IN THE SUPREME COURT OF BRITISH COLUMBIA

Citation:

McKnight v. Workers’ Compensation Appeal Tribunal,

 

2012 BCSC 1820

Date: 20121204

Docket: S106857

Registry: Vancouver

In the Matter of the Judicial Review Procedure Act, R.S.B.C. 1996, c. 241

Between:

Ivan McKnight, Hugh MacPherson, Lynne Williams,
Russell Reid, David Hill and David Martin

Petitioners

And

Workers’ Compensation Appeal Tribunal and Board of Education School District No. 5 (Southeast Kootenay)

Respondents

Before: The Honourable Mr. Justice A. Saunders

On judicial review from:  Workers’ Compensation Appeal Tribunal, August 18, 2010,
Decision Nos.WCAT-2010-02229; WCAT-2010-02227; WCAT-2010-02235;
WCAT-2010-02231; WCAT-2010-02225; and WCAT-2010-02230.

Reasons for Judgment

Counsel for the Petitioners:

S. Guenther

Counsel for the Respondent, Workers’ Compensation Appeal Tribunal:

T.J. Martiniuk

Counsel for the Board of Education School District No. 5 (Southeast Kootenay):

A.D. Winter
D. Rideout

Place and Date of Hearing:

Vancouver, B.C.

June 19-21, 2012

Place and Date of Judgment:

Vancouver, B.C.

December 4, 2012


 

[1]             This is a judicial review of workers’ compensation claims appeals concerning alleged cases of mercury poisoning. The six petitioners apply under the Judicial Review Procedure Act, R.S.B.C. 1996 c. 241, to quash decisions made by the Workers’ Compensation Appeal Tribunal (“WCAT”) on August 18, 2010. The petitioners seek to have their underlying appeals to WCAT from decisions of review officers of the Workers’ Compensation Board (“WCB”) remitted to WCAT for reconsideration, or alternatively for new hearings and decisions.

[2]             The petitioners were school teachers at Mount Baker Secondary School in Cranbrook, B.C. In 2004 and 2005, the petitioners each applied to WCB for benefits, on the basis of their allegedly having suffered mercury poisoning from exposure to mercury vapour during the course of their employment. Their claims were denied by WCB; in each case, it was held that it had not been proven that the claimant was suffering from mercury poisoning. Those denials were upheld by the WCB Review Division.

[3]             By consent of each of the petitioners, their appeals to WCAT were heard at the same time, by a panel consisting of three Vice Chairs. New evidence was permitted. The conjoined appeals proceeded as a rehearing, which took place in two stages. At the first stage, oral evidence, including evidence of each claimant, was heard over the course of four hearing days in July and August 2008. The second stage included oral evidence of three physicians: Dr. Youakim, a WCB medical advisor; Dr. Martin, a specialist in occupational medicine, who was retained by the employer; and Dr. Brands, a clinical associate professor in epidemiology, who was retained by the claimants. The second stage took place over a further four days in July 2009.

[4]             In August, 2010 the WCAT panel released its decisions, unanimously denying each claimant’s appeal and confirming the review officer’s decisions that the evidence does not support a finding of mercury poisoning.

[5]             There is a very substantial degree of overlap in the reasons given by WCAT for each decision. The parties to this petition have therefore agreed that the outcome in respect of the claim of the petitioner McKnight will govern the result of the other five claimants’ appeals.

Statutory Framework of the WCB Claims and WCAT Appeals

[6]             The subject claims were made under subsection 6(1) of the Workers Compensation Act, R.S.B.C. 1996 c. 492 (the “Act”), which provides for payment of compensation to workers suffering from occupational disease:

6 (1) Where

(a) a worker suffers from an occupational disease and is thereby disabled from earning full wages at the work at which the worker was employed or the death of a worker is caused by an occupational disease; and

(b) the disease is due to the nature of any employment in which the worker was employed, whether under one or more employments,

compensation is payable under this Part as if the disease were a personal injury arising out of and in the course of that employment. A health care benefit may be paid although the worker is not disabled from earning full wages at the work at which he or she was employed.

[7]             Because of the complexity of causation issues inherent in many occupational disease cases, subsection 6(3) of the Act creates a rebuttable presumption of causation in favour of the claimant, when the claimant has suffered a disease associated with a scheduled occupation:

(3) If the worker at or immediately before the date of the disablement was employed in a process or industry mentioned in the second column of Schedule B, and the disease contracted is the disease in the first column of the schedule set opposite to the description of the process, the disease is deemed to have been due to the nature of that employment unless the contrary is proved.

[8]             Schedule B to the Act makes the following reference to mercury poisoning:

Schedule B

Description of Disease

Description of Process or Industry

1.

Poisoning by:

 

. . .

 

(b)

Mercury

Where there is an exposure to mercury or mercury compounds.

 

[9]             The process of adjudication of claims is governed by section 99 of the Act:

Board decision-making

99 (1) The Board may consider all questions of fact and law arising in a case, but the Board is not bound by legal precedent.

(2) The Board must make its decision based upon the merits and justice of the case, but in so doing the Board must apply a policy of the board of directors that is applicable in that case.

(3) If the Board is making a decision respecting the compensation or rehabilitation of a worker and the evidence supporting different findings on an issue is evenly weighted in that case, the Board must resolve that issue in a manner that favours the worker.

Similar processes govern the hearing of appeals by WCAT:

Appeal tribunal decision-making

250 (1) The appeal tribunal may consider all questions of fact and law arising in an appeal, but is not bound by legal precedent.

(2) The appeal tribunal must make its decision based on the merits and justice of the case, but in so doing the appeal tribunal must apply a policy of the board of directors that is applicable in that case.

(3) The appeal tribunal is bound by a decision of a panel appointed under section 238 (6) unless

(a) the specific circumstances of the matter under appeal are clearly distinguishable from the circumstances addressed in the panel's decision, or

(b) subsequent to the panel's decision, a policy of the board of directors relied upon in the panel's decision was repealed, replaced or revised.

(4) If the appeal tribunal is hearing an appeal respecting the compensation of a worker and 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.

[10]         The policies of the board of directors referenced in ss. 99(2) and 250(2) are those formulated pursuant to section 82 of the Act. These include policies set out in the WCB Rehabilitation Services & Claims Manual (the “Manual”). Chapter 4 of the Manual, “Compensation for Occupational Disease”, discusses the significance of diseases having been listed in Schedule B:

#26.01 Recognition by Inclusion in Schedule B

...

The Board lists a disease in Schedule B in connection with a described process or industry wherever it is satisfied from the expert medical and scientific advice it receives that there is a substantially greater incidence of the particular disease in a particular employment than there is in the general population. ...

This chapter also notes the difficulties inherent in diagnosing diseases such a mercury poisoning:

#26.10 Suffers from an Occupational Disease

Part of the first requirement for compensability is that the worker suffers from, or in the case of a deceased worker the death was caused by, an occupational disease. Confirming the diagnosis of many occupational diseases may be difficult. This is particularly so for poisoning by some of the metals and compounds listed in Schedule B, the symptoms of which may be similar to the symptoms caused by common complaints that produce fatigue, nausea, headache and the like. ...

[11]         Chapter 12 of the Manual also prescribes the evidentiary burden which applies to adjudication of workers compensation claims: that issues with respect to which the evidence is evenly balanced must be resolved in the claimant’s favour:

#97.00 EVIDENCE

Under the old English system, which was an adversary system of workers’ compensation, there was a burden of proof imposed on the worker, but that is not the correct practice here. The Board officer must not start with any presumption against the worker, but neither must there be any presumption in the worker’s favour. The correct approach is to examine the evidence to see whether it is sufficiently complete and reliable to arrive at a sound conclusion with confidence. If not, the Adjudicator should consider what other evidence might be obtained, and must take the initiative in seeking further evidence. After that that has been done, if, on weighing the available evidence, there is then a preponderance in favour of one view over the other, that is the conclusion that must be reached. But if it appears upon the weighing of the evidence that the disputed possibilities are evenly balanced then the rule comes into play which requires that the issue be resolved in accordance with that possibility which is favourable to the worker.

