WCAT Decision Number:  
A2100606 (August 17, 2022)  
DECISION OF THE WORKERS’ COMPENSATION APPEAL TRIBUNAL  
WCAT Decision Number:  
A2100606  
WCAT Decision Date:  
August 17, 2022  
Introduction  
[1]  
[2]  
[3]  
This appeal arises out of a Review Division decision dated February 23, 2021, whereby the  
worker’s request for review was denied. In that decision, a review officer at the Workers’  
Compensation Board (Board)1 confirmed a prior decision of the Board dated June 1, 2020. The  
review officer denied the worker’s claim for carbon monoxide poisoning and a uterine fibroid as  
occupational diseases due to the nature of her employment.  
The worker now appeals the February 23, 2021 Review Division decision to the Workers’  
Compensation Appeal Tribunal (WCAT). The appeal proceeded by way of an oral hearing,  
which took place via videoconference on October 26, 2021. The worker represented herself in  
the appeal. The employer participated in the appeal and was represented by an employers’  
adviser.  
On appeal, the worker argued that beginning in the fall of 2017, she was exposed to  
carbon monoxide and other toxic airborne substances/heavy metals at work. As a result of this  
exposure, she suffered from carbon monoxide poisoning. She also developed a uterine fibroid  
and experienced miscarriages thereafter. The worker requested that I vary the review officer’s  
decision by allowing her claim for carbon monoxide poisoning as well as her uterine fibroid and  
subsequent miscarriages as occupational diseases due to the nature of her employment.  
[4]  
[5]  
On the other hand, the employer argued that there was insufficient evidence to support that the  
worker suffered from carbon monoxide poisoning, or that she was exposed to any other toxic  
levels of airborne substances/heavy metals that would have caused her uterine fibroid and/or  
miscarriages. The employer requested that I deny the worker’s appeal and confirm the review  
officer’s decision.  
Preliminary Matters  
At the hearing, the worker noted that she had all along argued that in addition to her exposure to  
carbon monoxide, she was also exposed to other toxic substances/heavy metals that caused  
her uterine fibroid and miscarriages. Despite this, the Board did not specifically address her  
miscarriages. She requested that I adjudicate the compensability of her miscarriages in my  
1
operating as WorkSafeBC  
1
150, 4600 Jacombs Road, Richmond, B.C. V6V 3B1  
Tel: (604) 664-7800 | 1-800-663-2782  
Fax: (604) 664-7898 | wcat.bc.ca  
WCAT Decision Number:  
A2100606 (August 17, 2022)  
decision. The employer argued that the review officer did not specifically consider the  
compensability of the worker’s miscarriages. As a result, I did not have the jurisdiction to  
consider that matter.  
[6]  
In the underlying June 1, 2020 Board decision on appeal, the case manager addressed the  
worker’s evidence about her reproductive issues/miscarriages. However, the claim was  
ultimately denied for carbon monoxide poisoning and the uterine fibroid. As a result, the case  
manager determined that no compensable consequences arising out of those injuries  
(and therefore the miscarriages) were compensable. In these circumstances, I am satisfied that  
the compensability of the worker’s miscarriages formed a part of the broader adjudication of the  
worker’s entitlement for claim acceptance of an occupational disease(s). As such, I find that I  
have the requisite jurisdiction to consider the worker’s miscarriages in my decision.  
[7]  
On a separate matter, I note that since the start of the claim in 2018, both parties have provided  
extensive evidence to the Board, Review Division, and WCAT. I have not recounted all of the  
evidence or the parties’ submissions, but I have read and considered them in their entirety.  
Some of the worker’s evidence/submissions pertained to her concerns about how the employer  
handled her complaints and its investigation in general, as well as other labour relations issues  
about her reassignment offer in 2018. These matters do not fall within my jurisdiction to consider  
in the context of the current appeal. As such, I have not addressed these aspects of the  
worker’s evidence/submissions in detail.  
Issue(s)  
[8]  
The issues on appeal are:  
1. Did the worker suffer from carbon monoxide poisoning as an occupational disease due to  
the nature of her employment?  
2. Are the worker’s uterine fibroid and/or miscarriages in 2018 occupational diseases due to  
the nature of her employment?  
Jurisdiction and Standard of Proof  
[9]  
This appeal is brought under section 288(1) of the Workers Compensation Act (Act),2 which  
permits appeals of Review Division decisions to WCAT.  
[10]  
WCAT 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 in an appeal before it  
(section 308 of the Act). It is not bound by legal precedent (section 303(1) of the Act).  
2
All references to the Act in this decision refer to the Workers Compensation Act, RSBC 2019, c 1.  
2
150, 4600 Jacombs Road, Richmond, B.C. V6V 3B1  
Tel: (604) 664-7800 | 1-800-663-2782  
Fax: (604) 664-7898 | wcat.bc.ca  
WCAT Decision Number:  
A2100606 (August 17, 2022)  
[11]  
The standard of proof is the balance of probabilities as modified by section 303(5) of the Act.  
That section provides that in compensation cases where the evidence supporting different  
findings on an issue is evenly weighted, WCAT must resolve that issue in a manner that favours  
the worker.  
Background and Evidence  
[12]  
[13]  
The worker was a high school industrial technology teacher. She started working at a new  
school in 2016.  
There were several welding processes that took place in the worker’s metal shop classroom  
including millwork, shielded metal arc welding, plasma welding, casting, and oxy-acetylene  
cutting. A foundry was also set up in the shop. It had a canopy local exhaust system, as did  
2 benches that were set up for welding work. The dimensions of the metal shop were  
approximately 100 feet x 60 feet, with a 20-foot high ceiling (120,000 cubic feet).  
[14]  
[15]  
In the summer of 2017, the employer upgraded the school’s entire ventilation system, which  
included replacing the fume extraction system in the metal shop.  
In October 2017, during the installation of a new heating, ventilation, and air conditioning  
(HVAC) unit, a contractor noted that the metal shop fume extractor was not working properly.  
There was a loose belt and the electrical breaker for the exhaust fan was locking out. A work  
request for repair was submitted on October 2, 2017, which was completed without delay.  
[16]  
[17]  
In an email to a school administrator dated November 3, 2017, the worker requested carbon  
monoxide detectors for the metal shop. She felt there was lack of ventilation in the classroom  
when all the equipment was being used. Although she was told that the HVAC unit was working,  
by lunchtime she was getting “major migraines” and felt like “puking.”  
On November 3, November 29, and December 6, 2017, the employer received complaints from  
staff about the school’s indoor air quality with reports of headaches, nausea, exhaustion, and  
facial erythema. According to an employer’s investigation report, the worker reported that since  
late October/early November 2017, she experienced headaches, nausea, and exhaustion when  
all the welding equipment was running in the metal shop.  
