Full opinion text
PER CURIAM: Alfred R. Taylor, Christian A. Hansen, and Randall W. Hansen appeal their convictions for conspiracy to commit environmental crimes, violating the Clean Water Act, violating the Resource Conservation and Recovery Act, and violating the Comprehensive Environmental Response, Compensation, and Liability Act. On appeal, they each assert several alleged trial and sentencing errors. Finding no merit to their claims, we AFFIRM. I. BACKGROUND Christian Hansen (“Hansen”) founded the Hanlin Group (“Hanlin”) in 1972, and served as its President, Chief Executive Officer, and Chairman of the Board until early April 1993. R19-160. Hanlin operated an industrial plant in Brunswick, Georgia, as LCP Chemicals-Georgia (“LCP”), R21-41, and Hansen served as the plant manager for approximately two months in 1993. R19-166-67. Randall Hansen (“Randall”), Hansen’s son, was hired as an executive vice president in 1992. R21-193. He became Chief Executive Officer in April 1993 and served in that capacity until November 1993. R21-195. Alfred Taylor (“Taylor”) began working for LCP in 1979, and became the Brunswick operations manager in 1991. R21-243-44. He served as plant manager from February until July 1993. R21-244-45. Hanlin purchased the Brunswick plant in 1979. R21-41. The plant, which is on a site adjacent to tidal marshes and Purvis Creek, operated continuously year-round, manufacturing caustic soda, hydrogen gas, hydrochloric acid, and chlor-alkali bleach. About 150 people worked at the plant in two “cell buildings” or “cellrooms.” Each cellroom was about the size of a football field and contained fifty mercury “cells,” the units used to produce the bleach, soda, gas, and acid ultimately sold by LCP. R8-200-2. “The production process generated hazardous wastes, including elemental mercury, mercury-contaminated sludge (or ‘muds’), wastewater, chlorine contaminated wastewater, and extremely caustic wastes with high pH values.” Id. at 2-3; R16-112-14. The wastes were subject to various environmental regulations, including wastewater limitations on pH, mercury, and chlorine set forth in LCP’s National Pollutant Discharge Elimination System (“NPDES”), and to regulations of the Resource Conservation and Recovery Act (“RCRA”), 42 U.S.C. § 6928(d)(2). LCP constructed a wastewater treatment system in 1989 and 1990, and was allowed, by NPDES permit, to discharge the treated wastewater into Purvis Creek. Although LCP represented that the system would have a continuous treatment capacity of 70 gallons per minute in the project description submitted to the Georgia EPD, Govt. Ex. 10-3b at SW5 00001807, the filtration and storage systems installed had a capacity of only 35 gallons per minute, R20-20-21; Govt. Ex. 1-12. LCP did not notify the Georgia EPD of the lower wastewater treatment capacity. R20-290. The plant was authorized to store wastewater which was awaiting treatment in the wastewater treatment plant on the floor of the eellrooms. R16-118; R21-145, 161. The eellrooms were constructed of concrete, with a downward slope which diverted the wastewaters to a sump and then to the wastewater treatment holding tanks. R19-33-34. If the cellroom became incapable of holding the wastewater, it leaked out onto the ground and accumulated in a lake. R16-131-32. LCP also used “Bunker C” oil tanks for additional wastewater storage. R19-291; R20-42-45. Due to accidental spills, bleach sometimes accumulated on the Cell-room 1 floor. R19-258. During the early 1990s, the maintenance at the plant began deteriorating. R20-177, 179. Replacement parts were not made available, and wastewater began accumulating around the plant. Id. The operations were subject to Occupational Safety and Health Administration (“OSHA”) regulations for the protection and safety of the employees. The workers exposed to mercury vapors in the mercury cell process were provided with liquids to drink in order to stay hydrated and deplete the mercury, and their exposure was periodically monitored through an extensive mercury urinalysis procedure. R20-145-46; R21-251-52. Employees who showed exposure to excess mercury were not allowed to return to work until they were seen by a medical physician, and were then relocated to other plant locations away from the mercury cells. R20-146, 164-65, 168-69, 174; R21-255, 258; R22-12, 24. In August 1992, OSHA inspected the plant “due to an employee complaint about safety hazards associated with water on cell room floors.” Govt. Ex. 10 — Yi. OSHA found this to be a “willful violation and demanded that no employees be allowed to work in contact with the water while the equipment was energized,” and “forced” LCP “to erect a boardwalk system above the water level around all the equipment until the water c[ould] be eliminated permanently.” Id. LCP added wooden elevated walkways in the cellrooms to prevent the workers from having contact with the water on the floor and to reduce the workers’ risk of electrical shock or chemical burns. R16-118; R21-145-46, 161. The chemicals used in LCP’s operations were very alkaline and caustic and could irritate and burn skin. R16-93; R19-43, 197; R20-188; R21-263-64. To minimize the workers’ risk of skin irritations and burns, LCP held routine safety meetings, encouraged and received safety inspections, and provided the employees with training, protective equipment to preclude skin contact, and first aid stations and showers to relieve inadvertent contact. R19-47, 194, 233-34, 246, 300-01; R20-170, 181-82, 186, 188, 190-91; R21-249. All employees, including those assigned to the cellrooms, were authorized to work elsewhere in the plant if they were concerned about their safety. R19-302; R20-186-87, 320-2; R21-156. In 1991, LCP’s parent corporation, Han-lin, filed a voluntary bankruptcy petition with pre-petition obligations exceeding $100 million. R19-119; R21-194. Shortly thereafter, Randall was hired as an executive vice president of LCP and charged with “developing the business and financial plans necessary to turn around the financial condition of the chemical business.” R21-193; R16-97. Randall worked closely with Hanlin’s bankruptcy attorneys, the law firm of McCarter and English, and the environmental law firm of Decher, Price and Rhoads. R19-140-43; R21-194, 215. Randall also worked closely with LCP’s corporate environmental manager and site environmental managers. R20-64-65; R21-210, 216. During the bankruptcy proceedings, available funds for maintenance, repair, and environmental compliance were restricted. R19-60-62. Randall attempted to find additional funds by selling excess equipment and reducing the payroll but the funds remained limited. Id. The ultimate decision-making for all major projects, capital and extraordinary expenditures, and the sale of assets, were subject to the approval of the Board and the bankruptcy creditor’s committee and court. R19-121, 143-47, 174-75; R21-196. Although funds were requested to address the cellrooms’ wastewater problem, the funds were usually not released. R21-259-60. In February 1992, the Brunswick plant manager, James L. Johns, advised Randall in writing that, without “extensive work,” to keep the wastewater treatment system operable, they would be unable to “operate the plan for more than a few days without ‘willfully’ violating EPD regulations which we will not do.” Govt. Ex. l-8a at HA 00024857. In April 1992, Randall visited the Brunswick plant and met with plant manager James