[12]         Section 97.10 of the Manual contains a detailed discussion of the concept of evidence being evenly weighted. As, the Manual notes, most complaints of a worker not having been given the benefit of the doubt are in respect of situations where there is doubt as to whether an injury arose in the course of employment. This discussion is phrased in terms of such situations. The Manual states:

While an absence of positive data does not necessarily mean that a condition is not related to a person’s employment, it may mean that there is a lack of evidence that any such relationship exists. The Board, as a quasi-judicial body, must make its decisions according to the evidence or lack of evidence received, not in accordance with speculations unsupported by evidence. Section 99(3) of the Act applies when “the evidence supporting different findings on an issue is evenly weighted in that case”. However, if the Board has no evidence before it that a particular condition can result from a worker’s employment, there is no doubt on the issue; the Board’s only possible decision is to deny the claim. If one speculates as to the cause of a condition of unknown origin, one might attribute it to the person’s work or to any other cause, and one speculated cause is no doubt just as tenable as any other. However the Board can only be concerned with possibilities for which there is evidential support and only when the evidence is evenly weighted does section 99(3) apply.

[13]         The Manual addresses the subject of conflicts in medical evidence as follows:

#97.34 Conflict of Medical Opinion

Where there are differences of opinion among doctors, or other conflicts of medical evidence, the Board officer must select among them as best she or he can. The Board officer must not do it by automatically preferring the opinions of one category of doctors to another category, nor should it be done by counting heads, so many opinions one way and so many another. The Board officer must analyze the opinions and conflicts as best as possible on each issue and arrive at her or his own conclusions about where the preponderance of the evidence lies. If it is concluded that there is doubt on any issue, and that the evidence supporting different findings on an issue is evenly weighted in that case, the Board officer must follow the mandate of section 99 and resolve that issue in a manner that favours the worker.

The WCAT Decisions

[14]         The entirety of the McKnight decision was reproduced in the certified record for the purposes of this petition; excerpts from the other five decisions were also included. On this petition, the most contentious aspects of the WCAT decisions are passages from Part 6, Reasons and Findings, found under Section 6.12, dealing with diagnostic certitude, and Section 6.13, dealing with the question of whether the worker suffered from mercury poisoning. These passages, which are common to each of the six decisions, are found in paragraphs 452 - 491 of the McKnight decision, and, together with the conclusion in paragraph 492, they are reproduced in their entirety as an Appendix to these reasons.[i] References in these reasons to specific paragraphs of the WCAT decisions utilize the numbering in the McKnight decision.

[15]          The WCAT panel’s decisions are lengthy. The text of the McKnight decision, some 492 paragraphs, spans 91 single-spaced pages; there are an additional ten pages which deal with reimbursement of expenses, and three appendices totalling 37 single-spaced pages, summarizing the oral evidence of Drs. Youakim, Martin and Brands. I will here attempt to summarize the panel’s discussion of the evidence and the conclusions it reached with respect to the issues they identified. The brevity of the following summary does not reflect the complexity of the evidence or the thoroughness of the panel’s discussion; it is provided solely to give some context to my own analysis of the panel’s reasoning.

[16]         While the panel’s decisions are lengthy, there were no specific findings made as to a number of issues:  the specific level of mercury in the school, or even whether there was sufficient mercury to cause the symptoms alleged; which doctor’s evidence was to be given more weight; or what level of certitude was appropriate to determining whether Mr. McKnight did indeed suffer mercury poisoning (the panel rejecting the notion that proof on a balance of probabilities was sufficient). Given the indeterminate nature of the panel’s discussion, I have simply outlined some observations of the panel which bear on these issues.

[17]         The panel reviewed the evidence as to the history of mercury in the school. There had been a spill of approximately 100 to 150 ml in 1954, not all of which had been recovered. There had been science classes in which bulk mercury had been passed around. There were frequent breakages of mercury thermometers, and significant spills from mercury barometers occurred in 2001 and 2004. Formal assessments of the amount of residual mercury in the school were conducted in 2005. Remediation was undertaken in 2005 and again in 2006.

[18]         A report authored by an industrial hygienist, a Mr. Chessor, had been submitted on behalf of the claimants. Mr. Chessor had concluded that the claimants had all been exposed to concentrations several times greater than the Threshold Limit Value/Occupational Exposure Limit (“TLV/OEL”) value (e.g. 25,000 ng/m3). Mr. Chessor characterized his conclusion that the handling of bulk mercury had resulted in the release of 750 ml of mercury, as a “scientific wild-ass guess”.

[19]         The panel indicated its concerns with Mr. Chessor’s calculations. They concluded that they were “not at all confident” that the total volume to which the claimants were exposed was as calculated by Mr. Chessor; the quantities, and the relevant air circulation, were “unknown and unknowable”.

[20]         In its final analysis under heading 6.13, the panel held that there was no reliable evidence as to what had happened to the bulk mercury that may have disappeared during the science classes; as to the exact number of thermometers that had broken; or as to the volume spilled from the thermometers. It went on to characterize the evidence of the “volume of mercury in the school (and any associated exposure level)” as “unreliable”.

[21]         However, the panel accepted that the claimants had all been exposed to mercury, at levels greater than normal background levels.

[22]         The panel recognized the relationship between a diagnosis of mercury poisoning, and a finding that a worker had been “exposed to mercury” within the meaning of Schedule B. The panel states:

[413] ...Evidence that establishes a person has symptoms consistent with mercury poisoning would be insufficient to support a finding that person has mercury poisoning, if the evidence also establishes the person has had no exposure to mercury...

Further on, the panel reformulates this statement as follows:

[416] ...As noted above, with respect to the first column, insufficient evidence of exposure to mercury means it is quite likely the presence of symptoms consistent with mercury poisoning fails to establish the existence of mercury poisoning...

The concept of the “sufficiency” or “insufficiency” of the evidence, as will be seen, re-enters the panel’s analysis at a later point.

[23]         The panel made no finding as to the likelihood of the claimants having been exposed to sufficient mercury to cause symptoms of mercury poisoning.

[24]         The panel undertook a lengthy discussion of the evidence of the three doctors who testified before WCAT at the second stage of the oral hearings - Drs. Youakim, Martin and Brands. Dr. Brands had been present during the testimony of Drs. Youakim and Martin. Dr. Youakim had not read Dr. Brands’ reports; Dr. Martin had read “bits and pieces”.

[25]         Dr. Youakim had concluded, in memoranda submitted to the WCB in respect of the initial claims, that it was highly unlikely that Mr. McKnight had been significantly exposed to mercury or that his symptoms were due to mercury toxicity. Dr. Martin fully accepted Dr. Youakim’s analysis and conclusions. Dr. Brands, however, had concluded that it was “at least as likely as not” that Mr. McKnight had suffered mercury poisoning.

[26]         Drs. Youakim and Martin were said to be “fairly firm” that they would only diagnose mercury poisoning if the TLV/OEL had been exceeded. Dr. Youakim believed a documented work history of elevated exposure above the OEL to be essential to a diagnosis; Dr. Martin would require reliable information indicating exposure for a significant period of time in excess of OEL.

[27]         Dr. Brands asserted that OEL levels are not necessarily ‘safe’. His approach was to ask whether there was a reasonable suspicion of mercury having been present in amounts consistent with amounts generally present at other outbreaks of toxicity.

[28]         The panel observed that none of the three physicians’ evidence established that mercury poisoning could not occur at exposure levels less than the OEL.

[29]         The panel noted that after Dr. Youakim’s initial memoranda had been released, further evidence had emerged as to more mercury having been released into the school.

[30]         The panel characterized the approach of Dr. Youakim and Dr. Martin to the question of mercury poisoning as one in which a diagnosis - which would entail a patient reacting to the poisoning, and the patient being treated - would only be made if they were “certain”. Dr. Youakim would not require 100% certainty, but, asked to locate his certainty on a spectrum, he referred to 75% or more. Dr. Martin’s evidence as to diagnostic standards was that he had never tried to attach a percentage; one had to be far more certain than 50%, “as close to 100% as possible”.

[31]         Dr. Brands was of the opinion that a diagnosis of a “probable” case was one where the likelihood of mercury poisoning was 50% or more. He relied in part on the U.S. Center for Disease Control (“CDC”) “Case Definitions of Chemical Poisoning”, under which potential cases of chemical poisoning are categorized as suspected, probable or confirmed. A probable case is:

... one in which a person has an illness that is clinically compatible with poisoning from particular chemical agent and in which a credible threat exists.

[32]         The CDC document, however, states specifically that:

Case definitions are not sufficient for establishing a medical diagnosis and should not be relied upon to initiate therapy.

[Emphasis added by WCAT]

Dr. Brands stated that one would not rely exclusively on the CDC criteria as it did not provide a comprehensive list of signs and symptoms. The CDC criteria would not be uses as a diagnostic tool by itself; doctors would access other pertinent literature.

[33]         The panel did also note that Dr. Brands concluded , apart from the CDC case definition, that the claimants had developed mercury poisoning, even before he became aware of the evidence of the broken thermometers and bulk mercury.

