WELCH, J.

The plaintiffs, Frances Robertson, Phillis Castille, Leslie Robertson, and Stewart Robertson, appeal a judgment that granted summary judgment in favor of defendant, The Sherwin-Williams Company ("Sherwin-Williams") and dismissed their survival and wrongful death claims against Sherwin-Williams and a judgment rendered following a "Daubert hearing"2 that prohibited certain testimony from the plaintiffs' expert on causation, Dr. Eugene J. Mark. For reasons that follow, we reverse both judgments of the trial court and remand for further proceedings.3

I. FACTUAL AND PROCEDURAL HISTORY

The factual and procedural history of the current dispute is so closely intertwined with our earlier opinion involving essentially the same issues, Robertson v. Doug Ashy Bldg. Materials, Inc., 2010-1552 (La.App. 1st Cir. 10/4/11), 77 So.3d 339, writs denied, 2011-2468, 2011-2430 (La. 1/13/12), 77 So.3d 972, 973, writs not considered, 2011-2433, 2011-2432 (La. 1/13/12), 77 So.3d 973, 974 ("Robertson III"4), that it is necessary to set forth in detail the relevant factual, procedural, and legal history from our earlier opinion prior to setting forth the factual and procedural history of the present appeal.

A. Robertson III, 77 So.3d at 342-345 (footnotes renumbered):

On appeal, this court reversed both the February 23, 2010 and April 5, 2011 judgments of the trial court.14 Robertson III, 77 So.3d at 352 and 359-360. In reversing the April 5, 2011 judgment granting Sherwin-Williams' motion for new trial on its motion for summary judgment and granting the motion for summary judgment, this court initially noted that the trial court erred in granting summary judgment on the issue of "substantial cause" (i.e., whether the exposure to asbestos-containing products purchased at or sold by Sherwin-Williams was a substantial factor in bringing about Harris Robertson's mesothelioma) because that issue was not raised in the underlying motion for summary judgment.15 Robertson III, 77 So.3d at 349; see also La. C.C.P. art. 966(E). On de novo review of the issue actually raised by Sherwin-Williams in its motion summary judgment (i.e., whether Harris Robertson had substantial asbestos exposure from products bought at Sherwin-Williams' stores or that Sherwin-Williams owned the stores in question), this court determined that the plaintiffs put forth sufficient evidence establishing that there were genuine issues of material fact as to whether "Gold Bond" was an asbestos containing joint compound, whether Harris Robertson routinely and regularly used and inhaled (and was thus significantly exposed to) the asbestos-containing "Gold Bond" joint compound in his dry wall finishing work, and whether Harris Robertson (or other people with whom he worked) purchased the asbestos-containing joint compound "Gold Bond" from Sherwin-Williams' stores. Robertson III, 77 So.3d at 349-352. Accordingly, this court determined that Sherwin-Williams was not entitled to summary judgment or to a new trial on its motion for summary judgment. Id.

With respect to the February 23, 2010 judgment granting Sherwin-Williams' motion to strike the testimony of Dr. Mark, this court determined that the trial court, when it concluded that Dr. Mark's expert opinion was unreliable, failed to comply with La. C.C.P. art. 1425(F) and failed to evaluate or analyze Dr. Mark's expert opinion under the standards set forth by the Unites States Supreme Court in Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579, 113 S.Ct. 2786, 125 L.Ed.2d 469 (1993), as adopted by the Louisiana Supreme Court in State v. Foret, 628 So.2d 1116 (1993). Robertson III, 77 So.3d at 358-359. Finding that this constituted legal error by the trial court, this court conducted a de novo review of Dr. Mark's expert opinion on causation and concluded that Sherwin-Williams failed to meet its burden of proving that Dr. Mark's expert opinions with regard to causation were unreliable. Id. Thus, the trial court erred in granting Sherwin-Williams' motion to strike. Robertson III, 77 So.3d at 359.

After reversing both the February 23, 2010 judgment of the trial court granting Sherwin-Williams' motion to strike the testimony of Dr. Mark and the April 5, 2011 judgment of the trial court granting Sherwin-Williams' motion for new trial and granting Sherwin-Williams' motion for summary judgment, this court remanded the matter to the trial court for further proceedings. Robertson III, 77 So.3d at 359-360.

B. Proceedings on Remand and the Present Appeal

On remand, Sherwin-Williams and the other defendants, Georgia Pacific and Union Carbide, filed a motion for a Daubert hearing on Sherwin-Williams' motion to strike portions of the opinion of Dr. Mark. Although the plaintiffs objected to another Daubert hearing on the basis it was unnecessary given this Court's decision in Robertson III, after a hearing, the trial court granted the motion.16 Thereafter, the trial court then conducted an evidentiary Daubert hearing, and at the conclusion of the hearing, the trial court rendered judgment granting the motion in part and denying the motion in part. On August 21, 2012, the trial court signed a "Daubert order" (or judgment) in accordance with its oral reasons, specifically providing that Dr. Mark was prohibited from testifying that each "special exposure" to asbestos constituted a significant contributing factor in the development of the disease, that Dr. Mark was prohibited from giving his definition of "special exposure," but otherwise, that Dr. Mark was allowed to give causation opinions.