L. Johns for “an update on regulatory compliance requirements.” Govt. Ex. 10-7b. He indicated that he would provide guidance on the approval of funds for a study for the NPDES permit, LCP’s commitment regarding the 1 June 1992 Georgia EPD deadline for eellroom floor repairs, and the possibility of a study or remediation plan for the “brine im-poundments.” Id. In June 1992, Randall was advised in writing that a conference with OSHA on 8 May 1992 noted 26 serious violations and 11 non-serious violations. Govt. Ex. 10-7d. During the summer of 1992, the Brunswick plant management changed. R16-104-05. In August 1992, Taylor advised Randall that Brunswick was “unable to meet current permit limitations,” that he anticipated “more restrictive” limitations, and that the “[performance of the waste water treatment system [was] a serious threat to the continued operation of the plant.” Govt. Ex. 1-12. Taylor said that while the “generation of waste water ha[d] greatly increased due to leaking brine tanks, [poor condition of the] brine pumps [and] ... brine filters, heavy rainfall, the necessity to destroy bleach, and numerous operating problems,” at the same time the capacity of the wastewater system was limited by the reduced capacity of the filtration and storage systems, was “further reduced” by the “[l]ack of maintenance,” and the system was “frequently shut down due to mechanical problems and operator errors.” Id. In November 1992, Randall visited the Brunswick plant to interview a candidate for plant manager, and spoke with the acting manager, Hugh Croom. R19-30. At that time, Croom advised Randall of problems with the caustic filters and the intentional dumping of caustic on the eellroom floors by some unknown employee. R19-30-31, 56-58. Croom testified that Randall “was just as concerned as we were about the problems” and authorized Croom to hire a task force. R19-50, 58. In February 1993, LCP offered the plant manager job to Taylor. R21-244. During his tenure as manager, Taylor stressed safety and strict adherence with LCP’s training and safety programs, and assured employees the right to refuse to perform any activity if the employee felt it to be unsafe. R19-302-03. When the wastewater overran the cellroom berms and streamed outside the building, the overflow was reported to the EPD and to the LCP Board by letters signed by Taylor. R20-25-27. The amounts reported in the letters were consistent with the data that the plant had at that time. R20-27. During the spring of 1993, Taylor attended a company meeting with Randall and Croom in which they discussed the condition of the Brunswick plant and possible solutions. R19-18-19. Taylor and Croom recommended “either shutting the plant down or shutting it down long enough to salvage one cellroom and rebuild the second cellroom, and then starting back up with just one cellroom.” R19-20, 22. Taylor worked up “the figures and costs” and submitted it to Randall, but Randall later advised them that “[t]hey won’t let me do it.” R19-22-23, 64. By letters to EPD, Taylor reported that the plant had exceeded the maximum daily allowable discharges seventeen times, and explained that the discharges were due to “heavy rainfall,” “miscommunication between operations supervision,” “a slight miscalculation,” and “storm, rainfall and process leaks.” Govt. Ex. 10 — Id, e.g. Taylor noted that the “waste water treatment operating efficiency and outfall discharge” was “positively] affect[ed]” by LCP’s decision not to replace a leaking brine tank. Govt. Ex. 10-lg. In April 1993, the Board of Directors, with the approval of the bankruptcy court, removed Hansen as Chairman, President, and CEO of Hanlin after he attempted to expel the outside directors from the board. R19-122-23, 160, 167-68. The Board and the bankruptcy creditors’ committee asked Randall to serve as LCP’s interim CEO and Chief Operating Officer [COO]. R19-160; R21-195, 200. His primary focus was financial and, with the support of the bankruptcy creditors committee and court, he sought to sell the company to a responsible party who could operate the business and have the financial resources to deal with the various environmental conditions. R19-147-48, 164, 174-76; R21-200-01, 219. In this capacity, Randall received daily reports concerning the Brunswick plant’s operations and problems. R16-97-98. After Hansen’s removal as CEO, he was no longer a corporate officer and became a director and employee. R19-136, 160, 168. Sometime later, the Board sent Hansen to Brunswick to help run the plant. R19-166-67. Taylor reported five discharge violations in April, and indicated that two violations were due to a problem in the wastewater treatment system that had been corrected, one violation was attributable to rainfall, and one violation was due to leaks which had been repaired. Govt. Ex. 10-lh. Taylor indicated that “[a]n upset in the wastewater treatment system caused a release of ineffectively treated wastewater” but that “the discharge was rerouted until the system resumed normal operation.” Id. Taylor reported 16 discharge deviations in May 1993, which he indicated were caused by an equipment failure which had been repaired, “overloading the wastewa-ter treatment system,” and rainfall. Govt. Ex. 10 — li. In June, Taylor reported 21 excessive discharges which were attributable to “upsets” and “operational problems” in the wastewater treatment system and equipment failures. Govt. Ex. 10 — lj and 10-lk. Hansen visited the plant in late June and began working with Taylor. R19-167. In July 1993, Taylor resigned as plant manager. R21-245. Upon Taylor’s resignation, Hansen assumed the running of the plant and served as plant manager from July through September 1993. R19-24, 167; R20-354. Taylor subsequently returned to the plant as a full time employee as a process or project engineer on the condition that he not have to “assume managerial type duties.” R21-246. He remained involved in environmental issues, however, and in October 1993, questioned the assistant production manager regarding the loss of mercury. R20-325, 337-38. The Georgia Environmental Protection' Division notified LCP in writing in June 1993 that it proposed revoking the NPDES permit to discharge treated wastewater in Purvis Creek based on “continuous violations ... since May 1992 of pH, total residual chlorine, and mercury.” Govt. Ex. 13-ld at 1. It explained that, although it had provided LCP “Notice of Violation” letters twice in 1992 and had requested that LCP “take all necessary measures to come into compliance,” “these violations have continued” and “significant noncompliance” was documented in 10 out of 13 months from May 1992 through May 1993. Id. The notification summarized that there had been “no progress ... in upgrading the plant or its operation” since the noncompliance had begun to be a serious problem. Id. at 2; R20-274-276. Randall submitted formal written comments on the revocation stating that “LCP has already taken steps to improve the situation by installing additional filter capacity, repairing or replacing equipment and reducing the load on the system” and referring to a 23 July plan addressing future corrective measures. Govt. Ex. 10-6 at 4. In July and August 1993, Hansen directed the plant employees to begin pumping the wastes into the large “bunker” tanks that had once been used to store oil although he knew that the wastewater mixed with oil could not be run through the wastewater treatment