fiber types (chrysotile, amosite, crocidolite, and anthopyllite) contributed to any patient’s mesothelioma.

Dr. Epstein’s views made him off limits to plaintiffs in non-malignancy cases, and off limits to defendants in lung cancer and mesothelioma cases.

Because of his careful alignment with both plaintiffs’ and defense bars, Dr. Epstein’s views were never forcefully challenged.  Of course, the Pennsylvania case law in the 1980’s and 1990’s was not particularly favorable to challenges to the validity of opinions about causation, but even as Rule 702 evolved in federal court, both plaintiffs’ and defense counsel were unable to antagonize Dr. Epstein.  The inanity of “each and every exposure” was not seriously hurtful in the early asbestos litigation, when the defendants were almost all manufacturers of asbestos-containing insulation, and if a manufacturer had supplied insulation to a worksite, then the proportion of asbestos exposure for that manufacturer would likely have been “substantial.”

Today, the nature of the asbestos litigation has changed, but it when we examine Pennsylvania law and procedure, it is not surprising to see that Dr. Epstein’s views have had a long-lasting effect.  Claimants with only pleural plaques have been relegated to an “inactive” docket.  Plaintiffs’ expert witnesses still opine that each and every exposure was substantial, without any basis in evidence, and they still recite the same 5x, 10x, and 50x risk ratios, based upon Selikoff’s insulator studies, even though the Philadelphia Court of Common Pleas probably has not seen more than a handful of insulators’ cases in the last decade.  Dozens of epidemiologic studies have shown that asbestos exposures of bystander trades, chrysotile factory workers, and other non-insulator, occupational exposures have lower risks of asbestos-related diseases.

The failure to challenge the Selikoff risk ratios is regrettable, especially considering that it was based upon politics, personalities, and not on scientific or legal evidentiary grounds.

As Irving Selikoff observed about his frequently cited statistics:

“These particular figures apply to the particular groups of asbestos workers in this study.  The net synergistic effect would not have been the same if their smoking habits had been different; and it probably would have been different if their lapsed time from first exposure to asbestos dust had been different or if the amount of asbestos dust they had inhaled had been different.”

E. Cuyler Hammond, Irving Selikoff, and Herbert Seidman, “Asbestos Exposure, Cigarette Smoking and Death Rates,” 330 Ann. N.Y. Acad. Sci. 473, 487 (1979).

The Selikoff risk figures were unreliable even for insulators, given that the so-called non-smokers were admittedly occasional smokers, and the low relative risk for smokers in the general population came from an historical cohort of relatively healthy American Cancer Society volunteers. The updated risk figures for smokers in the general population placed their lung cancer risk closer to, and above, 20-fold, which raised doubts about Selikoff’s neat multiplicative theory.

The more important lesson though is that the Philadelphia courts, with acquiescence from most defense counsel, never challenged the use of Selikoff’s 5x, 10x, and 50x risk ratios to describe asbestos effects and smoking interactions.  Dr. Epstein made such a challenge impolitic and imprudent.  In Philadelphia, the Selikoff risk ratios gained a measure of respectability that they never deserved in science, or in the courtroom.


Under Rule 702, the law has evolved to require reasonable exposure assessments of plaintiffs’ exposures, and supporting epidemiology that shows relevant increase risks at the level and the latency actual experienced by each plaintiff.  This criterion does not come from a “sufficiency” review as some have suggested; it is clearly a requirement of external validity of the epidemiologic studies relied upon by expert witnesses.

The following cases excluded or limited expert witness opinion testimony with respect to epidemiological studies that the court concluded were not sufficiently similar to the facts of the case to warrant the admission of an expert’s opinion based on their results:


General Electric Co. v. Joiner, 522 U.S. 136 (1997)(questioning the external validity of a study of massive injected doses of PCBs in baby mice, with an outcome unrelated to the cancer claimed by paintiff)

1st Circuit

Sutera v. Perrier Group of America Inc., 986 F. Supp. 655 (D. Mass. 1997)(occupational epidemiology of benzene exposure and benzene does not inform health effects from vanishingly low exposure to benzene in bottled water)

Whiting v. Boston Edison Co., 891 F. Supp. 12 (D. Mass. 1995) (excluding plaintiff’s expert witnesses; holding that epidemiology of Japanese atom bomb victims, and of patients treated with X-rays for spinal arthritis, and acute lymphocytic leukemia (ALL), was an invalid extrapolative model for plaintiff’s much lower exposure)

2d Circuit

Wills v. Amerada Hess Corp., 2002 WL 140542 (S.D. N.Y. 2002)(excluding plaintiff’s expert witness who attempted to avoid exposure assessment by arguing no threshold)(‘‘[E]ven though benzene and PAHs have been shown to cause some types of cancer, it is too difficult a leap to allow testimony that says any amount of exposure to these toxins caused squamous cell carcinoma of the head and neck in the decedent… . It is not grounded in reliable scientific methods, but only Dr. Bidanset’s presumptions. It fails all of the Daubert factors.’’), aff’d, 379 F.3d 32 (2d Cir. 2004)(Sotomayor, J.), cert. denied, 126 S.Ct. 355 (2005)