Thereafter, on December 5, 2012, Sherwin-Williams filed a motion for summary judgment claiming "that [the] [p]laintiffs have no evidence capable of sustaining their burden of proving that asbestos from products purchased at Sherwin-[Williams'] stores was a substantial contributing factor in causing Harris Robertson's mesothelioma." The plaintiffs opposed the motion, and following a hearing on January 8, 2013, the trial court granted Sherwin-Williams' motion for summary judgment. A written judgment in accordance with the trial court's ruling granting Sherwin-Williams' motion for summary judgment and dismissing the plaintiffs' claims against Sherwin-Williams with prejudice was signed on January 29, 2013.

The plaintiffs now appeal the January 29, 2013 judgment dismissing its claims against Sherwin-Williams, as well as the August 21, 2012 interlocutory judgment (or Daubert order) limiting the testimony of Dr. Mark.17 On appeal, the plaintiffs contend that the trial court: (1) abused its discretion in partially granting Sherwin-Williams' Daubert motion and (2) erred in granting Sherwin-Williams' motion for summary judgment and in failing to recognize the existence of genuine issues of material fact.

II. LAW AND DISCUSSION

A. Cause-In-Fact in a Mesothelioma Case

The issues raised in the previous appeals in this matter, Robertson I, Robertson II, Robertson III, and in the instant appeal, Robertson IV, and its companion appeals, Robertson V and Robertson VI, have essentially involved the plaintiffs' burden of proving the cause-in-fact element of their action for damages.18 Cause-in-fact is a question of fact. Robertson III, 77 So.3d at 347; Rando, 16 So.3d at 1087.

There is a universally recognized causal connection between asbestos exposure above background levels and the occurrence of mesothelioma. Robertson III, 77 So.2d at 349, n. 14; Robertson I, 77 So.3d at 335; see also Landry v. Avondale Industries, Inc., 2012-0950 (La.App. 4th Cir.3/6/13), 111 So.3d 508, 511. Brief exposures to asbestos may cause mesothelioma in persons decades later and every non-trivial exposure to asbestos contributes and constitutes a cause of mesothelioma. See Rando, 16 So.3d at 1091; Robertson I, 77 So.3d at 335; Landry, 111 So.3d at 511; Francis v. Union Carbide Corp., 2012-1397 (La.App. 4th Cir. 5/8/13), 116 So.3d 858, 862, writ denied, 2013-1321 (La. 9/20/13), 123 So.3d 177. The causal link between asbestos exposure and mesothelioma contraction has been demonstrated to such a high degree of probability, while at the same time, few if any other possible causes have been identified, that if one is diagnosed as having mesothelioma and that person was exposed to asbestos, that exposure is recognized to be the cause of the mesothelioma. Robertson I, 77 So.3d at 335-336.

However, due to the lengthy latency period between exposure to asbestos and manifestation of the asbestos-related disease, cause-in-fact of the plaintiff's injuries by a particular defendant is considered the "premier hurdle" faced by plaintiffs in asbestos litigation. Robertson III, 77 So.3d at 347; Rando, 16 So.3d at 1088. To prevail in an asbestos case, the plaintiff must show by a preponderance of the evidence, that he was exposed to asbestos and that he received an injury substantially caused by that exposure. Robertson III, 77 So.3d at 347; Rando, 16 So.3d at 1088. When multiple causes of injury are present, a defendant's conduct is a cause-in-fact if it is a substantial factor in generating plaintiff's harm. Robertson III, 77 So.3d at 347; Rando, 16 So.3d at 1088.

Mesothelioma can develop after fairly short exposures to asbestos. Rando, 16 So.3d at 1091. Simply because a plaintiff suffered asbestos exposure while working only a short period for an employer and had longer exposures while working for others, it cannot be said the relatively short asbestos exposure was not a substantial factor in causing his mesothelioma. Id.

In Robertson III, 77 So.3d at 347, this court noted that the Louisiana Supreme Court addressed the causation problem in asbestos-related disease cases in Rando, 16 So.3d at 1090-1091, by relying on the reasoning of Borel v. Fibreboard Paper Products Corporation, 493 F.2d 1076, 1094 (5th Cir.1973), cert. denied, 419 U.S. 869, 95 S.Ct. 127, 42 L.Ed.2d 107 (1974), an asbestosis case, which provided as follows:

The Borel court also stated that "[w]hether the defendant's conduct was a substantial factor is a question for the jury, unless the court determines that reasonable men could not differ." Id.

In Rando, the Supreme Court then noted, that "[b]uilding upon this early observation [in Borel], Louisiana courts have employed a `substantial factor' test to determine whether exposure to a particular asbestos-containing product was a cause-in-fact of a plaintiff's asbestos-related disease." Rando, 16 So.3d at 1091. Thus, in an asbestos case, the claimant must show he had significant exposure to the product complained of to the extent that it was a substantial factor in bringing about his injury. Robertson III, 77 So.3d at 347 and 359; Rando, 16 So.3d at 1091. Stated differently, the plaintiff must prove, by a preponderance of the evidence that: (1) his exposure to the defendant's asbestos product was significant, and (2) that this exposure caused or was a substantial factor in bringing about his mesothelioma (or other asbestos-related disease). Robertson III, 77 So.3d at 347-348; see also Rando, 16 So.3d at 1092. In meeting this burden of proof, the plaintiff is not required to prove the quantitative level of exposure, i.e., the exact or cumulative dose of asbestos or the concentration of asbestos to which the plaintiff was exposed (vis-á-vis air sampling or similar means). See Robertson III, 77 So.3d at 359 and Rando, 16 So.3d at 1090-1091. Rather, a qualitative evaluation of the exposures to asbestos, i.e., the level, frequency, nature, proximity, and duration of the exposures at issue, can sufficiently prove causation. See Rando, 16 So.3d at 1090-1092; Watts v. Georgia-Pacific Corp., 2012-0620 (La. App. 1st Cir. 9/16/13), 135 So.3d 53, 62, writ denied, 2013-2442 and 2013-2444 (La. 1/27/14), 131 So.3d 59.19 Thus, the plaintiff can meet his burden of proving causation through either a quantitative or a qualitative assessment of asbestos exposure.