system, R20-48, 183, 328-29, 350. The plant environmental/safety manager reported the use of the tanks to Randall in July. Govt. Ex. 10-7x. After the EPD moved to revoke the plant’s permit, Hansen advised the employees to “increase the flow on the wastewater treatment system to a level that was to keep the water from running out the [cellroom] door” and into the lake. R20-358-59. During their respective terms as plant manager, Hansen and Taylor were advised of and observed “water [ ] flowing] out the back door of the cellroom” as a result of a break in the cellroom berms, and “overflow[ing] on the ground.” R20-327-28, 335-36, 341. The employees complained to Hansen, Taylor, and Randall about “the water condition, the deterioration of the plant with the pipes, the leaks, and the safety equipment,” and, despite assurances that conditions would improve “[a]s soon as [the plant] g[o]t some money,” the plant did not get “any money” and conditions did not change. R21-146-50. The NPDES permit was revoked on 23 September 1993. R20-275. LCP filed an appeal which stayed the revocation. R20-275. Although EPD sought a temporary restraining order, it was denied by the state court judge. R20-302-03. During this same period of time, Allied Signal and HoltraChem indicated interest as buyers, and a financial agreement was worked out in which Allied Signal would provide needed money, personnel, and raw materials or maintenance parts for the plant, including an extra wastewater treatment facility. R9-228, Exs. A & B; R19-149-51; R20-18, 80. As a part of the financial agreement, Allied Signal loaned employee Mark White to LCP to serve as plant manager in October 1993. R19-152-53; R20-18. With the influx of Allied Signal’s resources, conditions at the plant improved. R20-80. The purchase agreement eventually fell through and shortly thereafter the facility closed. After the plant closed, Randall, through the bankruptcy counsel, requested $1,500,000 in additional funds from the bankruptcy court to deal with the environmental impact of closing but the request was denied. R9-228, Ex. C at 2, 7, Feb. 8, 1994, letter from M. Patrick M. Nuciarone. The Georgia EPD turned the closed plant over to the U.S. Environmental Protection Agency (EPA) for cleanup and EPA estimated that the cleanup will cost more than $50 million. R20-380; R21-57. Taylor, as one of the ten LCP employees approved by the EPA to participate in the site cleanup, assisted in the decommissioning of the cellrooms and ran the water treatment plant built by the EPA. R21-55-56. The cleanup was paid for by the government and Hanlin’s predecessors at the site: Allied Signal (successor to Allied Chemical), ARCO, and Georgia-Power Company. R21-39-40. The government indicted Christian Hansen, Randall Hansen, Douglas Brent Hanson, and Alfred R. Taylor for conspiracy to commit environmental crimes at the site between 1 July 1985, and 1 February 1994, 18 U.S.C. § 371, (Count 1), and various substantive crimes. Rl-1-1. The charges included: violating the Clean Water Act (“CWA”), 33 U.S.C. § 1319(c)(2)(A) and 18 U.S.C. § 2, by exceeding the NPDES permit between June 1993 and January 1994 (Counts 2-21); violating the Resource Conservation and Recovery Act (“RCRA”), 42 U.S.C. §§ 6928(d)(2)(A) and (e), and 18 U.S.C. § 2, by storing wastewa-ter on the cellroom floor and permitting some to escape into the environment between 29 May 1993 and 1 February 1994 (Counts 22-32), storing wastewater in the Bunker “C” tanks between 23 July 1993 and 1 February 1994 (Count 33), and knowingly endangering employees by exposing them to impermissibly stored wastes and wastewaters between 29 May 1993 and 1 February 1994 (Count 34); violating the Comprehensive Environmental Response, Compensation, and Liability Act (“CERCLA”), 42 U.S.C. § 9603(b)(3), by failing to notify the U.S. government of unpermitted releases of chlorine or waste-water into the environment between 21 July and 23 October 1993 (Counts 35-41); and violating the Endangered Species Act, 16 U.S.C. § 1538(a)(1)(B), 1538(g), and 1540(b)(1), by taking an endangered species, a Wood Stork, as a result of discharging mercury into the marsh, Purvis Creek, and the Turtle River (Count 42). Rl-1. Hansen was charged with Counts 1-42, Randall was charged with Counts 1-34 and 42, Hansen was charged with Counts 1-6, 10-22, 24, 26-32, and 34-42, and Taylor was charged with Counts 1-32, and 34-42. Id. Hanson, the former environmental and health and safety LCP manager, pled guilty to a CERCLA offense (Count 41) and the offense under the Endangered Species Act (Count 42) and testified against Hansen, Randall, and Taylor. R3-83; R20-6. At the conclusion of the defendants’ case, the district judge granted their motion for acquittal as to Count 42 but denied the motion as to all other charges. R6-123. Hansen was convicted of all counts, Randall was convicted of all charged counts, and Taylor was convicted of Counts 1-3, 10-11, 22-26, 29-32, 34-35, and 38-41. R22-214-15. Their renewed motions for acquittal and motions for judgment notwithstanding the verdict and/or for a new trial were denied. R7-145, 146, 153-54,163; R8-200. Hansen was sentenced to 108 months of imprisonment, a fine of $20,000, a special assessment of $2,050, and two years of supervised release. R8-214. Randall was sentenced to 46 months of imprisonment, a fine of $20,000, a special assessment of $1,700, and two years of supervised release. R9-236. ■ Taylor was sentenced to 78 months of imprisonment, a special assessment of $1,000, and two years of supervised release. R8-215. Each defendant appealed, and was allowed to remain on bond pending appeal. R8-219, 221; R19-226, 238^40. On appeal, Hansen raises four issues: (1) the district court erred in admitting the government’s expert witness testimony; (2) the district court’s instructions misstated the reasonable doubt standard, improperly applied the concept of reasonable corporate officer, improperly defined the elements of knowing endangerment, and effectively eliminated the mens rea requirement from each statutory violation; (3) the evidence was insufficient to support his convictions; and (4) the district court erred in concluding that it lacked the authority to depart from the applicable sentencing guidelines. Randall argues that: (1) district court erred by not granting his motion for judgment of acquittal because the evidence was insufficient to support his conviction for knowing endangerment under the RCRA and the government never proved causation on counts 2-33; (2) the district court’s instructions were erroneous on the elements of the charged substantive offenses and on the responsible corporate officer instruction as an alternative basis for criminal liability; (3) the district court erroneously admitted high prejudicially and irrelevant evidence; and (4) the district court erred by declining to depart downward. Taylor maintains that the district court erred: (1) by not granting his motion for judgment of acquittal and for a new trial based on insufficiency of the evidence; (2) in its instruction concerning the wastewater treatment system; and (3) in sentencing him. II. DISCUSSION A. Admission of Expert Witness Testimony Hansen argues that the district court erred in admitting testimony from government expert witness Daniel Teitelbaum because the government failed to disclose Teitelbaum’s checkered history of credibility and the court failed to conduct a hearing regarding the testimony. Hansen