[34]         The panel noted specifically Dr. Brands’ evidence, set out in his third report of June 14, 2009, of the dangers of under-diagnosing mercury poisoning through the use of excessively stringent diagnostic criteria. Dr. Brands had stated in that report that the effect of utilizing the diagnostic standard advocated by Drs. Youakim and Martin would be:

[316] ... to label many, if not most, people with mercury toxicity (according to consensus standards) as not having mercury toxicity.

The panel said:

[306] With respect to the clinical diagnosis of mercury toxicity and differential diagnosis, Dr. Brands comments that different standards of diagnosis exist in the ideal world of research and in the ideal world of clinical diagnosis. The ideal world standard of research is often called the efficacy standard of diagnosis, while the real world standard of diagnosis is called the effectiveness standard. It is important to note that the clinical effectiveness standard of diagnosis is broader and less rigorous than the research standard.

[307] He comments that mercury toxicity is recognized to be frequently missed or misdiagnosed clinically. It is a poisoning situation with potentially severe consequences if missed or misdiagnosed. There are ethical, medical, and legal hazards in insisting on close to absolute certainty about diagnosis in clinical situation. A clinical diagnosis scheme for mercury toxicity needs to be sensitive rather than specific. Because the consequences of missing a diagnosis are severe, and treatment is relatively benign, the physician will start treatment when what he describes as “... a certain enough that we need to treat, given that we are in the real-world standard is met [italics in original].”

[35]         Dr. Brands, the panel noted, did not state that the use of a greater level of certitude by a physician, as advocated by Drs. Youakim and Martin, was wrong as a matter of medicine. The panel did not interpret Dr. Brands' evidence as being to the effect that this was “inconsistent with the general approach of clinicians faced with making diagnoses.”

[36]         The panel held that s. 250(4) of the Act would require them to determine whether the evidence as to whether the workers had mercury poisoning “as that diagnosis is made by physicians” was evenly weighted.

[37]         The panel did not state its finding as to what level of certitude was appropriate to a diagnosis of mercury poisoning.

[38]         In its conclusion, the panel agreed with the claimants’ counsel that the cross-examination of Dr. Youakim had raised some concerns with respect to the persuasiveness of his medical opinions. However, the panel remarked that their concerns with the opinions of Drs. Youakim and Martin were not necessarily determinative of the appeal. The panel then again invoked the concept of the “sufficiency” of the evidence in the claimants’ favour:

[469] The issue before us is whether there is sufficient positive evidence to establish exposure to mercury and mercury poisoning. The issue is not whether evidence which is opposed to such a finding is adequate or persuasive.

[39]         The panel summarized its review of the positive evidence in favour of a finding of mercury poisoning, and noted its reservations. One of the panel’s reservations with the medical evidence was respecting the question of whether there were no other likely causes of Mr. McKnight’s symptoms. The panel stated,

[490] ... Certainly, evidence of the presence of a non-occupational cause is relevant to an assessment of whether symptoms are occupationally-induced. However, an absence of evidence of such a non-occupational cause does not mean it must be assumed that the symptoms are occupationally induced. This is especially so in cases in which there may be sources of information that have not been explored. In that regard, we note Dr. Youakim’s reference to psycho-social sources of information that he would need to explore as part of any global diagnosing of the workers.

[40]         The panel noted Dr. Brands’ assertion that Mr. McKnight’s presentation was typical of mercury poisoning. However, they concluded, the evidence was insufficient to establish a case of mercury toxicity. According to the panel, the evidence did not support a finding that he had experienced mercury poisoning.

[41]         The panel stated:

[491]    We are aware of section 250 of the Act, which provides at subsection (2) that WCAT must make its decision on the merits and justice of the case, and provides at subsection (4) that WCAT must resolve the issue in a manner that favours the worker where evidence supporting different findings is evenly weighted. We do not consider that the evidence in this case is evenly weighted such that the issue should be resolved in the worker's favour.

Issues

[42]         Although presented in a different order, the petitioners submitted that the following issues arise from the panel’s decision:

1.     Did the WCAT panel commit reviewable error in its conclusion that there was no evidence supporting a finding that the petitioner suffered mercury poisoning?

2.     Did the WCAT panel commit reviewable error in failing to weigh all of the relevant evidence to determine whether the evidence was at least evenly weighted on the issue of whether the petitioners suffered mercury poisoning?

3.     Did the WCAT panel commit reviewable error in misinterpreting and/or misapplying s. 250(4) to require proof of mercury poisoning “as that diagnosis is made by physicians”?

4.     Did the WCAT panel commit reviewable error in erroneously placing the burden of proof on the petitioner?

5.     Alternatively, did the WCAT panel commit reviewable error in failing to provide adequate reasons for rejecting the weight of evidence that favoured a finding that the petitioners suffered mercury poisoning?

Standard of Review

[43]         The Act contains a privative clause setting out the exclusive jurisdiction of WCAT:

254      The appeal tribunal has exclusive jurisdiction to inquire into, hear and determine all those matters and questions of fact, law and discretion arising or required to be determined under this Part and to make any order permitted to be made, including the following:

(a) all appeals from review officers' decisions as permitted under section 239;

(b) all appeals from Board decisions or orders as permitted under section 240;

(c) all matters that the appeal tribunal is requested to determine under section 257;

(d) all other matters for which the Lieutenant Governor in Council by regulation permits an appeal to the appeal tribunal under this Part.

[44]         Given the existence of that privative clause, the standard of review on judicial review of WCAT decisions is that of patent unreasonableness, as required by ss. 58(1) and 58(2)(a) of the Administrative Tribunals Act, SBC 2004, c 45:

58  (1) If the tribunal's enabling Act contains a privative clause, relative to the courts the tribunal must be considered to be an expert tribunal in relation to all matters over which it has exclusive jurisdiction.

(2) In a judicial review proceeding relating to expert tribunals under subsection (1)

(a) a finding of fact or law or an exercise of discretion by the tribunal in respect of a matter over which it has exclusive jurisdiction under a privative clause must not be interfered with unless it is patently unreasonable ...

[45]         The principles which govern application of the common law standard of patent unreasonableness were summarized by Josephson J., and endorsed by the B.C. Court of Appeal in Speckling v. British Columbia (Workers’ Compensation Board) 2003 BCSC 1487, aff’d 2005 BCCA 80. As stated by Levine J.A.:

[33] Having confirmed the correctness of the patently unreasonable standard of review, I agree with the chambers judge’s summary of the approach to be taken in applying that standard. He noted the following principles (at para. 8):

1. The standard of review is that of patent unreasonableness: Canada (Attorney General) v. P.S.A.C. (1993), 101 D.L.R. (4th) 673 (S.C.C.).

2. "Patently unreasonable" means openly, clearly, evidently unreasonable: Canada (Director of Investigation and Research) v. Southam Inc., [1997] 1 S.C.R. 748.

3. The review test must be applied to the result not to the reasons leading to the result: Kovach v. British Columbia (Workers' Compensation Board) (2000), 184 D.L.R. (4th) 415 (S.C.C.).

4. The privative clause set out in s. 96(1) of the Act requires the highest level of curial deference: Canada Safeway v. B.C. (Workers' Compensation Board) (1998), 59 B.C.L.R. (3d) 317 (C.A.)

5. A decision may only be set aside where the board commits jurisdiction error.

6. A decision based on no evidence is patently unreasonable, but a decision based on insufficient evidence is not: Douglas Aircraft Co. of Canada Ltd. v. McConnell,[1980] 1 S.C.R. 245, and Board of Education for the City of Toronto v. Ontario Secondary School Teachers' Federation et al (1997), 144 D.L.R. (4th) 385 (S.C.C.).

[46]         Levine J.A. further elaborated on the substance of the patent unreasonableness test at para. 37:

[37] As the chambers judge noted, a decision is not patently unreasonable because the evidence is insufficient. It is not for the court on judicial review, or for this Court on appeal, to second guess the conclusions drawn from the evidence considered by the Appeal Division and substitute different findings of fact or inferences drawn from those facts. A court on review or appeal cannot reweigh the evidence. Only if there is no evidence to support the findings, or the decision is “openly, clearly, evidently unreasonable”, can it be said to be patently unreasonable. That is not the case here.

[47]         Subsequent to Speckling, the common law standard of patent unreasonableness was ‘collapsed’ into the standard of unreasonableness, in the Supreme Court of Canada’s decision in Dunsmuir v. New Brunswick, 2008 SCC 9. However, the statutory standard prescribed by the Administrative Tribunals Act remains in effect in British Columbia, though, as stated by Binnie J., for the majority, in Canada (Citizenship and Immigration) v. Khosa, 2009 SCC 12 (at para. 19):

... the content of the expression, and the precise degree of deference it commands in the diverse circumstances of a large provincial administration, will necessarily continue to be calibrated according to general principles of administrative law.