B. Cause-In-Fact in the Present Case

In this case, with regard to cause-in-fact of the plaintiffs' injuries (by Sherwin-Williams), the plaintiffs will bear the burden of proving that: (1) Harris Robertson had substantial asbestos exposure from products bought at Sherwin-Williams, and (2) that Harris Robertson's exposure to asbestos containing products manufactured or sold by Sherwin-Williams was a substantial factor in bringing about or causing his mesothelioma. Robertson III, 77 So.3d at 352. The issues raised in this appeal concern the second prong of cause-in fact of the plaintiffs' injuries — whether Harris Robertson's exposure to asbestos-containing products manufactured or sold by the defendants was a substantial factor in bringing about or causing his mesothelioma.20 Specifically to be determined is whether the testimony of Dr. Mark, the plaintiffs' expert on this issue, was reliable under the standards set forth in Daubert and whether summary judgment on this issue was appropriate.

1. Sherwin-Williams' Motion to Strike and the Daubert Hearing

In Robertson III, 77 So.3d at 349 n. 14 and 352-353, we noted that the plaintiffs in this matter were relying on the expert opinion of Dr. Mark to establish that Harris Robertson's significant exposure to asbestos-containing joint compounds manufactured or sold by the defendants, including Sherwin-Williams, was a substantial factor in bringing about or causing his mesothelioma — in other words, that Harris Robertson's asbestos exposures were medically significant. See also Robertson I, 77 So.3d at 336. Dr. Mark, a 1967 Harvard Medical School graduate, is employed as a pathologist in the Department of Pathology at Massachusetts General Hospital and practices primarily in pulmonary and autopsy pathology. Robertson III, 77 So.3d at 353. Dr. Mark is also a professor at Harvard Medical School, and he serves as a co-director of several post-graduate courses relating to pathology and asbestos-related lung diseases. Id.

In Sherwin-Williams' earlier motion to strike, it sought an order precluding Dr. Mark from offering unreliable testimony that "any fiber" or "every exposure above background" was a substantial contributing factor in causing Harris Robertson's disease, and the trial court initially granted the motion, finding that Dr. Mark's opinions on causation in this case were unreliable. Robertson III, 77 So.3d at 353. In Daubert, the United States Supreme Court set forth the criteria for determining the reliability of expert scientific testimony. The United States Supreme Court found that when, "[f]aced with a proffer of expert scientific testimony, ... the trial judge must determine at the outset ... whether the expert is proposing to testify to (1) scientific knowledge that (2) will assist the trier of fact to understand or determine a fact in issue." Daubert, 509 U.S. at 592, 113 S.Ct. at 2796. The Supreme Court explained that this would entail a "preliminary assessment of whether the reasoning or methodology underlying the testimony is scientifically valid and of whether that reasoning or methodology properly can be applied to the facts in issue." Daubert, 509 U.S. at 592-593, 113 S.Ct. at 2796. The Supreme Court then enumerated factors that the trial court may consider in fulfilling this "gatekeeping role:" the testability or refutability of the expert's theory or technique; whether the technique has been subjected to peer review and/or publication; the known or potential rate of error; and whether the technique or methodology is generally accepted by the scientific community. See Daubert, 509 U.S. at 593-594, 113 S.Ct. at 2796-2797. This list of factors is meant to be helpful, not definitive. Kumho Tire Company, Ltd. v. Carmichael, 526 U.S. 137, 151, 119 S.Ct. 1167, 1175, 143 L.Ed.2d 238 (1999).21

The factual basis for an expert's opinion determines the reliability of the testimony. An unsupported opinion can offer no assistance to the fact finder and should not be admitted as expert testimony. Robertson III, 77 So.3d at 355. The trial court's inquiry must be tied to the specific facts of the particular case. Id. The abuse of discretion standard applies to the trial court's ultimate conclusion as to whether to exclude expert witness testimony and to the court's decision as to how to determine reliability. Id.

It is important to note, however, that there is a crucial difference between questioning the methodology employed by an expert witness and questioning the application of that methodology or the ultimate conclusions derived from that application. Only a question of the validity of the methodology employed brings Daubert into play. Id. Additionally, Daubert concerns admissibility of the expert's opinion and not his qualifications as an expert in the area tendered. Id.

Louisiana Code of Civil Procedure article 1425(F) sets outs exactly what is required from the parties and the court when conducting a Daubert hearing and ruling on the admissibility of an expert's testimony, and provides, in pertinent part as follows:

In Robertson III, 77 So.3d at 354, this court pointed out that both Sherwin-Williams (in its motion to strike) and the trial court (in its reasons for judgment granting the motion to strike) had mischaracterized the substance of Dr. Mark's testimony. After reviewing Dr. Mark's affidavit and expert report, we summarized his expert opinion as follows:

Id.

