Rost, Richard, M., Exec. v. Ford Motor Co., Aplt.

OPINION

We address again the proper application of the “frequency, regularity, and proximity” criteria in asbestos product liability litigation, seeking to provide further illumination on the principles set forth in our decisions in this area, Gregg v. V-J Auto Parts, Co., 596 Pa. 274, 943 A.2d 216 (2007), and Betz v. Pneumo Abex, LLC, 615 Pa. 504, 44 A.3d 27 (2012). For the reasons that follow, we conclude that the trial court and the Superior Court properly applied those principles in this case, and thus affirm the judgment entered in favor of Appellees.

In October 2009, Appellees Richard and Joyce Rost1 filed suit against multiple manufacturers of asbestos, averring that exposure to the defendants’ asbestos-containing products caused Richard Rost (“Rost”) to contract mesothelioma. Before trial, the Rosts settled their claims against all defendants *634except for Appellant Ford Motor Company (“Ford”). Over Ford’s objections, the trial court consolidated the case for trial with two other mesothelioma cases. Trial commenced in September 2011, at which time the trial court reminded the parties of a pre-trial ruling, in accordance with Gregg, precluding any expert from offering testimony that “each and every breath” of asbestos may constitute an evidentiary basis for the jury to find that the defendant’s product was a substantial cause of mesothelioma.2 N.T., 9/12/2011 (AM), at 37.

At trial, Rost testified that upon graduation from high school in 1950, he took a job at Smith Motors in Washington, New Jersey, for three to four months, working full time Monday through Friday and half a day on Saturday. N.T., 9/14/2011 (AM), at 101, 114. While Smith Motors was a full service garage, it serviced approximately eighty-five to ninety percent Ford vehicles. Id. at 151. The parties stipulated that all model year Ford vehicles, from 1945 until 1950, used asbestos brakes and asbestos clutches, and that Ford’s brakes and clutches were forty to sixty percent chrysotile asbestos by weight. Stipulation, Rost Exhibit 5. Rost described his job as being a “gofer,” which involved basic maintenance tasks (changing oil, lubrication, and undercoating). Id. at 103. It was also his job to keep the garage area clean. Id. Approximately three to five times per week, when the mechanics removed brake shoes before performing a brake job, Rost had to pop off the asbestos lining from each shoe and throw it away. Id. at 103-05. There were two linings on each brake shoe, so this necessitated that he remove eight linings in connection with each brake job. Id. Asbestos dust was released as each lining *635was popped off, and Rost testified that he would breathe this dust in on every occasion. Id. at 105. Once a day, the mechanics would use an air compressor to blow out the dirt and debris inside the brake drums, and this would result in a significant amount of asbestos dust circulating throughout the garage. Id. at 106. Rost was typically within thirty to forty feet of these blowouts. Id. at 149-50.

Rost was also exposed to asbestos based upon his proximity to mechanics sanding brakes, replacing clutches, and performing engine work (head gaskets containing asbestos). Id. at 105, 129-31. At the end of each day, Rost testified that he cleaned up all of the asbestos dust and debris generated from the brake jobs, blow outs, and clutch and engine work. Id. at 113— 14. He used a push broom to gather the waste from the mechanics’ work areas, and typically deposited three coal shovelfuls of waste into the garbage at the end of each day. Id. at 114. Smith Motors did not have an exhaust system, with only a single fan in the window for ventilation, and Rost testified that “there was a smell in the garage from the dust in the air the whole time we were working in there.” Id. at 111. Smith Motors also had no shower facilities, and so Rost wore his dirty dust-covered clothes home at the end of each day on the job. Id. at 131.