[Emphasis in original]

[48]         The B.C. Court of Appeal subsequently confirmed in Victoria Times Colonist, a Division of Canwest Mediaworks Publications Inc. v. Communications, Energy and Paperworkers Union of Canada, Local 25-G, 2009 BCCA 229, that though the standard of review did evolve through Dunsmuir and Khosa, decisions of the Labour Relations Board remain “located at the very high end of the range of deference” (per K.C. Mackenzie J.A. at para. 28). I take it as a given that the same deference continues to apply to decisions of WCB and WCAT: see Kerton v. British Columbia (Workers’ Compensation Appeal Tribunal), 2011 BCCA 7, and Phillips v. British Columbia (Workers’ Compensation Appeal Tribunal) 2012 BCCA 304.

Discussion

Did the WCAT panel commit reviewable error in its conclusion that there was no evidence supporting a finding that the petitioner suffered mercury poisoning?

[49]         From my review of the decision, I cannot find that the panel reached any such conclusion. There clearly was some evidence of mercury poisoning. The panel decided not that there was “no evidence”, but that the positive evidence of mercury poisoning was insufficient.

Did the WCAT panel commit reviewable error in failing to weigh all of the relevant evidence to determine whether the evidence was at least evenly weighted on the issue of whether the petitioners suffered mercury poisoning?

[50]         As set out in the legislation, the WCB is not to use the same standard of proof as applies in a civil action. The Manual sets out a different mechanism for dealing with evidence and causality in these claims. The Board is not to start with a presumption against the worker, and, for ailments listed in Schedule B, is to presume causation. The panel in must make a decision based on all of the evidence. Where the evidence on an issue is evenly weighted, the panel must resolve the issue in favour of the worker. In the present case, the panel was required to actually weigh all the evidence for and against a finding that McKnight had mercury poisoning. In the case of conflicting medical evidence, according to the Manual section 97.34 the panel cannot simply pick the medical report they prefer but rather must examine how and why the medical findings differ. The concept of “weighing” evidence requires a determination as to which body of conflicting evidence is more weighty, i.e. which evidence is to be preferred, and what significance it has in the panel’s overall assessment.

[51]         In their argument, the respondent School District says that the panel did in fact go through a process of weighing the evidence for and against mercury poisoning. The School District points to the words in para. 491 as indicative of the panel having weighed  evidence, as required:

We do not consider that the evidence in this case is evenly weighted such that the issue should be resolved in the worker’s favour.

[52]         The panel also makes reference to the concept of the weight of evidence in paragraph 450, where it said:

We find that the issue before us is whether the evidence is evenly weighted that the workers have mercury poisoning as that diagnosis is made by physicians. Thus, subsection 250(4) does apply in some fashion to matters of diagnosis.

Further, the panel, in preceding and succeeding paragraphs of the decision, did engage in a process of reviewing the relative merits of some of the evidence on a variety of issues, e.g. the degree of exposure to mercury, and the appropriate diagnostic criteria. There is certainly a great deal of discussion in the panel’s decision of the strengths, weaknesses, consistencies and inconsistencies of the opinions of various expert witnesses.

[53]         However, it is also the case that the panel, having discussed much of the evidence at length, made few specific findings as to which body of evidence on any particular issue was to be preferred. The panel’s review remained largely abstract and inconclusive.

[54]         Two examples from the McKnight decision are illustrative of the panel’s problematic approach to the evidence.

[55]         As noted above, the panel recognized that Dr. Brands was of the opinion that the petitioners had suffered mercury poisoning. Dr Brands came to this conclusion independent of his views as to the diagnostic utility of the CDC case definitions. The panel said that Dr. Brands had undertaken considerable research and that his opinions were generally well-informed. While the panel did not accept Dr. Brands’ conclusions, it did not state that it found the opinions of Drs. Youakim and Martin to be superior.

[56]         Further, the panel never determined whether the doctors’ need for proof of exposure to mercury in excess of TLV/OEL, on which their opinions had been premised, affected the weight to be given their opinions. Not only did the panel not make any conclusions regarding which evidence to accept, they did not even provide a framework to evaluate or weigh the different opinion evidence. From the reasons, no “weighing” of this evidence took place.

[57]         The panel stated:

[469] The issue before us is whether there is sufficient positive evidence to establish exposure to mercury and mercury poisoning. The issue is not whether evidence which is opposed to such a finding is adequate or persuasive.

[Emphasis added]

[58]         Despite the panel having discussed the strengths and weaknesses of various points made by Drs. Martin and Youakim relative to the other witnesses, and contrasting the reasoning and the conclusions of the two bodies of expert opinion, it apparently decided that no decision was necessary on its part as to the adequacy or persuasiveness of the evidence against the finding of mercury poisoning.

[59]         In the paragraphs which follow from the statement regarding sufficient positive evidence, the panel directs its attention, at paragraphs 470 - 488, to examining the evidence of the petitioners’ exposure to mercury. The panel then concludes:

[489] After having reviewed the matter, we confirm the review officer’s decision. In light of our analysis set out earlier in this decision, we find that the evidence fails to establish that the worker experienced an occupational disease due to the nature of his employment. We accept that the worker was exposed to mercury above background levels that naturally occur; therefore, his claim satisfies the second column of the Schedule B entry regarding mercury poisoning. However, we consider that the evidence as to the volume of mercury in the school (and any associated exposure levels) is unreliable. Our finding that the worker had exposure to mercury does not require a finding that any symptoms reported by him are due to such exposure. We do not consider that the evidence supports a finding that the worker experienced mercury poisoning. Our finding that the worker did not have mercury poisoning means that we do not need to consider subsection 6(1) of the Act. We find that the worker did not have an occupational disease due to the nature of him employment.

[60]         In other words, while acknowledging that there was some evidence in favour of the petitioners, the panel appears to have decided that such evidence, on its own, was insufficient to support the petitioners’ claim.

[61]         The panel did not conclude that there was no evidence, only that the evidence did not rise to a level of “sufficiency” of proof. As the evidence tendered on behalf of the petitioners was seen to be insufficient to support a finding of mercury poisoning, the panel appears to have concluded that the weight of evidence to the contrary did not have to be considered. Without consideration of such contrary evidence being required, the panel concluded there was no issue before them as to the evidence being evenly weighted. The panel, therefore, concluded that s. 250(4) was not engaged.

[62]         The panel’s statement that it did not consider the evidence “evenly weighted” is a bald assertion that the case did not require application of s. 250(4), rather than an actual engagement with the proper process of weighing the evidence. Instead of weighing the evidence, the panel chose to challenge and disregard evidence in favour of the finding of mercury poisoning without coming to any conclusions on evidence tendered against this finding. The panel framed the questions before them in terms of the “sufficiency” of the positive evidence. It appears that the panel was operating under the belief that before reaching the stage of weighing all of the evidence, positive and negative, it was obliged not just to determine whether there was any evidential support for a finding of mercury poisoning, but also to engage in an abstract evaluation of the weight or quality of that positive evidence.

[63]         At no point in its decisions does the panel state what criterion it is using in determining that the evidence is insufficient. One inference that can be drawn from the panel’s reasoning - given the extensiveness of its discussion of diagnostic criteria - is that regardless of whether the evidence might establish that there has been mercury poisoning on a balance of probabilities, the panel believed it was bound to determine whether a diagnosis could be positively established at a higher level of certainty. As will be seen in the discussion in the next section of these reasons, I am of the view that such an approach is patently unreasonable.

[64]         Another possible inference is that the panel considered the claimants as being under an onus to prove their case - much as a plaintiff in a civil action must call sufficient evidence to discharge the burden of proof, or face the possibility of its evidence being weighed and found insufficient.

[65]         Section 97.00 “Evidence” of the Manual requires the WCB - and, by extension, WCAT - to undertake a three-stage approach to evaluating evidence: reviewing initial evidence to determine whether sound conclusions can be reached; if not, obtaining further evidence; and then weighing all available evidence as to the issues, pro and con, and deciding the case on the basis of the preponderance of the evidence - that is, the balance of probabilities. There is no room in this analytical framework for disqualifying evidence from being weighed and tested on account of doubt as to its “sufficiency”. To do so is to treat claimants as if they are plaintiffs in a civil suit under an adversarial system, with the claimants bearing the burden of proof. The panel’s approach effectively cast a burden on the claimants to adduce persuasive evidence of their claims.

