This document summarizes a study that evaluated carbon monoxide (CO) and noise levels during an indoor monster truck show. CO and noise levels were continuously monitored during the 180-minute show. Average CO levels in the seating areas were 28ppm in the north section and 40ppm in the south, below health guidelines to limit COHb levels to 3%. Some attendees may have been overexposed to noise, with sound levels of 102.5dBA and 103.4dBA, depending on use of available hearing protection. Ventilation, vehicle restrictions, and warnings were implemented to control exposures. While this show did not significantly threaten health, continuous monitoring of CO is recommended for future indoor motorsport events due to unpredictable exposures

1. Evaluation of Carbon Monoxide and Noise during an
Indoor Monster Truck Show
By
James Broadhurst
Report of project carried out as a requirement of the M.Sc (applied) program in
Occupational Health Sciences
Department of Epidemiology, Biostatistics, and Occupational Health
McGill University

2. Executive Summary
Monster Truck shows are a popular recreational activity in North America. When these
shows are held in an enclosed arena, exhaust emissions generated by the show vehicles can result
in diminished air quality and create a health hazard for audience members. Carbon monoxide
(CO) is of particular concern because of its rapid generation and the sensitivity of some
subpopulations to exposure. The noise generated at recreational sports events is also known to be
substantial and represents a health hazard for audience members.
The purpose of this project was to perform a hygiene assessment of a Monster Truck
show held at the Colisée Pepsi in Quebec, Quebec in June 2015. The goal of the hygiene
assessment was to protect the health of audience members through the introduction of controls,
continuous monitoring of CO and noise levels, and interventions in the form of intermittent
breaks or show cancellation if necessary. Our results indicated that for the 180 minute duration
of the show, the audience was not overexposed to CO, with an average CO concentration in the
seating of 28ppm (north) and 40ppm (south). Some show attendees may have been overexposed
to noise with a LAeq for the show duration of 102.5dBA (north) and 103.4dBA (south), however,
this was dependent on the personal choice to wear the available hearing protection.
There were a number of controls implemented that contributed to the success of the
show, including but not limited to, natural ventilation, vehicle restrictions, and a warning
message at the start of the show. While this show did not significantly threaten spectator health,
due to the highly unpredictable nature of CO and noise exposure at indoor motorsports, this
cannot be assumed to be the case for all such shows. Therefore, continuous monitoring of CO
should be considered a necessity for any future indoor motorsport shows. Future investigations
may also consider a more complete characterization of the air contaminants present at indoor
Monster Truck shows, such as methanol, formaldehyde, PM2.5, and NO2.

3. Acknowledgements
The project herein was performed in collaboration with Contex Environment Inc., and
they provided all materials and equipment for data acquisition and analysis. I would like to thank
Simon Plouffe for providing technical assistance with the instrumentation used for sampling,
describing the sampling procedure, and subsequently performing the data analysis. I would also
like to thank my supervisor, Jean-Pierre Gauvin, for the initial development of this project as
well as for the guidance he provided in performing the sampling and writing the report.

4. Table of Contents
Introduction ...............................................................................................................................................1
Carbon Monoxide ...............................................................................................................................3
Exposure Limits..................................................................................................................................6
Noise........................................................................................................................................................7
Exposure Limits..................................................................................................................................9
Objectives..............................................................................................................................................9
Methods....................................................................................................................................................10
Results........................................................................................................................................................13
Carbon Monoxide .............................................................................................................................13
Noise......................................................................................................................................................14
Discussion.................................................................................................................................................14
Carbon Monoxide .............................................................................................................................14
Ventilation........................................................................................................................................17
Source Control................................................................................................................................18
Administrative controls.................................................................................................................19
Hygiene Assessment.....................................................................................................................21
Noise......................................................................................................................................................22
Controls.............................................................................................................................................25
Limitations ............................................................................................................................................27
Recommendations................................................................................................................................29
Conclusion...............................................................................................................................................31
References...............................................................................................................................................32
Appendix A – Pictures ..........................................................................................................................38
Appendix B – Data.................................................................................................................................41
Appendix C – Supplementary Materials.........................................................................................46
Appendix D – Sample Calculations..................................................................................................51

5. 1
Introduction
Monster Trucks have their origins in rural mud-bogging and truck-pulling in the United
States (US) (1). The first Monster Truck is believed to be the original Bigfoot, a 1974 F-250 four
wheel drive pickup truck, which was significantly modified by its inventor, Bob Chandler (2, 3).
The vehicle made its first paid appearance in 1979 and first stadium performance crushing cars
and pulling sleds in 1981 (4). The popularity of Monster Truck demonstrations grew rapidly after
this first stadium show, eventually leading to competitors, and the creation of a new industry (3).
In Canada and the US, Monster Truck shows are still a popular recreational pass-time and
popularity continues to grow internationally (1). There are a number of promoters and Monster
Trucks which tour North America each year, most of which are certified by the Monster Truck
Racing Association (MTRA) (4). These shows, while featuring Monster Trucks, often include a
myriad of other vehicles including dirt bikes, motorcycles, modified cars, mini-bikes, four(4)-
wheelers, BMX bicycles, and support vehicles (forklifts). The MTRA has rules to protect the
safety of fans, drivers, and support staff, although under some circumstances these shows can
still threaten the well-being of audience members.
Traditionally, audience safety has been of the utmost concern at Monster Truck shows.
Independent of the specific location or venue, there is always the risk of vehicle roll-overs, flying
debris, and detached wheels, which have injured and even killed audience members in the past
(5-8). However, when motorsports are specifically held at indoor arenas, the greatest risk to
audience members shifts from safety to health, particularly due to noise and poor air quality
exposure. An indoor arena refers to any building with spectator seating that has an entirely
enclosed and non-retractable roof. It represents a distinct situation from an outdoor arena or
venue because of the restricted interface with the outdoor environment. There are two lines of
evidence which suggest that audience health may be threatened at an indoor show. First, modern

6. 2
Monster Trucks are extremely large and powerful vehicles, typically boasting 1500 horsepower,
10,000lbs weight, engine volumes of 500-600 cubic inches (ci), characteristic 66 inch tires, and
racing alcohol fuel (Figure 1A) (9). Many of these parameters impact both exhaust emissions and
external noise generation (10, 11). Secondly, there is historical context suggesting poor air
quality control in enclosed arenas. In the past 50 years, there have been many documented cases
of acute CO poisoning in Canada and the US at ice skating arenas (12, 13). The cause of such
episodes has almost invariably been a combination of malfunctioning ice resurfacing equipment
and inadequate ventilation (12, 13). While cases of mass poisoning at ice arenas is most common
among active individuals, in extreme cases, a single polluting ice resurfacing machine has
resulted in the poisoning of players, referees, employees, and spectators (14). Ice arenas may also
be used as a venue for special events, like Monster Truck shows. Therefore, a history of poor air
quality in arenas related to vehicle operation and poor ventilation, combined with the number
and size of vehicles employed during a Monster Truck show, suggests air quality should be of
particular concern during such events.
From a public health perspective, Monster Truck shows are very similar to other popular
motorsports such as tractor-pulls, mud races, motocross shows, and demolition derbies.
However, after a thorough literature and internet search, no documented cases of adverse health
events among spectators was identified for any indoor motorsport show. Nevertheless, there have
been a number of published reports that have demonstrated that CO can reach extremely
dangerous levels at these demonstrations (15-19). In some cases peak concentrations of CO had
reached levels above the immediately dangerous to life and health (IDLH) limit of 1200ppm set
by the National Institute for Occupational Safety and Health (NIOSH) (16, 20). While there are a