Rost also testified regarding his subsequent occupational history and exposures to asbestos in connection therewith. After Smith Motors, he worked for Washington Woodcraft and Griffith <& Williams (a construction company), but was not exposed to asbestos in those jobs. Id. at 159-61. He then went to work for Tung-Sol, a manufacturer of television vacuum tubes, from 1952-53 and, after a term in the Army, from 1955-60. Id. at 115,166. Rost did not believe that he was exposed to asbestos at Tung-Sol, although he did perform maintenance work on the boiler once a week and worked on the turbines “twice a year for a couple of hours” during seasonal annual maintenance. Id. at 115-16, 165-67. In 1960, he went to work for Metropolitan Edison at its power plant near Portland, Pennsylvania, where he remained until his retirement in 1994. Id. at 116. He began as a janitor and served as a coal handler, *636boiler attendant, pump operator, instrument operator, and finally as the chief of instrumentation and controls. Id. at 118. During his time with Metropolitan Edison, he was exposed to asbestos in its boilers, turbines and generators. Id. at 131. Rost agreed that his asbestos exposure, especially in connection with his proximity to the turbines, was at “pretty high levels.” N.T., 9/14/2011 (PM), at 62. He also testified, however, that Metropolitan Edison became aware of the dangers of asbestos in or around 1970, and that by 1972 or 1973 he wore a face mask over his nose and mouth in high asbestos areas. N.T., 9/14/2011 (AM), at 122-23; N.T., 9/14/2011 (PM), at 62. Over a ten-year period, the company also incrementally replaced its asbestos-containing equipment. Id.

The Rosts called expert witnesses on medical and causation issues, including Dr. Arnold Brody, Ph.D., and Dr. Arthur Frank, M.D. Dr. Brody is an experimental pathologist and a professor at North Carolina State University. N.T., 9/20/2011 (AM), at 7-8. Dr. Frank is a physician and a professor at Drexel University School of Public Health and the Drexel University College of Medicine. N.T., 9/19/2011 (AM), at 8.

Dr. Brody did not testify regarding the specific eause of Rost’s medical condition, and instead offered more general testimony about how asbestos causes mesothelioma. He explained that there are two types or “families” of asbestos fibers, amphibole and chrysotile. N.T., 9/20/2016 (AM), at 82. About ninety-five percent of the asbestos-containing products used in the United States contained chrysotile fibers, including all of the Ford products at issue in this case. Id. at 86. Dr. Brody testified that on a fiber-per-fiber basis, amphibole fibers are more potent than chrysotile fibers, but that both types cause mesothelioma. Id. at 83-119. Given their smaller size, chrysotile fibers are more likely to get into the lymphatic flow and reach the pleura (the membrane on the outside lining of the lungs), and when investigators examine the target site of mesothelioma on the lung, they typically find a predominance of chrysotile fibers. Id. at 117.

Dr. Brody described for the jury precisely how asbestos causes mesothelioma. Mesothelioma is a cancer of the me-*637sothelial cells of the pleura. Id. at 27, 52. When asbestos fibers reach the mesothelial cells of the pleura, either through the blood stream or the lymphatic system, they act as a “complete carcinogen,” as they can lead to cancer without any other contributing agent. Id. at 50, 56. Asbestos fibers damage the DNA in the mesothelial cells that control cell reproduction. Id. Some damaged cells die and tumor suppressor genes stop others from reproducing. Id. at 64-65. Where suppressor genes do not stop the reproduction process, however, the damaged cells divide, replicating the damage in the sister cells. Id. at 68. As the division continues over decades, a tumor is formed. Id. This explains why mesothelioma has an extremely long latency period,3 as mesothelial cells have a very slow growth rate. Id. at 55.

The Rosts called Dr. Frank as an expert in “asbestos-related diseases and their causes, the ability of asbestos, including chrysotile asbestos, to cause mesothelioma in humans, the risk imposed from inhalation of chrysotile asbestos from brakes, the epidemiology of asbestos disease, asbestos industrial hygiene, asbestos toxicology and public health.” N.T., 9/19/2011 (AM), at 40. In his testimony, Dr. Frank referenced epidemiological studies, animal studies, and case reports, and indicated that he had himself performed epidemiological, animal, and cell and organ culture studies on individuals exposed to asbestos; he also participated in a study on the development of asbestos-related disease in brake mechanics, and has published many peer reviewed articles and book chapters on asbestos-related disease. Id. at 15-40. He stated that in his practice and research studies, he has seen “hundreds, if not thousands” of people exposed to asbestos. Id. at 25.

