Session Heard at Greeneville January 7, 2015 
Tenn. R. App. P. 11 ; Judgment of the Court of Appeals Affirmed as Modified; Case Remanded to the Trial Court.
Judgment of the Court of Appeals Affirmed as Modified; Case Remanded to the Trial Court.
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Randall A. Jordan, Grant C. Buckley, Karen Jenkins Young, and Christopher R. Jordan, St. Simons Island, Georgia; John W. Baker Jr. and Emily L. Herman-Thompson, Knoxville, Tennessee; and Evan Mark Tager and Carl J. Summers, Washington, DC, for the appellant, CSX Transportation, Inc.
Richard N. Shapiro, Virginia Beach, Virginia, and Sidney W. Gilreath, Knoxville, Tennessee, for the appellee, Anne Payne.
GARY R. WADE, J., delivered the opinion of the Court, in which SHARON G. LEE, C.J., and CORNELIA A. CLARK, JEFFREY S. BIVINS, and HOLLY KIRBY, JJ., joined.
GARY R. WADE, J.
A railroad employee who was diagnosed with lung cancer filed suit against the railroad under the Federal Employers' Liability Act, alleging that the railroad had negligently exposed him to asbestos, diesel exhaust fumes, and radioactive materials, all of which were contributing causes to his illness. The employee also alleged that the railroad was negligent per se by violating pertinent safety statutes or regulations. When the employee died prior to trial, his wife was substituted as plaintiff. By special verdict, the jury awarded the plaintiff $8.6 million, finding that the employee's cancer and subsequent death were caused not only by the railroad's negligence but also by its negligence per se. The jury also found that the employee was sixty-two percent at fault due to his history of cigarette smoking. After the return of the verdict, the trial court instructed the jury that because of its finding that the railroad had violated safety regulations, the Federal Employers' Liability Act did not allow for a reduction of the amount of damages based upon the employee's contributory fault, meaning that the plaintiff would receive the entire $8.6 million. The jury then deliberated for an additional eight minutes and returned with an amended verdict awarding the plaintiff $3.2 million " at 100%." The trial court entered judgment on the amended verdict but later granted a new trial and entered an order of recusal. A substitute judge granted the railroad's motion for summary judgment after excluding the plaintiff's expert proof on the issue of causation. On appeal by the plaintiff, the Court of Appeals reversed the summary judgment and remanded with directions for the original trial judge to review the evidence and enter judgment on either the original $8.6 million verdict or the amended $3.2 million verdict. We hold that the plaintiff's expert proof was properly admitted at trial, but that the original judge erred by granting the railroad's motion for a new trial based on evidentiary and instructional issues, and committed prejudicial error in assessing the amount of damages to be awarded. Under these circumstances, the appropriate remedy is to remand for a new trial as to damages only.
I. Facts and Procedural History
From 1962 until his retirement in 2003, Winston Carrol Payne was employed by CSX Transportation, Inc. (the " Defendant" ) as a switchman, switch foreman, and brakeman in the railroad transportation department. Less than three years after his retirement, Mr. Payne was diagnosed with lung cancer. In 2007, he sued the Defendant under the Federal Employers' Liability Act (" FELA" ), 45 U.S.C. § § 51-60 (2012), alleging that the Defendant had not only been negligent by exposing him to asbestos, diesel engine exhaust fumes, and radioactive materials, thereby causing his lung cancer and related complications, but also had violated various statutes and regulations designed to protect the safety of railroad employees. In response,
the Defendant denied liability, maintaining that Mr. Payne had developed lung cancer because of his history of cigarette smoking, and further, that even if the cause of his cancer was not entirely the result of his smoking, any award of damages based upon the railroad's negligence should be reduced by virtue of Mr. Payne's contributory negligence.