7. 3
number of exhaust emission constituents from motor vehicles that impact air quality, the primary
focus here is CO, due to its rapid generation and acute health effects.
Carbon Monoxide
CO is known as the silent killer, since it is impossible to detect by an exposed person,
being a colorless, odorless, tasteless, and non-irritating gas (21). It is a product of incomplete
combustion of any fuel containing carbon atoms and thus is a ubiquitous toxicant encountered
environmentally, occupationally, residentially, and recreationally (22-24). It is this combination
of abundant but insidious exposure that results in unintentional, nonfire-related CO poisoning
being a leading cause of accidental poisoning in the US and Canada (22, 25, 26). A significant
acute exposure to CO can have serious short- and long- term health implications.
When exposed, CO is readily absorbed into the bloodstream via inhalation where it
competes with oxygen (O2) for binding to hemoglobin (Hb). Since CO has a binding affinity for
Hb that is 210-240 times greater than O2, even at low concentrations, CO will form a slowly
reversible carboxyhemoglobin (COHb) complex (27, 28). The presence of COHb in the blood
reduces O2 carrying capacity and thereby the availability of O2 to tissues, resulting in hypoxia
(24, 27, 28). Hypoxia is exacerbated by the presence of COHb because the dissociation curve for
the remaining oxyhemoglobin (HbO2) is shifted to the left, further inhibiting O2 delivery (27). In
response to tissue hypoxia, the body will attempt to compensate by increasing heart rate,
coronary blood flow, and ventilation rate. However, the ability to compensate for hypoxia is also
diminished by CO exposure. CO binds to myocardial myoglobin, which impairs O2 supply and
thus the energy supply of the heart muscle, resulting in myocardial depression, hypotension, and
arrhythmias (28, 29). Furthermore, as the ventilation rate increases, the %CO in the alveoli also
increases, resulting in greater absorption of CO into the blood and ultimately more pronounced
toxicity (12). Compensation mechanisms and toxicological outcomes may also be influenced by

8. 4
CO binding to cytochromes, which disrupts energy production in the mitochondria, causes
oxidative stress, and is responsible for cytotoxicity (24, 28).
CO is generated endogenously during natural hemoglobin degradation, and appears to
have a role as a neurotransmitter in the body (30). Therefore, it is normal for a non-smoking
population, which is not otherwise routinely exposed to CO, to have a baseline COHb level of up
to 1% (30). A number of factors can elevate an individuals’ COHb baseline above normal levels,
such as a hemolytic anemia, air pollution exposure, and smoking. Humans seem to be largely
asymptomatic up to 2.0-2.5% COHb (31). Exogenous exposure to CO, resulting in COHb
concentrations beyond this threshold may begin to cause health effects. There is a direct
relationship between the COHb blood concentration and the experienced symptoms (12). While
the effects of acute CO exposure are widespread in the body, the brain and heart are the most
susceptible due to their high blood flow and O2 demand (26). Health effects range from subtle
cardiovascular and neurobehavioural responses at low levels of exposure, to flu–type symptoms
at moderate exposures, and seizures, coma, and death in the most severe cases (Table 1C) (27).
Single severe, but non-fatal, exposure to CO has also been associated with delayed neurological
sequelae including mental disorientation, incontinence, gait disturbance, and mutism lasting for
more than a year and in some cases permanent neurological effects (31, 32).
There are a number of subpopulations of people which are at an elevated risk of adverse
health events when exposed to CO. The World Health Organization (WHO) has identified young
infants, elderly people, people with cardiovascular deficiencies, anemias or hemoglobin
abnormalities, chronic obstructive lung diseases, and pregnant women as particularly sensitive
subpopulations (31). Essentially, subpopulations which are most susceptible either have elevated
metabolic rates, which ultimately increases the rate of CO absorption, or they have a condition

9. 5
which renders them incapable to compensate for the added burden imposed by the presence of
COHb. Among these groups, people with coronary heart disease (CHD) are the most well
studied and are believed to be the most sensitive. Normally the presence of elevated COHb
causes coronary vessels to dilate in order to provide sufficient cellular oxygenation (31).
However, people with CHD have a limited ability to dilate coronary blood vessels and thus
exposure to low levels of CO may disrupt normal heart function (27, 31). Signs of myocardial
ischemia, angina, and the number and complexity of cardiac arrhythmias have been documented
at COHb concentrations between 2.4% to 6.0% for this group (33-39). Thus, while cardiac
arrhythmias and myocardial infarction are ultimately the major cause of death due to CO
poisoning in all populations, these outcomes may occur faster and at lower exposures for people
with CHD (27). Another particularly important subpopulation are pregnant women because their
elevated O2 demand increases CO uptake. Significant exposures can negatively impact both the
mother, by an increase in complication rate, and the fetus, by causing fetal death, developmental
disorders and cerebral anoxic lesions (31, 40).
For Monster Truck shows it is important to consider that the exposed audience represents
the general public. Due to the abundance of high risk subgroups among the general population,
many spectators could be at risk of CO related toxicity. In 2007, 4.8% of Canadians, aged 12 or
over, had self-reported to be living with diagnosed heart disease (41). Similarly, approximately
4.0% of Canadians, aged 35 or older, self-reported to have been living with diagnosed chronic
obstructive pulmonary disorder (42). Anemias are also not uncommon, approximately 3% of
Canadians, aged 3 to 79, have some form of anemia (43). Of course the attendance of elderly
people, young children, and pregnant women (possibly unknowingly) is also to be expected. It is
clear that a substantial portion of the audience likely belongs to at least one high risk subgroup.

10. 6
Exposure Limits
In order to protect the well-being of audience members, there is a need to establish
reasonable exposure limits. In Quebec, the eight hour time weighted average (TWA8hr)
occupational exposure limit is 35ppm, and the ceiling limit is 200ppm, which is identical to the
NIOSH recommendations and are lower than the Occupational Safety and Health Administration
(OSHA) limits (20, 44, 45). These limits are intended to prevent acute toxicity and keep the
COHb concentration to a maximum of 5%, whereas the American Conference of Governmental
Industrial Hygienists (ACGIH) suggests a more protective 25ppm TWA8hr occupational limit
intended to limit COHb to 3.5% and maintain exercise capacity (15, 46). Occupational limits are
based on the average healthy male worker and are probably not stringent enough for a mixed
group attending a recreational show.
The US Environmental Protection Agency (EPA), Environment Canada, WHO, and
Health Canada Residential Air Quality Guideline all have established CO exposure limits for the
general public which are intended to protect the most vulnerable people by limiting COHb to
2.0-3.0% (Table 2C) (31, 47-49). Therefore, the recommended 3.0% COHb WHO limit should
be sufficient for voluntary spectators at the Monster Truck show. The Cobourn-Foster-Kane
(CFK) model is used to describe the positive linear relationship between environmental
concentrations of CO and alveolar absorption, and thus COHb concentration (31, 50). While it
considers a number of parameters, most are taken as constants, and thereby the amount of COHb
formed during exposure to CO depends principally on exposure duration, CO concentration, and
alveolar ventilation (28, 31, 50). For this show, the goal was to limit COHb to 3.0%, which
according to the CFK model, for a sedentary population (assumes a constant alveolar ventilation
of 6L/min), exposed for an estimated 180 minutes, is approximately 50ppm (16).

11. 7
Noise
Noise is a health risk. Noise exposure can cause sleep disturbance, stress, and annoyance
which has been suggested to contribute to the development of some illnesses, such as
cardiovascular disease (51). However, noise induced hearing loss (NIHL), which is sensorineural
hearing loss caused by noise exposure, is the only proven irreversible disease caused by noise
(52). Hearing loss ultimately impacts life quality by disrupting speech recognition and other
routine activities. The effects can be so profound that it has been linked to escalated cognitive
decline in older adults, and learning and social development impairment in children (53, 54). The
Global Burden of Disease estimates that 1.23 billion people are affected by hearing loss and rates
hearing loss as a top ten contributor to global years lived with a disability (55). In 2013,
approximately 4.6 million Canadians aged 20 to 79 (19%), had significant hearing loss affecting
their ability to hear normal speech in at least one ear (56). While there are a number of causes
and types of hearing loss, noise exposure is the leading cause of preventable hearing loss (51).
NIHL can be the result of long-term, repeated exposure to noise, or a single exposure to
an extremely intense impulse sound. High level, short duration exposures, exceeding 140dB can
cause structural damage to the middle and inner ear called acoustical trauma (57). However, this
type of damage is relatively rare, usually NIHL is insidious, and is the result of repeated
exposure to more moderate noise levels (54). This type of hearing loss can be either mechanical,
whereby hair cells lose their rigidity over time, or metabolic, in which the elevated O2 demand
associated with excessive noise exposure causes free radical accumulation and eventually
apoptosis of hair cells (58). However, the effects of noise on the auditory system can be either
temporary or permanent (52). Noise exposure of sufficient duration and intensity can lead to a
temporary threshold shift (TTS), which is reversible hearing loss, or temporary tinnitus, a
reversible ringing in the ears in the absence of an external sound source (52). Without complete

