Workers’ Compensation Appeal Tribunal Appellant v. Fraser Health Authority, Katrina Hammer, Patricia Schmidt and Anne MacFarlane, 2016 SCC 25

SUPREME COURT OF CANADA Citation: British Columbia (Workers’ Compensation Appeal Tribunal) v.

Fraser Health Authority, 2016 SCC 25, [2016] 1 S.C.R. 587 Appeal heard: January 14, 2016 Judgment rendered: June 24, 2016 Docket: 36300 Between: Workers’ Compensation Appeal Tribunal Appellant and Fraser Health Authority, Katrina Hammer, Patricia Schmidt and Anne MacFarlane Respondents And between: Katrina Hammer, Patricia Schmidt and Anne MacFarlane Appellants and Workers’ Compensation Appeal Tribunal and Fraser Health Authority Respondents - and - Attorney General of Canada, Attorney General of Ontario, Ontario Network of Injured Workers’ Groups, Industrial Accident Victims’ Group of Ontario, Community Legal Assistance Society and British Columbia Federation of Labour Interveners Coram: McLachlin C.J. and Abella, Moldaver, Karakatsanis, Wagner, Côté and Brown JJ.

Reasons for judgment: (paras. 1 to 40) Brown J. (McLachlin C.J. and Abella, Moldaver, Karakatsanis and Wagner JJ. concurring) Reasons dissenting in part: (paras. 41 to 82) Côté J. British Columbia (Workers’ Compensation Appeal Tribunal) v. Fraser Health Authority , 2016 SCC 25, [2016] 1 S.C.R. 587 Workers’ Compensation Appeal Tribunal Appellant v. Fraser Health Authority, Katrina Hammer, Patricia Schmidt and Anne MacFarlane Respondents - and - Katrina Hammer, Patricia Schmidt and Anne MacFarlane Appellants v.

Workers’ Compensation Appeal Tribunal and Fraser Health Authority Respondents and Attorney General of Canada, Attorney General of Ontario, Ontario Network of Injured Workers’ Groups, Industrial Accident Victims’ Group of Ontario, Community Legal Assistance Society and British Columbia Federation of Labour Interveners Indexed as: British Columbia (Workers’ Compensation Appeal Tribunal) v. Fraser Health Authority 2016 SCC 25 File No.: 36300. 2016: January 14; 2016: June 24.

Present: McLachlin C.J. and Abella, Moldaver, Karakatsanis, Wagner, Côté and Brown JJ. on appeal from the court of appeal for british columbia Workers’ compensation — Occupational disease — Causation — Evidence — Standard of proof — Hospital laboratory technicians diagnosed with breast cancer applying for compensation on basis that their cancers are occupational diseases — Compensation payable if employment is of causative significance in development of disease — Medical experts unable to find sufficient scientific basis to establish causal link between workers’ cancers and employment — Whether Tribunal erred in its approach to

causation in deciding that workers’ cancer was occupational disease arising due to nature of employment — Workers Compensation Act, R.S.B.C. 1996, c. 492, ss. 6 , 250(4) . H, S and M (the “workers”) were among seven technicians at a single hospital laboratory who were diagnosed with breast cancer. Each of them applied for compensation under the Workers Compensation Act on the basis that the cancer was an occupational disease.

The Act provides that where a worker is disabled from an occupational disease that is due to the nature of his or her employment, compensation is payable as if the disease were a personal injury arising out of and in the course of that employment. In accordance with the applicable policy, the payment of benefits is conditional upon the employment having been of “causative significance” in the development of the worker’s illness.

The medical experts who provided evidence concluded that there was a lack of a sufficient scientific basis to causally link the incidence of breast cancer to the workers’ employment in the laboratory. A review officer of the Workers’ Compensation Board denied each of the workers’ claims. The workers each appealed the Board’s decision to the Workers’ Compensation Appeal Tribunal. A majority of the Tribunal found that the workers’ breast cancers were indeed occupational diseases. Upon application by the employer to the Tribunal for reconsideration, a reconsideration panel upheld the original decision.

The employer’s application for judicial review of the Tribunal’s original and reconsideration decisions was allowed: both decisions were set aside and the matter was remitted back to the Tribunal. On appeal by the workers, the majority of the Court of Appeal dismissed the appeal, holding that the Tribunal’s reconsideration decision was a nullity and that the Tribunal’s original decision was patently unreasonable. The workers now appeal to this Court, raising the issue of whether the Tribunal erred in its approach to causation.

The Tribunal also appeals to this Court, raising the issue of whether it can, by way of a reconsideration decision, reopen an earlier decision to consider whether it was patently unreasonable. Held (Côté J. dissenting in part): The appeal by the workers should be allowed. The appeal by the Tribunal should be dismissed. Per McLachlin C.J. and Abella, Moldaver, Karakatsanis, Wagner and Brown JJ.: The standard of review applicable to the Tribunal’s original decision requires curial deference, absent a finding of fact or law that is patently unreasonable.

Because a court must defer where there is evidence capable of supporting a finding of fact, patent unreasonableness is not established where the reviewing court considers the evidence merely to be insufficient. The presence or absence of opinion evidence from an expert positing or refuting a causal link is not determinative of causation. Causation can be inferred — even in the face of inconclusive or contrary expert evidence — from other evidence, including merely circumstantial evidence. Subject to the applicable standard of review, the task of weighing evidence rests with the trier of fact.

In the instant case, the Tribunal’s original decision cannot be said to have been patently unreasonable. While the record on which that decision was based did not include confirmatory expert evidence, the Tribunal nonetheless relied upon other evidence which, viewed reasonably, was capable of supporting its finding of a causal link between the workers’ breast cancers and workplace conditions. In addition, according to the standard of proof set out in s. 250(4) of the Act , where the evidence is evenly weighed on causation, that issue must be resolved in the workers’ favour.

This standard of proof contrasts sharply with the scientific standards employed by the medical experts in the case at bar. The majority of the Tribunal was right to consider that the experts thus imposed a too stringent standard of proof. In relying upon the inconclusive quality of the experts’ findings as determinative of whether a causal link was established between the workers’ breast cancers and their employment, the chambers judge and the majority of the Court of Appeal erred in law.

With respect to the appeal by the Tribunal, the employer agrees with the Court of Appeal’s assessment that the Tribunal’s reconsideration decision was a nullity. Accordingly, there is no reason to interfere with that aspect of the Court of Appeal’s decision. Per Côté J. (dissenting in part): There is agreement with the majority with respect to the Tribunal’s appeal only. As for the workers’ appeal, it should be dismissed since the original decision of the Tribunal is patently unreasonable and ought to be set aside.

There is no evidence — and certainly no positive evidence — capable of supporting a causal link between the workers’ employment and the development of their respective diseases. Experts are responsible for providing decision-makers with precisely those inferences that decision-makers — due to the technical nature of the issues — are unable to formulate themselves. The Tribunal is not presumed to possess medical expertise. As a result, while the Tribunal is not bound by the medical experts’ findings, it cannot simply disregard their uncontradicted conclusions.

In this case, the expert reports before the Tribunal were unequivocal: the available evidence could not establish any causal relationship between the workers’ employment as laboratory technicians and the development of their breast cancer. In the instant case, the medical experts did not seek to establish causation on a level of scientific certainty. Having undertaken a more limited investigation, the medical experts simply found no workplace exposure that could plausibly have increased the risk of developing breast cancer.

As a result, even on the relaxed standard of proof applicable under s. 250(4) of the Act , there is still no positive evidence capable of establishing causative significance. While drawing inferences is important in fact finding, the evidence in the record must still be capable of supporting the inferences drawn. Otherwise, the fact-finder is at risk of straying outside the realm of inference and reasonable deductions and into the wilderness of mere speculation or conjecture.