A. Plaintiff's Proof at Trial
Prior to his death on February 24, 2010, Mr. Payne, whose grandfather, father, and three brothers had all worked for railroads, provided a videotaped deposition that was presented at the trial of this case, which was heard before a jury over the course of ten days in November of 2010. Mr. Payne, who admitted to smoking about twenty cigarettes per day between 1962 and 1988, testified that in October of 2005, two years after his retirement, his family doctor discovered a large mass in an x-ray of his lungs and referred him to a pulmonary specialist. Dr. Ross E. Kerns, an oncologist practicing in Knoxville, eventually diagnosed non-small-cell carcinoma and prescribed radiation treatment and chemotherapy. Mr. Payne underwent radiation treatment five days a week over the course of several months, with side effects including " a red rash all over [his] back" and a loss of taste. After his first round of chemotherapy, Mr. Payne suffered nausea, appetite loss, and insomnia. A second round of chemotherapy began in April of 2006 when his cancerous cells again became active. Because of the adverse effects of these treatments on his immune system, Mr. Payne developed pneumonia in May of 2006. By the summer of 2006, he " could hardly walk a hundred yards without having to stop and catch [his] breath." Although Mr. Payne's family physician, Dr. Rickey Manning, had diagnosed him with emphysema and chronic obstructive pulmonary disease in 1997, he claimed to have had no breathing problems before he was diagnosed with lung cancer. Upon finding active cancer cells in the summer of 2007, Dr. Kerns prescribed a third round of chemotherapy. A fourth round of chemotherapy, which Mr. Payne was still undergoing at the time of his videotaped deposition, was initiated in the spring of 2008. Mr. Payne calculated that by the time of his deposition he had completed a total of thirty-nine radiation treatments and forty-three chemotherapy sessions.
Mr. Payne maintained that his cancer was caused by regular exposure to asbestos, diesel engine exhaust fumes, and radioactive materials during his forty-one years of employment with the Defendant. Because Mr. Payne's duties regularly required him to travel on the Defendant's main railroad line between Etowah, Tennessee, and Corbin, Kentucky, when he would ride in the cabooses and open cars to protect the cargo and the rear of the train, he believed that he was continuously exposed to these three hazardous substances. He described the water pipes and heat shields on the stoves in the cabooses as being wrapped in asbestos insulation, and stated that when the trains' brakes, which contained asbestos materials, were applied, he was subjected to large amounts of dust and smoke that
" would come right into the caboose." Mr. Payne also observed asbestos in some of the cargo that he transported for the Defendant, including scrap metal that was " brought in from Oak Ridge [and taken] to [the] Witherspoon Junk Company," a scrapyard located in Knoxville. While Mr. Payne spent the majority of his forty-one years working in and around the trains, he expressed concern that asbestos materials were also located in the train car workshops where he would occasionally go for ten to twenty minutes at a time when he needed to " talk to the car man . . . so that [he] could figure [his] workload out." Mr. Payne testified that the Defendant never warned him of the dangers of exposure to asbestos and did not offer any protective equipment during the term of his employment.
Mr. Payne also testified that he " could see, smell, feel, [and] taste" the train engines' diesel fumes when he rode inside the engine cabs with the engineer. Although the windows and doors to the engine cab were often left open due to the heat, the diesel fumes would " trail into the engine cab" even if the doors were closed. Mr. Payne described the fumes as being so pervasive that " if you blew your nose, it was always black." He also described traveling through tunnels where the air quality was " terrible" because of the dense fumes. Mr. Payne stated that he worked in this kind of environment for some twenty years of his forty-one years of service, and that over the entire course of his employment he had never worked on a train without the presence of diesel fumes inside the engine cab. He recalled that he and other employees finally complained on one occasion because the conditions were " so bad" that " [they] just refused to work with it." He explained that he did not object to these conditions more often because, as with his lack of knowledge about the dangers of asbestos, " [he] didn't even know that diesel fumes [were] . . . a hazard." He further stated that the Defendant did not provide any warnings about the effects of diesel fumes, never tested the air quality levels on the trains, and did not offer a respirator or mask as protection from the fumes.