Dr. Frank testified that mesothelioma is a dose-response disease, by which “as the dose increases, the likelihood of developing the disease increases”: “small amounts carry small risks; larger amounts cause larger risks.” Id. at 82-83. Ac*638cording to Dr. Frank, it is not scientifically possible to identify the particular exposure or exposures that caused a patient’s mesothelioma, and instead the causative agent is “the series of exposures.” Id. at 71. All exposures to asbestos contribute to the cumulative dose of asbestos, and the cumulative dose causes mesothelioma. Accordingly, Dr. Frank testified that “[a]ll of the exposures that can be documented should all be considered as contributory to [Rost’s] developing his disease.”4 Id. at 122. It is also not scientifically possible to quantify how much asbestos is required to initiate the disease process, id. at 83, and varying individual susceptibility also plays a role. Id. at 72 (“Asbestos will cause disease in people who work, in people who don’t work.”); see also N.T., 9/19/2011 (PM), at 13 (“It creates a risk.... They don’t all develop [disease].”).

Moreover, Dr. Frank testified that while precise exposure threshold levels for the contraction of mesothelioma cannot be quantified, different asbestos-related diseases require different exposure levels. Contraction of asbestosis, the non-cancerous scarring of lung tissue, requires a “significant amount” of asbestos exposure before the condition will appear. N.T., 9/19/2011 (AM), at 83. Mesothelioma, in significant contrast, requires far less exposure. Dr. Frank testified that both case reports and animal studies reflect that there is evidence that both animals and humans may contract mesothelioma after a single day of exposure to asbestos. Id. at 84-85 (“very low levels will still produce the disease mesothelioma”). Even more, there is evidence that a single month of exposure to asbestos may double an individual’s risk of contracting meso-thelioma. Id. In this case, Rost was exposed to asbestos at Smith Motors for more than three months, in potentially high amounts on a daily basis. Based upon studies by a mineralogist, Dr. Frank testified that when a mechanic used an air *639compressor to blow out the inside of a brake drum, the resulting dust contained approximately seventeen fibers of chrysotile asbestos per cubic centimeter of air, and that even if Rost was as far as sixty feet away (he testified was typically ■within thirty to forty feet), the dust in the air would have been at elevated levels. Id at 100. Dr. Frank also found it significant that Rost wore his dust-covered clothes home each day after work, as it brought asbestos fibers into the home, which extended his exposure well beyond the three months he worked at Smith Motors. Id. at 118-19.

In response to a hypothetical question that detailed Rost’s exposure to asbestos while at Smith Motors, Dr. Frank testified that it was his opinion, within a reasonable degree of medical certainty, that Rost’s exposure to Ford products was a “significant contributing cause to developing mesothelioma.” Id. at 111-17. He then offered the following testimony:

Q. Now, Dr. Frank, I’ve asked you to assume that these exposures in 1950 for the three months approximately were at the Ford dealership. Now, if those were—now, you know in this case, that there are other exposures after 1950, correct?

A. Yes, sir.

Q. Now, if the only exposures that Mr. Rost had were those in 1950, would those have been enough alone without any of the ones he had later for you to say that was a significant contributing factor to his mesothelioma?

A. Yes.

* ⅜ *

Q. Okay. Now, we do know that in this case that there are other asbestos exposures. Given the fact that there were other asbestos exposures in this case, Doctor, is there any way for you to say that the early 1950s exposures didn’t contribute and the ones afterwards did?

A. There’s no scientifically plausible way to do that. They all contributed, his early exposures and his later exposures.

*640Q. Now, Doctor, is there any doubt in your mind that chrysotile asbestos from brakes contributed to Mr. Rost’s mesothelioma?

* * *

A. None whatsoever. No doubt.

Q. Is there any doubt in your mind that his exposures to insulation contributed to his mesothelioma?

A. No doubt whatsoever.

Q. Are all the exposures that he experienced to asbestos that can be demonstrated the causes of his mesothelio-ma?

A. All of the exposures that can be documented should all be considered as contributing to his developing the disease.

Q. Is there any doubt in your mind, Dr. Frank, that just working -with those brakes or around those brakes in 1950 at the Ford dealership could have caused his meso-thelioma?

* * *

A. If that would have been his only exposure, I would be sitting here saying that that was the cause of his disease. Given that he had other exposures, it was all contributory.

Id. at 120-23.