Common sense or inferential reasoning cannot bridge insuperable gaps in the evidence, in either a standard civil action or in an administrative claim under the Act . In the case at bar, the only support for the Tribunal’s original decision is the existence of a cluster of diagnosed cases of breast cancer. The Tribunal’s findings of fact simply do not rise above the level of mere speculation. The Tribunal disregarded the consensus view of the medical experts, in spite of its own lack of expertise in medical matters.

The Tribunal also ignored the applicable policy, which states that there must be sufficient positive evidence capable of supporting a finding of causative significance, failing which the only possible option is to deny the claim. Cases Cited By Brown J.

Referred to: Mustapha v. Culligan of Canada Ltd., 2008 SCC 27, [2008] 2 S.C.R. 114; Snell v. Farrell, (SCC), [1990] 2 S.C.R. 311; Toronto (City) Board of Education v. O.S.S.T.F., District 15, (SCC), [1997] 1 S.C.R. 487;Sam v. Wilson, 2007 BCCA 622, 78 B.C.L.R. (4th) 199; Moore v. Castlegar & District Hospital (1998), (BC CA), 49B.C.L.R. (3d) 100; Dunsmuir v. New Brunswick, 2008 SCC 9, [2008] 1 S.C.R. 190; Chandler v. Alberta Association of Architects, (SCC), [1989] 2 S.C.R. 848; Ediger v. Johnston, 2013 SCC 18, [2013] 2 S.C.R. 98; Speckling v.

Workers’ CompensationBoard (B.C.), 2005 BCCA 80, 209 B.C.A.C. 86; F.H. v. McDougall, 2008 SCC 53, [2008] 3 S.C.R. 41; Kovach, Re (1998), (BC CA), 52 B.C.L.R. (3d) 98, rev’d 2000 SCC 3, [2000] 1 S.C.R. 55; Pasiechnyk v. Saskatchewan (Workers’ CompensationBoard), (SCC), [1997] 2 S.C.R. 890; Medwid v. Ontario (1988), (ON SC), 63 O.R. (2d) 578;Clements v. Clements, 2012 SCC 32, [2012] 2 S.C.R. 181. By Côté J. (dissenting in part) Canada (Director of Investigation and Research) v. Southam Inc., (SCC), [1997] 1 S.C.R. 748; Dunsmuirv. New Brunswick, 2008 SCC 9, [2008] 1 S.C.R. 190; Toronto (City) Board of Education v.

O.S.S.T.F., District 15, (SCC), [1997] 1 S.C.R. 487; Lester (W.W.)

(1978) Ltd. v. United Association of Journeymen and Apprentices of the Plumbing andPipefitting Industry, Local 740, (SCC), [1990] 3 S.C.R. 644; R. v. Abbey, (SCC), [1982] 2 S.C.R. 24; R.v. Abbey, 2009 ONCA 624, 97 O.R. (3d) 330, leave to appeal refused, [2010] 2 S.C.R. v; Page v. British Columbia (Workers’Compensation Appeal Tribunal), 2009 BCSC 493; Snell v. Farrell, (SCC), [1990] 2 S.C.R. 311; Fairchild v. GlenhavenFuneral Services Ltd., [2002] UKHL 22, [2003] 1 A.C. 32; Caswell v. Powell Duffryn Associated Collieries, Ltd., [1940] A.C. 152;Kozak v. Funk (1997), (SK CA), 158 Sask.

R. 283, aff’g in part (1995), (SK KB), 135 Sask. R. 81;Meringolo v. Oshawa General Hospital (1991), 46 O.A.C. 260, leave to appeal refused, [1991] 3 S.C.R. vii; Canadian Union of PublicEmployees, Local 963 v. New Brunswick Liquor Corp., (SCC), [1979] 2 S.C.R. 227. Statutes and Regulations Cited Administrative Tribunals Act, S.B.C. 2004, c. 45, s. 58. Workers Compensation Act, R.S.B.C. 1996, c. 492, ss. 6, 96, 96.2 to 96.4, 245.1(w), 250(2), (4), 253.1, 254, 255(1), 256(2), Sch. B. Authors Cited Anderson, Glenn R. Expert Evidence, 3rd ed. Markham, Ont.: LexisNexis, 2014. British Columbia.

Workers’ Compensation Board. Rehabilitation Services & Claims Manual, vol. II (online:http://www.worksafebc.com). Cheifetz, David. “The Snell Inference and Material Contribution: Defining the Indefinable and Hunting the Causative Snark” (2005), 30Advocates’ Q. 1. Haack, Susan. Evidence Matters: Science, Proof, and Truth in the Law. New York: Cambridge University Press, 2014. Hill, Austin Bradford. “The Environment and Disease: Association or Causation?” (1965), 58 Proc. R. Soc. Med. 295. Occupational Health and Safety Agency for Healthcare in British Columbia.

Cancer Cluster Investigation within the Mission MemorialHospital Laboratory, Final Report by George Astrakianakis et al. March 31, 2006 (online: http://www.phsa.ca). Wright, Richard W. “Proving Causation: Probability versus Belief”, in Richard Goldberg, ed., Perspectives On Causation. Oxford: Hart,2011, 195. APPEALS from a judgment of the British Columbia Court of Appeal (Newbury, Chiasson, Frankel, Bennett andGoepel JJ.A.), 2014 BCCA 499, 364 B.C.A.C. 241, 82 Admin. L.R. (5th) 246, 67 B.C.L.R. (5th) 213, 380 D.L.R. (4th) 204, 625 W.A.C.241, [2015] 4 W.W.R. 1, [2014] B.C.J.

No. 3111 (QL), 2014 CarswellBC 3824 (WL Can.), affirming a decision of Savage J., 2013BCSC 524, [2013] B.C.J. No. 605 (QL), 2013 CarswellBC 795 (WL Can.). Appeal by the Workers’ Compensation Appeal Tribunaldismissed. Appeal by Katrina Hammer, Patricia Schmidt and Anne MacFarlane allowed, Côté J. dissenting. Timothy J. Martiniuk and Jeremy Thomas Lovell, for the appellant/respondent the Workers’ Compensation Appeal Tribunal. Tonie Beharrell, Randall J. Noonan and Kaity Cooper, for the appellants/respondents Katrina Hammer, Patricia Schmidtand Anne MacFarlane. Nazeer T. Mitha, Dianne D.

Rideout and Erin Cutler, for the respondent Fraser Health Authority. Christine Mohr and Alexander Pless, for the intervener the Attorney General of Canada. Sara Blake and Sandra Nishikawa, for the intervener the Attorney General of Ontario. Ivana Petricone, for the interveners the Ontario Network of Injured Workers’ Groups and the Industrial Accident Victims’Group of Ontario. Monique Pongracic-Speier, for the interveners the Community Legal Assistance Society and the British ColumbiaFederation of Labour.

The judgment of McLachlin C.J. and Abella, Moldaver, Karakatsanis, Wagner and Brown JJ. was delivered by Brown J. —

I. Introduction [ 1 ] These appeals call upon the Court to consider (1) whether the British Columbia Workers’ Compensation Appeal Tribunal can, by way of a “reconsideration” decision, reopen an earlier decision to consider whether it was patently unreasonable (the “WCAT Appeal”); and (2) whether, in the circumstances of this case, the Tribunal erred in its approach to causation [1] in deciding that each of three workers’ cases of breast cancer was an “occupational disease” arising “due to the nature of [their] employment” (the “Workers’ Appeal”).

A majority of the British Columbia Court of Appeal held that the Tribunal’s reconsideration decision (which simply affirmed its original decision) was a nullity, and that the Tribunal erred in its original decision in finding a causal link between the workers’ breast cancers and their employment. [ 2 ] I would allow the Workers’ Appeal and dismiss the WCAT Appeal. As to the WCAT Appeal, as I will explain, the respondent Fraser Health Authority agrees with the Court of Appeal’s assessment that the Tribunal’s reconsideration decision was a nullity.