[18]  
In an email to the school principal dated November 30, 2017, the employer’s occupational  
health and safety manager (OHS manager) noted that it was possible that some staff at the  
school had been exposed to carbon monoxide. She advised that carbon monoxide was  
produced when fuel was burned, and if it did not burn efficiently, there was an “increased risk.”  
The staff’s reported symptoms matched the symptoms for carbon monoxide exposure. The  
most common symptoms included headaches, dizziness, weakness, upset stomach, vomiting,  
chest pain, and confusion.  
3
150, 4600 Jacombs Road, Richmond, B.C. V6V 3B1  
Tel: (604) 664-7800 | 1-800-663-2782  
Fax: (604) 664-7898 | wcat.bc.ca  
WCAT Decision Number:  
A2100606 (August 17, 2022)  
[19]  
[20]  
On December 7, 2017, an HVAC contractor inspected the newly installed units and found one  
mechanical failure on the rooftop unit that supplied the school’s multi-purpose room. The claim  
file documents indicate that the necessary repairs were made to that HVAC unit soon after the  
issue was identified.  
In an email to the school’s staff dated December 11, 2017, the principal noted that she had  
received some air quality concerns in different areas of the school. The issue with the HVAC  
system attached to the multi-purpose room had been resolved and the science wing had been  
“checked” as well. Since then, another concern was raised in relation to the leadership room.  
The HVAC contractors were going to attend the school later on that day to review the entire  
ventilation system.  
[21]  
[22]  
In an email to several school administrators dated December 14, 2017, the worker noted that  
the HVAC contractors opened the vents in her classroom to allow for more outside air to come  
in. This was helpful when the equipment was not being used. However, she was still getting  
headaches when the foundry was running for casting purposes and during welding. This issue  
needed to be addressed as soon as possible given that it was a school-wide issue and not just  
related to her classroom.  
On Friday, December 15, 2017, the worker attended an emergency room department and  
reported intermittent headaches and nausea. She last felt these symptoms while working at the  
school one day earlier, but they had settled by the time she reported to the hospital. She was  
concerned about possible carbon monoxide exposure while working in her metal classroom.  
She experienced symptoms when the acetylene torches and metal foundry were operating at  
the same time. The worker’s vital signs were taken and she underwent bloodwork. Her  
carboxyhemoglobin level was documented at 2.8. The attending physician noted there was no  
evidence of carbon monoxide poisoning. The worker was advised to return to the hospital if she  
had any significant symptoms so that her carboxyhemoglobin levels could be reassessed while  
she was symptomatic. The worker was discharged from the hospital with a final diagnosis of  
“headache”.  
[23]  
[24]  
On December 18, 2017, a Board occupational hygiene officer (OHO) attended the school to  
investigate/test the air quality in various areas of the school including the metal shop. By that  
time, the employer had shut down some of the welding operations in the shop. The foundry was  
still operating, but no welding or cutting tasks were being undertaken. Testing revealed no  
carbon monoxide in the air of the work locations, and carbon dioxide levels were reportedly  
within acceptable levels.  
The OHO noted that the employer’s response to the indoor air quality complaints had failed to  
sample for contaminants possibly related to those complaints. This contravened the Board’s  
Occupational Health and Safety Regulation (OHS Regulation). As such, the OHO issued an  
order of compliance to ensure the employer updated its procedures on responding to indoor air  
quality complaints to include such sampling (order #1). Additionally, the OHO found that the  
employer’s welding, cutting, and similar processes were not being carried out using adequate  
4
150, 4600 Jacombs Road, Richmond, B.C. V6V 3B1  
Tel: (604) 664-7800 | 1-800-663-2782  
Fax: (604) 664-7898 | wcat.bc.ca  
WCAT Decision Number:  
A2100606 (August 17, 2022)  
ventilation pursuant to the requirements of the Canada Standards Association. As such, an  
order of compliance was issued to ensure these requirements were being followed (order #2).  
[25]  
[26]  
In a follow-up report dated January 29, 2018, the OHO noted the employer was in compliance  
with order #1 as it had updated its procedures for responding to indoor air quality complaints to  
include sampling for contaminants. The employer was also in compliance with order #2, as it  
had ordered local exhaust ventilation to be installed. In the meantime, it had ceased plasma  
welding and oxy/acetylene cutting until the installation was done.  
From February 19 to 21, 2018, the employer conducted air quality testing in the metal shop. A  
Q-track monitor was placed in the welding bay at table height (3 feet off the ground and 1 foot  
away from the exhaust hood). The monitor measured the carbon monoxide and carbon dioxide  
levels, and logged data for 3 consecutive days at 120 second intervals. At that time, students  
were using the welding equipment but not the casting or grinders. They were also not permitted  
to use the oxy-torch or handheld plasma cutters. The vents in the grinder and welding booth  
were running when classes were in session.  
[27]  
The Q-track monitor collected data for a total of 1,440 samples. The carbon monoxide levels  
were recorded mostly at 0 parts per million (ppm)3 with a range between 0.1 and 2.9 ppm on the  
rare occasion. The maximum level recording was documented at 7.6 ppm (on one occasion),  
but it went down to 0 ppm in the next sample (2 minutes later). The 8-hour time weighted  
average (TWA)4 concentration was 0.1 ppm. The Board’s permissible TWA exposure limit for  
carbon monoxide is 25 ppm. The carbon dioxide levels were mostly recorded below 1,000 ppm  
with the exception of a maximum level recording of 1,616 on one occasion. This went down to  
970 ppm in the next sample (2 minutes later). The TWA level was recorded at 880 ppm. The  
Board’s permissible TWA exposure limit for carbon dioxide is 5,000 ppm.  
[28]  
The employer commissioned an engineering firm to assess the adequacy of the ventilation  
system that serviced the metal shop (at the 2 welding booths and forging/foundry area) to  
ensure compliance with the current industry standards/codes. In the corresponding March 19,  
2018 report, the consultant noted that the existing areas utilized overhead capture hoods with  
3 localized exhaust fans installed on the roof. In the forge/foundry area, the overhead hood was  
an older system, which did not provide adequate exhaust of the heat and fumes generated by  
the casting process. While the airflow from the exhaust fan was sufficient (at 4000 cfm5), the  
design of the canopy hood and positioning of the forge made the overall system inadequate.  