When the Rosts rested their case-in-chief, Ford moved for a nonsuit, contending that Dr. Frank had offered “each and every breath” opinion testimony prohibited as evidence of substantial causation by this Court in Gregg. N.T., 9/26/2011 (AM), at 98-99. Concluding that Dr. Frank had not done so and that the Rosts had presented sufficient evidence to send the case to the jury, the trial court denied the motion. Id. at 99. At the close of the evidence, the jury awarded the Rosts $994,800 ($844,800 to Rost and $150,000 to Joyce Rost). N.T., 10/7/2011, at 8-11. The jury also found that the products of three companies with asbestos-containing equipment at Metropolitan Edison (General Electric, Ingersoll-Rand, and Westinghouse) were also substantial causes of Rost’s mesothelioma. Id. The trial court molded the verdict by dividing it into four *641equal parts, thus entering judgment against Ford in the amount of $248,700, Id. at 17. Ford filed post-trial motions for judgment notwithstanding the verdict and/or a new trial, arguing, inter alia, that the trial court had erred in (1) failing to rule that Dr. Frank’s alleged “each and every breath” testimony was legally insufficient to establish substantial causation as a matter of law, and (2) failing to grant Ford’s motion in opposition to consolidation of its case with two other mesothelioma cases. By order dated December 28, 2011, the trial court denied Ford’s post-trial motions and entered judgment in favor of the Rosts.

Ford raised these same two issues on appeal to the Superior Court. In an unpublished memorandum decision, the court affirmed. On the first issue, the Superior Court concluded that Drs. Brody and Frank “provided detailed testimony about the nature of mesothelioma and its causes, backed up by published research on the subject. Their testimony was internally consistent and by the admission of Ford’s own experts, supported by at least 50 asbestos scientists around the world.” Rost v. Ford Motor Company, 2014 WL 2178528, at *10 (Pa. Super. May 19, 2014) (unpublished memorandum). The Superior Court further indicated that “while it is true that the ‘every exposure’ theory does not, by itself, meet the standard for substantial causation in a legal sense, this record is more than sufficient to establish its general scientific legitimacy.” Id. With respect to consolidation, the Superior Court noted that this Court had previously instructed the Philadelphia courts of common pleas to implement procedural measures to handle the volume of mesothelio-ma litigation, Pittsburgh Corning Corp. v, Bradley, 499 Pa. 291, 453 A.2d 314, 317 (1982), and that, as such, it did not have any authority to address procedural issues in this instance “absent a claim of violation of constitutional rights.” Rost, 2014 WL 2178528, at *12.

This Court granted Ford’s petition for allowance of appeal to consider the following two issues, as stated by Ford:

1. Whether—contrary to Howard, Betz, and Gregg—a plaintiff in an asbestos action may satisfy the burden of establishing substantial-factor causation by an expert’s *642“cumulative exposure” theory that the expert concedes is simply an “any exposure” theory by a different name[?]

2. Whether the Philadelphia Court of Common Pleas’ mandatory practice of consolidating unrelated asbestos cases—even where the defendants suffer severe prejudice as a result—is consistent with the Pennsylvania Rules of Civil Procedure and Due Process; whether consolidation in this case was proper; and whether the Superior Court has the authority to review a trial court’s case-consolidation decisions in asbestos cases[?]

Allocatur Order, 11/6/2014, at 1.

With respect to the first issue, Ford presents two arguments. For its first argument, Ford contends that this Court has established a bright line rule in mesothelioma products liability cases: namely, that a causation expert may not, when opining on substantial causation, rely on the theory that every exposure to asbestos is substantially causative of the disease. Ford’s Brief at 17. Ford argues that Dr. Frank’s testimony5 regarding cumulative exposures, including that all of Rost’s exposures to asbestos contributed to his disease and that “any exposure ... would ... be causative in the development of Mr. Rost’s disease,” N.T., 9/19/2011 (AM), at 82-83, 120, was “each and every breath” testimony even if he did not use those precise words or place the word “substantial” before the word “causative.” Ford’s Reply Brief at 5. According to Ford, the context surrounding Dr. Frank’s statements shows that his intention was to convey to the jury that every exposure to asbestos was a substantial cause of Rost’s meso-thelioma. Id at 6.

The Rosts argue, conversely, that Pennsylvania law requires that a plaintiff in a mesothelioma products liability action demonstrate that his or her exposure to asbestos was frequent, proximate and regular, and that a causation expert *643cannot rely merely on the proposition that every exposure to asbestos is a substantial cause of the disease. Rosts’ Brief at 26-27. The Rosts posit that Dr. Frank testified in accordance with these basic principles. According to the Rosts, Ford is simply confusing, or intentionally conflating, the basic scientific axiom that “every exposure contributes” into the impermissible “every exposure is a substantial cause.” Id.