I therefore see no reason to interfere with that aspect of the Court of Appeal’s decision. On the issue of causation raised by the Workers’ Appeal, however, for the reasons that follow I am of the view that, in light of the applicable standard of review, the Tribunal’s finding of a causal link between the workers’ breast cancers and their employment should not have been upset. II. Overview of Facts and Proceedings A. Background and Statutory Provisions [ 3 ] Katrina Hammer, Patricia Schmidt and Anne MacFarlane were among seven technicians at a single hospital laboratory who were diagnosed with breast cancer.

Each of them applied for compensation under the Workers Compensation Act , R.S.B.C. 1996, c. 492, on the basis that the cancer was an “occupational disease”. [ 4 ] The Act establishes a comprehensive no-fault insurance scheme for workers who sustain workplace injuries or suffer from occupational diseases.

More specifically, s. 6 of the Act provides that where a worker is disabled from an occupational disease that is due to the nature of his or her employment, compensation is payable “as if the disease were a personal injury arising out of and in the course of that employment”. [ 5 ] Upon receiving a claim, the Workers’ Compensation Board inquires into, hears and determines all matters and questions of fact and law (s. 96). Certain decisions of the Board can be reviewed by a review officer ( ss. 96.2 to 96.4 ) and, further, can be appealed to the Tribunal.

Section 254 confers upon the Tribunal “exclusive jurisdiction to inquire into, hear and determine all those matters and questions of fact, law and discretion arising or required to be determined [on appeals under the Act ]”.

Further, the Tribunal may amend its own decisions to cure a clerical or typographical error, an “accidental or inadvertent error, omission or other similar mistake” or an arithmetical error ( s. 253.1 ), or it may reconsider a decision to cure a jurisdictional defect or if new evidence has become available or has been discovered (ss. 253.1(5) and 256(2) ). [ 6 ] As to whether a worker suffers from an occupational disease due to the nature of his or her employment, the Board’s Rehabilitation Services & Claims Manual , vol.

II (“ RSCM II ”) (online), the relevant policy which must be applied by the Tribunal to decide these appeals (s. 250(2) of the Act ), conditions payment of benefits upon the employment having been of “causative significance” in the development of the worker’s illness. This means “more than a trivial or insignificant aspect of the injury or death” ( RSCM II ,

Chapter 3, policy item #14.00), and entails consideration of whether: • there is a physiological association between the injury or death and the employment activity, including whether the activity was of sufficient degree and/or duration to be of causative significance in the injury or death; • there is a temporal relationship between the work activity and the injury or death; and • any non-work related medical conditions were a factor in the resulting injury or death. [ 7 ] Section 250(4) of the Act provides that, where the Tribunal is hearing an appeal respecting the compensation of a worker and the evidence is “evenly weighted” on an issue, the Tribunal must resolve that issue “in a manner that favours the worker”.

In other words, the applicable burden of proof is not the civil burden of “balance of probabilities”. Where the evidence leads to a draw, the finding must favour the worker. This extends to deciding whether the occupational disease is “due to” the nature of employment — that is, to the issue of causation: “. . . if the weight of the evidence suggesting the disease was caused by the employment is roughly equally balanced with evidence suggesting non-employment causes, the issue of causation will be resolved in favour of the worker” ( RSCM II ,

Chapter 4, policy item #26.22). [ 8 ] By joint operation of s. 245.1(

w) of the Workers Compensation Act and s. 58(2) (

a) of the Administrative Tribunals Act , S.B.C. 2004, c. 45, a reviewing court may not interfere with a finding of fact or law made by the Tribunal in respect of a matter over which it has exclusive jurisdiction unless it is patently unreasonable. B. Evidence on Causation [ 9 ] The causal issue before the Board, the Tribunal and the courts below was the etiology of the workers’ breast cancers. [2] The evidence on that question comprised three expert reports: (

a) the final report of the Occupational Health and Safety Agency for Healthcare in British Columbia (“OHSAH”) regarding the incidence of cancer in the laboratory where the workers were employed ( Cancer Cluster Investigation within the Mission Memorial Hospital Laboratory , Final Report, March 31, 2006, at p. 35 (online)) and two earlier draft reports, each produced by various OHSAH staff, consultants and trainees (collectively the “OHSAH reports”); (

b) the report of Dr. Jeremy R. Beach, a specialist in occupational medicine; and

(

c) the report of Dr. M. W. Yamanaka, a medical advisor to the Board specializing in occupational medicine. [10] The OHSAH reports contained a review of the scientific literature on factors associated with the risk of breastcancer, an epidemiological analysis of the cancer cluster among workers in the laboratory, and a field investigation into possibleexposure among laboratory technicians to potentially carcinogenic substances.

They confirmed that the number of diagnoses of breastcancer (7 of the 63 workers studied were so diagnosed) represented a statistically significant cluster, with a “standardized incidenceratio” for breast cancer approximately eight times the rate that would have been expected in the general population.

As to potentialcauses, the authors of these reports observed no current occupational chemical exposures, but noted that past exposures were “likelymuch higher”, and included one known human carcinogen (Final Report, at p. 35). [11] Ultimately, the authors of the OHSAH reports did not reach “scientific conclusions to support the associationbetween work-related exposures and breast cancer in this cluster” (Final Report, at p. iii).

More particularly, they explained that “[o]urreview of the literature was unable to establish the basis for [an etiological hypothesis based on scientific evidence of causal mechanismsfor breast cancer], as we did not find any scientific evidence for the plausibility of a laboratory work-related etiological hypothesisregarding breast cancer” (p. iv).

The authors speculated that the increased incidence of breast cancer among laboratory employees mayhave been due to “(1) a cluster of reproductive and other known, non-occupational, risk factors, (2) past exposures to chemicalcarcinogens and less likely to ionizing radiation, and (3) a statistical anomaly” (p. 39 (emphasis added)). [12] Dr. Beach’s report and Dr. Yamanaka’s report were each in substantial agreement with the OHSAH reports. Inparticular, Dr. Beach and Dr.

Yamanaka shared the OHSAH reports’ conclusion regarding the lack of a sufficient scientific basis tocausally link the incidence of breast cancer to the workers’ employment in the laboratory. Dr. Yamanaka went somewhat further than Dr.Beach, saying (without elaboration) that he “would prefer to refute than support” that posited link, and that he “would favor the opinionthat non-occupational factors were the cause of [the] breast cancer” (J.R., vol. 4, at p. 230). C. The Decisions Below

(1) The Workers’ Compensation Board [13] A review officer of the Board denied each of the claims, finding that “there is insufficient evidence . . . to concludethat [each worker’s] years of employment as a medical lab technician has played a significant role in causing breast cancer”, and pointingto various non-occupational risk factors for breast cancer (J.R., vol. 3, at p. 21).

(2) The Tribunal’s Original Decisions [14] The workers each appealed the Board’s decision to the Tribunal. At the Tribunal, a majority of two members foundthat the workers’ breast cancers were indeed occupational diseases. In doing so, the majority acknowledged the need for “positiveevidence linking the disease to employment” (J.R., vol. 1, at p. 16) and cited the decision of this Court in Snell v.

Farrell, (SCC), [1990] 2 S.C.R. 311, as authority for a fact-finder’s ability to draw a “common sense” inference of causation in the absence ofscientific proof of causation — scientific standards being more rigorous than the “lesser standard . . . demanded by the law” (J.R., vol. 1,at p. 17). The authors of the OHSAH reports, in seeking “to reach scientific conclusions to support the association between work-relatedexposures and breast cancer in this cluster” (Final Report, at p. iii), therefore applied a too stringent standard of proof.

The applicablestandard was not that which is necessary to support a scientific conclusion, but rather the standard set out in s. 250(4) of the Act. [15] The majority then analysed the evidence with reference to the indicia described by A. Bradford Hill (“TheEnvironment and Disease: Association or Causation?” (1965), 58 Proc. R. Soc. Med. 295) for weighing epidemiological evidence ofcausation.