[66]         A second example of the problematic approach of the panel is illustrated by its use of psychiatric and neuropsychological assessments, which went to the issue of other potential causes of Mr. McKnight’s symptoms. In addition to Dr. Brands’ examination, Mr. McKnight had also been assessed in October 2007 by a psychiatrist, Dr. Collins, on the referral of his disability insurer; a neuropsychologist, Dr. Hayden, who assessed him in November 2007 on referral from his counsel; and another neuropsychologist; Dr. Slick, who had assessed Mr. McKnight in March 2006, also at the request of his disability insurer. The panel disregarded their opinions, reasoning as follows:

488. We are aware that two neuropsychologists and a psychiatrist considered that Mr. McKnight had symptoms consistent with mercury poisoning. We do not attach much weight to those opinions. Those practitioners were not privy to all of the evidence that we have before us. As well, we are not persuaded that they possessed the necessary expertise in this area. Dr. Collins expressly stated that a diagnosis of mercury poisoning fell outside his expertise. Further, Dr. Hayden offered only a summary analysis of the issue of whether the worker had symptoms due t mercury poisoning. Dr. Slick commented that the worker’s symptoms were not inconsistent with mercury poisoning. That falls somewhat short of a confident diagnosis of mercury poisoning.

[67]         The panel’s readiness to dismiss the evidence of each of these experts is difficult to understand.

[68]         Dr. Collins had assessed Mr. McKnight for the specific purpose of determining his psychiatric diagnosis. He did not find any evidence of a psychiatric illness such as a mood disorder which could account for Mr. McKnight’s symptoms. He said:

I am unable to comment further on the diagnosis of mercury poisoning as this falls outside my area of expertise. However the symptoms that he described experiencing previously appear to be consistent with mercury toxicity.

[69]         Dr. Hayden’s discussion of the results of the neuropsychological testing spans four pages of her report (which totals 15 pages plus appendices). Dr. Hayden discusses the significance of her findings, with respect to mercury toxicity, as follows:

This neuropsychological pattern of deficits coupled with reports of behavioural indices, are most consistent with left frontal or frontal-temporal lobe dysfunction of a mild degree. Given review of available documentation and the consistency of these findings over time (i.e., with Dr. Slick’s findings) these deficits are most suggestive of the residual cognitive sequelae related to exposure to mercury in 2001 as described above. However, as mentioned by Dr. Slick, there is no specific cognitive profile for mercury exposure in the literature. Regardless, most recent studies... suggest that chronic exposure to mercury vapour, even years after the end of exposure, can result in residual cognitive and mood disturbance. The aforementioned cognitive profile demonstrated by Mr. McKnight, consistently in the assessments of 2006 and the present, seems to reflect symptoms reported in such studies.

[70]         It is not at all apparent why this “summary analysis” by Dr. Hayden - as the panel described it - should not have been recognized by the panel as an appropriate neuropsychological assessment and given all due weight. What more did the panel need from the neuropsychologists to consider their findings? The panel says that Dr. Hayden, Dr. Collins and Dr. Slick were “not privy to all of the evidence that we have before us”; but what other evidence was the panel in possession of which could have changed or even qualified the opinion of Dr. Hayden? The panel is not at all clear as to their reasons for not relying on the evidence of Dr. Hayden.

[71]         Dr. Slick was asked a number of specific questions by the disability insurer, which he answered. They included the following:

2.   Are Mr. McKnight’s complaints and test results are consistent with a focal legion or any other type of specific organic brain injury?

Mr. McKnight’s complaints and test results are not highly suggestive of a focal lesion (and such would not necessarily be expected with elemental mercury poisoning). The cognitive test results, described previously, do suggest some pathological central nervous system involvement however.

3.   Is there any evidence of any underlying primary psychiatric diagnosis that could reasonably explain Mr. McKnight’s symptoms?

As noted above Mr. McKnight likely has some mild degree of anxiety, irritability and depression; these may be symptomatic of mercury toxicity and also reflect a reactive psychological response to his illness. In any case, these cannot explain the cognitive weakness seen on testing.

6.   Provide any applicable neuropsychological diagnoses.

Mr. McKnight demonstrates complaints of mildly to moderately diminished cognitive function, fatigue, and emotional/adjustment difficulties secondary to Mercury poisoning. Neuropsychological test results are consistent with diminished attention and working memory, slowed math processing and loss of high-level math skills. These test findings are not inconsistent with mercury poisoning and as there is no available evidence of any other plausible etiology, they may be attributed to mercury poisoning...

[72]         As noted above, the panel stated its view of the significance to be attached to medical evidence concerning other potential causes of Mr. McKnight’s symptoms:

... an absence of evidence of such a non-occupational cause does not mean it must be assumed that the symptoms are occupationally induced. This is especially so in cases in which there may be sources of information that have not been explored. In that regard, we note Dr. Youakim’s reference to psycho-social sources of information that he would need to explore as part of any global diagnosing of the workers.

[73]         The panel’s evident willingness to reject the evidence of Drs. Slick, Hayden and Collins because of a concern as to the theoretical possibility of other factors, which were not in evidence before it, appears to be a violation of the principle stated in the Manual’s section on “Evidence Evenly Weighted”. The WCB “must make its decisions according to the evidence or lack of evidence received, not in accordance with speculations unsupported by evidence”.

[74]         The panel’s finding of deficiencies in the claimants’ case based on their failure to account for evidence that was not before the panel, effectively put the claimants to a considerable, if not impossible, burden.

[75]         The panel said that Dr. Slick’s opinion, and those of the other physicians, “falls somewhat short of a confident diagnosis of mercury poisoning.” This statement, however, miscasts the issue. The question was not whether Dr. Slick made a diagnosis (which the panel, in any event, implied would have been beyond his expertise). Rather, the question for the panel was whether the whole weight of the evidence in favour of a finding of poisoning - the medical evidence, including the psychiatric and neuropsychological evidence, and including the opinions expressed by Dr. Brands with regards to the epidemiological and occupational health issues; the evidence as to the level of mercury to which the petitioners had been exposed; and, whatever inferences as to mercury poisoning and mercury exposure might fairly be drawn from all that evidence - outweighed the evidence to the contrary. This question was fundamental to the analysis called for in the WCB policies, and is one which the panel failed to pose.

[76]         The panel’s finding of the insufficiency of evidence in support of there having been mercury poisoning due to employment, without having weighed that evidence against the evidence to the contrary and deciding the appeals on the preponderance of the evidence, was a breach of WCB policy, and a breach of the panel’s obligation under s.250(2). It was manifestly unfair to the petitioners. The panel’s conclusion was patently unreasonable.

[77]         The respondent School Board argues that there was a clear evidentiary basis before the panel for a finding that mercury poisoning was not likely to have occurred. That may or may not have been the case. We simply do not know what conclusion the panel would have reached, had it weighed all of the evidence appropriately. It is not for this court to impose its own view as to where the evidence ought to lead. The panel was obliged to weigh all of the evidence before coming to a conclusion, and it did not do so.

[78]         The petitioners succeed on this ground.

Did the WCAT panel commit reviewable error in misinterpreting and/or misapplying s. 250(4) to require proof of mercury poisoning “as that diagnosis is made by physicians”?

[79]         As discussed above, the panel reached a conclusion as to the sufficiency of the evidence, judging that it was free to do so without engaging s. 250(4). I analyze this ground of appeal in terms of whether the panel was patently unreasonable in its review of the evidence, in having imposed a requirement that there be proof of mercury poisoning as that diagnosis is made by physicians.

[80]         I note that a similar requirement of there having been a diagnosis was interpolated into s.6(3) of the Act by Mr. McKnight’s Review Officer, who, in his October 2006 decision, said:

Section 6(3) of the Act describes the manner in which claims can be considered under Schedule B. If “at or immediately before the date of disablement”, a worker is diagnosed with a disease listed in the first column of the Schedule and is employed in an industry listed in the second column opposite to the disease, “the disease is deemed to be due to the nature of the employment ...

[Emphasis added]

[81]         However, neither s. 6(1) nor s. 6(3) contain any such requirement; they are phrased only in terms of a worker having suffered or contracted an occupational disease. Indeed, the concept of “diagnosis” is largely absent from the Act. It appears only in two places: s. 5.1(1)(b), which provides that as a precondition to compensation for mental stress, the worker must have been diagnosed by a psychiatrist or psychologist as having suffered from a recognized mental or physical condition; and s.4(d) of Schedule B, under which causation is only to be presumed in cases of gastro-intestinal cancer when there has been a lengthy period of exposure to asbestos up to the date of diagnosis.