12. 8
recovery from the TTS or temporary tinnitus these conditions may result in permanent inner ear
damage, and with repeated events a permanent threshold shift (PTS) or chronic tinnitus may
develop (52, 54). Hair cells are finite but redundant, therefore, many damaging noise exposures
are required before PTS is detectable. While TTS and temporary tinnitus do not indicate the
magnitude of inner ear damage, they are regarded as a precursor to permanent effects (54, 59).
Significant noise exposure may be encountered in every aspect of day to day life, but it is
recreational exposures which are most controllable on an individual basis. However, while
occupational noise exposure has been generally decreasing since the 1980’s, the number of
young people with relevant degrees of recreational noise exposure has tripled in that time (60).
The commonality of recreational noise exposures has resulted in an increasing prevalence of
hearing loss among adolescents in the US, from 3.5% to 5.3% between 1994 and 2006 (61).
Health Canada also predicts that the prevalence of hearing loss among older adults (65 or older),
the age group for which hearing loss is most common, will double in the next 20 years largely
because of increasing recreational noise exposure among young people (56). The most important
recreational exposure is the use of personal listening devices, however; gunfire, nightclubs,
concerts, sporting events, and motorsports are also major sources of recreational noise (62, 63).
It is important to note that the effects of noise exposure on hearing loss are cumulative.
Therefore, all activities which result in a significant noise exposure can contribute to long term
hearing loss. This is particularly important in young people, since significant exposures
occurring at younger ages increases the lifetime risk of hearing loss (60). Also, working adults
who are routinely exposed to occupational noise, are at a greater risk. Exposure to noise during
leisure activities, such as Monster Truck shows, interrupts the needed recovery time after
occupational noise events, and thereby increases the likelihood of inner ear damage (63). There

13. 9
are many factors which elevate the risk- and severity of NIHL including age, genetics, gender,
race, smoking, diabetes, cardiovascular disease, diet, fitness, ototoxic drug use, and exposure to
certain solvents (64). In practice the breadth and complexity of these factors makes it impossible
to identify the most susceptible groups. Nevertheless, all spectators at a Monster Truck show
could be exposed to dangerous noise levels, thereby contributing to eventual hearing loss.
Exposure Limits
Safe exposure to sound depends on two interrelated factors; duration and intensity. The
equal-energy principal states that equal amounts of sound energy will produce equal amounts of
hearing impairment, irregardless of how the sound energy is distributed in time (54). Thus,
louder sounds for a short duration causes the same damage as quieter sounds for a longer period
of time. This concept is the basis for occupational exposure limits, but is applicable to all noise
exposures, and according to the WHO can be extrapolated for recreational activities (65).
ACGIH suggests an equivalent A-weighted sound level for eight hours (LAeq8hrs) of 85dBA with
a 3dB exchange rate (46). However, since the show was held in Quebec, the relevant limit is
LAeq8hrs of 90dBA with 5dB exchange rate, which is equivalent to 98.4dBA for 150 minutes (44).
From this, it is possible to calculate the daily dose for the recreational activity (Appendix D). The
ceiling limit for noise exposure is a 140dB for continuous, intermittent, or impact noise (46, 54).
Objectives
The purpose of this project was to perform a hygiene assessment of a Monster Truck
show in which CO and noise was continuously monitored with the primary goal of protecting the
health of all audience members. There were three main objectives in order to obtain this goal;
1. To provide the promoter and venue staff with information and recommendations for
controls of air quality and noise prior to and during the show,

14. 10
2. To ensure compliance with acceptable levels of audience exposure to CO (WHO
recommended limits) and noise (Quebec occupational limits) throughout the duration of
the show, and;
3. To intervene, in the form of additional breaks and even cancellation, in the event that
unsafe levels of CO are reached.
Achieving these three objectives should significantly reduce the likelihood of any adverse health
outcomes among audience members during and after the show.
Methods
Promoter X held the single day Monster Truck show at the Colisée Pepsi in Quebec,
Quebec in June 2015. The seating capacity of the arena is 15,800 and there was approximately
10,000 people in attendance for the show. The stadium has two separate ventilation systems, a 12
fan general (dilution) ventilation system with air supply and return, as well as four large ceiling
fans (spillway evacuators) located at the roof of the building. The complete ventilation system
has an exhaust capacity of 240,000ft3
/min. Since the arena has a total volume of 3,126,000ft3
, the
mechanical ventilation system is capable of providing one air exchange every 13 minutes when
operating at maximum capacity (66).
The entire show was monitored by myself and Simon Plouffe (Technical Advisor) as
representatives for Contex Environment Inc. We arrived at the Coliseé Pepsi at 16h30, three
hours prior to start time, in order to introduce ourselves and discuss controls with relevant
parties. This included meeting with the promoters management staff, Chief Operating Officer of
the stadium, and on-site paramedics. Communication throughout the show between myself and
Simon Plouffe was performed by “text’ via personal cell phones.
To evaluate air quality, we continuously monitored CO in the arena for the duration of
the show, including the VIP pit party (19h30-22h30). Prior to commencement of the show
(19h30), but after audience arrival (18h30), periodic measurements were taken at floor level near

15. 11
the vehicles, to determine initial levels of CO. For the purpose of continuous monitoring of CO,
two GasBadge Pro personal samplers were used, one worn by myself and one worn by Simon
Plouffe. The instruments were attached to a satchel strap at chest level for both wearers.
GasBadge Pro detectors are fitted with electrochemical CO sensors for single gas detection. The
smallest unit of measure for this device is one ppm. The accuracy is ± 5% of the value sampled
for concentrations between 100 to 1500ppm. For concentrations of less than 100ppm the
uncertainly is two units (2ppm). For validation of the GasBadge Pro CO levels, periodic
instantaneous measurements were also taken by Simon Plouffe using a Bachararch Snifit model
50, the accuracy of which is 1ppm. All measuring equipment was calibrated as per
manufacturer’s instructions. The GasBadge Pro is a direct reading instrument capable of data-
logging and continuous TWA calculations. We automatically recorded CO levels using a one
minute integration time for the entire show. In addition, we manually recorded instantaneous CO
concentrations at approximately two minute intervals for the same period (Tables 1B, 2B). The
overall goal was to keep the average CO concentration for the expected 180 minute show
duration (TWA3hr) below 50ppm. Considering we could not predict the exposure for the entire
show, we established an action level, based on 15-minute TWAs. The WHO recommends a short
term exposure limit (STEL), which is a 15-minute TWA, for CO exposure of 87ppm assuming
light duty work (Table 2C) (31). Repeated GasBadge Pro STEL “readings” above 87ppm was
considered actionable. Additionally, an instantaneous concentration of CO which approached the
ceiling limit of 200ppm was also considered actionable. In the situation where acceptable CO
limits were likely to be exceeded, we would immediately notify the promoter and modify the
show by introducing a break. Subsequently, Simon Plouffe and I would be responsible for
controlling the conditions in the arena.

16. 12
To evaluate noise exposure, we continuously monitored noise levels by personal
dosimetry for the entire duration of the show, excluding the VIP pit party (19h30-22h00). The
VIP pit party was not included in the noise assessment because it was apparent that noise levels
were dramatically reduced during this period. Two CEL-460 model, CEL Instruments Ltd noise
dosimeters were employed for the noise assessment, one worn by myself and one worn by Simon
Plouffe. The noise dosimeters were attached to each wearer’s belt and a small remote
microphone was fastened to the shirt collar of each wearer, approximately six inches from the
ear. A one minute integration time for data logging was used for both instruments. At the end of
the show, the dosimeters were paused and removed to stop data collection. Ultimately, the
equivalent sound level was determined for a 150 minute period, LAeq2.5hrs (19h30- 20h00) and the
daily dose was calculated (Appendix D) (44, 46). For the purpose of real-time monitoring of
noise, and validation of the noise dosimeters, noise was also monitored by sound level meters
(SLMs). I operated the Casella CEL Ltd, model CEL-62X, which has a resolution of 0.1dB.
Simon Plouffe operated a CEL instruments Ltd. Model CEL-328 SLM, which also has a
resolution of 0.1dB (data not available). Noise levels measured by SLM was performed
randomly throughout the show, with a sampling time of approximately two minutes for each
measurement (Table 3B). All instruments employed A-frequency weighting and slow response
time. All instruments were calibrated as per manufacturers’ instructions.
The show started at 19h30, and we initiated the sampling of CO and noise concurrently.
All measurements were made by myself and Simon Plouffe by dividing the stadium into two
regions, north and south, respectively (Figure 1C). Throughout the duration of the show, all
seating levels and gate entry points were sampled. This entailed ‘roaming’ to various locations of
stadium seating throughout the show. The movement between seating areas was generally