This court then set forth, in detail, the substance of Dr. Mark's January 21, 2010 affidavit, which established his opinion on causation in this matter, as follows:

This court then determined that the trial court legally erred in striking the testimony of Dr. Mark because it failed to comply with La. C.C.P. art. 1425(F) and further, on de novo review, concluded that Sherwin-Williams failed to prove that Dr. Mark's opinion on causation was unreliable, thus warranting reversal of the trial court's judgment granting the motion to strike the opinion of Dr. Mark, Robertson III, 77 So.3d at 358-359. On remand, Sherwin-Williams and the other defendants, interpreted Robertson III as a directive to the trial court to conduct a Daubert hearing in accordance with La. C.C.P. art. 1425(F). Specifically, the defendants' claimed that a Daubert hearing was necessary so that: (1) the parties could offer testimony in support of or in opposition to Sherwin-Williams' motion to strike the testimony of Dr. Mark and (2) the trial court could conduct a Daubert analysis of the anticipated causation testimony of Dr. Mark. The plaintiffs opposed the motion, arguing that a Daubert hearing was not necessary because Robertson III was dispositive of the issue of the admissibility of Dr. Mark's testimony, because this Court found Dr. Mark's causation opinion was reliable. The trial court granted the motion to set a Daubert hearing,23 and in doing so, stated as follows:

In August of 2012, the trial court then conducted a three-day contradictory Daubert hearing receiving volumes of documentary evidence, as well as live testimony24 from Dr. Mark; Dr. Suresh Moolgavkar, an epidemiologist, biostatistician, and quantitative risk assessor, who was accepted by the trial court as an expert in the field of epidemiology, biostatistics, quantitative risk assessment and carcinogenesis, including fiber carcinogeneis; Dr. Michael Graham, a pathologist, who was accepted by the court as an expert in pathology and forensic pathology and causation of asbestos-related diseases; and Dr. William Dyson, an industrial hygienist, who was accepted by the trial court as an expert in industrial hygiene and risk assessment. Despite the trial court's statements on the record when it initially granted the motion for a Daubert hearing that it was going to adopt this court's opinion in Robertson III and allow Dr. Mark to testify, at the conclusion of the Daubert hearing, the trial court ruled as follows:

The trial court then signed a "Daubert order" on August 21, 2012 that provided: "IT IS ORDERED that the defense motion is GRANTED in part and DENIED in part. Specifically, this court will prohibit testimony from Dr. Eugene Mark that each `special exposure' to asbestos constitutes a significant contributing fact and further prohibit Dr. Mark from giving his definition of special exposure. Otherwise, Dr. Mark is allowed to give causation opinions."

On appeal, the plaintiffs argue that the trial court abused its discretion in prohibiting Dr. Mark from using the phrase "special exposure" or defining it because Dr. Mark's use of this phrase was not a methodology, but rather a grammatical choice of words to more precisely express a well-established legal and medical principle. The plaintiffs also argue that Dr. Mark's causation analysis was not circular and that his methodology was soundly based on the scientific method. We agree, and find, based on our review of the record, that the criticisms or objections that the defendants (and their experts) have with regard to the causation opinion of Dr. Mark do not relate to Dr. Mark's methodology, but rather, relate to the application of his methodology and the conclusions derived from the application of that methodology. As previously noted, only a question of the validity of the methodology brings Daubert into play. MSOF Corporation v. Exxon Corporation, 2004-0988 (La.App. 1st Cir. 12/22/05), 934 So.2d 708, 718, writ denied, 2006-1669 (La. 10/6/06), 938 So.2d 78.

At the Daubert hearing, the testimony and evidence focused on: (1) Dr. Mark's use of the term "special exposures" (2) the medical and scientific studies that Dr. Mark did or did not rely on when formulating his opinion on causation; (3) Dr. Mark's assumption that absent therapeutic radiation or erionite exposure, mesothelioma is caused by asbestos exposure, without regard to the possibility of spontaneous or idiopathic mesotheliomas; (4) whether Dr. Mark took into account the potency of different asbestos fiber types — i.e., chrysotile vs. amphibole; and (5) Dr. Mark's failure to quantify dose.

Dr. Mark's opinion is that each "special exposure" to asbestos constitutes a significant contributing factor in the development of mesothelioma, and he defined "special exposure" as an exposure for which there is a scientific reason or evidence (including epidemiological evidence) to conclude that such exposures increased the risk of developing diffuse malignant mesothelioma. Dr. Moolgavkar believed that Dr. Mark's definition of "special exposure" was circular, and that "special exposure" should be defined in terms of some quantitative exposure level that was well-recognized, like fiber per cubic centimeter years. Dr. Graham testified that the term "special exposure" was "really not defined in the scientific literature" and that he had never heard that term being used in the scientific and medical community.

Although Dr. Mark acknowledged that this term has not been used by any other expert in assessing asbestos exposures, he stated that it was used by the United States government in assessing radiation exposure. Dr. Mark testified that he first began using the term "special exposure" in a peer-reviewed article that he co-authored for Seminars in Diagnostic Pathology in 2006, which was entitled "Pathological recognition of diffuse malignant mesothelioma of the pleura: the significance of the historical perspective as regards this tumor." Therein, Dr. Mark wrote that that "all special exposures to asbestos together contribute to cause [diffuse malignant mesothelioma] based on modern understanding of cellular and molecular pathology in the multistage pathway of oncogenesis and calculation of mortality rates based on cumulative lifetime exposure." Richard L. Kradin, M.D. and Eugene Mark, M.D., "Pathological recognition of diffuse malignant mesothelioma of the pleura: the significance of the historical perspective as regards this tumor," Seminars in Diagnostic Pathology 23 (2006); 25. (Footnotes omitted).