Additionally, the 2 welding booth areas were serviced with 2 individual 1,700 cfm exhaust fans,  
which were connected to canopy exhaust hoods. The consultant noted that the existing  
overhead canopy hood capture system was “not the best system” for welding and cutting. The  
recommended exhaust air velocities for welding was 2,000 to 2,500 fpm6, and the existing air  
3
1 ppm = 1 part of gas per million parts of air by volume  
TWA limits refer to exposure over a nominal 8-hour work period.  
cubic feet per minute  
feet per minute  
4
5
6
5
150, 4600 Jacombs Road, Richmond, B.C. V6V 3B1  
Tel: (604) 664-7800 | 1-800-663-2782  
Fax: (604) 664-7898 | wcat.bc.ca  
WCAT Decision Number:  
A2100606 (August 17, 2022)  
velocity was at 1,800 fpm. The consultant provided some recommendations for upgrades to the  
existing design of the canopy hoods and ventilation systems in the 2 areas.  
[29]  
Based on the engineering report, the employer continued to restrict the use of some welding  
equipment in the metal shop.  
[30]  
[31]  
Sometime in March 2018, portable welding fume extractors were placed in the metal shop.  
On May 24, 2018, the worker filed a teleclaim application for compensation with the Board  
(teleclaim application). She reported that on or about November 3, 2017, she started developing  
headaches, fatigue, nausea, and dizziness. Her symptoms got worse throughout November  
2017. She had notified the employer’s health and safety committee (which she was a member  
of). She attended a local hospital in December 2017 and was diagnosed with carbon monoxide  
exposure. Her carbon monoxide level was at 2.8, but she had not been using the shop  
equipment for about 36 hours prior to testing. The worker advised that she did not miss any time  
from work as a result of the indoor air quality issues at work.  
[32]  
[33]  
The employer’s report of injury dated May 29, 2018 documented the same information as the  
worker’s teleclaim application. The employer confirmed that the worker did not miss any time  
from work.  
On May 30, 2018, the worker sought medical attention from her family physician, Dr. Hollman.  
The worker reported that in mid-October 2017, she started developing headaches and nausea  
while working in the metal shop. Her symptoms were worse at work. The carbon dioxide levels  
at her school had been “very high” and she could not work. Dr. Hollman submitted a report to  
the Board stating that the worker was unable to work at that time. She diagnosed the worker  
with “possible recurrent carbon monoxide [and] carbon dioxide poisoning.”7  
[34]  
[35]  
The worker stopped working thereafter.  
On June 4, 2018, the worker attended a health and safety meeting to discuss the air quality  
issues in the school. The Board’s OHO was present at that meeting. The worker advised that  
she had been trying to get pregnant since February 2018 and was concerned about being  
exposed to toxins in the metal shop. Discussions about accommodating the worker ensued  
thereafter. The OHO noted that there were specific rules regarding reproductive toxins in the  
workplace. The allowable exposure limits were different for workers who were trying to get  
pregnant.  
[36]  
On June 11 and 13, 2018, the employer conducted further carbon monoxide testing using a  
Gas Alert Max Monitor. A substitute teacher wore the monitor while metal shop classes were in  
session. The teacher confirmed that typical class activities took place each day including  
welding, foundry work, and plasma cutting. The data indicated a spike in the carbon monoxide  
7
All quotes are reproduced as written, except as noted; block capitalization removed.  
6
150, 4600 Jacombs Road, Richmond, B.C. V6V 3B1  
Tel: (604) 664-7800 | 1-800-663-2782  
Fax: (604) 664-7898 | wcat.bc.ca  
WCAT Decision Number:  
A2100606 (August 17, 2022)  
levels at the start and end of testing. Other than that, no airborne carbon monoxide was  
detected on the first day. On the second day, carbon monoxide was detected at 5 ppm  
between 12:30 p.m. and 12:45 p.m. The employer’s OHS manager later advised the Board  
that the carbon monoxide monitor was calibrated before use on the first day and at the end of  
testing on the second day. For some reason, the data included the calibration in the results  
(which explained the momentary spike at the beginning and end of testing). The carbon dioxide  
levels were not tested because the Board’s OHO had requested that take place only after the  
new fume extractor had been installed.  
[37]  
In June 2018, the worker told a Board officer that her symptoms of fatigue, nausea, headaches,  
and dizziness started in mid-October 2017, and not in November 2017 as indicated on her  
teleclaim application form. Her symptoms were “not bad” on Mondays or Tuesdays. They got  
progressively worse from Wednesday to Friday. She believed that the build-up of carbon  
monoxide/dioxide made her feel worse at the end of the week. She felt better on the weekends.  
She missed sporadic time from work beginning in January 2018. She stopped working around  
May 29, 2018 as her doctor said that she was not getting better and needed to be off work.  
Additionally, she had 2 miscarriages since she started working at the school and her doctor said  
that she did not need the added stress. She was going to be off work for the remainder of the  
school year.  
[38]  
On July 30, 2018, Dr. Hollman noted that the worker was trying to get pregnant. The worker  
reported that she and her partner had stopped using condoms in February 2018. She had heavy  
and painful menstrual cycles. Dr. Hollman diagnosed “[a]bnormal uterine bleeding and  
difficulties getting pregnant.” She ordered blood work, which revealed normal blood count, iron  
studies, and thyroid stimulating hormone levels.  
[39]  
[40]  
An August 2018 pelvic ultrasound revealed the worker had a large hypervascular uterine mass,  
which was most likely a fibroid, with normal endometrium. A subsequent MRI revealed that the  
uterine fibroid measured up to 77 mm in diameter. The endometrium and ovaries were normal.  
On August 22, 2018, the worker consulted with Dr. Wroz (a gynecologist) and advised that she  
had been trying to get pregnant for the past 6 months. She was concerned that her fibroid and  
infertility were related to her work exposure to carbon monoxide/dioxide. Dr. Wroz assured her  
that there was no evidence to support her theory. He counselled the worker on infertility and  
noted that up to 80% of couples do not conceive within the first year of trying.  
[41]  
On August 27, 2018, Dr. Hollman noted the worker had ongoing painful menstrual cycles. The  
worker requested Dr. Hollman to fill out a form for modified duties (which she did). The worker  
was cleared to return to modified duties in September 2018. Dr. Hollman diagnosed “difficulties  
getting pregnant, menorrhagia with dysmenorrhea with large uterine fibroid, previous poisoning  
from carbon monoxide and carbon dioxide at work.”  
7
150, 4600 Jacombs Road, Richmond, B.C. V6V 3B1  
Tel: (604) 664-7800 | 1-800-663-2782  
Fax: (604) 664-7898 | wcat.bc.ca  
WCAT Decision Number:  
A2100606 (August 17, 2022)  
[42]  
[43]  
In August 2018, the employer offered the worker a reassignment position given that she was  
trying to get pregnant. The worker was not happy with the initial reassignment and declined the  
offer.  