17. 13
performed inside the arena, although occasionally it was necessary to move to different locations
through the corridors. During the intermission, most of the sampling time was spent at the floor
level near the vehicles, and to a lesser extent in the corridor. At the end of the show (22h00), the
noise sampling was stopped but we continued to monitor the ground floor near the vehicles for
CO during the VIP pit party (Figure 2A). No vehicles were being operated but we noted that the
CO concentration was still elevated during this period. CO data acquisition stopped once nearly
all the audience members had left the arena (22h30). In this way, we tried to mimic the exposure
of the highest exposed audience members throughout the entire show. Before leaving the venue,
we spoke to the on-site paramedics to determine the number of cases of audience members
reporting illness. The CO monitors and noise dosimeters were transported to the Contex
Environment Inc. offices in Montreal, where the data was downloaded to a personal computer
and analyzed using the manufacturers’ software.
Results
After meeting with the stadium Chief Operating Officer and the promoters’ management
staff, all the recommended controls for noise and CO were put into place for the show. The
implemented controls included natural and mechanical ventilation, vehicle number restrictions,
idling and warm-up restrictions, restrictive seating, strategic event scheduling, and a warning
message. Noise controls were limited to a warning message and the availability of ear plugs. No
additional breaks or interventions were needed. According to the on-site paramedics, by the
completion of the show, there had been no cases of reported illness.
Carbon Monoxide
The concentration of CO in the arena was zero during spectator entry (18h30) and the
start of the event (19h30). In the northern seating region, the TWA3hrs was 28ppm for a mobile
attendee (Figure 1B). This was confirmed by treating the manually recorded instantaneous

18. 14
concentrations of CO as grab samples. The average of the manually recorded data over the 180
minute show (which includes the 30 minute VIP pit party) was 30ppm. A 2ppm difference is
within the normal error range for this instrument for concentrations below 100ppm. The peak
instantaneous CO concentration of 124ppm in the northern seating of the arena occurred during
the Monster Truck side by side event. This was recorded in the lower level seating, directly at the
north end of the arena (Table 1B). There were two notable maximum STEL “readings” during
the show, 69ppm just after intermission and 71ppm just after the finale, which coincides with
Monster Truck events. In the southern region seating, the TWA3hrs was 40ppm for a mobile
attendee. The CO exposure recorded by the GasBadge Pro was validated with a second CO
monitor (Bachararch Snifit model 50). The two CO monitors were in good agreement (Table
2B). The peak instantaneous CO concentration of 154ppm in the southern seating of the arena
occurred during the Monster Truck wheelie event. This was recorded in the lower level seating,
directly at the south end of the arena (Table 2B). The maximum STEL “reading” during the
show of 86ppm occurred just after the start of intermission in the south seating (Figure 1B).
Noise
Results of the noise assessment indicate that noise exposure was similar in the north and
south seating regions of the arena during the course of the show. The LAeq2.5hrs (19h30-22h00)
was 102.5dBA and 103.4dBA in the northern and southern seating regions, respectively (Figure
2B). The most intense periods of noise exposure were associated with the presence of Monster
Trucks. During the final Monster Truck wheelie event a peak sound level of 137.0dBA was
recorded in the northern seating area of the arena by SLM (Table 3B).
Discussion
Carbon Monoxide
Spectators at the Monster Truck show were not over-exposed to CO, so it was unlikely
anyone developed more than 3% COHb in their bloodstream. Audience members were exposed

19. 15
to approximately 28ppm (north) and 40ppm (south) of CO for a maximum of 180 minutes, which
does not exceed the 50ppm limit set for this timeframe. Similarly, the 200ppm ceiling limit was
never breached. The action level, based on the WHO recommended STEL of 87ppm (assuming
light activity) for the general public, was also never exceeded at any point during the show, and
thus no interventions were required. It is worth noting that most audience members were only
exposed for approximately 150 minutes, since only VIP ticket holders were able to attend the 30
minute VIP pit party at the end of the show. Decreasing the duration of CO exposure would
allow for even higher exposure limits for these audience members while still limiting COHb to
3%. We can conclude that CO was not a significant threat to audience health during this show, as
was confirmed by the lack of any reported cases of acute illness.
This show included a number of events that involved motor vehicles, yet it was clear that
the highest CO concentrations in the arena were reached in association with the presence of
Monster Trucks (Figure 1B). This finding is consistent with previous reports regarding air
quality during Monster Truck shows (15, 16). Exhaust emission rate is impacted by external
vehicle factors such as weight, engine size, driving behaviour, and fuel type (10). Interestingly,
while most vehicles use high octane gasoline, Monster Trucks typically run on methanol, which
actually produces less CO exhaust (g/mile) than gasoline (67). However, the Monster Trucks
have a significantly larger engine size and weight than all the other show vehicles. For instance,
while the typical Monster Truck has an engine displacement of 8,200cc and weighs 10,000 lbs,
motocross dirt-bikes and 4-wheelers have engine displacements of 80cc to 250cc and weigh up
to 500lbs (9, 17). This largely explains the CO concentration peaks associated with Monster
Trucks, and indicates Monster Trucks as the major source of CO for the show.

20. 16
We found that there was a large difference in the TWA3hrs for CO between the north and
south seating in the arena. Large variations in air contaminant concentration by seating section is
not uncommon for indoor motorsports (15-17, 19). The variation could be in part due to poor air
distribution inherent in the mechanical ventilation system. However, since we also relied on
natural ventilation, factors such as wind speed, temperature gradients, and the location and size
of openings also affects the air movement inside the arena (68). One published hygiene
assessment of CO during a motocross show in Quebec in 1994 found the west seating to be more
exposed than the east seating, and they attributed the difference to gusty winds coming from the
west on that particular day (17). While wind conditions may have contributed to lower CO levels
in the northern section of the arena during this show, there is another contributing factor. The
physical arrangement of the arena for Monster Truck events has the main “action” of crushing
cars occurring in the south end (Figure 3A). Since Monster Trucks are also the heaviest polluters,
it indicates that the majority of CO is also emitted in the south end of the arena. Combined with
the unpredictable air distribution of natural ventilation, it is unsurprising that the south seating
had higher CO exposures.
Overall, average CO exposures among spectators for this show are comparable with
previous reports for indoor motorsports. At previous shows, average CO concentration in
audience seating over the entire show ranged between 15ppm and 140ppm (Table 3C) (15-19).
However, most of these shows employed interventions in the form of additional breaks to lower
the average CO exposure. This can be gleaned from the peak CO levels reported for these shows,
which often breached the NIOSH 200ppm ceiling limit (15-19). One show had even reported
peak concentrations as high as 1,645ppm, which is substantially greater than the IDLH limit
(16). Conversely, this event required no additional interruptions to maintain acceptable CO

21. 17
levels. The relatively low spectator exposure to CO during this show can be largely attributed to
the implementation of a number of effective controls.
Ventilation
Adequate ventilation is paramount with regard to maintaining acceptable air quality at
indoor Monster Truck shows. Since capturing the contaminant at the source is not feasible,
dilution ventilation is the only option for an arena. The mechanical ventilation system should be
operating at maximum capacity, with 100% fresh air intake, for the show duration. Failing to do
so can be disastrous (16). Unfortunately, most arenas were simply not designed to handle the
massive emissions produced by Monster Trucks (16, 17). As such, natural ventilation is also
necessary, and typically involves pre-emptively opening all crowd- and elephant gates, as was
the case here (Figure 4A). On the day of this Monster Truck show gusty high speed winds were a
factor (up to 43 km/h), helping to increase the arena air exchange rate, and thereby was likely a
major contributor to the relatively low average CO concentrations (16, 68). However, it is
important to recognize that there are a number of limitations to natural ventilation. The
effectiveness of natural ventilation will vary with different arenas and environmental conditions,
and thus cannot be assumed to be sufficient for all such shows (68). As described previously, the
air distribution inside the arena can also be very unpredictable. The air distribution problem can
be exacerbated during winter months. The extreme temperature difference between the cold
incoming fresh air and hot vehicle exhaust air, combined with the sunken nature of stadium
seating, tends to cause pollutants to be trapped in the upper levels of the arena. This has led to
CO over-exposure for some audience members at a past event (16). Furthermore, natural
ventilation is problematic during the winter months because paying audience members are not
likely to tolerate the cold air drafts, nor will the venue want to absorb additional heating costs
created by opening external gates and doors. With such uncertainty in regards to the adequacy of