also maintains that the district court erred in admitting the testimony of Teitelbaum and government expert witness Christopher Reh because the testimony was unreliable, irrelevant, and highly prejudicial. The government responds that Hansen waived the arguments regarding Teitelbaum’s testimony by failing to object to the testimony at trial. The week before trial, Hansen moved for a Daubert hearing and to ex-elude the testimony of expert witnesses regarding certain allegedly scientific conclusions and exhibits. R4-94-95; R6-110-1. Noting that the motion was directed to the expert testimony regarding the effect of high mercury levels on endangered species as charged in Count 42, the district court denied it, finding that the motion did “not identif[y] the source, the substance, or most importantly the underlying metN odology of this testimony” and that, therefore, there was “no underlying methodology or reasoning for the court to assess.” R6-110-1-2, 4. During the trial, Teitelbaum confirmed that he had previously testified as an expert witness, and explained that “it has been a regular portion of [his] practice over the years.” R20-230-31. Hansen neither objected nor examined Teitelbaum after the government moved to tender Teitelbaum as' an expert, and the court directed that the jury consider him an expert in his field. Id. at 232. Teitelbaum testified regarding the plant employees’ potential exposure to hazardous substances. Based on his review of “the large number of biological samples,” “many interviews,” the “documents concerning the health and hygiene program,” and other documents, he found “a substantial amount of spillage of sodium hydroxide,” “numerous chlorine leaks,” and spills and leaks of hydrochloric acid at the plant. R20-233-35; see also 248-49. He noted that, because the sodium hydroxide spillage had a very high pH and was quite caustic, contact with the spillage could cause a first- to third-degree burn, or even be lethal. Id. at 233-34. Teitelbaum explained that exposure to the chlorine leaks could cause “severe injuries to eyes, upper airways, and lungs, and, under some circumstances, death.” Id. at 234. He commented that hydrochloric acid was a “classic poison” which would also cause burns and potential death. Id. at 234-35. Based on the biological samples, he concluded that the employees were “in danger of death or serious bodily injury.” Id. at 244-45, 248. Finally, Teitelbaum noted that the data showed the mercury levels in the workers’ urine were “between two and five times the acceptable level of excretion, based on the World Health Organization or the NIOSH recommendations.” Id. at 244 — 45. No objections were raised to his testimony. Id. at 232-63. At sentencing, the probation officer noted that he had “discredit[ed]” one of Hansen’s witnesses “because he was not even at the LCP Plant” and “did not have firsthand knowledge to see this.” R13-26. Hansen’s attorney responded that, based on the probation officer’s theory, Teitel-baum’s testimony should also be discounted “because he never went to the plant before it was shut down.” Id. at 28. The district judge commented that Teitelbaum “made a very credible witness. I think the best witness that the Government had.” Id. at 29. We review for abuse of discretion both the district court’s decisions regarding the admission of expert testimony and reliability of an expert, Kumho Tire Co., Ltd. v. Carmichael, 526 U.S. 137, 152, 119 S.Ct. 1167, 1176, 143 L.Ed.2d 238 (1999), and the denial of a Daubert hearing, United States v. Nichols, 169 F.3d 1255, 1263 (10th Cir.1999). “Absent an objection, we can review the challenged evidence only for plain error.” Christopher v. Cutter Labs., 53 F.3d 1184, 1192 (11th Cir.1995). Scientific expert testimony is admissible if “(1) the expert is qualified to testify competently regarding the matters he intends to address; (2) the methodology by which the expert reaches his conclusions is sufficiently reliable as determined by the sort of inquiry mandated in Daubert; and (3) the testimony assists the trier of fact, through the application of scientific, technical, or specialized expertise, to understand the evidence or to determine a fact in issue.” City of Tuscaloosa v. Harcros Chems., Inc., 158 F.3d 548, 562 (11th Cir.1998). In Daubert, the Supreme Court suggested a flexible inquiry regarding the methodology considering such factors as “whether it can be (and has been) tested,” whether it “has been subjected to peer review and publication,” the “known or potential rate of error,” “the existence and maintenance of standards controlling the technique’s operation, and the degree it is accepted as reliable within the relevant scientific community.” 509 U.S. at 591, 593-94, 113 S.Ct. at 2795-96. Daubert hearings are not required, but may be helpful in “complicated cases involving multiple expert witnesses.” City of Tuscaloosa, 158 F.3d at 564-65 n. 21. A district court should conduct a Daubert inquiry when the opposing party’s motion for a hearing is supported by “conflicting medical literature and expert testimony.” Tanner v. Westbrook, 174 F.3d 542, 546 (5th Cir.1999). Consistent with Daubert, the evidence must be scientifically related to the disputed facts at issue in the case. Allison v. McGhan Med. Corp., 184 F.3d 1300, 1312 (11th Cir.1999). Hansen’s motion for a Daubert hearing was neither addressed to the charges to which Teitelbaum testified, or his testimony in general, nor supported by the source, substance, or methodology of the challenged testimony. Hansen failed to object to either Teitelbaum’s qualification as an expert or his testimony during trial. Teitelbaum’s testimony was based on his review of biological samples, interviews, and documents, and assisted the trier of fact in understanding the potential injuries that could result from the conditions at the plant. The district judge did not abuse his discretion by denying the motion or by admitting the testimony. To the extent that Hansen raises a Brady claim that the government suppressed exculpatory or impeachment evidence by failing to disclose Teitelbaum’s “checkered” past, we find that it is without basis. In order to state such a claim, a defendant must show (1) “that the government possessed evidence favorable to the defendant (including impeachment evidence) ...; (2) that the defendant does not possess the evidence nor could he obtain it himself with any reasonable diligence ...; (3) that the prosecution suppressed the favorable evidence ...; and (4) that had the evidence been disclosed to the defense, a reasonable probability exists that the outcome of the proceedings would have been different.” United States v. Meros, 866 F.2d 1304, 1308 (11th Cir.1989) (per curiam). In this case, the evidence which Hansen alleges the government failed to disclose consists of court opinions either disregarding or discrediting Teitelbaum’s testimony. Although Hansen argues that the government knew of this discredited testimony based on Teitelbaum’s previous testimony for the government, Hansen fails to show that the government was in actual possession of the information or actually suppressed it. Further, the information was available to Hansen through reasonable diligence both before and during the trial. The cases were all available through legal research and information on them could have been, but was not, addressed during Teitelbaum’s testimony. Finally, the cases relied on by Hansen all relate