Mr. Payne testified that he had also been exposed to radioactive substances throughout his term of employment with the Defendant, particularly during one year in the 1980s when he transported cargo from the Oak Ridge Y-12 Nuclear Facility, and from 1962 until 1993 when he switched the train cars at the Witherspoon scrapyard. Mr. Payne stated that none of the train cars that he worked on were marked with radioactive symbols, although some of the cars were protected by Oak Ridge security guards. He recalled that " open top gondola cars" were often used to transport metal drums, which did bear a radioactive symbol, but that the Defendant treated these as " just another car" and never provided any special instructions for transporting the metal drums. Mr. Payne further testified that he often had to ride inside these cars when the train crossed the Tennessee River bridge in Knoxville, where he would be " right next to [the radioactive drums], inside [the car] with them." He stated that " [a]round twenty or thirty" metal drums marked with a radioactive symbol were stored next to the railroad track at the Witherspoon scrapyard, which he entered " hundreds of times" over the course of more than thirty years. According to Mr. Payne, the Defendant did not offer any training or protective materials to its employees and " never said one thing to [him] about radioactivity . . . or . . . any chemical hazard." When asked what the Defendant should have done differently as to all of these contaminants, Mr. Payne responded, " I think they should have given me training
of what to do in case we were handling or being close to radiation or asbestos or diesel fumes. They should have offered protective clothing, respirators, whatever it took to protect a man's health."
When Mr. Payne died in 2010 at the age of sixty-seven, his widow, Anne Payne (the " Plaintiff" ), was substituted as plaintiff. At trial, the Plaintiff's testimony largely corroborated Mr. Payne's videotaped deposition and provided more detail as to the negative effects of his radiation and chemotherapy treatments. Buffy Wilmoth, Mr. Payne's chemotherapy nurse, confirmed the side effects of his treatments. Donnie Carringer, who was employed by the Defendant from 1971 until 2005, corroborated the conditions that he and Mr. Payne experienced at the railroad, including exposure to " asbestos brakes" and dust; diesel fumes and " black looking smoke" ; and radioactive materials. Two other co-workers, Donnie Witt and Walter Cooper, offered similar testimony.
The Plaintiff also presented the videotaped deposition of William Bullock, a company representative for the Defendant, who testified as an adverse witness. While denying that Mr. Payne had been exposed to any hazardous materials, Mr. Bullock acknowledged the presence of asbestos on the Defendant's train engines, brakes, and cabooses, and the possible presence of plutonium at the Witherspoon scrapyard. As detailed in relevant part below, the Plaintiff offered additional testimony by numerous lay and expert witnesses who provided historical accounts of railroad industry standards, statistical data on hazardous materials in the workplace, and opinions as to what factors contributed to Mr. Payne's lung cancer.
Terry Rhodes, who from 1976 until 2002 was employed as a train engine repairman for Conrail and Norfolk Southern Railway Company, testified that he had worked primarily as a pipefitter and sheet metal worker, but that in 1990, " asbestos was added to [his] job" when Conrail began an abatement program. Mr. Rhodes acknowledged that he had " handled asbestos from the date [he] was hired at the railroad" and that 1990 was significant because it was the first time that Conrail provided " any formal training in how to remove asbestos." Although Mr. Rhodes was not employed by the Defendant, he testified that he was responsible for handling and removing asbestos from diesel train engines of the same model used by the Defendant. He confirmed that asbestos appeared in several places on the train engines, such as " on the radiator heater pipes[,] . . . the feed line and the discharge line to an air compressor[,] . . . the pipes running from the governor to the load regulator[,] . . . [a]nd . . . the . . . cab heater lines that ran all the way to the sump area of the locomotives up into the cab area." Mr. Rhodes, who had received training in identifying the materials containing asbestos, testified that he had removed " friable asbestos" from train engines that contained " airborne asbestos fibers."