On September 10, 2018, the worker told Dr. Hollman that her school was deemed unsafe due to  
carbon monoxide, carbon dioxide, and other toxic fumes. The employer was not doing what it  
needed to do, and was not providing her with alternate work duties. Dr. Hollman provided a  
medical note stating that the worker needed to stay off work for the remainder of the school  
year.  
[44]  
On September 20, 2018, the worker told a Board officer that she was looking for a new  
gynecologist because Dr. Wroz advised that her work environment did not cause her  
miscarriages. She disagreed with Dr. Wroz because carbon monoxide was a well-known  
reproductive toxin. Due to her exposure at work, she had suffered 3 miscarriages.  
[45]  
[46]  
On October 1, 2018, the worker told Dr. Wroz that she had some information from the Board  
showing that her work environment was inadequately ventilated and the presence of  
reproductive toxins. Dr. Wroz referred the worker to a fertility specialist, Dr. Bediway.  
On October 11, 2018, the worker told a Board officer that the employer should test the air  
quality in the metal shop with all the equipment running simultaneously. In her typical work day,  
all the equipment was running for 3 to 4 hours per day. The employer was not doing this type of  
testing because it knew that it was unsafe to do so, and it did not want to expose anyone else to  
the risks. It was a “no-brainer” that there was something wrong in the work environment  
considering the employer would not even perform this type of testing. The worker felt that the  
employer was “sandbagging” the investigation because new ventilation was going to be installed  
in the following week. Once this happened, it would be impossible to obtain the relevant data.  
The Board officer asked the worker if she had any confirmed past pregnancies, or whether she  
sought medical treatment for her pregnancies/miscarriages. He noted the medical reports from  
Drs. Wroz and Hollman specifically documented the worker’s inability to conceive, but did not  
mention conception or miscarriage. The worker advised that she did not seek medical attention  
for her miscarriages.  
[47]  
[48]  
Between mid-October 2018 and January 2019, the worker sought treatment by a naturopathic  
doctor, Dr. Spooner. The worker underwent a urine element analysis that tested for potential  
toxic elements including aluminum, antimony, arsenic, bismuth, cadmium, cesium, gadolinium,  
indium, lead, mercury, nickel, tellurium, thallium, thorium, tin, tungsten, and uranium. In his  
corresponding report, Dr. Spooner provided some general information on each element. He also  
documented the worker’s urine test results, but did not address whether there was evidence of  
any occupational exposure.  
Sometime in October/November 2018, the employer carried out the recommended  
modifications to the hood design over the foundry in the metal shop.  
8
150, 4600 Jacombs Road, Richmond, B.C. V6V 3B1  
Tel: (604) 664-7800 | 1-800-663-2782  
Fax: (604) 664-7898 | wcat.bc.ca  
WCAT Decision Number:  
A2100606 (August 17, 2022)  
[49]  
On November 16, 2018, the worker saw Dr. Bediway in relation to her fertility issues. He noted  
the worker had been trying to get pregnant for the past 8 months (starting in February 2018).  
The worker’s past medical/gynecological history was documented in detail without mention of  
any prior miscarriages. Dr. Bediway recommended further hormone testing to assess the  
worker’s ovarian reserve. He noted that cavity-uterus fibroids increased the likelihood of  
miscarriages, and recommended the worker undergo surgical removal of her fibroid.  
Dr. Bediway also addressed the worker’s concerns about being exposed to biochemical hazards  
in her work environment and how it related to her inability to conceive for the past 8 months. He  
told the worker that there was limited information on whether the biochemical hazards that she  
was exposed to impacted her ovarian reserve.  
[50]  
On November 21, 2018, the employer conducted further air quality testing in the metal shop  
while classes were in session. The teacher advised that in the first two blocks, the kiln and  
welding machines were running for the majority of the time. In the third block, the students  
mainly used the hand tools and some minor welding took place. In the last block, the lathe,  
welding, and kiln were running for 90% of the time. The data revealed no detection of airborne  
carbon monoxide. For the most part, carbon dioxide levels were below 1,000 ppm, with the  
exception of a few sporadic readings over 1,000 ppm, with a maximum level of 1,774 ppm  
during a single 2-minute interval, which went down to 983 ppm immediately thereafter.  
[51]  
On December 5, 2018, the worker told a Board officer that Dr. Bediway told her that the medical  
system did not allow him to comment on a connection between her fibroid and heavy metal  
exposure. He was not allowed to comment on why her hormones were “out of whack” and the  
medical system did not allow him to look into why they were “out of whack.” He could only treat  
symptoms. The worker also advised that Dr. Spooner said that her “problems” were related to  
exposure to heavy metals in her job. He said that her exposure to carbon monoxide was the  
“least of her worries.” Dr. Spooner’s testing revealed that her levels were high for quite a few  
heavy metals that were reproductive toxins such as lead, mercury, and cadmium. The worker  
noted that lead and cadmium were known reproductive toxins. Lead reacts with cadmium and  
they “feed off each other” resulting in the cadmium becoming more toxic than it would be on its  
own. Dr. Spooner advised that it was the lead and cadmium in her system that was blocking her  
hormones. This caused the formation of her fibroid and inability to conceive. Dr. Spooner  
treated the worker with a series of injections in order to extract the heavy metals from her  
system.  
[52]  
[53]  
On December 7, 2018, Dr. Wroz noted the worker gave him some studies pertaining to heavy  
metal exposure and fibroids. He referred the worker to a fertility clinic to see Dr. Yupze, an  
endocrinology/infertility specialist with an expertise in heavy metal exposure and infertility.  
In a claim investigation report dated January 8, 2019, two Board OHOs addressed the worker’s  
potential exposure to carbon monoxide/dioxide and other substances in her welding  
environment in the school. The OHOs noted that they had reviewed the claim file documents  
including the chronology of events and timelines in relation to the worker’s reported symptoms,  
the air sampling testing/data, the March 2018 engineering report, and various literature on  
9
150, 4600 Jacombs Road, Richmond, B.C. V6V 3B1  
Tel: (604) 664-7800 | 1-800-663-2782  
Fax: (604) 664-7898 | wcat.bc.ca  
WCAT Decision Number:  
A2100606 (August 17, 2022)  
carbon monoxide and other contaminants. The OHOs also spoke with the initial OHO who had  
conducted the air sampling at the workplace in December 2017; they also reviewed his  
corresponding inspection reports and compliance orders.  