22. 18
the ventilation for any given indoor motorsport show, there is a clear need to utilize additional
control methods.
Source Control
Monster Trucks are the primary CO emission source at a Monster Truck show. Any
restrictions on these vehicles that minimize CO generation can be viewed as a source control.
Ultimately, the goal of source control is to minimize the total CO output for the show and avoid
spikes in concentration. The maximum generation rate of CO can be limited by controlling the
number of vehicles operating at once; in this case, a maximum of two Monster Trucks were
allowed to perform simultaneously. The number of vehicles running simultaneously had been
shown to be one of the most important determinants of peak CO concentration reached during a
motocross show (17). This is self-evident as fewer vehicles means less total fuel consumption,
and thus less exhaust emissions. The generation rate was also minimized by forbidding any
vehicle idling, that is, all vehicles were turned off when not specifically performing.
Unfortunately motorsports do not lend themselves to more substantial source control.
This is evident in the MTRA rule book which includes a number of safety requirements for
drivers and spectators, but has no restrictions on emissions (4). There is also no specific legal
obligation to restrict emissions from Monster Trucks as they are specialized vehicles, not “road”
driven, and therefore not governed by the On-Road Vehicle and Engine Emissions Regulation
(SOR/2003-2) (69). Most importantly, it is the nature of motorsports to maximize vehicle
performance, which often comes at the expense of greater exhaust emissions (70). Nonetheless,
there are ways in which CO generation could be reduced from these vehicles for future shows.
The primary constituents in vehicle exhaust are CO, NOx, H2O, CO2, and hydrocarbons
(70). The relative abundance of these species in exhaust emissions is strongly affected by the air-
to-fuel ratio (AFR) during the combustion stroke (70). The AFR can be adjusted for carbureted

23. 19
or direct fuel injection engines to a leaner mix (higher AFR), which will significantly reduce CO
formation (70). However, AFR tuning requires a trade-off. A leaner AFR increases engine
temperature which favors NOx generation, but more importantly, reduces power output (70).
Nonetheless adjusting the AFR has been used in practice at a previous Monster Truck show to
help control CO levels. A specialized mechanic was employed to tune the Monster Trucks before
the show and was able to reduce the CO emissions in three of six trucks by 1.45% to 6% (16).
Tuning is only one aspect of exhaust emission control. An additional possibility to reduce total
emissions is to install a catalytic converter, which can be up to 80% efficient at removing all
toxicants (67, 70). However, catalytic converters have a small negative impact on power output
due to the back pressure created in the exhaust system (67). This is less desirable for
performance vehicles, and probably explains why Monster Trucks are not currently equipped
with these devices (16).
Traditionally, when there is a risk of significant CO exposure, the primary control is
source elimination. This usually means swapping fossil fuel powered equipment for an electrical
version, as is the case with ice resurfacing machines at skating rinks (12, 13). For Monster Truck
shows, this type of control would not seem to be a realistic option, given the preference to
maximize vehicle performance. Astonishingly however, exhaust-free Monster Trucks do exist. In
2012, the Bigfoot team developed the first full-size Monster Truck that is entirely battery
operated (3). Even with this development, the combustion engine Monster Truck may never be
replaced, but this type of technology does exist and should be encouraged.
Administrative controls
It is clear that when Monster Trucks are performing, the CO in the arena spikes. This
suggests contaminants are accumulating because the generation rate has exceeded the ventilation
rate (68). As discussed above, we have limited control over both of these parameters. Therefore,

24. 20
to minimize the intensity and duration of the CO concentration spikes, we need to allow the
ventilation systems to recover. This could be accomplished by adding additional breaks or
extending time between events, but this is not ideal. Instead, we rely on strategic event-
scheduling. Essentially, heavy polluting events are staggered between lower polluting events.
This allows a recovery period for the ventilation systems after a CO concentration spike, without
extending total show duration (Figure 1B, note scheduling).
Not every audience member is equally exposed to CO during Monster Truck events. This
is the case in part because of the problems with air distribution, but also because of variation in
distance between spectators and the source. This effect has been noted during previous air
quality assessments of indoor motorsport shows which have reported that lower level seating is
subject to higher CO exposure than upper level seating (15, 18). At this show, the institution of
restrictive seating, whereby seating closest to the arena floor was blocked to spectators,
increased the distance between the audience and source (Figure 5A). Increasing the distance
from the source enhances air-mixing, helping to reduce CO exposure for the closest spectators.
It is very important to control the length of time spectators are exposed to CO. We
minimized the duration of audience exposure to CO by restricting vehicle warm-ups prior to
audience arrival. In doing so, the CO concentration in the arena was zero between audience
arrival and the start of the show. Past indoor motorsport shows have neglected this control. For
these shows, average CO concentration during audience arrival varied between 13 and 77.5ppm
(18, 19). High initial concentrations of CO increases the likelihood of exceeding STEL and
ceiling limits during events, and thus the need for additional breaks in the shows (17-19).
Furthermore, CO in the arena during audience arrival increases the duration for which spectators
are exposed to CO, and thereby increase the likelihood of over-exposure by excessive COHb

25. 21
formation. CO in the arena during audience arrival also adds to the complexity of assessing
overall audience exposure. Not all audience members arrive at the same time, and will vary in
where they spend their time inside the arena leading up to the show. A greater heterogeneity in
individual exposure weakens the approximation of the average audience member by monitoring
only a couple of people. It is simpler and safer to ensure a zero concentration until the show start.
Hygiene Assessment
The fundamental difficulty with the protection of audience health at indoor motorsport
shows is the unpredictability of CO exposure. The two most important determinants of CO
concentration in the arena, the generation rate of CO and the air exchange rate of the arena
(assuming natural ventilation) are both unknowns. Furthermore, the individual effectiveness of
controls are not clear and could vary by show. For example, a very similar Monster Truck show
held in the same venue in 2014 had resulted in considerably higher audience exposures to CO
even with identical controls, and ultimately professional intervention in the form of additional
breaks was required (Table 3C) (71). It is simply not possible to know with any certainty, even
with pre-emptively employed controls, that spectators will be safe from air contaminants during
the show. Thus the key aspect of the hygiene assessment is the real-time monitoring of CO for
audience exposure levels. The monitoring is not intended for simple observation but rather as a
tool for indicating audience safety. If threatening levels of CO are approached during the show it
would trigger additional control measures such as breaks, cancellation, or other measures to be
implemented immediately. In this way, the hygiene assessment protects the health of spectators
by proactively addressing air quality with professional skill.
Hygiene assessments like the one described here are unfortunately not representative of
most indoor motorsport shows. In most cases, hygiene assessments as a control are not
implemented and shows are performed without any knowledge of CO in the arena. One problem

26. 22
is that motorsport promoters’ tour rather than routinely perform in a single venue. This means
that the legal obligation to implement the hygiene assessment as a control will vary by
jurisdiction. Some provinces, Ontario, British Columbia, Manitoba, Alberta, Nova Scotia, and
Prince Edward Island have an Occupiers Liability Act. The act essentially states that the owner
of a premise must take reasonable steps to protect the safety of persons on those premises,
whether the hazard is created by the conditions of the premise or activities performed there (72).
While it may be argued that CO exposure is an inherent risk of such events, the act imposes
indirect legal responsibility to control such hazards at these types of shows. An additional
challenge with regard to regulating the air quality of indoor motorsport shows concerns the lack
of specific exposure limits. In Canada, a number of provinces produce air quality guidelines for
arenas, but these are specific to ice arenas, and are not practical for motorsport shows (Table 2C)
(73-75). In the US, there are currently three states (Minnesota, Massachusetts, and Rhode Island)
which have legal requirements for periodic monitoring and exposure limits for air quality in
arenas, but similarly suffer from limited applicability to motorsports (13).
There is insufficient legislative pressure, clarity, and consistency for indoor motorsport
promoters to regularly employ hygiene assessments as a control for air quality at shows. One
exception is Cincinnati in which the city’s safety department requires a public permit for indoor
events where internal combustion engines are used. They set specific exposure limits and require
continuous monitoring during the show (15). This type of regulation should be adopted at the
provincial level to force proper control of air quality for spectators at indoor motorsport shows.
Noise
Based on the occupational exposure limit in Quebec, 98.4dBA for 150 minutes, all
audience members that did not wear hearing protection were over-exposed to noise. Over the
duration of the show, the northern and southern seating regions were exposed to a LAeq2.5hrs of