Dr. Robert Leonard Vance, a board-certified industrial hygienist and licensed engineer, testified that the American Railway Association had " concerns with dust-related diseases in railroad men" as early as 1932, and that by 1935 the railroads
were aware that asbestos, commonly used in diesel-engine locomotives, caused various dust-related diseases. Dr. Vance also identified documents showing that by 1958, the Association of American Railroads had recognized the " carcinogenicity of asbestos and . . . how exposure to it induces cancer." In 1971, when the Occupational Safety and Health Administration (" OSHA" ) was established, " [t]he first material that it . . . regulated was asbestos," and OSHA thereafter continuously evaluated the amount of asbestos to which a person could be exposed without being harmed. After reviewing Mr. Payne's occupational history, Dr. Vance opined that Mr. Payne suffered " injurious levels of exposure" to asbestos during his term of employment with the Defendant, and that the workplace of the Defendant was not safe " with respect to asbestos." 
Dr. Vance further testified that " key information" about the dangers of diesel exhaust as a carcinogen was made available by 1955, some seven years prior to Mr. Payne's employment. In Dr. Vance's opinion, Mr. Payne " was [also] exposed to injurious levels of diesel exhaust," which " could have been significantly lessened if the [Defendant] had utilized appropriate control technology." Dr. Vance pointed to several diesel-exhaust regulations promulgated by the Federal Railroad Administration, which required " that the products of combustion . . . be released entirely outside of the cab and the other compartments, . . . that exhaust stacks . . . be of sufficient height . . . to prevent entry of products of combustion into the cab or other compartments," and that " the cab . . . be provided with proper ventilation." According to Dr. Vance, there were available methods of ventilation and personal protection that were not utilized by the Defendant, which led to his opinion " that the [Defendant] did not provide [Mr. Payne] with a reasonably safe place to work as far as diesel exhaust exposure [was] concerned."
Dr. Vance, who had been " involved with writing the regulations governing chemical exposures in the workplace" when he was the director of health standards at OSHA from 1982 until 1986, also determined that Mr. Payne had been exposed to radioactive substances at the Witherspoon scrapyard, which processed " tons and tons of recycled material that was contaminated with radiation."  Dr. Vance found that Mr. Payne had been exposed to radiation in a variety of ways during his term of employment, especially when he was required to walk along the railroad tracks in areas where radioactive materials were present. He further concluded that the Defendant had failed to provide training and educational programs for its employees or to implement protective measures such as respirators and radiation monitoring devices. Dr. Vance testified that Mr. Payne had worked for the Defendant for some nineteen years " before the [Defendant] hired a competent industrial hygienist to design a workplace safety program" in 1981. In consequence,
Dr. Vance opined that Mr. Payne was deprived of a " safe place to work as far as his radiation exposures were concerned." He confirmed that all of his opinions were provided " to a reasonable degree of certainty in the field of industrial hygiene." On cross-examination, Dr. Vance agreed that it was " not possible" to determine the amounts or " doses" of asbestos, diesel exhaust, and radiation to which Mr. Payne was exposed " because the [Defendant] never did [any] monitoring to determine what his levels of exposure were."
Daniel Stephen Mantooth, a health physicist specializing in radiation protection in the workplace, also testified on behalf of the Plaintiff. He identified uranium and plutonium as " highly dangerous" radioisotopes that could cause cancer if inhaled in sufficient quantities. Asked if he knew " how much plutonium needs to be inhaled before a person can have injury or death or develop cancer," Mr. Mantooth responded that " there's been no safe level for plutonium intake." He further testified that files obtained from the Tennessee Department of Radiological Health indicated that, during the term of Mr. Payne's employment, the Witherspoon scrapyard had received, by train or by truck, " gross tons of . . . contaminated scrap [metal] . . . from the Oak Ridge operations alone that was . . . enriched in uranium-235." He confirmed that uranium was found on the Witherspoon site in the 1960s and 1970s, and that one inspection indicated that " the material was leaching from the metal and the equipment into the ground." Inspections revealed the continued presence of uranium in the 1980s. Mr. Mantooth also found documentation indicating detectable levels of uranium and plutonium at the Witherspoon scrapyard in the 1990s, when environmental cleanup efforts had begun to take place. Mr. Mantooth testified that a health hazard report issued in 2007 " still . . . found detectable levels of uranium and plutonium on the site," even though this was " long after the metal ha[d] been taken out" and there had been " remediation of the soil and everything else." According to Mr. Mantooth's reading of the 2007 report, the levels of plutonium were high enough to consider it a " contaminant of concern," and the levels of uranium were above background levels. He testified that the uranium and plutonium had to have been transported to the Witherspoon scrapyard because the radioisotopes are not created " through natural causes."