to Teitelbaum’s testimony in tort actions as to causation of a specific injury. They do not, therefore, have probative value as to his testimony regarding potential health effects of the chemicals or the employees’ risk of death or serious injury after exposure to these chemicals. Hansen is unable to show a reasonable probability that the information would have changed the outcome of the proceedings. Christopher Reh, an employee of the National Institute for Occupational Safety and Health (“NIOSH”), also testified for the government. R20-192. The district judge qualified him as an expert in the field of industrial hygiene. Id. at 194. Reh explained that he was assigned to the Brunswick plant as the project officer after NIOSH received “a valid request for a health hazard evaluation” from one of the plant’s unions in 1987. Id. at 196. He said that, during the initial site visit, he and his team met with Taylor, a plant engineer, and a few union representatives to discuss the request. Id. at 196-98. They visited the plant, and observed “mercury in many places on the cellroom floor in cracks or crevices,” and passively monitored mercury exposure in the workers’ “breathing zone.” Id. at 198-99. They found that the plant was not using the creatnine monitoring scale, but was reporting mercury levels by “micrograms per liter.” Id. at 204. The monitors found that mercury exposure exceeded the NIOSH and OSHA recommended levels. Taylor’s objection to further testimony from Reh on the grounds of relevance was overruled. Id. at 201. Reh and his team advised Taylor of their findings by letter and recommended use of creatnine correction urine mercury monitoring which would indicate the amount of mercury per gram of creatnine. Id. at 201-03; Govt. Ex. 40-lb. From the results of the first visit, the team made a second visit to conduct a more in-depth study in 1988. R20-202. During the second visit, the team used an active sampling method to determine 28 workers’ breathing zone exposure levels, collected urine samples from 58 workers, and administered questionnaires to and conducted physical examinations of 65 workers. Id. at 205-07. Taylor was provided with a written interim report in 1988 and a final report in 1991, both of which showed that workers had mercury levels above recommended standards. Id. at 207-08, 210, 214; Govt. Exs. 40-1c and Id. The government offered Reh’s testimony to show that the workers were placed “in imminent danger of death or serious bodily injury” and that Hansen, Randall, and Taylor were aware of the workers’ exposure to hazardous substances. This testimony supports both of those propositions. The district court did not abuse its discretion by admitting the testimony of Reh. B. Insufficiency of the Evidence We review the denial of a motion for a new trial for abuse of discretion, and the denial of a motion for judgment of acquittal de novo. United States v. Pistone, 177 F.3d 957, 958 (11th Cir.1999) (per curiam). To uphold the denial of a motion for judgment of acquittal, we “need only determine that a reasonable fact-finder could conclude that the evidence established the defendant’s guilt beyond a reasonable doubt.” Id. When considering the sufficiency of the evidence, we “view the facts and draw all reasonable inferences therefrom in the light most favorable to the government.” United States v. Slocum, 708 F.2d 587, 594 (11th Cir.1983). 1. Position of authority “To prove aiding and abetting, the government must demonstrate that a substantive offense was committed, that the defendant associated himself with the criminal venture, and that he committed some act which furthered the crime.” United States v. Hamblin, 911 F.2d 551, 557 (11th Cir.1990). “[T]he government must show that the defendant shared the same unlawful intent as the actual perpetrator” but does not need to prove that “the defendant was present at the scene when the crime occurred, or that he was an active participant.” Id. at 557-58; United States v. Pepe, 747 F.2d 632, 665 (11th Cir.1984) (“aider and abettor ... need not even be present”). “Encouraging” a violation and “discouraging” the reporting of the violation, United States v. Sinskey, 119 F.3d 712, 718 (8th Cir.1997), and “personally attempting to avoid [a violation’s] detection by the [RCRA] -inspectors,” United States v. Self, 2 F.3d 1071, 1089 (10th Cir.1993), have been held sufficient to show that a defendant aided and abetted the commission of a crime. The indictment alleged that the defendants, “after learning that the Brunswick facility was disposing of hazardous wastes ... without a RCRA permit, continued to operate the Brunswick facility in such a manner as to continue the disposal of these hazardous wastes without expending adequate funds ... to prevent the disposal of such hazardous wastes into the environment.” Rl-1-11. The jury was instructed that the defendants were responsible for the acts of others that they “wilfully directed,” “authorized,” or aided and abetted by “willfully joining together with [another] person in the commission of a crime.” R22-181. The district court denied Taylor’s motion to acquit or for a new trial on these charges finding that “the Defendants worked for LCP in positions of responsibility and authority while ... the violations took place.” R8-200-23. a. Hansen Hansen maintains that the evidence failed to show that he was in a position of authority after he was deposed as CEO in April 1993 until he began serving as plant manager on 16 July 1993, and after he was officially replaced as plant manager by Allied employee Mark White on 18 October 1993. Therefore, he contends that the district court erred in not granting his motion for judgment of acquittal as to the 18 counts that occurred after 18 October 1993 (Counts 6-9, 14-15, 19-21, 23, 25, 29, 30-32, 38^=0), the two counts that occurred between April and July 1993 (Counts 2 and 10), and the count that arose on 22 October 1993 (Count 33). The testimony at trial indicated that Hansen was aware that wastewater was permitted to flow out the cellroom back door in June 1993, and directed the use of the old Bunker C storage tanks for storage of wastewater, including the inadequately treated wastewater from the treatment system, from July through September 1993. Although the acts continued after Hansen left his decision-making position, the acts occurred at his direction. This evidence was sufficient for the jury to reasonably conclude beyond a reasonable doubt that his acts were in furtherance of the violations. The district court did not err in denying Hansen’s motion for judgment of acquittal or motion for new trial. b. Randall Randall claims that the government presented no evidence that he personally treated, stored, or disposed of a hazardous waste, personally effected a CWA violation, or instructed an agent to do so. He maintains that, under the laws of bankruptcy and corporate governance, he lacked the authority to close the plant or to allocate the funds for the needed capital improvements. He contends that LCP needed the bankruptcy court’s approval to use the bankruptcy estate’s assets, or to obtain a new debt, to perform the needed repairs at the Brunswick plant. In February 1994, LCP applied to the bankruptcy court for the funds “to shutdown” the plant and for new equipment, but the motion was denied. Def. Randall Ex. 1, Amended Notice of Motion at 5; R9-228, Ex. C and 8 Feb letter. Hanlin Board of Directors member James Mathis