Ford asks this Court to enter judgment notwithstanding the verdict in its favor or, alternatively, grant it a new trial. We will reverse a trial court’s grant or denial of a request for judgment notwithstanding the verdict only when we find an abuse of discretion or an error of law. Reott v. Asia Trend, Inc., 618 Pa. 228, 55 A.3d 1088, 1093 (2012); Dooner v. DiDonato, 601 Pa. 209, 971 A.2d 1187, 1193 (2009). An award of judgment notwithstanding the verdict is appropriate only if, reading the record in the light most favorable to the appellees as the verdict winners, and affording them the benefit of all reasonable inferences, we would conclude that there is insufficient competent evidence to sustain the verdict. Pennsylvania Dep’t of Gen. Servs. v. U.S. Mineral Products Co., 587 Pa. 236, 898 A.2d 590, 604 (2006). The appellate court must reject all evidence which does not support the verdict. Fitzpatrick v. Natter, 599 Pa. 465, 961 A.2d 1229, 1244 (2008). Regarding Ford’s contention that the prejudice resulting from Dr. Frank’s “any exposure” testimony entitles it to a new trial, our standard of review is one of abuse of discretion. Bruckshaw v. Frankford Hosp. of City of Philadelphia, 619 Pa. 135, 58 A.3d 102, 106 (2012); Harman v. Borah, 562 Pa. 455, 756 A.2d 1116, 1122 (2000).

We begin with a review of our decisions in Gregg and Betz. In Gregg, the estate of John Gregg, Jr. (“Gregg”), a mesothe-lioma victim, sought to recover against a manufacturer and a supplier of brake products, contending that Gregg had installed and removed brake linings during his lifetime. Gregg, 943 A.2d at 219. The trial court, relying on the Superior Court’s decision in Eckenrod v. GAF Corp., 375 Pa.Super. 187, 544 A.2d 50 (1988), granted summary judgment, concluding that the record at most supported Gregg’s use of asbestos-contain*644ing products sold by the defendants on two or three occasions. Id. at 52 (“Whether a plaintiff could successfully get to the jury or defeat a motion for summary judgment by showing circumstantial evidence depends upon the frequency of the use of the product and the regularity of plaintiffs employment in proximity thereto”). A panel of the Superior Court reversed, holding that Eckenrod did not apply when a plaintiff could offer direct testimony concerning exposure to a defendant’s products. Gregg, 943 A.2d at 220-21.

This Court granted review to consider whether the trial court erred in its application of the Eckenrod “frequency, regularity, and proximity” test on motions for summary judgment in mesothelioma cases. Id. at 221. In so doing, we recognized “the difficulties facing plaintiffs in this and similar settings, where they have unquestionably suffered harm on account of a disease having a long latency period and must prove specific causation under prevailing Pennsylvania law which may be insurmountable.” Id. at 226. Nevertheless, we concluded that these difficulties did not warrant the indulgence “in a fiction that each and every exposure to asbestos, no matter how minimal in relation to other exposures, implicates a fact issue concerning substantial-factor causation in every ‘direct evidence’ case.” Id. at 226-27. As such, we held that an “every exposure” generalized opinion does “not suffice to create a jury question in a case where exposure to the defendant’s product is de minimis....” Id. at 226.

Instead, to permit trial courts to make a reasoned determination at the summary judgment stage as to whether the plaintiff has proffered sufficient evidence to permit a jury to make the “necessary inference of a sufficient causal connection between the defendant’s product and the asserted injury,” id. at 227, we adopted the “frequency, regularity, and proximity” test, as refined and applied by the United States Court of Appeals for the Seventh Circuit in Tragarz v. Keene Corp., 980 F.2d 411 (7th Cir. 1992):

Tragarz explains that these criteria do not establish a rigid standard with an absolute threshold necessary to support liability. Rather, they are to be applied in an evaluative *645fashion as an aid in distinguishing cases in which the plaintiff can adduce evidence that there is a sufficiently significant likelihood that the defendant’s product caused his harm, from those in which such likelihood is absent on account of only casual or minimal exposure to the defendant’s product. Further, Tragarz suggests that the application of the test should be tailored to the facts and circumstances of the case, such that, for example, its application should become “somewhat less critical” where the plaintiff puts forth specific evidence of exposure to a defendant’s product. Similarly, under Tragarz, the frequency and regularity prongs become “somewhat less cumbersome” in cases involving diseases that the plaintiffs competent medical evidence indicates can develop after only minor exposures to asbestos fibers.