Dr. Mark, noting that the word "special" means "distinctive or unique," chose the term "special exposure" because he wanted to be clear that in reaching an opinion or conclusion about causation, he was excluding trivial or inconsequential exposures, which do not contribute to or cause mesothelioma. Dr. Mark found the use of the phrase "special exposure" to be useful because it reflected that the cause of mesothelioma is not based on an absolute dose (such as fiber per cubic centimeter years), but on whether there was a scientific reason to believe that the form of the exposure, based on the knowledge of that exposure, would be an exposure expected to increase one's risk of developing mesothelioma. Stated differently, the term was intended to reflect the exposures that Dr. Mark considered, based on a qualitative cumulative assessment of the exposures, to have substantially contributed to causing mesothelioma and the exposures that could be excluded as having substantially contributed to it. Dr. Mark stated that the term "special exposure" had nothing to do with the methodology that he followed in reaching his conclusion on causation. Thus, we find the term "special exposure" was a phrase chosen by Dr. Mark to express the results of his methodology for determining causation of mesothelioma; it was not part of his methodology.

With regard to the methodology actually employed by Dr. Mark in reaching the conclusion that Mr. Robertson's mesothelioma was caused by his special or cumulative exposures to asbestos, we find that the evidence establishes that Dr. Mark followed and based his opinion on a scientifically valid method and that he properly applied that method in this case. The methodology employed by Dr. Mark was: (1) he reviewed the medical records and pathology materials and determined the disease that afflicted Mr. Robertson; (2) he then reviewed the sworn deposition testimony of Mr. Robertson's co-workers that detailed the type and scope of Mr. Robertson's work history and exposure to asbestos; (3) he correlated the exposure data with his library of scientific articles detailing the levels of asbestos exposure generated by the use of asbestos containing joint compounds, including the "Helsinki paper." and his knowledge of other peer-reviewed medical literature and ascertained that there was a basis in the literature, through epidemiological studies, case reports, and other biological evidence, supporting general causation (i.e., that the inhalation of chrysotile asbestos from joint compound products can cause mesothelioma); and (4) he then applied all of this information to the facts of Mr. Robertson's specific history of asbestos exposure, ruling out other possible causes of mesothelioma, such as therapeutic radiation and erionite exposure. The validity of this scientific methodology was confirmed by Dr. Moolgavkar, who stated that his methodology for determining causation in a mesothelioma case would be to evaluate the exposure history, determine the trade that the individual was engaged in, and then look at the epidemiological literature to see what studies have shown about whether that trade was at an increased risk of developing mesothelioma. And, Dr. Graham, who is the defendant's expert on causation, utilized the same methodology when formulating his opinion on causation. When an expert's opinions are grounded in methods and procedures of science rather than just speculative belief or unsupported speculation, the Daubert standard of reliability is satisfied. Arceneaux v. Shaw Group, Inc., 2012-0135 (La. App. 1st Cir. 9/24/12), 103 So.3d 1086, 1093, writ denied, 2012-2732 (La.3/1/13), 108 So.3d 1177.

Dr. Moolgavkar criticized Dr. Mark's opinion, claiming that he did not think that Dr. Mark reviewed and fairly considered all of the available epidemiological evidence on the issue of chrysotile exposure and diffuse malignant mesothelioma. While Dr. Moolgavkar admitted that Dr. Mark relied on epidemiological studies, he disagreed that those studies supported Dr. Mark's conclusions. However, this disagreement over the interpretation of the scientific literature is not a criticism of Dr. Mark's methodology, but rather a criticism of the application of or the conclusions derived from the application of that methodology, and thus, does not bring Daubert into play. See MSOF Corporation, 934 So.2d at 718. Additionally, Dr. Moolgavkar claims that Dr. Mark should have considered epidemiological studies involving other trades that Mr. Robertson was not engaged in, such as auto mechanics, to evaluate the risk of developing mesothelioma from low levels of exposure to chrysotile asbestos. However, Dr. Mark, noting that epidemiology was one of many tools to be considered in determining causation,25 chose to rely on epidemiological studies pertaining to drywall workers (the trade in which Mr. Robertson was engaged) and other trades that overlapped with or utilized drywall workers in the process of finishing walls, including carpenters, painters and plasterers. Dr. Moolgavkar also criticized Dr. Mark for relying on case studies, stating that case studies were limited and insufficient establish causation, although he later admitted there were instances when it was appropriate to rely on case studies. Dr. Mark relied on epidemiological and case studies or reports and found there was a basis to conclude that the inhalation of chrysotile asbestos from joint compound products can cause mesothelioma. To the extent that Dr. Mark may not have reviewed all of the epidemiological evidence that Dr. Moolgavkar thought was appropriate and to the extent that he relied on case studies that Dr. Moolgavkar deemed inappropriate, these factors affect only the weight to be afforded his conclusions and may serve as a basis for attack by the defendants on cross examination at trial, but it does not make the opinion evidence unreliable or inadmissible under Daubert. See MSOF Corporation, 934 So.2d at 720.