testified that Randall was responsible for “run[ning] the day-to-day operations of the company” once he became the interim CEO and COO. R19-160. He said that the Board was “very interested in whether the environmental problems-whether we were in a position of compliance with the environmental regulations. But the information that we had indicated that, really, compliance was not a problem.” Id. at 164. He explained that, as a result of the weekly reports on the plant’s operations, the Board believed that “there were really no excursions of any significance going on”. Id. at 165. Mathis said that Randall “had the primary responsibility” for providing information regarding the environmental compliance issues to the Board and that Hansen fed “information to Randall in that regard.” Id. at 166. He agreed that the decision to sell the plant would have been a board decision requiring the approval of the bankruptcy court. Id. at 174-75. LCP, as a debtor in possession, could “use the property of the estate in the ordinary course of business,” but needed court approval to “use, sell, or lease, other than in the ordinary course of business, property of the estate.” 11 U.S.C. § 363(c)(1) and (b)(1). It could “obtain unsecured credit ... in the ordinary course of business,” but needed court approval “to obtain unsecured credit or to incur unsecured debt other than” “in the ordinary course of business.” Id. at 364(a) and (b). Bankruptcy does not insulate a debtor from environmental regulatory statutes. In reviewing an injunction to clean up a hazardous waste site, the Supreme Court commented: [W]e do not suggest that [the debtor’s] discharge [in bankruptcy] will shield him from prosecution for having violated the environmental laws ... or for criminal contempt for not performing his obligations under the injunction prior to bankruptcy.... [W]e do not hold that the injunction ... against any conduct that will contribute to the pollution of the site or the State’s wasters is dis-chargeable in bankruptcy ... Finally, we do not question that anyone in possession of the site ... must comply with the environmental laws .... Plainly, that person or firm may not maintain a nuisance, pollute the waters of the State, or refuse to remove the source of such conditions. Ohio v. Kovacs, 469 U.S. 274, 284-85, 105 S.Ct. 705, 710-11, 83 L.Ed.2d 649 (1985). See also Midlantic Nat’l Bank v. New Jersey Dept. of Envtl. Protection, 474 U.S. 494, 507, 106 S.Ct. 755, 762 (1986) (A bankrupt debtor in possession “may not abandon property in contravention of a ... regulation that is reasonably designed to protect the public health or safety from identified hazards.”). Although Randall claims that his role as Executive Vice-President and acting CEO was limited to financial matters, he also received daily reports about the plant’s operations and environmental problems, R16-97-98, R21, 359, wrote and received memos regarding specific plant operational problems, Govt. Ex. 104, l-6f, l-8a, 1-12, received monthly written environmental reports, Govt. Ex. 10-lo-10-lnn, 10-7c-7d, 10-7f, and oral environmental reports, R21-64, 359. He admitted that Hanlin’s bankruptcy was not an excuse for violating environmental laws. R21-219-21. There is no indication that he asked the Hanlin Board or the bankruptcy court to close the plant. The evidence indicates that he apparently misled them into believing that environmental compliance was not a problem. After the Georgia EPD attempted to revoke the plant’s NPDES permit in June 1993, Randall contested the revocation, explaining that the plant’s CWA violations were due to a lightning strike and equipment failures, and asserted that “LCP has already taken steps to improve the situation.” Govt. Ex. 10-6. This evidence was sufficient for the jury to conclude that Randall actions were in furtherance of the violations. c. Taylor Taylor argues that he should not be held responsible for the environmental violations that occurred after he resigned as plant manager, specifically counts 2-3, 25, 29-32, 38-41. Taylor resigned as plant manager on 16 July 1993, R21-245, but returned shortly thereafter as a project engineer and continued in that position until the plant closed, R21-246-47, 317-18. As project engineer, Taylor was directly involved in responding to the plant’s environmental and safety problems and, at Hansen’s request, developed a list of short-term solutions to the problems with estimated costs. R20-338; R21-247-48. Taylor’s proposed solutions were subsequently funded. R21-247-48. Although Taylor left his managerial position, he continued to work in a position in which he directed or authorized acts of the employees on environmental and safety problems. Testimony at trial indicated that, in October 1993, Taylor was aware of the wastewater overflow from the cell-rooms, the excess loss of mercury, and the use of the tank cars for wastewater storage, and that he supervised the release of the overflow. This evidence was sufficient for the jury to conclude beyond a reasonable doubt that these acts were in furtherance of the violations. The district court did not err in denying his motion for a new trial. 2. Hazardous substances or materials Taylor and Hansen argue that the government failed to prove that the untreated wastewater contained enough mercury and caustic to meet the environmental laws’ definition of hazardous substances or materials, or that the untreated wastewater was improperly stored. a. Hazardous substances as defined OSHA chemist Clinton Leroy Merrell testified that samples which were submitted from LCP on 9 September 1992 tested as containing 8 to 30 parts per ■million of mercury, and six to ten-percent caustic, with a pH of 14. R21-163, 165-67; Govt Exs. 45-6, 45-9. Former LCP plant manager Hugh Leroy Croom testified that, in January 1993, the untreated wastewater may have had “a high pH, and ... some mercury,” but would not have contained mercury sludge. R16-91, 131-32. He said that the pH could be high enough to be a danger “at times” but that it did not stay high and varied according to the spills. Id. at 132; R19-35-36. However, he testified that muds containing mercury and caustic were washed onto the cellroom floors every three or four days when the treatment system’s filters were back washed. R16-127-28; R19-103. When asked whether the wastewater on the cell-room floors would be considered a hazardous waste, Croom responded “[m]ost of the time, probably it was.” R16-112-13; see also id. at 128 (Croom admitted that wastes on the cellroom floor were listed as hazardous wastes). Dr. Teitelbaum testified that a fall and submersion into caustic soda with a pH of 14 would cause a third-degree burn over the entire body with a likelihood of death. R20-241-42. LCP former employee Duane Carver testified that, some time between 1987 and 1993, he stepped into the cellroom sump hole and went in up to his waist. R19-226-28. He knew that the pH was “pretty high” because he quickly felt it. Id. at 228. He showered and was able to get most of it off so that he “didn’t get burned all the way” and did not seek medical attention. Id. at 229-30, 251. Environmental Protection Agency regulatory expert Paul Peronaud explained the hazardous waste classifications to the jury, R21-11-13, and the jury was instructed as to various types of hazardous wastes, R22-199-200. The Waste Water Treatment Operators Logs for the periods of the indictment showed that the wastewater often contained more than 200 parts per billion of mercury. Govt. Exs. 4, 5, 6-1. Former LCP employee Dunn testified that Taylor directed the employees to “put a sign up” labeling the wastewater in the rail cars as “[h]azardous waste materials.” R20-345. Taylor testified that the pH of the plant’s wastewater was normally between seven and ten, and in concentration of eight to ten percent. R21-262, 264. A “hazardous waste” is defined as a solid waste, or combination of solid wastes, which because of its quantity, concentration, or physical, chemical, or infectious characteristics may— (A) cause, or significantly contribute to an increase in mortality or an increase in serious irreversible, or incapacitating reversible, illness; or (B) pose a substantial present or potential hazard to human health or the environment when improperly treated, stored, transported, or disposed of, or otherwise managed. 