Gregg, 943 A.2d at 225 (citing Tragarz, 980 F.2d at 421) (citations omitted).

In Betz, this Court addressed a trial court’s decision to exclude “each and every breath” expert testimony under principles derived from Frye v. United States, 293 F. 1013 (D.C. Cir. 1923). The expert witness in Betz (Dr. John C. Maddox, M.D.) testified at the Frye hearing that he did not need to know the exposure histories of mesothelioma plaintiffs to offer an opinion on causation “so long as they could establish exposure to a single fiber from each defendant’s product.” Betz, 44 A.3d at 55. We held that the trial court did not abuse its discretion in excluding this expert testimony, as it was “right to be circumspect about the scientific methodology underlying the any-exposure opinion” because it presented no “coherent methodology supporting the notion that every single fiber from among, potentially, millions is substantially causative of disease.” Id at 53. “Simply put, one cannot simultaneously maintain that a single fiber among millions is substantially causative, while also conceding that a disease is dose responsive.”6 Id.

*646Together, Gregg and Betz establish two basic precepts important to resolution of the issues presented here. First, expert testimony based upon the notion that “each and every breath” of asbestos is substantially causative of meso-thelioma will not suffice to create a jury question on the issue of substantial factor causation. Second, to create a jury question, a plaintiff must adduce evidence that exposure to defendant’s asbestos-containing product was sufficiently “frequent, regular, and proximate” to support a jury’s finding that defendant’s product was substantially causative of the disease.7

*647Ford contends that Dr. Frank’s testimony regarding the cause of Rost’s mesothelioma violates the first precept because it rested upon an “each and every breath” theory of causation. Ford argues that Dr. Frank revealed the true nature of his testimony when he told the jury that “[wjhatever exposures you can show [Rost] had would have been contributory” and that “[t]he cumulative exposures contributed to his disease.” N.T., 9/19/2011 (PM), at 22. Ford further relies upon Dr. Frank’s indication that he could not separate the causative effects of Rost’s exposure to Ford products from those associated with other asbestos products. N.T., 9/19/2011 (AM), at 82-83.

In offering this testimony, however, Dr. Frank never indicated that a single exposure was a substantial cause of Rost’s mesothelioma. Dr. Frank explained to the jury, in some detail, about the dose response relationship between exposure to asbestos and the possibility of contracting mesothelioma. Id. at 82 (“As the amount of asbestos, as the dose increases, the likelihood of developing a disease increases.”). Dr. Brody offered the same opinion. N.T., 9/20/2011 (AM), at 71. In an amicus brief, fifty-eight physicians and scientists describe the fundamental notion that each exposure to asbestos contributes to the total dose and increases the person’s probability of developing mesothelioma or other cancers as an “irrefutable scientific fact.” Amicus Brief of Fifty-Eight Physicians/Scientists at 2. According to these physicians and scientists, cumulative exposure is “merely an extension of the ancient concept of dose-response, which is the “oldest maxim in the field.” Id. at 12 (citing Bernard D. Goldstein, Toxic Torts: The Devil is in the Dose, 16(2) J.L. & Pol’y. 661 (2008)). At the same time, *648while the threshold level of asbestos exposure for developing mesothelioma is unknown (and unquestionably varies by individual susceptibility), it is well-established that mesothelioma can occur in cases with relatively low exposure levels. N.T., 9/19/2011, at 83.

Similarly, Dr. Frank’s testimony regarding the inability to separate the causative effects of different exposures to asbestos was an effort to convey certain scientific limitations to the jury. Dr. Brody concurred, testifying, “You can’t just pick out one and say, ‘This exposure caused this set of errors.’ You can’t do that. It’s just not possible,” N.T., 9/20/2011 (AM), at 71.

We must agree with the Rosts that Ford has confused or conflated the “irrefutable scientific fact” that every exposure cumulatively contributes to the total dose (which in turn increases the likelihood of disease), with the legal question under Pennsylvania law as to whether particular exposures to asbestos are “substantial factors” in causing the disease. It was certainly not this Court’s intention, in either Gregg or Betz, to preclude expert witnesses from informing juries about certain fundamental scientific facts necessary to a clear understanding of the causation process for mesothelioma, even if those facts do not themselves establish legal (substantial factor) causation. In this case, while Dr. Frank clearly testified that every exposure to asbestos cumulatively contributed to Rost’s development of mesothelioma, he never testified that every exposure to asbestos was a “substantial factor” in contracting the disease.