Additionally, both Dr. Moolgavkar and Dr. Graham criticized Dr. Mark for making the assumption that absent a history of erionite exposure or therapeutic radiation, diffuse malignant mesothelioma is asbestos related. Both Dr. Moolgavkar and Dr. Graham believed that mesotheliomas could occur spontaneously or ideopathically (without exposure to asbestos). Essentially, Dr. Mark stated that because asbestos is so strongly associated with mesothelioma, proof of significant exposure is proof of specific causation; that diffuse malignant mesothelioma is known as a signal tumor for asbestos exposure; and that once he has made a diagnosis of diffuse malignant mesothelioma and finds no history of erionite exposure or therapeutic radiation, he assumes that the diffuse malignant mesothelioma is asbestos related. Dr. Mark acknowledged that there was literature about varying percentages of diffuse malignant mesotheliomas that were not associated with a prior history of asbestos exposure; however, he did not believe that there were any idiopathic diffuse malignant mesotheliomas or spontaneous malignant mesotheliomas and that such cases could be attributed to inadequate occupational histories. The existence or non-existence of idiopathic or spontaneous mesotheliomas is a factual dispute between the experts, and thus goes to the credibility of the testimony and not its admissibility or reliability. See Dixon v. Tucker, 47,113 (La.App. 2nd Cir. 5/16/12), 92 So.3d 1100, 1105, writ not considered, 2012-1838 (La. 11/9/12), 100 So.3d 824. Furthermore, as previously noted, the Daubert inquiry must be tied to the specific facts of the particular dispute. Robertson III, 77 So.3d at 359. The dispute between Drs. Mark, Moolgavkar, and Graham over the existence of spontaneous or idiopathic mesotheliomas is irrelevant under the facts of this case, as Mr. Robertson's mesothelioma was not spontaneous or idiopathic. Rather, it was confirmed to have been caused by asbestos exposure, given the evidence of asbestos bodies in his lung.

Dr. Moolgavkar and Dr. Graham also criticized Dr. Mark because he did not make a distinction between exposures to chrysotile asbestos and amphibole asbestos when reaching his conclusions on causation. Specifically, Dr. Moolgavkar and Dr. Graham thought that Dr. Mark did not account for the fact amphibole asbestos was far more potent of a mesotheliogen than chrysotile. Dr. Mark acknowledged that there were physical, chemical, and potency differences between various asbestos fiber types; however, he believed, in accordance with the various scientific and cancer research organizations, that all commercial types of asbestos were capable of causing diffuse mesothelioma and that there was no known safe level of exposure to asbestos. Dr. Moolgavkar acknowledged that the International Agency for Research on Cancer, the highly respected cancer agency of the World Health Organization, had concluded that there was sufficient evidence in humans for the carcinogenicity of all forms of asbestos in causing mesothelioma and cancer, and that asbestos, in all of its forms was both an occupational and environmental hazard responsible for the ongoing increases in the number of mesotheliomas, lung cancer, asbestosis, and other diseases. Thus, with regard to the distinction between chrysotile and amphibole asbestos fiber types, herein, the issue is not whether chrysotile is capable of causing mesothelioma, but rather on its potency — i.e., whether in Mr. Robertson's case, there was sufficient exposure to chrysotile asbestos to substantially contribute to the development of his disease. This is a factual issue, and thus, more appropriately, a question for the jury. See Rando, 16 So.3d at 1091, citing Borel 493 F.2d at 1094.

Lastly, Drs. Moolgavkar and Graham criticized Dr. Mark because he did not make a quantitative cumulative assessment of the dose of asbestos to which Mr. Robertson was exposed. Dr. Mark admitted that he made no quantitative calculation of Mr. Robertson's cumulative exposure to asbestos because the data was not available. Dr. Graham, while admitting that Mr. Robertson would have had exposure to joint compounds that contained asbestos, confirmed that there was insufficient detail to make a quantitative cumulative assessment of the dose. Furthermore, Dr. Mark noted that while quantitative cumulative fiber dose, as expressed in fiber per cubic centimeter years, was an important parameter to consider when trying to apportion the relative risk of products, he believed that it was not relevant when a patient already has the disease because there is no speculation as to whether the patient is at risk for developing the disease. Dr. Mark opined that while dose has to be taken into consideration when making a determination about a special exposure, since there is no known safe level of exposure to asbestos, the usual concept of dose only means that there is a dose-response relationship between exposure to asbestos and mesothelioma, and that the absolute dose is not the relevant issue.

As noted hereinabove, the plaintiff can meet his burden of proving causation through either a quantitative or a qualitative assessment of asbestos exposure. Dr. Moolgavkar, was unable to provide any opinion on the qualitative exposure and occupational history of Mr. Robertson. However, the record reveals that Dr. Mark did a qualitative assessment of Mr. Robertson's exposures (i.e., he evaluated the exposures based on their frequency, based on their proximity and based on their intensity) and determined that Mr. Robertson had substantial, sequential, incremental, heavy exposures to chrysotile fibers for a long period of time (19 years) and that these exposures constituted special exposures.26

In our review of the trial court's Daubert order in conjunction with the evidence offered at the hearing, we are mindful that it is not within our province to weigh the evidence or testimony of the experts and their opinions, but rather to ensure that the trial court properly performed its gatekeeping function when it evaluated the reliability of the testimony of Dr. Mark under the standards set forth in Daubert. Although the trial court is afforded broad discretion in determining whether expert testimony is reliable under Daubert, that discretion is premised upon an understanding that Daubert is intended to protect the sanctity of the fact finding process by assessing the validity of the methodology employed by an expert and not the expert's application of that methodology or his conclusions derived from the application of that methodology. Certainly, not all experts are equal; however, issues involving the credibility of the expert, the weight to be given to the expert's testimony, and the resolution of conflicts between expert opinions testimony are to be assessed at trial by the trier of fact.