42 U.S.C. § 6903(5). Hazardous wastes are categorized as either “listed” hazardous substances or “characteristic” hazardous substances. 40 C.F.R. § 261.3(a); R21-11-15. The “characteristic” hazardous substances are not per se hazardous but may be classified as hazardous if, because of a mixture with a hazardous substance, testing proves that the substance exhibits characteristics of hazardous waste. 40 C.F.R. §§ 261.3(a)(2)(i) and 261.20(a). Characteristics of hazardous waste include ignitability, corrosivity, reactivity, and toxicity. 40 C.F.R. §§ 261.21, 261.22, 261.23, and 261.24. Wastewater containing mercury is classified as a characteristic hazardous substance when the water contains 200 parts per billion or more of mercury. Id. at § 261.24(a), Table. “Wastewater treatment sludge from the mercury cell process in chlorine production” is listed as hazardous waste K106. Id. at § 261.32. Wastewater containing caustic is classified as a characteristic hazardous substance when the water “has a pH less than or equal to 2 or greater than or equal to 12.5.” Id. at § 261.22(a)(1). Once solid wastes are mixed with sludge or caustic, they are defined as hazardous. Id. at § 261.3(a)(2)(iv). Where there is no sampling of the actual wastes, the government may prove the hazardous nature of the material by inventories, hazardous waste logs, internal memoranda, and trial testimony. United States v. Baytank (Houston), Inc., 934 F.2d 599, 614 (5th Cir.1991). The government is not required to prove that material is hazardous by EPA testing. United States v. Self, 2 F.3d 1071, 1086 (10th Cir.1993). We find that the testimony of the former LCP employees and the wastewater logs were sufficient for the jury to find that the untreated wastewater contained enough mercury and caustic to meet the environmental laws’ definition of hazardous substances or materials. b. Storage of hazardous materials. Taylor and Hansen maintain that the accumulation of wastewater on the cell-room floors did not violate federal law because the wastewaters were not stored there for the statutory requisite of 90 days. Croom testified that hazardous wastewater was on the cellroom floors “[a]t times,” R16-114, and that hazardous materials were shipped, turned over, or treated within 90 days, R19-41. In response to a question as to whether waste-water on the cellroom floors was a regular occurrence in 1992, he responded that it was in both cellrooms in 1992, but when he left “it was just mostly in # 2.” R16-114. Former LCP employee Roger Cooper testified that on 28 June 1993, although wastewater was pumped to the railcars for storage from cellroom two, the cellroom one floor was dry. R19-275-76, 281-82; Govt. Ex. 6-1. He explained that they “tried to keep [the wastewater in cellroom one] pumped over to #2 cellroom” because of the possibility that water would escape from cellroom one as a result of cracks in its floor. R19-284-85. Dirt dikes were constructed in the cellrooms to prevent the wastewater from leaking, but the dikes were frequently breached. R19-256; R25-26. The cellrooms were often “full of water” so that the employees had to wade into standing wastewater to repair the pumps. R20-318; R19-205. Hazardous waste generators are permitted to “accumulate hazardous waste on-site for 90 days or less without a permit” if “the waste is placed” in tanks visibly marked with “[t]he date upon which each period of accumulation begins” and clearly labeled as “Hazardous Waste.” 40 C.F.R. § 262.34(a)(1)(h), (2), and (3). A “tank” is “a stationary device, designed to contain an accumulation of hazardous waste which is constructed primarily of non-earthen materials ... which provide structural support.” 40 C.F.R. § 260.10. There was no evidence that suggested that the cellrooms, in which earthen berms were constructed to contain the wastewa-ter, were marked with the date of accumulation or labeled as containing hazardous wastes and thus qualified as “tanks.” The testimony and logs indicate that the waste-water, which may have abated in cellroom one during various periods of time, remained in cellroom two and was present for more than 90 days. Therefore, the evidence was sufficient for the jury to find that the wastewater was improperly stored. 3. Knowing Endangerment Under RCRA Hansen, Randall, and Taylor argue that the evidence was insufficient to convict them for knowing endangerment. They acknowledge that the government may have shown that they “could have been aware” of the inherent dangers of working in a chlor-alkali plant, but argue that it failed to show that they knew and had an actual belief that the conduct which allegedly violated the environmental laws was substantially certain to cause death or serious bodily injury to others. Specifically, they maintain that, while the evidence showed that the employees were exposed to mercury, the evidence did not show that they were endangered due to any RCRA violation. They contend that the evidence of the employees’ exposure to caustic was not sufficient to support the conviction for knowing endangerment. They claim that the government did not show that they had actual knowledge that their conduct in causing the RCRA violation was at that time substantially certain to place the employees in imminent danger of death or serious bodily injury. They also posit that there was no evidence that they were participants in any alleged conspiracy. For a conviction of knowing endangerment under the RCRA, the government must prove that the defendants knowingly caused the illegal treatment, storage, or disposal of hazardous wastes while knowing that such conduct placed others in imminent danger of death or serious injury. 