Instead, by way of, inter alia, the lengthy hypothetical that detailed the entirety of Rost’s exposure to asbestos-containing Ford products while at Smith Motors, Dr. Frank testified that Rost’s actual exposures to asbestos at Smith Motors over three months was substantially causative of his mesothelioma. N.T., 9/19/2011 (AM), at 121. In other words, Dr. Frank did not testify that a single breath of asbestos while at Smith Motors caused Rost’s mesothelioma, but rather that the entirety of his exposures during the three months he worked there caused his disease. In this regard, Dr. Frank stressed *649that, unlike with some other asbestos-related diseases (e.g., asbestosis), mesothelioma may develop after only relatively small exposures. Id at 83. Moreover, in offering his testimony on the issue of legal (substantial factor) causation, Dr. Frank testified strictly in accordance with this Court’s dictates in Gregg and Betz—namely, that Rost’s exposures to asbestos at Smith Motors were sufficiently frequent, regular, and proximate to permit the inference that these exposures were substantially causative. Id. at 111-17. Dr. Frank reviewed the nature of the multiple exposures to asbestos at Smith Motors (e.g., removing brake shoe linings, his proximity to mechanics blowing out brake drums, sanding brakes, replacing clutches, replacing head gaskets, and sweeping up the dust and debris at the end of each day8), id. and the length of time the exposure continued (in excess of three months, while noting studies showing that a single month of regular exposure to asbestos can double one’s likelihood of developing mesothelio-ma). Id. at 84. He also reviewed Rost’s exposure history elsewhere, acknowledging that his exposures at Metropolitan Edison were also causative of his disease. Id at 122. Given all of this information, Dr. Frank testified that the totality of Rost’s exposure to asbestos at Smith Motors, standing alone, was sufficient to have caused his mesothelioma, even if there had been no other exposures (at Metropolitan Edison or elsewhere).

Unlike the expert witness in Betz, who unabashedly offered “each and every breath” testimony, in this case Dr. Frank relied upon a generally accepted methodology, taking into consideration exposure history, individual susceptibility, bio*650logical plausibility, and relevant scientific evidence (including epidemiological studies).9 Brief of Fifty-Eight Physicians/Scientists at 6. Moreover, per Gregg, his testimony regarding the frequency, regularity and proximity of Rost’s exposures to asbestos while at Smith Motors provided a sufficient basis to create a jury question regarding the existence of a causal connection between his exposure to asbestos-containing Ford products and the subsequent development of mesothelioma. In Gregg, this Court adopted the “frequency, regularity, and proximity” test as a refinement to the substantial factor requirement for proving causation in mesothelioma cases. In the context of expert testimony on substantial factor causation, Gregg provides the legal test, not an additional legal test, for proving substantial factor causation in cases involving disease resulting from asbestos exposure.

For its second argument in support of its first issue on appeal, Ford contends that this Court in Betz established another test, in addition to “frequency, regularity, and proximity,” that plaintiffs in mesothelioma cases must meet to establish substantial factor causation. In Betz, this Court noted that the expert in that case (Dr. Maddox) indicated that individual exposures differ “in the potency of the fiber to which an individual is exposed, to the concentration or intensity of the fibers to which one is exposed, and to the duration of the exposure to that particular material.” Betz, 44 A.3d at 56. These considerations, according to Dr. Maddox, go into “trying to estimate the relative effects of different exposures” and are “required for causal attrition as a matter of science.” Id. at 56, 58. Based upon this language in Betz, Ford argues that a *651causation expert in a mesothelioma ease must compare all of the plaintiffs exposures to asbestos over his or her lifetime to “determine which among a plaintiffs exposures substantially caused mesothelioma.” Ford’s Reply Brief at 11-12. According to Ford, the “question for an expert is not whether plaintiffs exposure to a given product is ‘substantial’ standing alone, but whether exposure to that product is a substantial cause in light of other exposures.” Id at 12. Because Dr. Frank did not compare Rost’s exposures at Smith Motors with his exposures at Metropolitan Edison (including fiber type, intensity and duration), Ford insists that his testimony failed to satisfy this second test. Id at 12.