[82]         The respondent School Board argues that the panel was correct in apprehending the consequences of utilizing a standard of proof lower than would be used in making a medical diagnosis. The panel said:

[447]    In reviewing this matter, we consider that using subsection 250(4) in the manner urged by Mr. Guenther could put decision-makers at significant odds with matters of medicine. As an example, using subsection 250(4) of the Act in the manner urged by him could result in a decision-maker finding that a worker has cancer even though no physician would likely make such a diagnosis.

[448]    By that we mean that a decision-maker could find that an image on a CT scan or x-ray which had been interpreted a possibly being that of a tumour could be accepted as amounting to cancer, even though no biopsy or further testing had been done. We have significant difficulty in accepting that a claim should be adjudicated on such a basis. We accept that this example may not be completely apt, but it does illustrate our concerns associated with use of subsection 250(4) in the manner urged by Mr. Guenther.

[83]         This illustration is indeed inapt. To find that a tumour identified on an image is cancer, where cancer is only one possibility, is to engage in conjecture or speculation. If a sound conclusion could not be reached with confidence on the basis of an image alone, further evidence such as biopsy or testing results would be required before a claim could be adjudicated, as described in the Manual section #97.00.

[84]         It is possible to conceive of hypothetical situations in which a WCB adjudicator could be asked to reach a conclusion as to the presence of a disease or illness, which a physician might be reluctant to endorse. It would not be improper, as a matter of law, for an adjudicator to do so, if the conclusion was one supported by the evidence.

[85]          As noted above, the Manual acknowledges the inherent difficulty of confirming diagnoses of poisoning by some of the metals and compounds listed in Schedule B.

[86]         The panel acknowledged Dr. Brands’ evidence that a proper diagnosis of mercury toxicity is frequently missed, and that applying diagnostic criteria that are too stringent will lead to under-diagnosis.

[87]         Therefore, it appears evident that the panel’s approach of applying a diagnostic criterion higher than the balance of probabilities standard advocated by Dr. Brands to the evaluation of the evidence , could effectively deny compensation at least to some deserving workers who, on a balance of probabilities, have suffered or contracted an occupational disease, within the meaning of s.6(1). No such result is contemplated by the Act. This approach is indefensible, and patently unreasonable.

[88]         In its discussion of the interplay between a finding of mercury poisoning, and a finding of exposure, the panel at para. 417 of the McKnight decision quotes from the discussion of exposure in a previous appeal, WCAT-2009-01704:

While there might be reduced scope for considering the medical and scientific literature as part of an examination of the terms of the second column of Schedule B of the Act, we do not consider that the ability to consider such literature is limited when one addresses the terms of the first column of Schedule B: “Does the worker indeed have mercury poisoning?” Envision a case in which a worker demonstrates symptoms of mercury poisoning but the literature establishes that the worker’s level of exposure to mercury is not normally associated with symptoms of mercury poisoning.

Such circumstances would weigh against finding that a worker indeed has mercury poisoning. They would not preclude a finding that a worker has mercury poisoning. For example, such circumstances would not preclude a finding that a highly susceptible worker developed mercury poisoning in response to exposure levels not usually associated with mercury poisoning.

[89]         In my respectful view, the reasoning in that passage reflects the proper approach to determining whether a claimant has suffered mercury poisoning. It will be noted that the word “diagnosis” does not appear. The board’s - and the WCAT panel’s - inquiry under s. 6(1) is limited to the question of whether, on the balance of probabilities, (with an evenly balanced case to be decided in the claimant’s favour), a claimant has suffered an occupational disease due to the nature of the claimant’s employment. A finding of an occupational disease having been sustained is a finding of fact, to be proven on a preponderance of the evidence - just as is any other fact. Evidence that a disease has been diagnosed - or that it would, or would not, be diagnosed by an expert witness in given circumstances - will be of significant weight in the board’s deliberations. Conflicts in the medical evidence are to be resolved as provided for in the Manual, under section # 97.34. WCB and WCAT are free - indeed, in the case of exposure to metals and compounds listed in Schedule B, where there is a known risk of under-diagnosis, must be free - to make findings of fact on a balance of probabilities, regardless of whether the higher degree of certainty some physicians might insist upon in arriving at a diagnosis can be satisfied.

[90]         The petitioners succeed on this ground.

Did the WCAT panel commit reviewable error in erroneously placing the burden of proof on the petitioner?

[91]         As set out previously, the panel’s characterization of evidence as being insufficient appears to have erroneously subjected the claimants to a burden of proof.

Alternatively, did the WCAT panel commit reviewable error in failing to provide adequate reasons for rejecting the weight of evidence that favoured a finding that the petitioners suffered mercury poisoning?

[92]         As set out previously, the panel did not weigh the evidence. Any inadequacies in the panel’s articulation of its reasoning are accounted for by the panel having improperly disqualified evidence from consideration on the basis of its supposed insufficiency.

Conclusion

[93]         The petitioners have succeeded in demonstrating that the WCAT panel was patently unreasonable in failing to weigh all of the relevant evidence, and in imposing a requirement that mercury poisoning be proven as that diagnosis would be made by physicians.

[94]         The WCAT decisions regarding each of the six petitioners are set aside, and the petitioners’ appeals are remitted to WCAT for rehearing and redetermination in accordance with these reasons.

“A. Saunders J.”

Appendix

Excerpts from the August 18, 2010 WCAT Decision re: Ivan McKnight

            6.12     Diagnostic certitude

[441]    Mr. Guenther's submissions and Dr. Brands' evidence were predicated on the assumption that diagnostic certitude must only be established at the level of 50%. Mr. Guenther's submissions were to the effect that, in the workers' compensation system, the evidence concerning a diagnosis must only satisfy the language of subsection 250(4) of the Act, which provides that WCAT must resolve the issue in a manner that favours the worker where evidence supporting different findings is evenly weighted. He submitted that the positions of Drs. Youakim and Martin which required exposure in excess of the TLV and lab test confirmation were pre-conditions to get to their higher standard of proof. He contended that was too high a standard. He contended that, while not a practicing clinician, Dr. Brands had reviewed a large body of evidence, which included diagnostic criteria, and had brought scientific rigour to the matter.

[442]    We note that a need for greater certitude with respect to diagnosis was espoused by Drs. Youakim and Martin. It is clear they were approaching the matter as clinicians who would not make a diagnosis, which would entail a reaction by, and treatment of, a patient, unless they were certain. That diagnosis would be made based on their training, knowledge, and expertise.

[443]    In his closing submissions, Mr. Davies asserted it was a good thing that physicians used greater certitude. He submitted that the decisions and diagnoses physicians make affect life and death. Physicians need that greater certitude because quality of life depends on their diagnoses. He contended that the job of the decision-maker was not to merely count opinions but to look at the expert evidence and assess the reasoning behind those opinions He said that we were not here to "lower the level of diagnosis." Decision-makers were to deal with the level that physicians have and then come to a conclusion.

[444]    Notably, Dr. Youakim acknowledged that in an assessment of causation in the workers' compensation system only the level of proof associated with subsection 250(4) of the Act was required.

[445]    We consider one could argue that Dr. Brands had, in effect, been asked by Mr. Guenther to provide more of a legal opinion rather than a medical opinion. Dr. Brands had been "asked to state whether diagnosis had been established if one employed a standard of proof associated with subsection 250(4). As part of that he reviewed whether the case definitions were equivalent to the standard of proof found in subsection 250(4).

[446]    We did not interpret Dr Brands' evidence as being to the effect that the greater certitude espoused by Drs. Martin and Youakim was inconsistent with the general approach of clinicians faced with making diagnoses. He did not state that such certitude was wrong as a matter of medicine.

[448]    By that we mean that a decision-maker could find that an image on a CT scan or x-ray which had been interpreted as possibly being that of a tumour could be accepted as amounting to cancer, even though no biopsy or further testing had been done. We have significant difficulty in accepting that a claim should be adjudicated on such a basis. We accept that this example may not be completely apt, but it does illustrate our concerns associated with use of subsection 250(4) in the manner urged by Mr. Guenther.

[449]    We find that adjudication of matters of diagnosis does not require us to ignore levels of certitude that clinicians bring to such assessments. Thus, our task is not to inject subsection 250(4) into matters of diagnosis in such a fashion that we attach little significance to whether, as a matter of medicine, a physician would find that a worker had a particular condition or disease. Certainly our task includes critically evaluating medical evidence in the manner in which we evaluate all forms of evidence and ascertaining whether the evidence is evenly weighted. But, that assessment of whether the evidence is evenly weighted with respect to diagnosis does not involve applying subsection 250(4) in the manner submitted by Mr. Guenther.