[54]  
The OHOs noted that carbon monoxide is an odorless and colorless gas that provides no  
warning until exposure results in adverse health symptoms. Symptoms of mild carbon monoxide  
poisoning include headaches, dizziness, nausea, and vomiting. It was known that welding tasks  
do not normally generate carbon monoxide at harmful levels of any concern except in cases of  
confined work spaces where it can accumulate over time. In BC, the OHS Regulation  
established exposure limits for contaminants with references to the American Conference of  
Governmental Industrial Hygienists (ACGIH) exposure limits. The relevant exposure limits were:  
Carbon monoxide:  
TWA-8 hour  
STEL-15 minute8  
25 ppm  
100 ppm  
Carbon dioxide:  
TWA-8 hour  
STEL-15 minute  
5,000 ppm  
15,000 ppm  
[55]  
[56]  
The OHOs noted that carbon dioxide levels can be used as an indicator of sufficient outdoor air  
being delivered to the work environment. Normally, indoor levels around 1,000 ppm are a good  
indication that the HVAC system is functioning well for the work environment.  
Regarding the worker’s exposure to carbon monoxide and carbon dioxide, the OHOs noted the  
following:  
The new HVAC systems were installed in early October 2017, at which time the contractor  
noticed that the fume extraction system servicing the metal shop was not working properly  
(loose belt and electrical breaker locked out). The necessary repair was completed without  
delay. Although it was not known how long this unit was not working properly, it was  
possibly since the start of the school year in September 2017. While welding operations  
typically do not generate high levels of carbon monoxide, it was possible during this time  
period that carbon monoxide from welding and forging operations was permitted to  
accumulate at low levels in the metal shop. It was unlikely that airborne carbon monoxide  
ever approached the exposure limit because there were 2 other exhaust fans servicing the  
shop. Additionally, the work activities were student based, and not production based.  
On December 7, 2017, the HVAC contractor inspected all components of the new  
HVAC systems and found a mechanical failure on the rooftop HVAC unit servicing the  
multi-purpose room. The necessary repairs were made to this unit soon after being  
identified. Improper operation of heating components of an HVAC system can give rise to  
8
STEL limits refer to short-term or peak exposures  
10  
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Tel: (604) 664-7800 | 1-800-663-2782  
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WCAT Decision Number:  
A2100606 (August 17, 2022)  
incomplete combustion of natural gas, which can give rise to elevated carbon monoxide  
levels in a workplace. Although there was no evidence that the mechanical failure of the  
rooftop HVAC system failed in a way that would give rise to carbon monoxide emission, this  
was possible, and aligned with the staff’s air quality complaints.  
A further HVAC issue within the metal shop was identified when the engineering firm  
assessed the exhaust ventilation system. The report indicated that while the exhaust fans  
were, for the most part, properly sized for the scope and nature of welding and forging work,  
the canopy hood design was outdated. As such, recommendations to upgrade the  
ventilation design were provided (to include a source capture type design). This poor  
ventilation design would likely have contributed more to the accumulation of welding fumes  
in the work area rather than welding gases, as gases are light and will become easily  
entrained in the upward ventilation flow.  
The Board’s air quality inspection on December 18, 2017 did not find any evidence of  
elevated levels of carbon monoxide or carbon dioxide. Repeat measurements were  
undertaken by the employer in February 2018 and again in June 2018, which found  
comparable levels, all well below the respective exposure limits. All the HVAC system  
defaults had been repaired by the time that these surveys took place.  
[57]  
Overall, the OHOs noted that the timeline of the air quality complaints from the employer’s staff  
aligned with the HVAC malfunctions. Therefore, it seemed likely that the HVAC malfunctions  
may have caused, or at least contributed to, the air quality complaints from October 2017 to  
early December 2017. However, after December 2017, staff in the multi-purpose room and  
science room did not continue to report adverse health symptoms or air quality complaints.  
However, the worker reported ongoing symptoms, which she attributed to the air quality in the  
metal shop. In that regard, while the exhaust ventilation system in the metal shop was  
determined to be less than optimal, ventilation gases are light and would have easily become  
entrenched in the ventilation flow created by the 3 exhaust fans. It was unlikely that carbon  
monoxide or carbon dioxide levels would have approached or exceeded the respective  
exposure limits during typical student tasks. For these reasons, it was expected that the  
airborne levels of welding gases in the metal shop would have been very low despite the poor  
ventilation design.  
[58]  
The OHOs also considered the worker’s potential exposure to welding/casting fumes. They  
noted that welding tasks and plasma cutting can generate welding fumes such as iron oxide,  
magnesium oxide, and manganese oxide. Aluminum forging can generate airborne aluminum  
oxide. The OHOs outlined the exposure limits for these contaminant as set out in the OHS  
Regulation, which I have not summarized. Regarding the worker’s potential exposure to welding  
fumes, the OHOs noted the following:  
Given the fan failure identified in October 2017, it was possible that welding fumes may  
have accumulated in the shop at low levels in the one-month time period (from the start of  
the school year in September 2017 to early October 2017). Any gases would not likely have  
lingered in the shop as they would have been drawn up in the air flow created by the other  
11  
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Tel: (604) 664-7800 | 1-800-663-2782  
Fax: (604) 664-7898 | wcat.bc.ca  
WCAT Decision Number:  
A2100606 (August 17, 2022)  
2 exhaust fans and the general HVAC system servicing the metal shop. Additionally,  
students routinely entered and exited the metal shop and this movement would have also  
provided some air movement and helped to facilitate any accumulation of fumes out of the  
shop, where it would have been drawn into the school HVAC air systems servicing the  
common areas and adjacent work locations.  
While the worker believed that the sampling was not indicative of the full spectrum of tasks  
undertaken in the metal shop, there were exhaust fans and a general HVAC system in the  
shop. The low levels of carbon monoxide and carbon dioxide levels measured from the air  
quality testing indicated that these ventilation systems were serving to remove contaminants  
from the work environment.  
While there was no available data confirming airborne levels of metal fume present in the  
metal shop during typical student tasks, there were 2 large canopy hood exhaust ventilation  
systems servicing both the forge and welding areas. The fans servicing these areas were  
assessed by a ventilation engineer, and while the canopy hood design was determined to be  
of a poor design for the scope of work, the exhaust fans were more or less appropriately  
sized for the scope and nature of the student-centered tasks. Nonetheless, the employer  
took steps to restrict the use of certain equipment within the shop and/or put conditions on  
their use until such time that the recommended upgrades could be completed. As such, it  
was unlikely that welding fume and gas levels would have approached or exceeded the  
BC regulated exposure limits for these substances.  
The findings of the investigation suggested that it was unlikely that the worker was exposed  
to harmful levels of metal oxide fumes during her work in the metal shop.  
[59]  
On January 17, 2019, Dr. Hollman noted the worker’s PAP test revealed atypical squamous  
cells. The worker believed this was caused by her exposure to heavy metals at work. However,  
Dr. Hollman advised that these abnormalities were usually caused by human papillomavirus  
(HPV) disease.  