In this case, the criteria of “strength of association” (the ratio of the incidence of disease among exposed workers whencompared to the incidence within the general population) and “temporal relationship” (the proximity in time between exposure and theonset of the disease) were clearly satisfied, although other criteria were not. The majority concluded, however, that it was not necessaryto identify a specific causal agent, it being sufficient for the evidence merely to point to a causal link between a disease and anoccupation.

Here, the evidence of past carcinogenic exposure, coupled with the statistically significant cluster of breast cancer casesamong laboratory workers, comprised “positive evidence” supporting a conclusion that it was as likely as not that the workers’ breastcancers were caused by workplace exposure. [16] The dissenting member explained that, while she agreed that scientific certainty was not required, the expert reportsprovided no “positive evidence” of a causal link. Without more, they were therefore insufficient to support a conclusion that workplaceexposures were of causal significance.

(3) The Tribunal’s Reconsideration Decisions [17] Fraser Health applied under s. 253.1(5) of the Workers Compensation Act for reconsideration[3] of the Tribunal’soriginal decisions. While s. 253.1 permits the Tribunal to amend its decisions to correct clerical, typographical or mathematical errors, orto clarify its decisions, subs. (5) provides that “[t]his

section must not be construed as limiting the appeal tribunal’s ability, on request ofa party, to reopen an appeal in order to cure a jurisdictional defect.” Fraser Health’s argument was that a “jurisdictional defect” arosehere, since the Tribunal’s finding in the original decisions of a causal link between the workers’ breast cancers and their employmentlacked supporting evidence and was, as such, patently unreasonable. [18] The reconsideration panel (comprising a single member) reviewed the original decisions for patent unreasonablenessand determined that, given the elevated standard incidence ratio and the past exposure to carcinogens, the original panel had sufficientevidence to support its conclusions regarding causation.

(4) British Columbia Supreme Court, 2013 BCSC 524 [19] Fraser Health sought judicial review of the Tribunal decisions — the original decisions and the reconsiderationdecisions. Savage J. (as he then was) explained that he would review the original decision for patent unreasonableness and the

reconsideration decision for correctness. He observed that the Tribunal’s decisions are entitled to the highest level of curial deferenceand, in particular, that “the [Tribunal] has a right to be wrong provided that there is some evidence capable of supporting its conclusion”(para. 11 , citing Toronto (City) Board of Education v. O.S.S.T.F., District 15, (SCC), [1997] 1 S.C.R. 487, atpara. 44). [20] That said, the chambers judge observed, the Tribunal “was not entitled to ignore the expert evidence in favour of itsown expertise or common sense, and it was patently unreasonable [for it] to do so” (para. 34).

Here, he relied on British Columbia Courtof Appeal authority — specifically, Sam v. Wilson, 2007 BCCA 622, 78 B.C.L.R. (4th) 199, at para. 41, citing Moore v. Castlegar &District Hospital (1998), (BC CA), 49 B.C.L.R. (3d) 100 (C.A.), at para. 11 — which holds that, “where there isaffirmative medical evidence leading to a medical conclusion it is not open to the court to apply ‘the common sense reasoning urged inSnell v. Farrell’”. This precluded “the purported application of common sense on matters of causation where there is contrary expertopinion” (chambers judge’s reasons, at para. 40).

Here, the experts clearly and unambiguously concluded that there was no evidence thatworkplace factors caused the workers’ breast cancers. Given “the absence of any evidence and in the face of expert opinion to thecontrary” (para. 49), the Tribunal’s original decision was patently unreasonable and the reconsideration decision was incorrect. He setaside both decisions and remitted the matter back to the Tribunal.

(5) British Columbia Court of Appeal, 2014 BCCA 499, 67 B.C.L.R. (5th) 213 [21] The workers appealed Savage J.’s decision, and the Court of Appeal invited the parties to make submissions as to,inter alia, the jurisdiction of the Tribunal to reconsider its original decision in this matter. Chiasson J.A., joined by Frankel and GoepelJJ.A., held that s. 253.1(5) of the Workers Compensation Act merely preserves the Tribunal’s common law power to reopen a proceedingto complete its statutory task, and therefore does not permit it to correct errors made within its jurisdiction. The Tribunal’s

interpretationof s. 253.1(5) as permitting it to review its own decisions to identify and correct patently unreasonable errors is supported neither by thatcommon law power to reopen nor by the Act’s legislative history. Since no true jurisdictional defect had been alleged, the Tribunal’sreconsideration decision was a nullity. Chiasson J.A. therefore dismissed the appeal of the chambers judge’s order setting aside thereconsideration decision. [22] Newbury J.A., joined by Bennett J.A., disagreed.

The meaning of “jurisdictional defect” in s. 253.1, having beendrafted prior to the decision of this Court in Dunsmuir v. New Brunswick, 2008 SCC 9, [2008] 1 S.C.R. 190, should not be confined topermitting the Tribunal to review for errors of “true” jurisdiction as that term was described in Dunsmuir. Rather, it should be understoodin light of the common law power to reopen which, in her view, included the power of a tribunal to determine whether an originaldecision was patently unreasonable.

As a practical matter, limiting the Tribunal’s scope to reconsider its own decisions for patentunreasonableness would mean more court proceedings, contrary to the purpose of the Act and to the principles of administrative lawgenerally. [23] On the issue of causation, Chiasson J.A., joined by Frankel J.A., held that, while there was “some evidence” tosupport the Tribunal’s finding of causation (specifically, the “statistical anomaly” of elevated breast cancer rates among laboratoryworkers), “something more” was required (paras. 198-99).

The Tribunal’s finding of causation was, therefore, patently unreasonable. [24] Goepel J.A., writing separately, agreed that the chambers judge did not err in setting aside the original decision aspatently unreasonable. Resolving issues of causation in this case required expert “medical” and “scientific” evidence (para. 209). Lackingsuch expertise, the Tribunal cannot disregard uncontradicted expert evidence in order to substitute its own opinion.

In the absence of“positive evidence linking the disease to employment” (para. 211), and in the face of expert evidence to the contrary, the Tribunal’sdecision was patently unreasonable. [25] Newbury J.A., again joined by Bennett J.A., observed that the standard of review of “patent unreasonableness”denotes the highest level of deference, permitting curial interference only where there is “no evidence” to support the Tribunal’s findingsor where its decision was “openly, clearly, or evidently unreasonable” (para. 70 (emphasis in original)).

Here, the experts did not rule outa causal connection between laboratory conditions and the workers’ cancers. While the experts acknowledged that present chemicalexposures were minimal, past exposures had likely been much higher and included at least one known human carcinogen. The Tribunal’sconclusion that the likelihood of a statistical anomaly did not exceed the likelihood that breast cancers in these cases were occupationaldiseases was reached appropriately, after a careful review of all the evidence.

Viewed through the scheme and underlying objectives ofthe workers’ compensation system, which requires the Tribunal to resolve issues in favour of a worker where the evidence supportingdifferent findings on an issue is evenly weighted, the Tribunal’s original decision was not patently unreasonable and should not havebeen upset by the chambers judge. III. Analysis A.

The Tribunal’s Jurisdiction to Reconsider Its Own Decision [26] Fraser Health, having sought reconsideration by the Tribunal, now takes the position that the majority at the Courtof Appeal correctly characterized the reconsideration decision as a nullity. The Tribunal’s power to reconsider a decision under s.253.1(5) of the Workers Compensation Act “to cure a jurisdictional defect” is, it says, limited to the common law power to reopen asstated by the Court in Chandler v.