[450]    We find that the issue before us is whether the evidence is evenly weighted that the workers have mercury poisoning as that diagnosis is made by physicians. Thus, subsection 250(4) does apply in some fashion to matters of diagnosis.

[451]    Therefore, our conclusion should not be interpreted as finding that subsection 250(4) does not apply to matters of diagnosis. It does apply to diagnosis as it applies to adjudication generally, but not in the manner urged by Mr. Guenther.

6.13     Did Mr. McKnight suffer from mercury poisoning?

[452]    In considering whether the worker suffered from mercury poisoning, we have not placed any weight on the urine test results obtained in 2004 with the use of a chelation agent. The medical specialists who commented on those tests in their reports did not consider them to be a reliable way to measure the level of mercury in the workers' bodies. The workers' representatives did not rely on them in their submissions. There are no other laboratory tests that reliably show whether the worker had elevated mercury levels. As seen in the specialist reports before us, this is largely a question to be determined from medical opinion that is based on information about past symptoms and estimates of historical exposure levels.

[453]    Mr. Guenther argued that Drs. Martin and Youakim brought an attitude that was not objective to their opinions. In response to Mr. Guenther's submissions, and as part of our assessment of the evidence generally, we note that there were some considerations that may be relevant to the weight that may be attached to the testimony of Drs. Martin and Youakim.

[454]    Dr. Youakim may have been somewhat dismissive of Dr. Brands' opinion and Mr. Chessor's report and somewhat argumentative with Mr. Guenther.

[455]    Mr. Guenther argued that Dr. Youakim did not bring sufficient care to preparing for the oral hearing and contended one could infer that Dr. Youakim applied the same level of care to his claim log entries. We find that an assessment of whether care was brought to the claim log entry memoranda can be judged on their contents.

[456]    Unfortunately, owing to other obligations and the busy nature of their schedules, neither Dr. Youakim nor Dr. Martin was able to comprehensively review the materials sent to them in advance of the oral hearing. Such circumstances may occur in cases in which experts attend an oral hearing not at the behest of parties who might be expected to ensure that their experts are fully prepared. That said, we are satisfied the parties had full opportunities to put questions to those experts. One day was put aside for each physician to testify. The panel benefitted greatly from the testimony of Drs. Youakim, Martin, and Brands. All three experts brought considerable expertise to testimony that was often wide-ranging in subject matter. They were very informative with respect to matters of significant complexity associated with these appeals.

[457]    In considering Dr. Youakim's memoranda, we note that Mr. Guenther took exception to Dr. Youakim speculating on the likely exposure of Mr. McKnight based on the results of post-provocation testing. He contrasted that speculation with Dr. Youakim's declaration during testimony that one should not speculate. We acknowledge Mr. Guenther's point, but we note that Dr. Youakim's written opinion does not rely in any significant manner on his analysis of the figures associated with the results of Mr. McKnight's post-provocation testing.

[458]    Mr. Guenther contrasts Dr. Youakim's comments regarding the vacuum cleaner with comments in the literature that use of a vacuum cleaner is not recommended. Mr. Guenther noted that testing of the vacuum cleaner four years after the 2001 spill revealed levels greater than 28,000 ng/m3. We accept that such a level establishes that Dr. Youakim was likely incorrect regarding his view of the risks associated with the use of a vacuum cleaner. All of the mercury had not been blown out of the vacuum cleaner in connection with the first few uses Dr. Youakim's error with regard to the matter of the vacuum cleaner does not establish a significant error in his medical analysis.

[459]    Certainly, subsequent to Dr. Youakim issuing his initial memoranda more evidence emerged as to more mercury having been released into the school.

[460]    Mr. Guenther asserted that, when pressed, Dr. Youakim only questioned the results of Mr. Chessor's calculations because the figures exceeded exposure numbers associated with industries that use mercury. He contended that Dr. Youakim was prepared to disagree with Mr. Chessor simply on the basis that the exposure was significant.

[461]    Mr. Guenther contended that there were 50 years of misuse of mercury in the school. This was not an industrial setting with protection and safe handling guidelines. He noted that in 2005 globules of mercury were found in room #208, some four years after the spill in 2001.

[462]    Mr. Guenther noted Dr. Youakim's calculations as to number of air changes and Mr. Chessor's assertion that such calculations were erroneous. He contended Mr. Chessor pointed out that the ventilation system did not run continuously and that Mr. Chessor produced charts reflecting assumptions that were reasonable. Mr. Guenther submitted that Dr. Youakim stated that the calculations of Mr. Chessor did not matter. Mr. Guenther asserted that the calculations did matter: an assessment of the ventilation system must be relevant, otherwise why would Dr. Youakim have mentioned the ventilation system in his memoranda?

[463]    Mr. Guenther submitted that, while Dr. Youakim contended that residual mercury would merely dissipate, any assumption that the 2000 report regarding the ventilation system supported such a belief was discounted by Mr. Borgstrom's evidence.

[95]          [464]    Mr. Guenther asserted that Dr. Brands' evidence made it questionable that mercury vapour sank. Mr. Guenther contended the stratification of vapour does not occur.

[465]    Mr. Guenther asserted that Dr. Brands reviewed a great deal of literature and brought rigour to the task at hand. He contrasted the position of clinicians such as Drs. Youakim and Martin - that diagnostic criteria included exposure in excess of the TLV - with Dr. Brands' position that nowhere in the literature could he find consensus that that was a necessary criterion in the diagnosis of mercury poisoning.

[466]    Mr. Guenther asserted that Dr. Youakim agreed that the CDC case definition was the only available diagnostic criteria. He observed that Dr. Youakim read into that case definition a requirement of a certain exposure level. He contended that was Dr. Youakim's own position and was contrary to that of Dr. Brands. He further contended that the diagnosis of "not mercury poisoning" offered by Drs Youakim and Martin was based on their mistaken position of a requirement of exposure in excess of the TLV and lab confirmation He considered that Dr. Martin's written opinions contained a categorical requirement of excessive exposure, and he contrasted that with the Board's own cautionary comments regarding the TLV.

[467]    We accept that Mr. Guenther has raised some concerns with respect to the persuasiveness of Dr Youakim's written opinions and his testimony. We accept that any analysis of the persuasiveness of that evidence is germane to our task. However, such an analysis, and a similar analysis with respect to the evidence of Dr. Martin, is not necessarily determinative of the outcome of this appeal.

[468]    In that regard, we heard Mr. Guenther's submissions to the effect that Dr. Martin did not bring rigour to the task at hand He asserted there were inaccuracies in the foundational information in Dr. Martin's reports. He drew attention to Dr. Brands' discussion of the study cited by Dr Martin regarding the workers in a mercury plant, a study that Dr. Brands would not have included in any discussion of mercury toxicity

[469]    The issue before us is whether there is sufficient positive evidence to establish exposure to mercury and mercury poisoning. The issue is not whether evidence which is opposed to such a finding is adequate or persuasive.

[470]    We are aware that Dr. Youakim indicated that he would diagnose mercury poisoning if the teachers were indeed exposed to 400 μg/m3 of mercury. We do not consider that sufficient weight can be placed on Mr. Chessor's report to reliably find that the teachers were exposed to such a level.

[471]    We will not attempt to calculate the specific level to which the teachers had been exposed. We consider that engaging in such calculations would be folly. Quite simply, among other matters, we have no reliable evidence as to (i) what happened to the bulk mercury that may have disappeared from the beakers in Mr. Reid's classes, (ii) the number of thermometers broken, or (iii) the volume spilled from those thermometers. As noted earlier, that bulk mercury looms large in Mr. Chessor's calculations as to the amount of mercury in the school. Owing to our concerns regarding the accuracy of any figures regarding the volume of mercury and any associated exposure figures, we do not consider that any reliable figures emerge from Mr. Chessor's report and testimony.

[472]    We appreciate one can argue that we have some obligation to recalculate to determine if a figure of 25 μg/m3 would emerge. This is so, given that Drs. Youakim and Martin expressed a strong preference for such an exposure level as part of making a diagnosis, and one can argue that a diagnosis could be confirmed if such an exposure level could be confirmed.

[473]    However, we consider that an assessment of exposure levels does not resolve the matter. Further, we have not forgotten that Dr. Brands asserted that such a level was not required to diagnose mercury poisoning. As well, we are aware of Mr. Guenther's assertion that, while she may have referred to the TLV, Dr. Hilliard made no assertion that such an exposure level was required. We are aware that Dr. Hilliard indicated that the absence of specific tests at the time of maximum exposure meant she was unable to determine a definitive link between symptoms and exposure.