27. 23
102.5dBA and 103.4dBA, respectively. This represents a daily dose of 177% (north) and 200%
(south) based on the Quebec occupational limits. For comparison, the more conservative ACGIH
recommended exposure limits yield doses of 1,782% (north) and 2,195% (south) (Appendix D).
The SLM measurements made in the northern seating recorded a peak sound level of 137dBA
during the Monster Truck wheelie event, which is approaching the threshold for acoustic trauma
(140dB) (Table 3B). Generally, periods of highest noise intensity were associated with the
presence of Monster Trucks. This is unsurprising given that vehicle exterior noise depends on,
among other factors, engine size, engine load, and the use and effectiveness of a muffler (11, 76).
Monster Trucks are not only the largest vehicles, they are also the only ones not equipped with a
muffler (15). The small difference in noise exposure between seating areas may have been
affected by the physical arrangement of the arena during Monster Truck runs. However, subtle
sampling differences between seating areas, such as time in the corridor and lower level seating,
affects the distance from the primary noise source and thus could have also played a role.
To date, there is only one Monster Truck show for which noise exposure has been
documented in published literature. It reported a range in LAeq of 96.4-99.5dBA, depending on
event day and seating location for spectators (Table 4C) (15). It is not immediately clear why the
Monster Truck show here was considerably louder. It is possible that there were differences in
the sound power from the Monster Trucks or other show vehicles. Event scheduling could play a
role, since the average noise exposure would also be impacted by the number and length of
breaks. A more likely cause is the inherent differences in acoustical properties between arenas,
which are affected by seating geometry, materials, and reverberant contributions (77, 78). Crowd
noise is another major source of variation. The number and excitement level of audience
members will also have a considerable impact. Overall, the audience noise exposure at this show

28. 24
is similar to other activities with comparable noise sources, such as motorsports (F1 racing and
NASCAR), hockey, soccer, basketball, and football events (Table 4C) (76, 78-83).
One of the most well-studied recreational noise exposures is music concerts. Based on a
meta-analysis of these events, the average noise exposure for a concert has been reported to be
103.4dBA (63). Ignoring spectral differences, the total noise energy of this Monster Truck show
is very similar to attending a typical rock concert. Generally, studies have shown that attendance
to a music concert causes moderate temporary tinnitus or TTS for most people, with full
recovery taking hours to days (63). Therefore, it is likely that most unprotected audience
members at this Monster Truck show will also have experienced at least temporary hearing
effects. While experiencing a TTS does not necessarily indicate the magnitude or occurrence of
any permanent inner ear damage, it is an indicator of long-term hearing loss (54). People who are
also significantly exposed elsewhere, occupationally primarily, are unlikely to have sufficient
recovery time, and are at particularly high risk of some permanent hearing damage (54).
Unlike many other recreational events with high noise exposure, indoor motorsports
have an additional element which increases the risk of hearing damage, the simultaneous
exposure to CO. Acute CO poisoning has been shown to cause hearing loss independent of noise
exposure (84). Chronic low level exposure to CO has also been associated with a greater degree
of hearing loss in working adults and the elderly (85, 86). Furthermore, there is a known additive
effect of smoking and occupational noise exposure on the risk of hearing loss, which further
implies a relationship between CO, noise, and hearing loss in humans (87). The relationship
between CO and noise exposure has been best studied in animal models, where acute CO
exposure has been shown to potentiate high frequency threshold shifts induced by noise (88-90).
Since hearing loss is at least partly metabolic in nature, the impact of CO is clear. The hypoxic

29. 25
conditions created by CO absorption increases the likelihood of metabolic stress of hair cells
during noise exposure and hinders recovery between exposures. It is not yet clear how impactful
low CO exposure is on TTS or PTS in humans. It has been suggested that CO concentrations
above 22ppm, based on extrapolation from animal studies, would be above the ‘no adverse effect
level’ in humans (90). Thus the CO exposure at this show was high enough to possibly have had
a potentiation effect on noise exposure. This relationship is likely to be a concern for any indoor
motorsport show in the future as well.
Controls
Given the intensity of noise exposure at Monster Truck shows, there is a definite need for
controls. In an arena, there is both direct (source) and reverberant contributions to the noise
experienced by the audience. Sound absorbing materials could be added to the building surfaces
to minimize reverberant noise, however, this option is impractical given the irregularity of these
types of shows at a given venue. There are two major noise sources for a motorsport show, the
crowd and the motor vehicles. At a NCAA basketball game, with a comparable crowd size to this
show, the average noise level for spectators was 98dBA (78). Similarly, at this show, for a two
minute sampling during the BMX (non-motorized) event there was a LAeq of 97.4dBA (Table
3B). Taken together, the crowd appears to generate a considerable portion of noise at indoor
motorsports. Given that crowd noise cannot be controlled, the ability to reduce noise at the
source is limited. However, it is possible to attenuate motor vehicle noise. The addition of a
muffler into the exhaust system of a vehicle could achieve a 30-35dB insertion loss (11).
Unfortunately, Monster Trucks are not currently equipped with mufflers, and are unlikely to be
in the future. While adding a muffler does negatively impact power, the primary limitation to its
implementation is the audience itself. In motorsports, like most recreational noise exposures, the

30. 26
noise is actually a desired component of the activity. Dampening engine sound on performance
vehicles has typically been unpopular among fans (76).
In practice, noise control for recreational activities relies on hearing protection and
informing spectators. For this show, we informed the audience of high noise levels, the possible
damaging effects, and recommended the use of hearing protection by warning message at the
start of the show. Ear plugs were made available for purchase at various locations throughout the
arena. The noise reduction rating (NRR) for standard foam disposable ear plugs from a reputable
supplier can be as high as 33dB (91). Under real world conditions, the actual attenuation is likely
closer to 50% of the manufacturers NRR, due to variation in fit and imperfect insertion (92-95).
Nonetheless, if hearing protection was worn for the entire show, those audience members would
have been effectively protected from noise. However, it was apparent from personal observation
that very few people actually wore hearing protection. This is a common problem for noisy
recreational activities. Cursory causes for low compliance with wearing hearing protection
during recreational activities is a lack of comfort, undesirable image, and loss of enjoyment (54,
96). Fundamentally, the lack of use of hearing protection points to a lack of awareness of the risk
associated with recreational noise exposure. Thus, protection from noise exposure during
recreational activities needs to rely on changing individual risk perception by improving how
information is conveyed and perceived. Generally, recreational noise exposure is a public health
issue, and information needs to be presented by schools, medical professionals, and other public
forums (54, 64). For indoor motorsports specifically, more could be done on-sight, by having
pamphlets available and large warning signs inside the corridors of the arena, in addition to the
warning announcement at the start of the show.

31. 27
Limitations
Ultimately the goal of monitoring hazards is to protect the health of all audience
members. Unfortunately, it is simply not practical to individually assess every person’s exposure
and risk factors. Alternatively, we must rely on a number of approximations, the quality of which
can impact the protection afforded to some audience members. Here, we used two roaming show
attendees to represent two similar exposure groups (SEG), constituting north and south seating.
This approximation suffers in two ways. Roaming likely does not accurately represent the
average exposure of the relatively stationary audience members. Additionally, the very large
SEGs of approximately 5,000 people probably poorly represent some individuals, especially for
CO which tends to have a variable distribution within the arena. Thus the inclusion of area or
stationary personal sampling at more locations would improve the confidence of the assessment.
Another important assumption is that the CFK model accurately predicts COHb concentration
for all audience members. While there are a number of parameters considered in this model, the
one most subject to error is the alveolar ventilation. We assume a sedentary rate (6L/min) for
everyone, but considerable deviations could be caused by physical conditioning, behavioural
differences, and even consumption of beverages, such as coffee and beer. Alcohol, a depressant,
reduces metabolic rate and blood flow, thus slowing the delivery of CO to tissues and providing
protection from hypoxia (97, 98). Reason dictates that stimulants, such as caffeine, which elevate
the metabolic rate would have the opposite effect, potentially enhancing the rate of CO uptake
and toxicity. When considering the health of spectators, some individuals will be affected by
specific behavioural choices, which is not accounted for in our assessment.
Traditionally, CO is the primary focus for diminishing air quality due to exhaust
emissions indoors. However there are a number of abundant constituents in exhaust emissions
which could pose a health risk, specifically, NO2, volatile organic compounds (VOCs), and