Alberta Association of Architects, (SCC), [1989] 2 S.C.R. 848, at p. 861: “. . . [afinal] decision cannot be revisited because the tribunal has changed its mind, made an error within jurisdiction or because there has beena change of circumstances”. [27] Conversely, the Tribunal submits that s. 253.1(5)’s language of “cur[ing] a jurisdictional defect” is sufficiently broadto permit reconsideration for patent unreasonableness.

In the Tribunal’s view, when it undertakes to reconsider its own decision, iteffectively operates as a court on judicial review by applying the standard of review of patent unreasonableness stated in s. 58(2)(

a) ofthe Administrative Tribunals Act. [28] In light of the position taken by Fraser Health — that it should not have been able to obtain reconsideration of theTribunal’s original decision and that the reconsideration decision is a nullity — I see no basis for interfering with the decision of the

Court of Appeal on this issue. B. Causation

(1) Standard of Review [29] As already noted, and as the parties agree, the applicable standard of review requires curial deference, absent afinding of fact or law that is patently unreasonable (Administrative Tribunals Act, s. 58(2)(a)). [30] The Tribunal’s conclusion that the workers’ breast cancers were occupational diseases caused by the nature of theiremployment was a finding on a question of fact (Ediger v. Johnston, 2013 SCC 18, [2013] 2 S.C.R. 98, at para. 29).

That finding istherefore entitled to deference unless Fraser Health demonstrates that it is patently unreasonable — that is, that “the evidence, viewedreasonably, is incapable of supporting a tribunal’s findings of fact” (Toronto (City) Board of Education, at para. 45). Because a courtmust defer where there is evidence capable of supporting (as opposed to conclusively demonstrating) a finding of fact, patentunreasonableness is not established where the reviewing court considers the evidence merely to be insufficient (Speckling v. Workers’Compensation Board (B.C.), 2005 BCCA 80, 209 B.C.A.C. 86, at para. 37).

Simply put, this standard precludes curial re-weighing ofevidence, or rejecting the inferences drawn by the fact-finder from that evidence, or substituting the reviewing court’s preferredinferences for those drawn by the fact-finder.

(2) The Tribunal’s Finding on Causation [31] Understandably, the workers stress s. 250(4) of the Workers Compensation Act which signifies that, where theevidence is evenly weighted on causation, that issue must be resolved in their favour. We agree that this represents an importantdistinction from civil tort claims, where causation must always be established on a balance of probabilities (F.H. v. McDougall, 2008SCC 53, [2008] 3 S.C.R. 41, at para. 49; Ediger, at para. 28; Kovach, Re (1998), (BC CA), 52 B.C.L.R. (3d) 98(C.A.), at para. 30 (per Donald J.A., dissenting), rev’d 2000 SCC 3, [2000] 1 S.C.R. 55).

This less stringent burden of proof, like theRSCM II’s direction that the workplace need only be of “causative significance” or “more than a trivial or insignificant aspect” in thedevelopment of a worker’s illness, furthers at least one of the core policy goals of workers’ compensation schemes identified by theCourt in Pasiechnyk v. Saskatchewan (Workers’ Compensation Board), (SCC), [1997] 2 S.C.R. 890, at para. 27, citingMedwid v. Ontario (1988), (ON SC), 63 O.R. (2d) 578 (H.C.), at p. 586, being to have “compensation to injuredworkers provided quickly without court proceedings”.

Section 250(4) therefore reflects the legislature’s intention that workers shouldobtain compensation for occupational diseases without having to satisfy the requirements of a civil tort claim. [32] Section 250(4)’s standard of proof contrasts sharply with the “scientific” standards employed by the authors of theOHSAH reports.

Their inability “to reach scientific conclusions” (Final Report, at p. iii) to support the causal association betweenworkplace conditions and the workers’ breast cancers, or to “find any scientific evidence for the plausibility of a laboratory work-relatedetiological hypothesis regarding breast cancer” (p. iv), spoke not to the burden imposed upon the workers by s. 250(4), nor even to theburden imposed upon plaintiffs in a civil tort claim (Ediger, at para. 36; Clements v. Clements, 2012 SCC 32, [2012] 2 S.C.R. 181, atpara. 9; Snell, at pp. 328-30), but to a standard of scientific certainty.

The majority of the Tribunal considered that the OHSAH reportsthus imposed a too stringent standard of proof. I agree. This standard is wholly inapplicable to determining causation in the workers’claims (R. W. Wright, “Proving Causation: Probability versus Belief”, in R. Goldberg, ed., Perspectives On Causation (2011), 195; S.Haack, Evidence Matters: Science, Proof, and Truth in the Law (2014), at p. 22).

In my respectful view, therefore, in relying upon theinconclusive quality of the OHSAH reports’ findings as determinative of whether a causal link was established between the workers’breast cancers and their employment, the chambers judge and the majority of the Court of Appeal erred in law. [33] All that said, the central problem in the handling of causation in the courts below arose not in their failure to haveappropriate regard to the less stringent standard of proof required by s. 250(4), but from their fundamental misapprehension of howcausation — irrespective of the standard of proof — may be inferred from evidence. [34] As I have recounted, the evidence before the Tribunal on causation comprised, principally, the OHSAH reports(supported by the reports of Dr.

Beach and Dr. Yamanaka), which (1) confirmed a “statistically significant cluster” of breast cancer, witha standard incidence ratio approximately eight times the rate of breast cancer in the general population; and (2) noted that pastoccupational chemical exposures were likely “much higher” than current exposures, and included one known carcinogen; but also (3)reported that they were unable “to reach scientific conclusions to support the association between work-related exposures and breastcancer in this cluster” (Final Report, at p. iii).

Consequently, the OHSAH reports would only speculate that the increased incidence ofbreast cancer among the laboratory workers may have been due to non-occupational risk factors, to occupational risk factors such aschemical carcinogens or ionizing radiation, or to a statistical anomaly. [35] The Tribunal, in lengthy and comprehensive reasons explaining why it found “causative significance” in theevidence of past carcinogenic exposure and in the statistically significant cluster of breast cancer cases, gave careful consideration to theOHSAH reports.

It correctly noted that the OHSAH reports “did not exclude the possibility of occupational causation”, and that theTribunal did not have before it “much detailed evidence as to historical exposures” (J.R., vol. 1, at p. 47). And, it acknowledged that “it ispossible that the breast cancer cluster is a statistical anomaly”, and that “this matter is not without some uncertainty” (p. 48).

TheTribunal chose, however, to “attach weight” to the reports’ observations that past exposures were “likely much higher” (p. 47), leading itto find that the likelihood of a statistical anomaly did not exceed the likelihood that the workers’ breast cancers were an occupationaldisease caused by the nature of their employment. As it explained: Perhaps the most compelling evidence for us involves the fact that the workers with breast cancer were exposed to carcinogens and thereis a very elevated statistically significant [standardized incidence ratio] for breast cancer.

Our decision does not simply rest on theoccurrence of a very elevated statistically significant [standardized incidence ratio] for breast cancer. That [standardized incidence ratio] occurs against the backdrop of the particular standard of proof employed by us, the workers’exposure to carcinogens, and the comments of [the Final Report] to the effect that all cancer causing agents have the potential to initiateand promote cancer, little is known about the possible synergistic, additive or antagonistic effects of multiple chemical exposures, and

past exposures were likely much higher. [J.R., vol. 1, at p. 48] [36] The chambers judge, seeing “no evidence that workplace factors caused [the workers’] cancers” (para. 44), viewedthe Tribunal as having impermissibly “ignore[d] the expert evidence in favour of its own expertise or common sense” (para. 34).Similarly, at the Court of Appeal, having found there to be no “positive evidence linking the disease to employment” (para. 211), GoepelJ.A. (for the majority on this point) agreed that “[t]he issue for determination is one that required expert scientific evidence” (para. 209),which expertise the Tribunal could not be presumed to have. [37] With respect, the issue that the Tribunal decided was precisely the sort of issue that the legislature intended that itshould decide.