In this case, the majority of the evidence presented at the Daubert hearing was framed by specific objections that Sherwin-Williams (and the other defendants) had with regard to the causation opinion of Dr. Mark, which did not relate to his methodology, but rather, involved the conclusions derived from applying that methodology to the facts of this case, and thus pertained to his credibility and the weight of his opinion testimony. The evidence at the hearing concerning the proper methodology to be utilized in formulating an opinion on causation established that Dr. Mark's methodology was typical of the process undertaken by an expert, conformed to accepted scientific principles, and thus was reliable under the standards set forth in Daubert. Therefore, we find that the trial court abused its discretion in granting, in part, Sherwin-Williams' motion to strike and in prohibiting Dr. Mark from testifying that each "special exposure" to asbestos constituted a significant contributing fact and in prohibiting Dr. Mark from giving his definition of special exposure. Accordingly, the August 21, 2012 judgment of the trial court or "Daubert order" is hereby reversed.

2. Sherwin-Williams' Motion for Summary Judgment

a. Summary Judgment Law

A motion for summary judgment is a procedural device used to avoid a full-scale trial when there is no genuine issue of material fact. Robertson III, 77 So.3d at 345. Summary judgment is proper only if the pleadings, depositions, answers to interrogatories, and admissions on file, together with any affidavits, show there is no genuine issue of material fact and that the mover is entitled to judgment as a matter of law. La. C.C.P. art. 966(B); Robertson III, 77 So.3d at 345-346.

Summary judgments are reviewed on appeal de novo. Robertson III, 77 So.3d at 346. Thus, this court uses the same criteria as the trial court in determining whether summary judgment is appropriate — whether there is a genuine issue of material fact and whether mover is entitled to judgment as a matter of law. Id.

On a motion for summary judgment, the initial burden of proof is on the moving party. If, however, the moving party will not bear the burden of proof at trial on the matter before the court, the moving party's burden of proof on the motion is satisfied by pointing out to the court that there is an absence of factual support for one or more elements essential to the adverse party's claim, action, or defense. Thereafter, the non-moving party must produce factual support sufficient to establish that it will be able to satisfy its evidentiary burden of proof at trial. Failure to do so shows that there is no genuine issue of material fact. Id.; La. C.C.P. art. 966(C)(2). Once the motion for summary judgment has been properly supported by the moving party, the failure of the non-moving party to produce evidence of a material factual dispute mandates the granting of the motion. Robertson III, 77 So.3d at 346; see also La. C.C.P. art. 967(B). Any doubt as to a dispute regarding a genuine issue of material fact must be resolved against granting the motion and in favor of a trial on the merits. Robertson III, 77 So.3d at 346.

A "genuine issue" is a "triable issue," that is, an issue on which reasonable persons could disagree. If, on the state of the evidence, reasonable persons could reach only one conclusion, there is no need for a trial on that issue. Id. In determining whether an issue is genuine, a court should not consider the merits, make credibility determinations, evaluate testimony, or weigh evidence. Id. A fact is material if it potentially ensures or precludes recovery, affects a litigant's ultimate success, or determines the outcome of the legal dispute. Id. Because it is the applicable substantive law that determines materiality, whether a particular fact in dispute is material can only be seen in light of the substantive law applicable to the case. Id.

b. Merits of Sherwin-Williams' Motion for Summary Judgment

As noted above, the plaintiffs will bear the burden of proving at trial that that Harris Robertson's significant exposure to asbestos containing products manufactured or sold by Sherwin-Williams was a substantial factor in bringing about or causing his mesothelioma. Sherwin-Williams, as a defendant, will not bear the burden of proof at trial; however, as the mover in the motion for summary judgment, it had the initial burden of proof pursuant to La. C.C.P. art. 966(C)(2) to support and point out that there was an absence of factual support for this element of the plaintiffs' claim. In Robertson III, 77 So.3d at 349 n. 14, this court specifically set forth that for Sherwin-Williams to meet its initial burden on summary judgment on this issue, Sherwin-Williams had to either: (1) offer "evidence in support of its motion to show that Harris Robertson's exposures were not medically significant" or (2) offer evidence that the plaintiffs' "did not have a medical causation expert on this issue." In the absence of such evidence, a motion for summary judgment on the issue would be unsupported and would not shift the burden to the plaintiffs to demonstrate, at the summary judgment stage, that the exposures on which the plaintiffs were relying were medically significant. Id.

In Sherwin-Williams' motion for summary judgment, it claimed "that [the] [p]laintiffs have no evidence capable of sustaining their burden of proving that asbestos from products purchased at Sherwin-Williams' stores was a substantial contributing factor in causing Harris Robertson's mesothelioma." Essentially, in the motion for summary judgment, the defendants claimed that there was an absence of factual support for the plaintiffs' claims because the plaintiffs did not have an expert industrial hygienist (or anyone else qualified to opine about the intensity and duration of or total dose or amount of exposure Harris Robertson had to asbestos containing products) and because the trial court limited Dr. Mark's causation testimony in the Daubert hearing to general causation and specifically prohibited him from testifying that each "special exposure" to asbestos constituted a substantial contributing factor in causing Harris Robertson's mesothelioma.