32. 28
particulate matter (70). NO2 is a strong pulmonary irritant at even very low concentrations and
significant levels have been detected at a previous Monster Truck show (16). Furthermore, a
number of VOCs have also been qualitatively detected at another Monster Truck show (15).
Among these, methanol and formaldehyde are the most important, since they are major exhaust
constituents from methanol fuels (70). While both can cause acute health effects, it is not yet
clear whether either are likely to be present at dangerous concentrations. Particulate matter with
an aerodynamic diameter of 2.5µm or less (PM2.5) may be the most concerning because of a
probable additive interaction with CO (99). Elevated exposure to PM2.5 poses an acute threat of
cardiovascular stress, non-fatal events, and mortality, particularly among susceptible groups,
which includes people with pre-existing CHD or structural heart disease (99). While there are no
published investigations on audience exposure to PM2.5 at indoor motorsports, significant
exposures have been documented for indoor Go-Karting (100). There is a need for better
characterization of air contaminants at indoor motorsports to protect audience health.
The presence of VOCs in the arena could interfere with the accuracy of CO monitoring.
The instruments used in this assessment rely on an electrochemical sensor to detect CO. Because
electrochemical detectors measure differences in chemical potential, they are subject to cross-
sensitivities from other substances which have a redox potential that is equal or lesser than the
target gas (21). Among the numerous VOCs capable of cross-sensitivity with electrochemical
CO detectors, methanol and ethanol generate particularly strong positive responses, even at
concentrations below the ACGIH TWA8hr (101). Since the magnitude of cross-sensitivity is
dependent on the specific device and concentration of the interfering species, it is not possible to
quantitatively assess the potential impact, if any, for this assessment. Given that both ethanol and
methanol have been qualitatively detected at a previous Monster Truck show though does raise

33. 29
concerns (15). A photo-acoustic type device for CO measurement has been used in the past to
circumvent this problem (16). It is worth noting that the reported interferences always caused an
over-estimation of CO concentration, and thus should not affect the safety of the audience.
Based on the adherence to strict exposure limits for CO exposure and the lack of reported
illness to on-site paramedics, the health of all spectators seems to have been protected. There is,
however, the possibility of unreported illness or symptoms during and after the show. It is
important to recognize that even in the absence of acute illness, attendance to this show and other
similar recreational activities, may affect the well-being of attendees. More specifically, the
average person will likely increase their risk of injury, particularly in the form of driving
accidents after the show. CO exposure resulting in COHb concentrations as low as 2% has been
suggested to affect safe driving behaviours because of the impact on coordination, judgement,
psychomotor tasks, reaction time, and visual acuity (102, 103). Furthermore, a 3.4% increase in
COHb has been demonstrated to be sufficient to cause impaired driving (104). Significant noise
exposure is also associated with an increased risk of driving accidents. A number of studies have
indicated that loss of hearing acuity, permanent or temporary, increases the risk of driving
accidents by impacting driving skill, behaviour, and alertness (105-107). The combination of
noise and CO exposure probably has a small but significant risk on safety even with low
exposures. Given that many people drive to the arena, these events are never risk-free, even for
the average healthy person.
Recommendations
There was a number of controls implemented for this Monster Truck show which helped
to minimize CO and noise exposure among spectators. These basic controls, including
mechanical and natural ventilation, vehicle and seating restrictions, strategic event scheduling,
and a warning message should be considered mandatory for all indoor motorsports. However,

34. 30
there are some other additional controls which are recommended for future events. 1) Source
controls should be encouraged. It is possible to reduce CO emissions by installation of a
catalytic converter or AFR tuning on Monster Trucks. Similarly, installation of a muffler would
reduce noise generation. While this may be hard to sell to promoters, perhaps incentives could be
provided for those promoters willing to make these adjustments, such as subsidized arena rental
costs. 2) Inclusion of a warning message prior to ticket purchase. Improvement in risk awareness
for both noise and CO needs to occur on many fronts. While bolstering awareness on-site with
signs and pamphlets, although still recommended, may have a limited impact. It renders little
time for people to receive and comprehend information, and more importantly limits the
opportunity for behavioural change. Whereas a warning message at ticket purchase, which is
usually done online well in advance of the show, allows for detailed information content and
provides ample opportunity for people to make an informed decision about their health risks. 3)
Hearing protection included with the price of admission. Ultimately, reducing the health risk
associated with recreational noise exposure depends on wearing hearing protection. Previous
research has demonstrated that providing ear plugs free to concert attendees would increase the
number of people that wore them (96). Thus, including ear plugs in the price of admission and
distributing them at entry could help to reduce the number of people over-exposed to noise. 4)
Design consideration for new arenas. Most enclosed arenas and stadiums have inadequate
ventilation to safely host a motorsport show, and in most cases retrofitting the ventilation system
would be cost prohibitive (18). New arenas should consider the ventilation demands of indoor
motorsports in the design phase if they want to be a host venue. A good example is the
Prudential Center built in New Jersey in 2007. The arena was designed to be able to constantly

35. 31
monitor CO at many areas throughout the arena simultaneously, and can automatically adjust
fresh air intake to ensure safe concentrations of CO for players and spectators (108).
Conclusion
For this Monster Truck show the health of the entire audience was reasonably protected,
and thereby, the primary goal of the assessment was achieved. While the implementation of basic
controls presumably contributed to this success, there are some additional measures that should
be considered for future shows. Source controls for the reduction of Monster Truck emissions by
use of low polluting fuels, AFR tuning, and catalytic converters are of utmost importance.
However, even with the institution of all these aforementioned controls, indoor arenas are not
well suited to host motorsports. Noise and air contaminants are simply too unpredictable in this
environment. Therefore, above all, a professional hygiene assessment, including the real-time
continuous monitoring of hazards, is a necessity for the protection of all audience members.
This report describes the health risks associated with a Monster Truck show held at an
indoor arena. However, many of these shows are held at outdoor arenas or fairgrounds. For these
situations the threat to audience well-being is different. It reasons that poor air quality is less
likely to threaten audience health because of improved natural ventilation. There is however a
lack of published literature on this topic and it is possible that some audience members could be
affected by poor air quality. Outdoor shows may also include additional hazards such as liberal
use of pyrotechnics, which were not employed for this show, but may need to be considered at
future events. Noise and safety hazards are also still an issue at outdoor arenas. Therefore,
outdoor shows cannot necessarily be assumed to be safe for all spectators.
Overall, there is a clear need for formal air quality and noise standards for motorsports.
Future investigations could consider a more complete characterization of the hazards present
from exhaust emissions, including PM2.5, NO2, methanol, and formaldehyde.

36. 32
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Appendix A – Pictures
Figure 1A: Example of a modern Monster Truck, which was one of the six monster trucks that performed for the
show held at the Colisée Pepsi. Overkill Evolution has 1500hp, 572 ci engine volume, 66” tires, and runs on racing
alcohol (pure methanol) (9).

43. 39
Figure 2A: Demonstration of the VIP pit party. Audience members with VIP tickets have access to Monster Trucks
during intermission and before and after the show. VIP ticket holders represent the highest CO exposure group
among audience members due to the greater duration and closer distance to the primary source.
Figure 3A: Demonstration of the arena organization for Monster Trucks events. The main operation of Monster
Trucks, crushing cars, is performed primarily in the southern end of the arena, whereas the monster trucks in the
northern section are NOT running or idling.

44. 40
Figure 4A: Demonstration of natural ventilation by the opening of the west crowd gate (left), south crowd gate
(bottom right), and northern elephant gate (upper right).
Figure 5A: Demonstration of Restrictive Seating. Notice the lowest seating level of the Arena is physically blocked
from occupants by a large overlaid red tarp. In addition, yellow warning tape blocks entry to these seating areas.

45. 41
Appendix B – Data
Table 1B: Northern section CO instantaneous concentrations recorded manually at approximately two minute
intervals throughout the duration of the Monster Truck show. Measurements from GasBadge Pro.
Time CO (ppm) Section Level Area
18:26:00 0 114 Lower North-East
19:32:00 0 116 Lower North-East
19:34:00 0 116 Lower North-East
19:36:00 0 120 Lower North
19:38:00 0 120 Lower North
19:41:00 0 218 Upper North-East
19:43:00 0 218 Upper North-East
19:45:00 0 220 Upper North
19:47:00 0 220 Upper North
19:49:00 0 221 Upper North
19:51:00 4 221 Upper North
19:53:00 0 219 Upper North
19:55:00 7 219 Upper North
19:59:00 7 217 Upper North-West
20:01:00 6 217 Upper North-West
20:03:00 5 213 Upper North-West
20:05:00 4 213 Upper North-West
20:07:00 4 119 Lower North
20:09:00 9 119 Lower North
20:11:00 11 119 Lower North
20:13:00 5 113 Lower North-West
20:15:00 6 113 Lower North-West
20:17:00 8 111 Lower North-West
20:19:00 6 111 Lower North-West
20:21:00 0 217 Upper North-West
20:24:00 4 217 Upper North-West
20:26:00 4 217 Upper North-West
20:28:00 7 219 Upper North
20:31:00 12 219 Upper North
20:32:00 29 219 Upper North
20:33:00 71 219 Upper North
20:34:00 27 221 Upper North
20:36:00 25 221 Upper North
20:38:00 21 221 Upper North
20:40:00 32 220 Upper North
20:42:00 33 220 Upper North
20:44:00 41 216 Upper North-East
20:46:00 38 216 Upper North-East
20:48:00 33 120 Lower North
20:50:00 33 120 Lower North
20:52:00 34 120 Lower North
20:53:00 48 121 Lower North
20:54:00 92 121 Lower North
20:55:00 124 121 Lower North
20:57:00 64 121 Lower North