Section 254 of the Act provides that, on appeals from decisions of the Board, the Tribunal has exclusive jurisdiction todetermine all questions of fact. While, in doing so, the Tribunal may choose to draw from the expert evidence put before it (as it drewhere from expert evidence of historical exposures and of a statistically significant cluster of breast cancer cases among laboratoryworkers), the decision remains the Tribunal’s to make. [38] The presence or absence of opinion evidence from an expert positing (or refuting) a causal link is not, therefore,determinative of causation (e.g.

Snell, at pp. 330 and 335). It is open to a trier of fact to consider, as this Tribunal considered, otherevidence in determining whether it supported an inference that the workers’ breast cancers were caused by their employment. This goesto the chambers judge’s reliance upon the Court of Appeal’s decisions in Sam and Moore and to Goepel J.A.’s statement that there mustbe “positive evidence” linking their breast cancers to workplace conditions.

Howsoever “positive evidence” was intended to beunderstood in those decisions, it should not obscure the fact that causation can be inferred — even in the face of inconclusive or contraryexpert evidence — from other evidence, including merely circumstantial evidence. This does not mean that evidence of relevanthistorical exposures followed by a statistically significant cluster of cases will, on its own, always suffice to support a finding that aworker’s breast cancer was caused by an occupational disease. It does mean, however, that it may suffice.

Whether or not it does sodepends on how the trier of fact, in the exercise of his or her own judgment, chooses to weigh the evidence. And, I reiterate: Subject tothe applicable standard of review, that task of weighing evidence rests with the trier of fact — in this case, with the Tribunal. [39] In light of the foregoing, the Tribunal’s original decision cannot be said to have been “patently unreasonable”.

Whilethe record on which that decision was based did not include confirmatory expert evidence, the Tribunal nonetheless relied upon otherevidence which, viewed reasonably, was capable of supporting its finding of a causal link between the workers’ breast cancers andworkplace conditions. IV. Conclusion [40] I would allow the Workers’ Appeal, with costs to Katrina Hammer, Patricia Schmidt and Anne MacFarlane in thisCourt and in the courts below as against Fraser Health Authority. The Tribunal’s original decisions are restored. I would dismiss theWCAT Appeal, without costs.

The following are the reasons delivered by [41] Côté J. (dissenting in part) — I part ways with my colleague Justice Brown with respect to the appeal by KatrinaHammer, Patricia Schmidt and Anne MacFarlane (the “Workers’ Appeal”) because, in my view, the original decision of the Workers’Compensation Appeal Tribunal is patently unreasonable. On my reading, there is no evidence — and certainly no positive evidence —capable of supporting a causal link between the workers’ employment and the development of their respective diseases.

The three expertreports before the Tribunal only established the existence of a cluster of diagnosed cases of breast cancer, and nothing more. In my view,the Tribunal relied on what it called “ordinary common sense” to speculate about a possible causal link, while openly disregarding themedical experts’ consensus view. As such, the Tribunal’s decision is “openly, evidently, clearly” wrong and ought to be set aside:Canada (Director of Investigation and Research) v.

Southam Inc., (SCC), [1997] 1 S.C.R. 748, at para. 57. [42] Regarding the appeal by the Tribunal (the “WCAT Appeal”), raising the issue of the nullity of the Tribunal’sreconsideration decision, I agree with my colleague Brown J. that it should be dismissed. The conclusion of the majority of the BritishColumbia Court of Appeal should not be disturbed. A. Background [43] The issue before the Tribunal was whether each of the three workers’ breast cancer was “due to” her employment asa laboratory technician at the Mission Memorial Hospital, a causal link required by s. 6(1)(

b) of the Workers Compensation Act,R.S.B.C. 1996, c. 492 (“WCA”). [44] While

Schedule B of the WCA lists a number of occupational diseases which are deemed to be “due to the nature of[the] employment” in the context of specific processes or industries, breast cancer is not listed among them. As a result, a causal linkmust be established on the basis of the evidence before the Tribunal. [45] A policy of the Workers’ Compensation Board, the Rehabilitation Services & Claims Manual, vol.

II (“RSCM II”)(online), specifies that in order for the disease to be “due to” the nature of the employment, the employment “has to be of causativesignificance, which means more than a trivial or insignificant aspect of the injury or death”: c. 3, policy item #14.00 (emphasis added). [46] The Board’s policy goes further, however, and requires that there be sufficient positive evidence to ground a findingof causative significance.

The RSCM II states that “[i]f the Board has no or insufficient positive evidence before it that tends to establishthat the disease is due to the nature of the worker’s employment, the Board’s only possible decision is to deny the claim”: c. 4, policyitem #26.22 (emphasis added). As my colleague Brown J. has observed, policies of the Board must be applied by the Tribunal in makingits decisions: s. 250(2) of the WCA. The Tribunal also recognized this requirement: WCAT-2010-03503 (the “Original Decision”), atparas. 46-47.

[47] In this case, the workers’ claims were initially denied by the Board. A review officer with the Board’s ReviewDivision confirmed these decisions, finding that there was insufficient evidence to conclude that each worker’s years of employment as alaboratory technician had played a significant role in causing breast cancer.

On appeal, a two-member majority of the Tribunal concludedthat there was sufficient positive evidence to establish that the workers’ breast cancer was due to their employment, but a dissentingmember disagreed, finding that the expert reports had provided insufficient positive evidence of a causal link.

That dissenting member’sconclusion was later vindicated, as the British Columbia Supreme Court set the Tribunal’s decision aside, an order which was upheld bya majority of the British Columbia Court of Appeal. [48] It is common ground that a reviewing court can only interfere with the Tribunal’s decision if it is patentlyunreasonable: s. 58 of the Administrative Tribunals Act, S.B.C. 2004, c. 45; s. 255(1) of the WCA. On the authority of jurisprudence pre-dating Dunsmuir v.

New Brunswick, 2008 SCC 9, [2008] 1 S.C.R. 190, a decision is patently unreasonable if it is “openly, evidently,clearly” wrong: Southam, at para. 57. More specifically, findings of fact will be “patently unreasonable” where they are either based on“no evidence” or where “the evidence, viewed reasonably, is incapable of supporting” the finding of fact in question: Toronto (City)Board of Education v. O.S.S.T.F., District 15, (SCC), [1997] 1 S.C.R. 487, at paras. 44-45; Lester (W.W.)

(1978) Ltd. v.United Association of Journeymen and Apprentices of the Plumbing and Pipefitting Industry, Local 740, (SCC), [1990]3 S.C.R. 644, at p. 669. [49] Neither the British Columbia Supreme Court nor the majority of the Court of Appeal sought to reweigh the evidencebefore the Tribunal. The lower courts did not, in other words, depart from this highly deferential standard of review. Rather, Chiasson,Frankel and Goepel JJ.A. of the Court of Appeal and Savage J. of the Supreme Court were of the view that there was no evidence beforethe Tribunal capable of supporting an inference of causative significance.

I agree. Even on this highly deferential standard of review, theTribunal’s decision should be set aside. B. The Expert Reports Before the Tribunal [50] All three of the expert reports before the Tribunal were unequivocal. In the experts’ collective view, expressed inclear, unambiguous language, the available evidence could not establish any causal relationship between the workers’ employment aslaboratory technicians and the development of their breast cancer. [51] Speaking of one of the workers, Ms. Katrina Hammer, the Board’s medical advisor Dr.

Yamanaka concluded that“there is insufficient medical evidence to support that the work environment caused or significantly contributed to the development ofMs. Hammer’s breast carcinoma left side”: J.R., vol. 4, at p. 226. That conclusion was stated more forcefully in the final version of areport titled Cancer Cluster Investigation within the Mission Memorial Hospital Laboratory, prepared by seven authors for theOccupational Health and Safety Agency for Healthcare in British Columbia (the “OHSAH Final Report”) (online).