In support of their motion for summary judgment, Sherwin-Williams pointed to the deposition testimony of Harris Robertson's three brothers (Harold Robertson, Raoul "Bobby" Robertson, and Raymond Robertson), Glynn Pierret, and Ray Montgomery, all of whom had previously worked with Harris Robertson in the drywall finishing and painting business. Collectively, this testimony established that Harris Robertson used asbestos-containing dry wall joint compound (or "sheetrock mud"), including "Gold Bond," "USG," and "Welcote," which was purchased from several different stores or suppliers, including Sherwin-Williams. In addition, Sherwin-Williams pointed to deposition testimony of Dr. Mark, wherein he stated that with regard to Sherwin-Williams, his opinion was simply that "Mr. Robertson purchased supplies from Sherwin-Williams." Based on this evidence, as well as the Daubert ruling, Sherwin-Williams claimed that the evidence established only that Harris Robertson used many brands of drywall joint compound purchased from many different stores and did not establish that the products bought at Sherwin-Williams contributed to Harris Robertson's disease or death to any particular degree or proportion, much less that its products substantially contributed to his disease or death.

The plaintiffs opposed the motion with the deposition testimony from Harris Robertson's two brothers (Harold Robertson and Raymond Robertson) and a new affidavit from Dr. Mark.27 The deposition testimony of Harris Robertson's brothers established that Harris Robertson performed drywall work starting in the 1960's and that he used dry wall joint compound (or "sheetrock mud"), including "Gold Bond," "USG," and "Welcote," which was purchased from several different stores or suppliers, including Sherwin-Williams. Their testimony also established that the entire drywall process — mixing, sanding, and clean up — was very dusty and that the joint compound dust from the process was inhaled.28

The new affidavit of Dr. Mark, executed on December 21, 2012, sets forth his qualifications, an explanation of the scientific method, and recent developments in the study of asbestos. Dr. Mark explained that these studies, when taken as an aggregate, indicate that all types of asbestos are fibrogenic and oncogenic, albeit to different degrees depending upon the chemistry and physics of the asbestos. Dr. Mark further explained that these studies also indicate that diffuse malignant mesothelioma is caused by asbestos and that it is the only established cause in the United States, apart from radiotherapy given to the site of the tumor. With regard to Harris Robertson's exposure to Gold Bond joint compound, Dr. Mark stated as follows:

With regard to Sherwin-Williams, Dr. Mark stated as follows:

The plaintiffs contended that this evidence was sufficient to establish that they would be able to satisfy their evidentiary burden of proving that Harris Robertson's significant exposure to asbestos containing products sold by Sherwin-Williams was a substantial factor in bringing about or causing his mesothelioma.

A hearing on the motion for summary judgment was held on January 8, 2013. Following the argument of counsel, the trial court granted Sherwin-Williams' motion for summary judgment for the following reasons:

Based on our de novo review of the record, we find Sherwin-Williams failed to meet its initial burden of pointing out that there was an absence of factual support for the plaintiffs' claim that Harris Robertson's exposure to asbestos-containing products purchased at (or sold by) Sherwin-Williams was a substantial factor in bringing about his mesothelioma. The evidence offered by Sherwin-Williams established only what this court has already determined — that there are genuine issues of material fact as to whether Harris Robertson routinely and regularly used and inhaled (and thus was significantly exposed to) the asbestos-containing "Gold Bond" joint compound in his dry wall finishing work and whether Harris Robertson (or other people for or with whom he worked) purchased the asbestos containing joint compound "Gold Bond" from Sherwin-Williams' stores. See Robertson III, 77 So.3d at 352.

Sherwin-Williams did not offer, in support of its motion for summary judgment, evidence to show that Harris Robertson's exposures to asbestos-containing products sold by Sherwin-Williams were not medically significant. Instead, Sherwin-Williams chose to rely on the trial court's Daubert ruling that limited Dr. Mark's testimony in order to establish that the plaintiffs did not have a medical causation expert on this issue. Since the trial court's Daubert ruling has been reversed herein and considering the lack of evidence offered by Sherwin-Williams to establish that the exposures on which the plaintiffs were relying were not medically significant, Sherwin-Williams' motion for summary judgment was unsupported and was improvidently granted.

Furthermore, even though Sherwin-Williams' unsupported motion for summary judgment did not shift the burden to the plaintiffs to show that there were issues of fact — i.e., that Harris Robertson's exposures to asbestos from products purchased at Sherwin-Williams were medically significant — we find, on de novo review, that the evidence offered by the plaintiffs in opposition to the motion for summary judgment, including the new affidavit of Dr. Mark sufficiently established that there were genuine issues of material fact as to whether Harris Robertson's exposures to asbestos-containing products sold by Sherwin-Williams was a substantial factor in his causing his mesothelioma. Accordingly, Sherwin-Williams was not entitled to summary judgment, and we reverse the January 29, 2013 judgment of the trial court that granted Sherwin-Williams' motion for summary judgment and dismissed the plaintiffs' claims against Sherwin-Williams.

CONCLUSION

For all of the above and foregoing reasons, the August 21, 2012 judgment of the trial court prohibiting certain testimony from Dr. Eugene Mark is reversed and the January 29, 2013 judgment of the trial court granting Sherwin-Williams' motion for summary judgment and dismissing the plaintiffs' claims against Sherwin-Williams, with prejudice, is reversed. This matter is remanded to the trial court for further proceedings.

All costs of this appeal are assessed to the defendant/appellant, The Sherwin-Williams Company.

AUGUST 21, 2012 JUDGMENT REVERSED; JANUARY 29, 2013 JUDGMENT REVERSED; REMANDED.

PETTIGREW, J., concurs.