[60]  
[61]  
On January 28, 2019, Dr. Bediway noted that the worker’s ovarian screen//hormone testing  
came back normal, which supported that she had a normal ovarian reserve.  
On March 5, 2019, the worker was seen by another gynecologist, Dr. Adams, in relation to her  
abnormal PAP smear. He noted the worker had questions about heavy metal exposure and  
cervical dysphasia. Dr. Adams advised that the pathophysiology of dysplasia was well  
understood, and in the vast majority of cases, it was HPV-related. To the best of his knowledge,  
there was no known causal association with heavy metal exposure.  
[62]  
[63]  
On March 21, 2019, the worker underwent an x-ray that revealed a normal-appearing  
endometrial cavity. Other than the fibroid, no other abnormality was seen.  
On March 29, 2019, the worker saw Dr. Yupze, and advised that she had been trying to get  
pregnant for the past year. Her partner had a son from a previous relationship, but she had  
12  
150, 4600 Jacombs Road, Richmond, B.C. V6V 3B1  
Tel: (604) 664-7800 | 1-800-663-2782  
Fax: (604) 664-7898 | wcat.bc.ca  
WCAT Decision Number:  
A2100606 (August 17, 2022)  
never been pregnant. The worker reported that her work environment had very poor ventilation.  
She believed that she had been exposed to various substances that could be reproductive  
toxins such as cadmium, mercury, and carbon monoxide.  
[64]  
[65]  
Dr. Yupze noted the worker had brought a huge 3-ring binder full of articles, test results,  
statistics, and other materials addressing environmental toxins and their effects on fertility. She  
also provided articles suggesting a relationship between these substances (and cadmium in  
particular) and uterine fibroids. Dr. Yupze noted these substances were considered to be  
endocrine disruptors, and the worker suggested that they caused her uterine fibroid. Dr. Yupze  
advised that he was not aware of such correlation. To his knowledge, the presence of fibroid  
ceilings had to be present in order for a fibroid to develop.  
The worker went on to tell Dr. Yupze that physicians do not look at hormone levels “below the  
line” but only looked at levels that were “above the line.” Dr. Yupze was not certain what the  
worker was referring to in that regard. He noted that she had previously undergone 2 endocrine  
studies, which showed normal hormone levels. Her thyroid level was normal and she had a  
good ovarian reserve. Dr. Yupze had no explanation for why the worker had not yet become  
pregnant; however, it was not uncommon that women of her age did not get pregnant within  
12 months of trying. Unexplained infertility, which was the worker’s diagnosis at that point,  
accounted for at least 50% of his patients being assessed for fertility issues. That said, there  
was an association between the worker’s failure to conceive and her fibroid. Dr. Yupze  
recommended the worker undergo surgical removal of her fibroid, and try to conceive on her  
own for approximately 6 months thereafter.  
[66]  
[67]  
Dr. Yupze noted the worker was likely not completely satisfied with their discussion. He was not  
trying to convince her that all her theories on chemical endocrine disrupters were irrelevant to  
her case. However, based on the endocrine testing done up to that point in time, there was no  
evidence of anything actually having been affected.  
In an investigation report dated March 29, 2019, a Board OHO further considered the worker’s  
potential exposure to heavy metals (including cadmium) during her work as a welding instructor.  
In doing so, the OHO reviewed the material safety data sheets for products used in the metal  
shop, the employer’s exposure control plan (ECP) and risk assessment, the prior OHO  
inspection reports and associated documents, and relevant literature. The OHO noted the  
following:  
Welding will produce fumes containing various metals. The specific form and concentration  
of metals present in welding fume and dust will depend on the composition of the filler metal,  
base metals, metal coatings, atmosphere, flux, and the welding process. Welding fumes are  
essentially a mixture of complex but often predictable metallic oxides, fluorides, and  
silicates. Welding processes may involve the metals themselves and the use of a filler or  
flux. Welding may occur on new clean stock metal, new metal with residual compounds from  
manufacture, and/or used metal with residual contamination from prior use, including  
coatings.  
13  
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Tel: (604) 664-7800 | 1-800-663-2782  
Fax: (604) 664-7898 | wcat.bc.ca  
WCAT Decision Number:  
A2100606 (August 17, 2022)  
The employer’s ECP for welding fumes listed the products used in the metal shop. From the  
employer’s inventory of products, none of the products used contained cadmium. Some  
metal products, such as steel, could be plated with a thin layer of cadmium to increase  
resistance to corrosion. This cadmium coating was normally between 5 and 25 micrometers  
in thickness. It was unknown if the school had any plated materials; however, given the  
extremely thin coating and low level of use, it was unlikely that this created a hazardous  
exposure.  
Other metals found in the products used in the metal shop included manganese, iron,  
copper, and aluminum. The products also contained titanium dioxide, sodium fluoride,  
kaolin, calcium fluoride, barium compounds and mica-like minerals.  
Based on the engineering report of March 2018, the capture hood in the forge area did not  
provide adequate exhaust of heat and fumes generated by the casting process, and the  
welding area had an air velocity below what it should be. However, the size of the metal  
shop would provide some general dilution of contaminants. Even though the exhaust fans  
were not performing optimally, they had some capacity to remove gases and fumes.  
Welding fume was generated daily while students worked on projects. However, the small  
number of students using the equipment at any one time kept the level of contaminants low.  
When students received instruction and caught up on paperwork, there were no  
contaminants generated. In the instructional setting at school, the level of welding fume  
contaminants generated were lower than in a production facility. Therefore, it was likely that  
the worker experienced frequent exposure to low levels of welding fume contaminants  
through her work as an instructor.  
[68]  
On April 25, 2019, Board medical advisor Dr. Raghukumar provided a lengthy opinion  
addressing the worker’s potential exposure to carbon monoxide and the cause of her uterine  
fibroid. She summarized the worker’s exposure history, key reporting documents, the Board’s  
investigation reports, and medical record, which is in keeping with my summary above.  
Dr. Raghukumar noted the worker attended the hospital in mid-December 2017. Examination of  
her vital signs were noted to be stable in relation to her temperature, pulse, respiratory rate,  
blood pressure, and oxygen saturation levels. The remainder of the examination findings were  
unremarkable. The worker’s blood work results were unremarkable in relation to her white blood  
cell count, hemoglobin, electrolytes, renal function, and blood gases. Her carboxyhemoglobin  
was reported at 2.8, which was normal. In Dr. Raghukumar’s opinion, there was no confirmed  
diagnosis of carbon monoxide poisoning.  