The authors notedthat they “did not find any scientific evidence for the plausibility of a laboratory work-related etiological hypothesis regarding breastcancer”: p. iv (emphasis added). Finally, Dr. Beach, an expert in occupational medicine who was tasked with reviewing the OHSAHFinal Report, largely supported its findings. [52] The importance of these unanimous expert opinions cannot be overstated. Experts are responsible for providingdecision-makers with precisely those inferences that decision-makers — due to the technical nature of the issues — are unable toformulate themselves: R. v.

Abbey, (SCC), [1982] 2 S.C.R. 24, at p. 42; R. v. Abbey, 2009 ONCA 624, 97 O.R. (3d) 330,at para. 71, leave to appeal refused, [2010] 2 S.C.R. v; see also G. R. Anderson, Expert Evidence (3rd ed. 2014), at p. 625. [53] I would note here that the Tribunal is not presumed to possess medical expertise: Page v. British Columbia(Workers’ Compensation Appeal Tribunal), 2009 BCSC 493, at paras. 62-66 . As a result, while the Tribunal is not bound bythe medical experts’ findings, it cannot simply disregard their uncontradicted conclusions.

In the absence of any other evidence to thecontrary, one may wonder how the Tribunal could find a causal link where the experts, together, could see none. [54] In the case at bar, the Tribunal’s two-member majority was of the view that the experts had sought to establish acausal link on a level of scientific certainty, rather than on the ostensibly lower standard of proof prescribed by s. 250(4) of the WCA:Original Decision, at paras. 180-82.

If this were true, it would certainly justify the Tribunal’s rejection of the experts’ common findings.Indeed, the Tribunal’s analysis echoes the principle established in Snell v. Farrell, (SCC), [1990] 2 S.C.R. 311, to theeffect that causation need not be determined by scientific precision. This principle applies with even greater force in the context of claimsmade under the WCA. [55] However, the instant case differs from Snell. The authors of the three expert reports did not seek to establishcausation on a level of scientific certainty.

Rather, they question repeatedly whether certain workplace exposures “could” or “may” havebeen related to an “increase in risk”, “contribute measurably”, or have been of “causative significance”. [56] Having undertaken this more limited investigation, the medical experts could not even make out a plausible basis forestablishing a causal link between the workers’ employment and their respective diseases. [57] The OHSAH Final Report, which constituted the main piece of medical evidence before the Tribunal, is a goodillustration. That report was simply a “preliminary epidemiological study”.

Its authors were tasked with identifying any “exposures thatmay be associated with excess cases in a workplace”: p. 32 (emphasis added). In the event such exposures were identified, the authorswould then recommend proceeding to a “full-scale epidemiological study” which could “determine the association between the exposureand [the] increased risk” of developing breast cancer: p. 32. Thus, in their executive

summary, the authors of the OHSAH Final Reportspoke not of whether certain workplace exposures caused the workers’ breast cancer on a level of scientific certainty, but rather whetherexposure to certain chemicals “could be related to the increase in risk”: p. iii (emphasis added). [58] Ultimately, the authors of the OHSAH Final Report did not recommend proceeding to a full-scale epidemiologicalstudy, on the basis that they “did not find any scientific evidence for the plausibility of a laboratory work-related etiological hypothesisregarding breast cancer”: p. iv (emphasis added).

The authors went on to state in their conclusion that “no current occupational chemicalexposures, or records of past occupational exposures were found that might relate working in the [Mission Memorial Hospital] laboratory

environment to elevated breast cancer risk, or cancer in general”: p. 38 (emphasis added). [ 59 ] In short, these are not the words of medical experts seeking “but for” causation on a standard of scientific certainty. Rather, the authors simply found no workplace exposure that could plausibly have increased the risk of developing breast cancer. On my reading of the OHSAH Final Report, even on the relaxed standard of proof applicable to the workers’ compensation regime under s. 250(4) of the WCA , there is still no evidence capable of establishing “causative significance”. C.

The Bases on Which the Tribunal Inferred Causative Significance [ 60 ] In spite of overwhelming expert evidence to the contrary, a two-member majority of the Tribunal nevertheless saw in the expert reports sufficient evidence of a causal link. [ 61 ] The key passages of the Tribunal’s majority decision read as follows: As noted above, we have considered the factors in the Protocol. Perhaps the most compelling evidence for us involves the fact that the workers with breast cancer were exposed to carcinogens and there is a very elevated statistically significant [standardized incidence ratio] for breast cancer.

Our decision does not simply rest on the occurrence of a very elevated statistically significant [standardized incidence ratio] for breast cancer.

That [standardized incidence ratio] occurs against the backdrop of the particular standard of proof employed by us, the workers’ exposure to carcinogens, and the comments of [the authors of the OHSAH Final Report] to the effect that all cancer causing agents have the potential to initiate and promote cancer, little is known about the possible synergistic, additive or antagonistic effects of multiple chemical exposures, and past exposures were likely much higher. (Original Decision, at paras. 192-93) [ 62 ] It does not take much probing to see that there is little to no support for these statements in the evidence before the Tribunal.

(1) The Cluster of Diagnosed Cases of Breast Cancer [ 63 ] First, the presence of a cluster of diagnosed cases of breast cancer does not, on its own, constitute evidence of causative significance. [ 64 ] As the OHSAH Final Report explains, clusters can occur naturally as a result of an uneven distribution of non- occupational risk factors amongst the general population. For breast cancer, these factors can include age, weight, family history, age of first menstruation, age at pregnancy and first birth, and certain lifestyle factors.

As the authors of the OHSAH Final Report explained: Cluster research has shown that elevated rates occur by chance at some geographic locations and times. In fact, clusters always occur and it is a statistical phenomenon — even when there is no causal factor that is responsible for the increased incidence (this is why so few cluster investigations uncover any new risk factors).

So, if we look around at many geographic areas and times we will find some clusters; if a specific cluster is related to statistics and not an etiologic agent, it is most likely that in the next time period at this location the rate will not be significantly elevated. Thus, it would be very prudent to continue to evaluate the incidence of breast cancer in [Mission Memorial Hospital] Laboratory employees to see if the rate comes closer to what is expected. [Emphasis added; p. 39.] [ 65 ] A cluster might also represent a statistical anomaly.

Indeed, since only a total of seven diagnosed cases of breast cancer were identified at the Mission Memorial Hospital laboratory over a period of 34 years, the possibility that this cluster represents such an anomaly is significant. [ 66 ] It is clear that, on its own, correlation is no proof of causation. On that same logic, I am of the view that, without more, the mere presence of a cluster of diagnosed cases within a workplace is not sufficient evidence of any causal link between the disease and the nature of the employment.

(2) Exposure to Chemical Substances [ 67 ] Second, on the question of exposure to chemical substances, Dr. Yamanaka and the authors of the OHSAH Final Report were unwavering.

In their view, the available evidence regarding the workers’ exposure to chemical substances like formaldehyde, xylene, o -toluidine or ethylene oxide could not be related to an increase in the workers’ risk of developing breast cancer. [ 68 ] Among these chemical substances, ethylene oxide is the only one that has a recognized association with the development of breast cancer in human beings and, according to the evidence, this association is weak. Dr. Yamanaka’s report, drawing on research from the U.S.

National Institute for Occupational Safety and Health, stated that only women exposed to “very high levels” of ethylene oxide would be at an increased risk of developing breast cancer. There is no evidence in the record capable of supporting a conclusion that any of the workers were exposed to such “high levels” at Mission Memorial Hospital. [ 69 ] Indeed, the OHSAH Final Report concluded that current exposure to chemical substances was minimal “because liquid volumes are small and handling is often minimized through the use of ‘lock and load’ systems”: p. 36. Dr.

Yamanaka noted in a May 31, 2007 log entry that, even in the past, high levels of exposure to ethylene oxide were “highly unlikely”.