Amorgianos v. National RR Passenger Corp., 137 F. Supp. 2d 147 (E.D. N.Y. 2001), aff’d, 303 F.3d 256 (2d Cir. 2002);

Mancuso v. Consolidated Edison Co., 967 F.Supp. 1437, 1444 (S.D.N.Y. 1997)

3d Circuit

Magistrini v. One Hour Martinizing Dry Cleaning, 180 F. Supp. 2d 584(D.N.J. 2002), aff’d, 68 Fed. Appx. 356 (3d Cir. 2003);

In re W.R. Grace & Co., 355 B.R. 462 (Bankr. D. Del. 2006)

4th Circuit

White v. Dow Chemical Co., 321 F.Appx. 266, 273 (4th Cir. 2009)

Newman v. Motorola, Inc., 78 Fed. Appx. 292 (4th Cir. 2003)

Cavallo v. Star Enterprise, 892 F. Supp. 756, 764, 773 (E.D. Va. 1995) (excluding opinion of expert witness who failed to identify plaintiff ’s exposure levels to jet fuel, and failed to characterize the relevant dose-response relationship), aff’d in relevant part, 100 F.3d 1150, 1159 (4th Cir. 1996)

5th Circuit

LeBlanc v. Chevron USA, Inc., 396 Fed. Appx. 94 (5th Cir. 2010)

 Knight v. Kirby Inland Marine Inc.,482 F.3d 347 (5th Cir. 2007);

Cotroneo v. Shaw Environmental & Infrastructure, Inc., 2007 WL 3145791 (S.D. Tex. 2007)

Castellow v. Chevron USA, 97 F. Supp. 2d 780, 796 (S.D. Tex. 2000) (‘‘[T]here is no reliable evidence before this court on the amount of benzene, from gasoline or any other source, to which Mr. Castellow was exposed.’’)

Moore v. Ashland Chemical Inc., 151 F.3d 269, 278 (5th Cir. 1998) (en banc);

Allen v. Pennsylvania Engineering Corp., 102 F.3d 194, 198-99 (5th Cir. 1996)

6th Circuit

Pluck v. BP Oil Pipeline Co., 640 F.3d 671 (6th Cir. 2011)(affirming district court’s exclusion of Dr. James Dahlgren; noting that he lacked reliable data to support his conclusion of heavy benzene exposure; holding that without quantifiable exposure data, the Dahlgren’s causation opinion was mere “speculation and conjecture”)

 Nelson v. Tennessee Gas Pipeline Co., 243 F.3d 244, 252 (6th Cir. 2001)(noting ‘‘with respect to the question of dose, plaintiffs cannot dispute that [their expert] made no attempt to determine what amount of PCB exposure the Lobelvill subjects had received and simply assumed that it was sufficient to make them ill.’’)

Conde v. Velsicol Chemical Corp., 24 F.3d, 809, 810 (6th Cir. 1994)(excluding expert testimony that chlordane,although an acknowledged carcinogen that was applied in a manner that violated federal criminal law, caused plaintiff’s injuries when expert witness’s opinion was based upon high-dose animal studies as opposed to the low-exposure levels experienced by the plaintiffs)

7th Circuit

Cunningham v. Masterwear Corp., 2007 WL 1164832 (S.D. Ind., Apr. 19, 2007)(excluding plaintiff’s expert witnesses who opined without valid evidence of plaintiffs’ exposure to perchloroethylene (PCE)), aff’d, 569 F.3d 673 (7th Cir. 2009) (Posner, J.)(affirming exclusion of expert witness and grant of summary judgment)

Wintz v. Northrop Corp., 110 F.3d 508, 513 (7th Cir. 1997)

Schmaltz v. Norfolk & Western Ry. Co., 878 F. Supp. 1119, 1122 (N.D. Ill. 1995) (excluding expert witness opinion testimony that was offered in ignorance of plaintiff’s level of exposure to herbicide)

8th Circuit

Junk v. Terminix Intern. Co. Ltd. Partnership, 594 F. Supp. 2d 1062, 1073 (S.D. Iowa 2008).