46. 42
20:59:00 53 121 Lower North
21:00:00 59 121 Lower North
21:02:00 62 121 Lower North
21:09:00 11 NA NA corridor
21:14:00 53 NA NA Floor Level
21:18:00 16 NA NA Promoter Area
21:24:00 46 NA NA Basement ( vehicle entrance)
21:30:00 29 118 Lower North-East
21:32:00 28 118 Lower North-East
21:34:00 36 118 Lower North-East
21:36:00 31 118 Lower North-East
21:37:00 38 120 Lower North
21:38:00 38 120 Lower North
21:40:00 47 120 Lower North
21:42:00 45 216 Upper North-East
21:44:00 59 218 Upper North-East
21:46:00 54 214 Upper North-East
21:48:00 57 214 Upper North-East
21:49:00 62 214 Upper North-East
21:50:00 50 212 Upper North-East
21:52:00 71 212 Upper North-East
21:54:00 65 212 Upper North-East
21:56:00 71 120 Lower North
21:57:00 78 121 Lower North
21:58:00 80 121 Lower North
21:59:00 86 121 Lower North
22:06:00 37 NA NA Floor Level
22:10:00 28 NA NA Floor Level
22:21:00 19 NA NA Floor Level
22:27:00 14 NA NA Floor Level
Average 30
Table 2B: Southern section CO instantaneous concentrations recorded manually at approximately two minute
intervals throughout the duration of the Monster Truck show. *refers to measurements taken using the GasBadge
Pro. **refers to measurements taken using Bachararch Snifit model 50.
Time Conc.(ppm), GBP* Conc. (ppm), Snifit** Level Area
18:23:00 0 0 Lower West
18:36:00 0 0 Lower West
19:30:00 0 0 Lower West
19:32:00 0 0 Lower West
19:36:00 0 1 NA NA
19:40:00 0 0 Lower South-West
19:46:00 38 26 Lower East
19:50:00 22 22 Lower East
19:52:00 17 14 Lower South-West
19:55:00 10 10 Lower South-West
20:00:00 22 15 Lower South
20:02:00 0 4 Lower South-West
20:04:00 9 7 Lower South-West

47. 43
20:06:00 16 12 Lower South
20:08:00 25 18 Lower South
20:10:00 14 13 Lower South
20:14:00 31 17 Lower South
20:18:00 15 10 Lower South-East
20:20:00 10 8 Lower South
20:22:00 82 76 Lower South
20:24:00 40 53 Upper South
20:26:00 78 63 Upper South
20:28:00 154 120 Lower South
20:30:00 92 82 Lower South-West
20:32:00 38 27 Lower West
20:32:00 35 25 Lower West
20:36:00 81 67 Lower South-East
20:38:00 71 58 Lower South-East
20:40:00 67 61 Lower South-East
20:42:00 74 66 Lower South-East
20:45:00 53 47 Upper South-East
20:48:00 148 121 Lower South
20:50:00 121 120 Upper South
20:52:00 120 116 Upper South
20:54:00 88 87 Upper South
20:54:00 103 103 Lower South
21:00:00 53 50 NA NA
21:30:00 35 28 NA NA
21:34:00 32 26 Lower South
21:38:00 62 62 Upper South
21:40:00 48 50 Lower South
21:42:00 49 44 Lower South
21:42:00 88 83 Lower South
21:43:00 61 49 Lower South-East
21:45:00 62 58 Lower South-East
21:46:00 63 61 Upper South-East
21:48:00 89 91 NA NA
21:49:00 92 92 Lower South-East
21:50:00 77 72 Lower East
21:50:00 86 85 Lower East
21:51:00 66 65 Lower South-East
21:52:00 88 100 Lower South
21:56:00 104 103 NA NA

48. 44
Figure 1B: Average CO concentration over Monster Truck show duration from personal monitoring of mobile
attendees representing north (upper panel) and south (lower panel) arena seating. *TWA is based on 240 minute
exposure in this figure, however, the reported average is over 180 minute and thus represents the TWA3hrs for
audience members in that section.

49. 45
Figure 2B: Noise levels (LAeq) during the Monster Truck show assessed by personal dosimetry of two mobile show
attendees. Noise was monitored for the duration of the show, but not during the VIP pit party. Note that there was an
error with the internal timer for the noise dosimeter used in the northern section. The results for the northern section
are slightly shifted in time, but in actuality, represent the same real time period as the southern section.
Table 3B: Noise level recorded by sound level meter in the northern region seating during the Monster Truck show.
Sampling was performed randomly throughout the show, for approximately 2 minute sampling periods. * refers to
the nearest gate location.
Time (start) Duration (min) Place(gate)* Event Leq(A) Lpeak
19:38:00 2:00 120 Introductions 94.8 114.6
19:55:00 2:00 219 BMX 97.4 119.0
20:13:00 2:00 113 FMX 96.2 119.6
20:38:00 2:00 221 Quad racing 98.2 121.9
21:02:00 2:00 121 Intermission 88.2 114.7
21:34:00 2:10 118 Monster Truck, Wheelie 110.6 137.0
21:49:00 2:15 214 Modified Cars 99.7 126.7
22:00:00 2:05 121 Closing Statements 92.5 115.9

50. 46
Appendix C – Supplementary Materials
Table 1C: Symptoms associated with the absorption of COHb, modified from (12).
COHb Concentration Effects
0.0% - 2.5% No Apparent Symptoms (endogenous)
2.5% - 5.0% Altered Vision
Arterial Dilation
Reduced attention span particularly while driving an
automobile
Myocardial ischemia in people with CHD
5.0% - 10% Altered brightness sensitivity
Unusual increase in strained breathlessness
Distortion of fine manual dexterity
Reduced exercise capacity
20% - 30% Headaches
Start of nausea
Coordination problems
30% - 40% Severe headaches
Dizziness
Nausea and vomiting
Judgement alteration
40% - 50% Aggravation of the same symptoms
Confusion
50% - 60% Loss of Consciousness
Convulsions
> 60% Comma
Respiratory Arrest
Death

51. 47
Table 2C: Summary of the exposure limits to Carbon Monoxide in North America.
Time Weighted Average (ppm) Max. COHb
conc. %8-hour 1-hour 15 min Ceiling
Occupational
Occupational Regulation
(Quebec) (44)
35 - - 200 5
American Conference of
Governmental Industrial
Hygienists (ACGIH) (46)
25 - - - 3.5
Occupational safety and
Health Administration
(OSHA) (45)
50 - - 200 (5min) -
National Institute of
Occupational Safety and
Health (NIOSH) (20)
35 - - 200
(1200 IDLH)
5
Ambient Air
US Environmental
Protection Agency (EPA)-
NAAQS (47)
9 35 - - 3
Environment Canada
(NAAQO): maximum
acceptable level (48)
13 30 - - 3
Environment Canada
(NAAQO): maximum
desirable level (48)
5 13 - - 2
General Public and Residential
World Health Organization
(31)
9 26 87 - 3
Health Canada Residential
Air Quality Guideline (49)
10 (24 hour) 25 - - 2
Guidelines for Arenas
Air quality guideline for
Arenas (Quebec) (73)
- - - 20 -
Air Quality guideline for
Arenas (Ontario) (74)
5* - - - -
Air Quality guideline for
Arenas (Manitoba) (75)
25 12.5 - - -
Public Assembly for Arenas
(Cincinnati, Ohio) (15)
- - 35 200** -
*refers specifically to the offices inside the arena, not the arena floor or the seating areas. ** Ceiling is breached if
two consecutive samples (15 minute interval) is above 200ppm

52. 48
Figure 1C: Colisée Pepsi (Quebec, Quebec) stadium floor plan. Maximum seating capacity is 15,800. For the
purpose of sampling for Noise and CO, the arena was divided into north and south sections. Northern seating was
sampled by myself, and south seating was sampled by Simon Plouffe (109).