42 U.S.C. § 6928(e). A defendant acts “knowingly” “if he is aware or believes that his conduct is substantially certain to cause danger of death or serious bodily injury.” Id. at 6928(f)(1)(C). The defendant must have possessed “actual awareness or actual belief.” Id. at 6928(f)(2)(A). Circumstantial evidence, “including evidence that the defendant took affirmative steps to shield himself from relevant information,” may be used to prove the defendant’s awareness or belief. Id. The knowing endangerment statute was drafted to “assure to the extent possible that persons are not prosecuted or convicted unjustly for making difficult business judgments where such judgments are made without the necessary scienter” “however dire may be the danger in fact created.” S. Rep. 96-172, at 37-38 (1979), reprinted, in 1980 U.S.C.C.A.N. 5019, 5036-38. The penalties imposed by the knowing endangerment section were “designed for the occasional case where the defendant’s knowing conduct shows that his respect for human life is utterly lacking and it is merely fortuitous that his conduct may not have caused a disaster.” Id. at 38, 1980 U.S.C.C.A.N. at 5038. We have held that “[t]he government need only prove that a defendant had knowledge of the general hazardous character of the chemical” and knew “that the chemicals have the potential to be harmful to others or to the environment.” United States v. Goldsmith, 978 F.2d 643, 645-646 (11th Cir.1992) (per curiam) (internal quotations and citation omitted). “[W]hile knowledge of prior illegal activity is not conclusive as to whether a defendant possessed the requisite knowledge of later illegal activity, it most certainly provides circumstantial evidence of the defendant’s later knowledge from which the jury may draw the necessary inference.” Self, 2 F.3d at 1088. The statute defines “serious bodily injury” as “(A) bodily injury which involves a substantial risk of death; (B) unconsciousness; (C) extreme physical pain; (D) protracted and obvious disfigurement; or (E) protracted loss or impairment of the function of a bodily member, organ, or mental faculty.” 42 U.S.C. § 6928(f)(6). A condition which may cause one of the statutorily defined conditions is sufficient to show “serious bodily injury.” See United States v. Protex Industries, Inc., 874 F.2d 740, 743 (10th Cir.1989) (finding that a serious bodily injury was suffered by employees who contracted psy-choorganic syndrome which may cause a mental faculties impairment). a. The Evidence of Endangerment Former LCP employees testified that they suffered serious skin and respiratory conditions from the wastewater on the cellroom floors. A November 1992 memorandum from Taylor to Randall showed Taylor’s concern for needed repairs “to avert severe safety and environmental problems.” Govt. Ex. 1-5. The urinalysis testing on employees showed “an increase” in the number with mercury levels which exceeded the 150 action level from 1986 to 1993. R21-294-96. Taylor admitted that most of the employees in the cellroom were removed to other plant locations “before any medical condition occurred” but said that he did not see any “reason to draw any correlation between” the rise in the number of employees exposed to excess mercury and the dumping of hazardous wastes and mercury. Id. at 294, 296. Expert testimony and reports linked exposure to mercury and caustic to a variety of serious health problems. The National Institute for Occupational Safety and Health (NIOSH) report on sodium hydroxide caustic indicated that local contact with caustic could result in “extensive damage to tissues, with resultant blindness, cutaneous burns, and perforations of the alimentary tract,” with potential for development of “squamous cell carcinomas.” Govt. Ex. 17-7b. The NIOSH report on inorganic mercury warned of the effects of mercury and mercury vapors to the central nervous system. Govt. Ex. 17-7c. Dr. Teitelbaum testified that exposure to caustic could cause burns ranging from first- to third-degree and could be lethal, and that exposure to mercury could cause mild tremors, personality changes, some detectable neurological abnormalities, changes in kidney function to severe kidney damage with potential death, and immune system problems. R20-229, 239-42. Dr. Teitelbaum opined that the employees were “in danger of death or serious bodily injury.” R20-248. The evidence was sufficient for the jury to find that the defendants placed others in danger of death or serious bodily injury. b. The Evidence of Mens Rea The evidence showed that Hansen, Randall, and Taylor knew that the conditions of the plant were dangerous and that the conditions posed a serious danger to the employees. LCP former employee Wilbur Duane Outhwaite testified that he voiced his opposition to the use of the Bunker “C” storage with Hansen, and that Hansen responded that it was “his decision to make, and he decided to use them.” R20-350. LCP acting plant manager Hugh Croom discussed his concerns regarding the dangerous conditions in the cellroom and the danger to the employees with Randall. R16-129-30. Croom and LCP former employee Outhwaite testified that Randall received daily reports from the plant managers concerning plant operations and “safety problems.” R16-97-98; R20-359, 374. Randall was aware of the water on the cellroom floor and “wouldn’t say that [he] wasn’t unaware of the hazard,” but thought that the walkway was “an acceptable resolution” to “eliminating the hazard to the employees while we worked to dry the cellroom floor.” R21-224-25. He conceded that he was aware that the company was cited for willful violation of OSHA safety regulations as a result of water on cellroom floors. Id. at 225; Govt. Ex. 10-7L Jesse Jones, a former LCP employee and a union representative, met with Randall to discuss the employees’ safety issues, and Randall promised the needed repairs. R21-148. He said that he discussed the safety concerns, specifically “the water condition, the deterioration of the plant with the pipes, the leaks, and the safety equipment ]” with Hansen and Taylor. Id. at 146. Between 3 August 1993, and 4 February 1994, Randall was sent 22 reports listing 110 different violations of the NPDES standards. Govt. Exs. 10-lo-10-lnn. As LCP’s environmental manager, Brent Hanson regularly advised Randall of the plant’s environmental problems “[wjhenever he was interested in things” and by monthly reports. R20-64-65. As early as 1988, NIOSH informed Taylor that the plant employees had “extremely high” levels of mercury in their bodies which created “an unacceptably high potential for health effects,” and that the mercury-contaminated wastes should be kept in vapor-proof containers. Govt Ex. 40-lc at 2. Despite this, the employees’ exposure to high levels of mercury continued. In 1992, Taylor addressed his concerns about “severe safety” problems in a memorandum to Randall. Govt. Ex. 1-5. Taylor was aware that, during the spring of 1993, 23 cellroom employees were removed from their duty in the cellrooms due to their high levels of mercury and that the mercury level in the workplace increased. R21-294-95, 297. Taylor was aware of and concerned by the mercury-contaminated waste which was stored in drums in the cellrooms’ basement and which was emitting elevated levels of mercury fumes. Id. at 298-303. He admitted that the mercury-contaminated mud on the cellroom floors posed a health risk and needed to be monitored. Id. at 301-02. He testified that, on occasion, he would get into the water wearing protective equipment to make repairs and improvements to the pumps, and admitted that, if the wastewater got onto bare skin and was caustic, “you would start to feel a little burning or a little heat sensation” but that it could be neutralized by washing with the safety solution. Id. at 263-64. He said that such burns were “not unusual” in a caustic soda manufacturing plant through employee carelessness and equipment failures. Id. at 264. c. Consent to the Risks The RCRA knowing endangerment provision can be affirmatively defended if “the conduct charged was consented to by the person endangered and that the danger and conduct charged were reasonably foreseeable hazards of — (A) an occupation, a business, or a profession.” 42 U.S.C. § 6928(f)(3). The evidence showed that the plant’s environmental violations seriously end