At the request of the Plaintiff, Mr. Mantooth had developed two reports detailing the Defendant's operations related to radioactive materials during the term of Mr. Payne's employment. In the first, he " found no evidence that [the Defendant] had any . . . radiation protection program in place," indicating that Mr. Payne had been exposed to radiation " above background level," which qualified as " an unsafe level of radiation exposure." Mr. Mantooth pointed out that five elements of radiation protection should have been in place: (1) " [a] formal hazard assessment methodology to assess potential risk of employees from the transport of radioactive materials" ; (2) " a radiological survey program to verify that radiation and radioactive contamination levels . . . remain[ed] within the applicable limits . . . [and] that no residual contamination remain[ed] on
rail cars" ; (3) " a personal protective equipment program to provide appropriate types of protective clothing, respiratory protection equipment[,] and training on their use" ; (4) " [a] personal monitoring program" for both external and internal monitoring of employees; and (5) " [a] program to create and maintain records of the radiation safety program." Mr. Mantooth further testified that the Defendant had failed to utilize readily available methods of radiation monitoring or survey any of its train cars for radiation prior to 1983, even though the Defendant knew or should have known by the 1970s at the latest that the railroad was transporting radioactive materials to and from the Witherspoon scrapyard. In his opinion, the Defendant had violated two federal regulations by requiring Mr. Payne to be near the radioactive materials without proper protection and by failing to survey its train cars " with appropriate radiation detection instruments." In his second report, Mr. Mantooth found fault with the " input data" used by the Defendant's experts to estimate Mr. Payne's radiation exposure levels. While concluding that the exposure was at far higher levels than estimated by the Defendant's experts, Mr. Mantooth opined that " there[ was] just not enough information to do a credible dose reconstruction."
Dr. Kerns, Mr. Payne's treating oncologist from 2005 until his death in 2010, documented Mr. Payne's workplace exposures to asbestos, diesel exhaust fumes, and radiation, as well as his history of cigarette smoking. Dr. Kerns made note of the fact that Mr. Payne had stopped using tobacco products over fifteen years prior to his diagnosis of lung cancer. Describing Mr. Payne as a " very tough" and " motivated" patient, he provided detail as to the course of Mr. Payne's treatment, the progression of his cancer, and the ill effects of the combination of his chemotherapy and radiation. In developing his medical opinion as to the cause of Mr. Payne's lung cancer, Dr. Kerns opined that the workplace carcinogens and the cigarette smoking " contributed to his development of lung cancer." Observing that it was medically impossible to " know the precise amount of carcinogens that [Mr. Payne] inhaled" or to determine " that one single factor [was] the causation," Dr. Kerns concluded, " to a reasonable degree of medical certainty," that " asbestos, smoking, radiation[,] and diesel exhaust exposure" all contributed to Mr. Payne's lung cancer. While Dr. Kerns conceded on cross-examination that cigarette smoking " put [Mr. Payne] at an increased risk of lung cancer," he disagreed with defense counsel's suggestion that " cigarette smoking . . . [was] the major cause of [Mr. Payne's] cancer."
Dr. Arthur Leonard Frank, who holds both a medical degree and a Ph.D. in biomedical sciences, testified on behalf of the Plaintiff in his capacity as a board-certified physician in the field of occupational medicine. As a professor and chair of the Department of Environmental and Occupational Health at Drexel University, Dr. Frank has taught a variety of courses including topics related to occupational and environmental cancers. In preparation for the trial, he had considered several sources of information, including a lengthy interview with Mr. Payne taken prior to his death. Dr. Frank, who had authored an estimated 170 publications during his career, " [v]irtually all" of which had been subjected to peer review, testified that " about half of [his publications] ha[d] something to do with asbestos." He had also researched and written on the subjects of ...