[69]  
Dr. Raghukumar also opined that the worker’s fibroid was unrelated to her work. She noted that  
uterine fibroids were mostly benign gynecologic tumors in women of reproductive age. They  
were common with about 77% of women likely to develop them in their lifetime. The medical  
literature documented various known risk factors for uterine fibroids including a patient’s age at  
menarche, parity, ethnicity, and weight/obesity. Dr. Raghukumar was unable to find any specific  
epidemiological studies pertaining to uterine fibroids among welders. She noted that fibroids  
were not listed among the known health hazards to welding fume exposure (as per the  
14  
150, 4600 Jacombs Road, Richmond, B.C. V6V 3B1  
Tel: (604) 664-7800 | 1-800-663-2782  
Fax: (604) 664-7898 | wcat.bc.ca  
WCAT Decision Number:  
A2100606 (August 17, 2022)  
information on health impacts of welding from the Canadian Centre for Occupational Health  
Safety and Government of Canada).  
[70]  
On June 28, 2019, the Board requested Dr. Spooner to provide further information regarding the  
worker’s diagnosis, causation, and treatment in relation to her reproduction/fertility/fibroid  
issues. Dr. Spooner forwarded his chart notes to the Board (which were previously submitted)  
but did not provide any new information or opinion on the other requested matters.  
[71]  
[72]  
In a clinical record dated July 17, 2019, Dr. Wroz noted that the worker was approximately  
10 weeks pregnant.  
The worker submitted an information sheet on acceptable indoor air quality levels to the Board.  
It notes that the Board publishes occupational exposure limits for various air quality  
contaminants including carbon dioxide, carbon monoxide, and dust. Additionally, standards for  
acceptable indoor air quality have been developed by ASHRAE9 to establish minimum  
requirements for optimal health and comfort in buildings, and in particular, office environments.  
According to ASHRAE, carbon dioxide levels below 1,000 ppm (TWA) indicate that there is  
adequate air circulation for indoor environments. For carbon monoxide, levels of indoor  
environments should generally not exceed 5 ppm (TWA).  
[73]  
The worker submitted various other documents including: safety data sheet information on  
acetylene and Blueshield 8; school emails addressing OHS issues and, in particular, a  
December 2019 incident whereby a carbon dioxide detector was beeping in the metal shop as a  
result of the acetylene torch being left open slightly; hand-written notes from OHS committee  
meetings held at the school; minutes from a joint health and safety district committee meeting  
that documented the December 2019 carbon dioxide incident; pages from the employer’s ECP;  
various articles addressing the effects of exposure to various types of airborne substances, the  
relationship between heavy metals accumulated in the body and the development of uterine  
fibroids and infertility, and general exposure to hazardous fumes and particles in the welding  
field; an August 2017 quote for exhaust fume downdraft tables for various high schools within  
the employer’s district; and information about her reassignment. As mentioned earlier, I have  
reviewed all this information in my adjudication of the appeal, but will not summarize it.  
WCAT Oral Hearing  
[74]  
The worker’s oral hearing testimony repeated much of the information that was already in the  
claim file. As such, the following is only a brief summary of her testimony dealing with any new  
or contradictory information:  
In the first 2 weeks of school in September 2017, she conducted safety tests in the metal  
shop and the welding equipment was not used.  
9
The American Society of Heating, Refrigerating, and Air-Conditioning Engineers  
15  
150, 4600 Jacombs Road, Richmond, B.C. V6V 3B1  
Tel: (604) 664-7800 | 1-800-663-2782  
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WCAT Decision Number:  
A2100606 (August 17, 2022)  
Her job was not stationary. She was always “on the go” while helping students at various  
stations including the welding booth, foundry, and milling machines. All the equipment was  
in operation at the same time. She stood behind students and watched them weld.  
She did not notice much difference in her symptoms after the employer had shut down some  
of the welding processes in December 2017; however, it helped to open the big bay door.  
She used to stand next to the foundry to take out the impurities. This is where the engineer  
found that the ventilation was inadequate.  
Regarding the employer’s June 2018 air quality sampling, the substitute teacher who wore  
the monitor was working on his own projects and letting the students do “whatever.” He  
showed the worker what he worked on during class.  
Between September 2017 and May 30, 2018, she sporadically missed 4 or 5 days from  
work because she felt unwell. Most of her medical appointments were scheduled after  
school hours.  
In September 2019, two students passed out around the welding booths. Other students  
had passed out in 2018. She did not know if this was a coincidence, but it was relevant.  
She showed Dr. Raghukumar’s opinion to her treating physicians including Dr. Bediway. He  
knew that she had a compensation claim but did not want to get involved. She showed the  
opinion to Dr. Spooner as well, and he said that it was a typical Board response.  
She had been trying to get pregnant since 2016. She had 2 miscarriages between January  
and April/May 2018. She had no prior miscarriages.  
She became pregnant in 2019, but there were a lot of complications. Her baby had a stroke  
while still “inside.” The hospital wanted to terminate the pregnancy when she was 5 months  
pregnant. Her son was born on January 20, 2020. She got pregnant naturally.  
Submissions  
[75]  
[76]  
The worker argued that the Board OHO had determined that the ventilation in the metal shop  
was not up to code and inadequate, and the March 2018 engineering report supported that  
fumes were not being removed from the classroom. This supported her position that she was  
inhaling toxic fumes.  
The worker also argued that the employer’s air quality testing did not accurately reflect what she  
was exposed to because some of the equipment in the metal shop had been shut down in  
December 2017. The February 2018 test results were inaccurate because the Q-track  
monitoring equipment was placed 5 feet away from the aluminum foundry. The worker argued  
that the welding particles/fumes were still in the air, even if not condensed in the welding booth  
area that was tested. She did not stand in front of the welding machine for the entire class.  
Irrespective of that, the recorded carbon dioxide levels went above 1,000 ppm, which exceeded  
16  
150, 4600 Jacombs Road, Richmond, B.C. V6V 3B1  
Tel: (604) 664-7800 | 1-800-663-2782  
Fax: (604) 664-7898 | wcat.bc.ca  
WCAT Decision Number:  
A2100606 (August 17, 2022)  
the exposure limits. This supported her position that she was exposed to toxic levels of airborne  
substances.  
[77]  
[78]  
The worker submitted that the medical journals established a link between heavy metals and  
fibroid growth. The employer acknowledged that the metal shop had reproductive toxins, and  
that she was exposed to them. This was the reason that she was reassigned to a different  
position. These reproductive toxins caused her uterine fibroid and subsequent miscarriages.  