[474]    Aside from their concerns with respect to the exposure level encountered by Mr. McKnight, Drs. Youakim and Martin had concerns as to what they considered was a change in the teachers’ description of symptoms over time. Dr. Youakim was emphatic that he was not saying that the teachers were lying. Dr. Brands considered that more detailed descriptions emerging over time was consistent with the teachers being questioned by more thorough and better informed questioners.

[475]    In considering this case, we have the benefit of Mr. McKnight's "Chronological Record" which comprises pages 49 through 56 of Mr. Chessor's report. (It includes most of the information found in Mr. McKnight's "Chronological Health Record" which covers the period from February 2001 to February 2005.) Mr. McKnight's record is meticulous.

[476]    As indicated at the oral hearing Mr. McKnight testified that his notes were made contemporaneously and then typed up to form the "Chronological Record." The first reference to ill health is a reference to flu-like symptoms on April 6, 2001. We note that an onset of ill health in April 2001 would have transpired before any possible suggestion that the worker was experiencing illness due to the June 2001 spill, but not necessarily before he was exposed to mercury vapour in the school.

[477]    A note that follows a June 7, 2001 note regarding the spill in Mr. McKnight's room asserts that he was not able to run from April to August 2001 and he was unable to complete full riding circuits. There are no entries concerning the period September to December 2001 when he would have been in his classroom. The first entry for 2002 concerns March.

[478]    There is no suggestion that, at that time, he was experiencing cognitive problems. The first reference to such problems is a note for September to December 2003. His testimony at the oral hearing referred to such problems in 2003.

[479]    The year 2003 is some two years after the spill and more than two years after the introduction of the new ventilation system. By 2000, all the bulk mercury associated with its use in Mr. Reid's classroom between 1983 and 1993 had been released into the school and almost all the thermometers had been broken. (We are aware that the spill in the chemical storage room, possibly ongoing since 1998, was not discovered until 2004.) The pre-2000 release of mercury would have been subject to a different ventilation system.

[480]    To the extent that the ventilation system installed in 2000 may have resulted in retention rather than dispersal of mercury, one might think that any illness that the worker would have experienced due to mercury in the school would have had its onset shortly after 2000 and would have achieved full fruition shortly thereafter. Certainly, after 2000, mercury was not being released in the school in anywhere near the volume asserted for the period between 1983 and 1993 or between 1983 and 2000. The passage of years after the earlier release of mercury is of note. Dr. Youakim observed in his testimony that the movement of doors, windows, and individuals over periods of years affects the volume of mercury available to affect the health of individuals. We appreciate that such considerations would not apply to the possible effects of the spill in June 2001, any pre-June 2001 release of mercury associated with the presence of the box in room #208, and the spill in the chemical storage room.

[481]    We do not doubt that Mr. McKnight reported the symptoms that he has noted in his chronological record. Further, we note that Dr. Youakim's opinion in his memorandum did not contest that the worker reported the symptoms noted in his "Chronological Record."

[482]    We appreciate that Dr. Youakim's testimony could be interpreted as his taking some issue with the symptoms reported by the worker. We consider, however, that Dr. Youakim's opinion is consistent with his considering that a patient with concerns regarding poisoning is hypersensitive to the existence of possible symptoms. Therefore, such a patient may consider some vagaries of human existence, such as occasional lapses in memory, as evidence of pathology associated with toxic exposure, and report having experienced such symptoms

[483]    Dr. Brands considered that the worker had mercury poisoning. He did so with the use of a standard of proof much less than that utilized by Drs. Youakim and Martin. We appreciate that his written opinions and his testimony establish that he undertook considerable research. His opinions are generally very well-informed.

[484]    We note with some concern that his recitation of Mr. McKnight's clinical presentation is at odds with what is in Mr. McKnight's "Chronological Record", despite the fact that Dr. Brands indicates his discussion of that clinical presentation is based on that record. A particular instance is his assertion that through 2001/2002 Mr. McKnight's symptoms progressed to include changes in mood, anxiety, irritability, and depression, with associated difficulty in focusing his thoughts and sustaining attention, memory disturbance, and slurred speech. Notably, Mr. McKnight's "Chronological Record" contains no such assertion.

[485]    We are aware that the chronological record refers to cognitive problems in the period from September to December 2003. However, there is little persuasive evidence that the worker experienced such problems earlier. In saying that, we note Dr. Slick’s report contains a recitation of symptoms similar to that found in Dr. Brands' report and it may be that Dr. Brands obtained that information from Dr. Slick's report. Dr. Slick's report suggests that the worker had cognitive problems before his fall 2002 hospitalization. Again, that is not borne out by Mr. McKnight's "Chronological Record."

[486]    Further, both Dr. Slick and Dr. Brands refer to the worker experiencing depression during 2002, whereas Dr. Kotlarz's December 10, 2003 referral letter is to the effect that everything from depression to a physical problem was discussed, and there was nothing wrong. Notably, that letter makes no reference to the changes in mood, anxiety, irritability, difficulty focusing thoughts, sustaining attention, memory disturbance, and slurred speech, noted by Drs. Brands and Slick as having been present in 2002.

[487]    While we are mindful of Dr. Brands' assertion that the worker's presentation is typical of that seen with mercury toxicity, we find the evidence is insufficient to establish that the worker had mercury toxicity.

[488]    We are aware that two neuropsychologists and a psychiatrist considered that Mr. McKnight had symptoms consistent with mercury poisoning. We do not attach much weight to those opinions. Those practitioners were not privy to all of the evidence that we have before us. As well, we are not persuaded that they possessed the necessary expertise in this area. Dr. Collins expressly stated that a diagnosis of mercury poisoning fell outside his expertise. Further, Dr. Hayden offered only a summary analysis of the issue of whether the worker had symptoms due to mercury poisoning. Dr. Slick commented that the worker's symptoms were not inconsistent with mercury poisoning. That falls somewhat short of a confident diagnosis of mercury poisoning.

[489]    After having reviewed the matter, we confirm the review officer's decision, in light of our analysis set out earlier in this decision, we find that the evidence fails to establish that the worker experienced an occupational disease due to the nature of his employment. We accept that the worker was exposed to mercury above background levels "that naturally occur; therefore, his claim satisfies the second column of the Schedule B entry regarding mercury poisoning. However, we consider that the evidence as to the volume of mercury in the school (and any associated exposure levels) is unreliable. Our finding that the worker had exposure to mercury does not require a finding that any symptoms reported by him are due to such exposure. We do not consider that the evidence supports a finding that the worker experienced mercury poisoning. Our finding that the worker did not have mercury poisoning means we do not need to consider subsection 6(1) of the Act. We find that the worker did not have an occupational disease due to the nature of his employment.

[490]    We do not consider it is incumbent upon decision-makers to point to an alternative cause in cases in which they find that the evidence does not support a conclusion that a worker suffers an occupational disease due to the nature of his or her employment. Certainly, evidence of the presence of a non-occupational cause is relevant to an assessment of whether symptoms are occupationally induced. However, an absence of evidence of such a non-occupational cause does not mean it must be assumed that the symptoms are occupationally induced. This is especially so in cases in which there may be sources of information that have not been explored. In that regard, we note Dr. Youakim's references to psycho-social sources of information that he would need to explore as part of any global diagnosing of the workers.

[491]    We are aware of section 250 of the Act, which provides at subsection (2) that WCAT must make its decision on the merits and justice of the case, and provides at subsection (4) that WCAT must resolve the issue in a manner that favours the worker where evidence supporting different findings is evenly weighted. We do not consider that the evidence in this case is evenly weighted such that the issue should be resolved in the worker's favour.

7. Conclusion

[492]    We deny the worker's appeal. We confirm the review officer’s decision. The evidence does not support a finding that the worker suffers mercury poisoning due to the nature of his employment.

 



[i] The certified record of WCAT appeals filed as evidence in this petition included the entirety of the “6.12 Diagnostic certitude” discussion in the McKnight decision, but not the entirety of the parallel passages in the decisions concerning the other five petitioners. Except where the name of the worker has been changed, paragraphs 449 - 451 under heading “6.12 Diagnostic certitude”; paragraphs 452 - 474, 480 - 483, 487, and 489 - 491 under heading “6.13 Did Mr. McKnight suffer from mercury poisoning”; and paragraph 492 under the heading “7. Conclusion”, from the McKnight decision, are duplicated in the other five decisions; paragraph 479 is substantially similar.