[70] The OHSAH Final Report did note that past exposures to certain chemicals were “likely much higher”, but thisstatement must be read in context. For one, the mention of “past exposures” does not seem to refer to ethylene oxide, the onlycarcinogenic substance with a recognized association with the development of breast cancer in humans. [71] More importantly, a passing reference to “likely much higher” past exposures says nothing about whether these pastexposures are “as likely as not” to have increased the workers’ risk of developing breast cancer. Rather, in their executive

summary, theauthors of the OHSAH Final Report observed that a “chemical assessment of carcinogens in the workplace also did not show anyobvious and extreme exposures in the past (based on current scientific literature), which could be related to the increase in risk”: p. iii(emphasis added).

This point was restated in their conclusion, where the authors explained that “no current occupational chemicalexposures, or records of past occupational exposures were found that might relate working in the [Mission Memorial Hospital] laboratoryenvironment to elevated breast cancer risk, or cancer in general”: p. 38 (emphasis added).

Ultimately, as I have said, in spite of this“likely much higher” exposure to certain chemicals in the past, the authors of the OHSAH Final Report nevertheless concluded that they“did not find any scientific evidence for the plausibility of a laboratory work-related etiological hypothesis regarding breast cancer”: p. iv(emphasis added). [72] Finally, rather than suggest that multiple exposures can have a “synergistic” or “additive” effect, as the Tribunalseems to imply, the OHSAH Final Report indicated that no synergistic or additive effect has been identified in the literature. [73] Respectfully, there is simply no basis for inferring “causative significance” from these passages of the Final Report. [74] It is true, as my colleague Brown J. notes, that the OHSAH Final Report did not exclude the possibility that pastexposures to certain chemicals could have contributed to the development of the workers’ breast cancer.

At the conclusion of their report,the authors stated that [i]n

summary, this study confirmed that the perceived cluster was an observed cluster and that [Mission Memorial Hospital] Laboratoryemployees were experiencing an elevated rate of breast cancer. The factors associated with this increased incidence could not bedetermined but may have been due to: (1) a cluster of reproductive and other known, non-occupational, risk factors, (2) past exposures tochemical carcinogens and less likely to ionizing radiation, and (3) a statistical anomaly. [p. 39] [75] This statement, however, should not be mistaken for evidence, and certainly not positive evidence.

The authors ofthe OHSAH Final Report only meant to set out an exhaustive list of what could possibly explain the higher incidence of breast cancer inlaboratory technicians at Mission Memorial Hospital. The inability to rule out a possible explanation simply does not transform thatexplanation into positive evidence of a causal link. Moreover, a list of three exhaustive possibilities says nothing about the likelihood of“causative significance”.

Put simply, this passage provides no basis for inferring such a causal link, especially when the OHSAH FinalReport otherwise goes to great lengths to refute the proposition that exposure to workplace chemicals could have increased the workers’risk of developing breast cancer. D. The Tribunal’s Findings of Fact Amount to Mere Speculation [76] I am left with the view that the only support for the Tribunal’s original decision is the existence of a cluster ofdiagnosed cases of breast cancer. The Tribunal’s findings of fact simply do not rise above the level of mere speculation.

The Tribunal iseven candid about the speculative nature of its own conclusion. For instance, the two-member majority stated as follows: . . . we acknowledge that the amount of exposure is not known and the specific carcinogens which contributed to their development ofbreast cancer are not known.

As part of that exercise of “ordinary common sense”, we reiterate we are weighing the evidence using astandard of proof as set out by subsection 250(4) of the [WCA]. (Original Decision, at para. 179) [77] In speculating in this way, the Tribunal disregarded the consensus view of the medical experts, in spite of theTribunal’s own lack of expertise in medical matters. The Tribunal also ignored the Board’s policy, set out in the RSCM II, which statesthat there must be sufficient positive evidence capable of supporting a finding of causative significance, failing which the only possibleoption is to deny the claim.

I would add that, in giving effect to so low a standard of proof, the Tribunal failed to respect the legislature’swish not to include breast cancer among the list of occupational diseases which are deemed to have been caused by the nature of certaintypes of employment in

Schedule B of the WCA. [78] Furthermore, while s. 250(4) of the WCA relaxes the burden of proof to a limited extent, it is of no assistance to theworkers here. Section 250(4) provides that where the “evidence supporting different findings on an issue is evenly weighted in that case,the appeal tribunal must resolve that issue in a manner that favours the worker”. On a literal reading of these words, before s. 250(4) canapply, there must be evidence capable of supporting two different findings, with each being equally plausible.

In the present case, there issimply no evidence capable of supporting a finding of “causative significance”. Section 250(4) simply cannot serve to bridge such amajor gap in the evidence. [79] My colleague Brown J. has emphasized the importance of drawing inferences in fact finding. While this may be so, Imust insist that the evidence in the record must still be capable of supporting the inferences drawn. Otherwise, the fct-finder is at risk ofstraying outside the realm of inference and reasonable deductions, and into the “wilderness of ‘mere speculation or conjecture’”:Fairchild v.

Glenhaven Funeral Services Ltd., [2002] UKHL 22, [2003] 1 A.C. 32, per Lord Rodger, at para. 150, citing Caswell v.Powell Duffryn Associated Collieries, Ltd., [1940] A.C. 152, per Lord Wright, at pp. 169-70; see also D. Cheifetz, “The Snell Inferenceand Material Contribution: Defining the Indefinable and Hunting the Causative Snark” (2005), 30 Advocates’ Q. 1, at pp. 46-47. [80] This kind of “common sense” or inferential reasoning simply cannot bridge insuperable gaps in the evidence — ineither a standard civil action or in an administrative claim under the WCA: see e.g. Kozak v. Funk (1997), (SK CA),

158 Sask. R. 283 (C.A.), at para. 22, aff’g in part (1995), (SK KB), 135 Sask. R. 81 (Q.B.); Meringolo v. OshawaGeneral Hospital (1991), 46 O.A.C. 260, at para. 89, leave to appeal refused, [1991] 3 S.C.R. vii. [81] In this case, as I have said, there is simply no evidence — and certainly no positive evidence — capable ofsupporting a finding of causative significance.

Having allowed mere speculation to suffice, the Tribunal’s decision is “openly, evidently,clearly” wrong and therefore ought to be set aside: Southam, at para. 57; Toronto (City) Board of Education, at para. 44; CanadianUnion of Public Employees, Local 963 v. New Brunswick Liquor Corp., (SCC), [1979] 2 S.C.R. 227. E. Disposition [82] For these reasons, I would dismiss the Workers’ Appeal and the WCAT Appeal. Appeal by the Workers’ Compensation Appeal Tribunal dismissed. Appeal by Katrina Hammer, Patricia Schmidt and AnneMacFarlane allowed with costs, Côté J. dissenting.

Solicitor for the appellant/respondent the Workers’ Compensation Appeal Tribunal: Workers’ Compensation AppealTribunal, Richmond. Solicitors for the appellants/respondents Katrina Hammer, Patricia Schmidt and Anne MacFarlane: Health SciencesAssociation of British Columbia, New Westminster; Hospital Employees’ Union, New Westminster. Solicitors for the respondent Fraser Health Authority: Harris & Company, Vancouver; Health Employers Association ofBritish Columbia, Vancouver. Solicitor for the intervener the Attorney General of Canada: Attorney General of Canada, Toronto.

Solicitor for the intervener the Attorney General of Ontario: Attorney General of Ontario, Toronto. Solicitors for the interveners the Ontario Network of Injured Workers’ Groups and the Industrial Accident Victims’ Groupof Ontario: IAVGO Community Legal Clinic, Toronto. Solicitors for the interveners the Community Legal Assistance Society and the British Columbia Federation ofLabour: Ethos Law Group, Vancouver.