The employer argued that the medical evidence did not establish that the worker had carbon  
monoxide poisoning, or that she was exposed to toxic levels of carbon monoxide. The employer  
relied on the various air quality testing performed by the Board and employer, as well as the  
Board’s OHO’s investigation reports as support for its position in that regard. The employer also  
argued that the medical evidence did not establish an occupational link between the worker’s  
uterine fibroid and exposure to heavy metals/toxic substances during her employment. It also  
did not support that the worker had suffered miscarriages as a result of any occupational  
exposure. The employer noted that the worker had been assessed by several specialists, none  
of whom supported her position on this matter.  
Applicable Law and Policy  
[79]  
WCAT must make its decision on the merits and justice of the case, but in so doing, must apply  
policy of the Board’s board of directors that is applicable in the case. The Board’s Rehabilitation  
Services and Claims Manual, Volume II (RSCM II)10 contains the policy applicable to this  
appeal.  
[80]  
[81]  
Section 136(1) of the Act states that compensation is payable for an occupational disease that  
is due to the nature of a worker’s employment.  
The Act defines an occupational disease as any disease: (1) mentioned in Schedule 1 to the  
Act11; (2) that the Board has designated or recognized as an occupational disease; or (3) that  
the Board has recognized by order in a specific case. The definition includes disablement  
resulting from exposure to contamination.  
[82]  
Policy item C4-25.00 of the RSCM II sets out the following 3 basic requirements for  
compensation under section 136 of the Act: (1) the worker must be suffering from an  
occupational disease; (2) the disease must be, or have been, due to the nature of any  
employment in which the worker was employed; and (3) the worker must be disabled from  
earning full wages where he or she was employed as a result of the disease.  
10  
Several policies in the Board’s RSCM II were amended on February 1, 2020 and April 6, 2020.  
Those amendments apply to this appeal.  
Found in Appendix 2 of the RSCM II. I have referred to “Schedule 1” and “the schedule”  
11  
interchangeably throughout my decision.  
17  
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Tel: (604) 664-7800 | 1-800-663-2782  
Fax: (604) 664-7898 | wcat.bc.ca  
WCAT Decision Number:  
A2100606 (August 17, 2022)  
[83]  
Section 137(2) of the Act addresses occupational diseases that are specifically set out in  
Schedule 1. It states that if a worker contracts a disease set out in the first column of the  
schedule and, at or immediately before the date of the disablement, was employed in a process  
or industry mentioned in the second column of the schedule opposite to that disease, the  
disease is presumed to have been due to the nature of that employment unless the contrary is  
proven. This is known as the rebuttable presumption.  
[84]  
[85]  
[86]  
Policy item C4-25.10 of the RSCM II states that any disease listed in Schedule 1 is by definition  
designated or recognized as an occupational disease. I will address this policy in more detail  
later.  
Item 1(8) of Schedule 1 recognizes carbon monoxide poisoning as an occupational disease that  
is presumed to be due to the nature of employment where there is exposure to products of  
combustion or to any other sources of carbon monoxide.  
Claims for occupational diseases can also be accepted under section 136 of the Act in cases  
where the disease is not listed in Schedule 1, and if the Board has not previously designated or  
recognized a disease an occupational disease. Policy item C4-25.10 states that the lack of a  
prior designation or recognition by the Board of a disease as an occupational disease does not  
mean a claim for such disease will not be considered on its merits. If the merits and justice of an  
individual claim for such a disease warrant its recognition, section 138(3) of the Act provides  
that the Board may by order, designate or recognize a disease as an occupational disease in a  
specific case.  
[87]  
[88]  
[89]  
If a disease is not listed in Schedule 1, but is recognized by regulation or in a specific case, the  
presumption of work causation is not applicable, and it is necessary to establish that the disease  
was due to the nature of the worker’s employment based on the merits and justice of the claim  
(based on a balance of probabilities). The same is true for claims where the requirements of  
section 137 have not been met. In these scenarios, an occupational disease will be due to the  
nature of the worker’s employment if the employment was of causative significance in producing  
the disease. Causative significance means more than a trivial or insignificant aspect.  
Policy item #97.32 governs statements of workers about their own conditions, which I will  
address in more detail later.  
Reasons and Findings  
Did the worker suffer from carbon monoxide poisoning as an occupational disease that was due  
to the nature of her employment?  
Pursuant to the law and policy discussed above, in order for the worker to have a successful  
claim for carbon monoxide poisoning under Schedule 1, the evidence must establish two things:  
(1) that she had carbon monoxide poisoning; and (2) there was exposure to products of  
combustion or other sources of carbon monoxide at work. If both of these conditions are met,  
18  
150, 4600 Jacombs Road, Richmond, B.C. V6V 3B1  
Tel: (604) 664-7800 | 1-800-663-2782  
Fax: (604) 664-7898 | wcat.bc.ca  
WCAT Decision Number:  
A2100606 (August 17, 2022)  
then there is a rebuttable presumption that the carbon monoxide poisoning was due to the  
nature of the worker’s employment. In turn, this will satisfy the first two requirements for  
compensation under section 136 of the Act and policy item C4-25.00.  
[90]  
[91]  
[92]  
Before addressing the merits of the appeal, I note the worker’s claim relates to potential  
exposure that took place throughout the 2017/2018 school year (September 2017 to May 2018).  
Speaking generally, I find the evidence supports that the circumstances from September 2017  
to mid-December 2017 were significantly different than those from mid-December 2017 to  
May 30, 2018.  
More specifically, I find that prior to mid-December 2017, some mechanical issues with the  
newly installed ventilation system and HVAC units had been identified and repaired.  
Additionally, although the employer had received some indoor air quality complaints from its  
staff (including the worker), no indoor air quality testing took place prior to mid-December 2017.  
In addition to this, all the welding equipment in the metal shop was fully operational and running.  
On the other hand, after mid-December 2017, no further mechanical malfunctions with the new  
ventilation system/HVAC units were identified, and the employer did not receive further  
complaints from its staff (other than from the worker) about the indoor air quality. Additionally,  
some of the welding equipment/processes in the metal shop were shut down, and various  
indoor air quality testing took place. I will come back to these points later. For now, it is sufficient  
to say that the different circumstances before and after mid-December 2017 requires  
consideration of the worker’s exposure in each time period separately.  
September 2017 to mid-December 2017  
[93]  
[94]  
The first question to consider is whether the worker suffered from an occupational disease,  
namely carbon monoxide poisoning. Policy item C4-25.10 acknowledges that 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 1, the symptoms of which may be similar  
to those caused by common complaints that produce fatigue, nausea, headache, and the like.  
In this case, I agree with the Board that the medical evidence does not establish a definitive  
diagnosis of carbon monoxide poisoning. In deciding this, I note the worker’s bloodwork in  
December 2017 revealed her carboxyhemoglobin level was 2.8. In that regard, I accept