Medalen v. Tiger Drylac U.S.A., Inc., 269 F. Supp. 2d 1118, 1132 (D. Minn. 2003)

National Bank of Commerce v. Associated Milk Producers, Inc., 22 F. Supp. 2d 942 (E.D. Ark. 1998)(excluding causation opinion that lacked exposure level data), aff’d, 191 F.3d 858 (8th Cir. 1999)

Bednar v. Bassett Furniture Mfg. Co., Inc.,147 F.3d 737, 740 (8th Cir. 1998) (“The Bednars had to make a threshold showing that the dresser exposed the baby to levels of gaseous formaldehyde known to cause the type of injuries she suffered”)

Wright v. Willamette Industries, Inc., 91 F.3d 1105, 1106 (8th Cir. 1996) (affirming exclusion; requiring evidence of actual exposure to levels of substance known to cause claimed injury)

National Bank of Commerce v. Dow Chemical Co., 965 F. Supp. 1490, 1502 (E.D. Ark., 1996)

9th Circuit

In re Bextra & Celebrex Marketing Sales Practices & Product Liab. Litig., 524 F. Supp. 2d 1166, 1180 (N.D. Cal. 2007)(granting Rule 702 exclusion of expert witness’s opinions with respect to low dose, but admitting opinions with respect to high dose Bextra and Celebrex)

Henricksen v. ConocoPhillips Co., 605 F. Supp. 2d 1142, 1157 (E.D. Wash. 2009)

Valentine v. Pioneer Chlor Alkali Co., Inc., 921 F. Supp. 666, 676 (D. Nev. 1996)

Abuan v. General Electric Co., 329 F.3d 329, 333 (9th Cir. 1993) (Guam)

10th Circuit

Maddy v. Vulcan Materials Co., 737 F.Supp. 1528, 1533 (D.Kan. 1990) (noting the lack of any scientific evidence of the level or duration of plaintiff’s exposure to specific toxins).

Estate of Mitchell v. Gencorp, Inc., 968 F. Supp. 592, 600 (D. Kan. 1997), aff’d,165 F.3d 778, 781 (10th Cir. 1999)

11th Circuit

Brooks v. Ingram Barge Co., 2008 WL 5070243 *5 (N.D. Miss. 2008)) (noting that plaintiff’s expert witness “acknowledges that it is unclear how much exhaust Brooks was exposed to, how much exhaust it takes to make developing cancer a probability, or how much other factors played a role in Brooks developing cancer.”)

Cuevas v. E.I. DuPont de Nemours & Co., 956 F. Supp. 1306, 1312 (S.D. Miss. 1997)

Chikovsky v. Ortho Pharmaceutical Corp., 832 F. Supp. 341, 345–46 (S.D. Fla. 1993)(excluding opinion of an expert witness who did not know plaintiff’s actual exposure or dose of Retin-A, and the level of absorbed Retin-A that is unsafe for gestating women)

Savage v. Union Pacific RR, 67 F. Supp. 2d 1021 (E.D. Ark. 1999)




Jones v. Ortho Pharmaceutical Corp., 163 Cal. App. 3d 396, 404, 209 Cal. Rptr. 456, 461 (1985)(duration of use in relied upon studies not relevant to plaintiffs’ use)


Nelson v. American Sterilizer Co., 566 N.W. 2d 671 (Mich. Ct. App. 1997)(affirming exclusion of expert witness who opined, based upon high-dose animal studies, that plaintiff’s liver disease was caused by low-level exposure to chemicals used in sterilizing medical equipment)


Watts v. Radiator Specialty Co., 2008 WL 2372694 *3 (Miss.2008);


Valentine v. PPG Indus., Inc., 158 Ohio App. 3d 615, 821 N.E.2d 580 (2004)


Christian v. Gray, 2003 Okla. 10, 65 P.3d 591, 601 (2003);

Holstine v. Texasco, 2001 WL 605137 (Okla. Dist. Ct. 2001)(excluding expert witness testimony that failed to assess plaintiff’s short-term, low-level benzene exposure as fitting the epidemiology relied upon to link plaintiff’s claimed injury with his exposure)


Merrell Dow Pharm., Inc. v. Havner, 953 S.W.2d 706, 720 (Tex. 1997) (“To raise a fact issue on causation and thus to survive legal sufficiency review, a claimant must do more than simply introduce into evidence epidemiological studies that show a substantially elevated risk. A claimant must show that he or she is similar to those in the studies.”).

Merck & Co. v. Garza, 347 S.W.3d 256 (Tex. 2011)

Frias v. Atlantic Richfield Co., 104 S.W.3d 925, 929 (Tex. App. Houston 2003)(holding that plaintiffs’ expert witness’s testimony was inadmissible for relying upon epidemiologic studies that involved much higher levels of exposure than experienced by plaintiff)

Daniels v. Lyondell-Citgo Refining Co, 99 S.W.3d 722 (Tex. App. 2003) (claim that benzene exposure caused plaintiff’s lung cancer had to be supported with studies of comparable exposure, and latency, as that observed and reported in the studies)

Austin v. Kerr-McGee Refining Corp., 25 S.W.3d 280, 292 (Tex. App. Texarkana 2000)

Print Friendly, PDF & Email

Comments are closed.