Ford misconstrues our decision in Betz for several reasons. First, Betz did not involve any consideration of multiple asbestos exposures or any attempts to parse causally significant exposures from de minimis exposures. Instead, in Betz we addressed a trial court’s exclusion of “each and every breath” expert testimony after a Frye hearing. In so doing, we expressly disregarded the appellant’s contention that we should take into consideration that his four-decade history as an auto mechanic was “not a case of a de minimis occupational exposure.” Betz, 44 A.3d at 55. We indicated that because the expert (Dr. Maddox) testified that his opinion on causation did not depend upon any knowledge of a plaintiffs exposure history, our consideration of the issue presented would proceed without regard to the appellant’s actual exposure to asbestos. Id. Since no issues associated with multiple exposures were before the Court, Betz could not and did not add a significant new requirement for plaintiffs to establish substantial factor causation in cases involving multiple asbestos exposures. Because the issue was not presented, any attempt to create such an additional legal hurdle would have been mere obiter dicta. See generally Rendell v. Pennsylvania State Ethics Comm’n, 603 Pa. 292, 983 A.2d 708, 714 (2009) (holding that statements which were “unnecessary to the resolution of the controversy” were non-binding dicta).

Second, Ford takes the relevant language in Betz, specifically that a “comparative assessment of impact among *652differing exposures ... is required for causal attrition ... under Pennsylvania law,” Betz, 44 A.3d at 58, out of context. This language in Betz was intended to disabuse the Superior Court from any further reliance upon a statement in Tragarz that where “there is competent evidence that one or a de minimis number of asbestos fibers can cause injury, a jury may conclude the fibers were a substantial factor in causing a plaintiffs injury.” Id. (quoting Tragarz, 980 F.2d at 421). Of course, in Betz we merely reaffirmed our holding in Gregg that, contrary to the quoted statement in Tragarz, causation experts may not testify that a single exposure (i.e., “one or a de minimis number of asbestos fibers”) is substantially causative. Id at 56-57; Gregg, 943 A,2d at 226-27. Rather than offering “each and every breath” theoretical constructs, causation experts must provide concrete testimony of causal attribution by assessing the frequency, regularity, and proximity of the plaintiffs exposure to the defendant’s product. Gregg, 943 A.2d at 226-27. This assessment, in turn, requires a focus on the precise nature of the plaintiffs exposure to the defendant’s product, not on other asbestos-containing products. As we advised in Gregg, the Tragarz “frequency, regularity, and proximity” factors should be applied “in an evaluative fashion as an aid in distinguishing cases in which the plaintiff can adduce evidence that there is a sufficiently significant likelihood that the defendant’s product caused his harm.” Id at 225; see also Lindstrom v. A-C Prod. Liab. Trust, 424 F.3d 488, 493 (6th Cir. 2005) (“The requirement ... is that the plaintiff make a showing with respect to each defendant that the defendant’s product was a substantial factor in plaintiffs injury.”). Moreover, we indicated that, consistent with Tra-garz, application of the factors becomes “somewhat less critical” where the plaintiff puts forth specific evidence of exposure to a defendant’s product, and that the frequency and regularity prongs become “somewhat less cumbersome” in cases involving diseases that the plaintiffs competent medical evidence establishes can develop after only minor exposures to asbestos fibers. Gregg, 943 A.2d at 225.10

*653In this case, Rost’s testimony confirmed his frequent, regular and proximate exposures to asbestos from Ford products while at Smith Motors, and Dr. Frank, in part through the hypothetical question incorporating this exposure history, opined within a reasonable degree of medical certainty that the exposures at Smith Motors were sufficient, in and of themselves, to cause Rost’s mesothelioma.11 Comparison of Rost’s other occupational exposures to asbestos was unnecessary. We are unaware of any state or federal court that requires such a comparison. While some states continue to permit “each and every breath” testimony, e.g., Morin v. AutoZone Ne., Inc., 79 Mass.App.Ct. 39, 943 N.E.2d 495, 500 (2011); Weakley v. Burnham Corp., 871 A.2d 1167, 1177 (D.C. Ct. App. 2005); Purcell v. Asbestos Corp. Ltd., 153 Or.App. 415, 959 P.2d 89, 94 (1998); Sheffield v. Owens-Corning Fiberglass Corp.,