HETA 96-0052-2583

National Western Stock Show

Denver, Colorado

Charles McCammon

Kenneth Martinez

This Health Hazard Evaluation (HHE) report and any recommendations made herein are for the specific facility evaluated and may not be universally

applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved.

Additional HHE reports are available at http://www.cdc.gov/niosh/hhe/reports

This Health Hazard Evaluation (HHE) report and any recommendations made herein are for the specific facility evaluated and may not be universally

applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved.

Additional HHE reports are available at http://www.cdc.gov/niosh/hhe/reports

This Health Hazard Evaluation (HHE) report and any recommendations made herein are for the specific facility evaluated and may not be universally

applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved.

applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved.

Additional HHE reports are available at http://www.cdc.gov/niosh/hhe/reports
ii

PREFACE

The Hazard Evaluations and Technical Assistance Branch of NIOSH conducts field investigations of

possible health hazards in the workplace. These investigations are conducted under the authority of

Section 20(a)(6) of the Occupational Safety and Health Act of 1970, 29 U.S.C. 669(a)(6) which

authorizes the Secretary of Health and Human Services, following a written request from any employer

or authorized representative of employees, to determine whether any substance normally found in the

place of employment has potentially toxic effects in such concentrations as used or found.

The Hazard Evaluations and Technical Assistance Branch also provides, upon request, technical and

consultative assistance to Federal, State, and local agencies; labor; industry; and other groups or

individuals to control occupational health hazards and to prevent related trauma and disease. Mention of

company names or products does not constitute endorsement by the National Institute for Occupational

Safety and Health.

ACKNOWLEDGMENTS AND AVAILABILITY OF REPORT

This report was prepared by Charles McCammon of the NIOSH Denver Field Office and Kenneth

Martinez, of the Hazard Evaluations and Technical Assistance Branch, Division of Surveillance, Hazard

Evaluations and Field Studies (DSHEFS). Field assistance was provided by Diane Bullock, Bambi

Jones, Jane McCammon, Lyle McKenzie, Michelle Heinzman, Tom Stauch, Ken Douglas, and John

Martyny. Desktop publishing by Bambi Jones.

Copies of this report have been sent to employee and management representatives at NWSS and the

OSHA Regional Office. This report is not copyrighted and may be freely reproduced. Single copies of

this report will be available for a period of three years from the date of this report. To expedite your

request, include a self-addressed mailing label along with your written request to:

NIOSH Publications Office

4676 Columbia Parkway

Cincinnati, Ohio 45226

800-356-4674

After this time, copies may be purchased from the National Technical Information Service (NTIS) at

5825 Port Royal Road, Springfield, Virginia 22161. Information regarding the NTIS stock number may

be obtained from the NIOSH Publications Office at the Cincinnati address.

For the purpose of informing affected employees, copies of this report shall be

posted by the employer in a prominent place accessible to the employees for a

period of 30 calendar days.
iii

Health Hazard Evaluation Report 96-0056-2583

National Western Stock Show

Denver, Colorado

March 1996

Charles McCammon

Kenneth Martinez

SUMMARY

In response to a request from the City & County of Denver, NIOSH conducted a health hazard evaluation at the

National Western Stock Show (NWSS) held January 6-21, 1996 in Denver, Colorado. The request was

prompted by reports of health problems repeatedly experienced by City & County employees after working at

the NWSS. These health problems included a variety of allergic and flu or cold-like symptoms, such as runny

nose, congestion of the nose, throat and lungs; fever, and eye irritation. These symptoms had become so

commonplace that workers and visitors to the NWSS had collectively termed them the “Stock Show Crud”. 

The request specified assistance in monitoring exposures to carbon monoxide, carbon dioxide (as an indicator

of ventilation efficiency), total and respirable dust, free silica, and bioaerosols.

The National Western Stock Show is one of the top five stock shows and rodeos in the country. 

Approximately 500,000 visitors attend the NWSS each year. The show is held in a large multi-building

complex near downtown Denver. Twenty-two rodeos occur during the two-week period of the NWSS. The

stock show also includes daily stock competition for numerous breeds of cows, sheep, and hogs; competition

classes for horses; and a wide variety of other activities including sheep shearing contests, wagon-drawn

vehicle competitions, a petting zoo, and numerous vendor booths.

Monitoring was conducted on six different days during the two-week duration of the NWSS. On four of these

days, fixed location monitoring was conducted in the three large arenas (the Coliseum, Stadium, and Event

Center) and at different sites around the NWSS complex. Fixed location monitoring was conducted for carbon

monoxide (CO), carbon dioxide (CO2), temperature, humidity, total and respirable dust, respirable silica,

particle counts over several size distributions, ergosterol, spore counts, and endotoxins. Portable monitors were

used to sample for CO and CO2 throughout the complex. One personal sample was collected for CO using a

personal data logger.

Levels of CO, total and respirable dust, and respirable silica were all well below established evaluation criteria. 

Particle counts were significantly greater than those commonly found in office buildings, but less than those

found in many industrial settings. Spore counts, ergosterol and endotoxin levels were all significantly elevated

over background levels. Spore concentrations throughout the first floor of the Hall of Education building were

1 to 11⁄2 orders of magnitude greater (ranging as high as 1,430,000 spores per cubic meter of air [spores/m3

] in

Expo Hall 1) than background concentrations (geometric mean of 30,000 spores/m3

). This difference indicates

a significant increase in the exposure potential in areas that house animal populations.
iv

Ergosterol (an indicator for fungi) concentrations in the Hall of Education were an order of magnitude greater

(ranging up to 258 nanograms per cubic meter of air [ng/m3

] in Stadium Hall 1) than background

concentrations (geometric mean of 7 ng/m3

). This correlates with the spore sampling results, although larger

differences were observed with the spore data. This larger disparity between the high concentration areas and

background may be due to the increased sensitivity of the sampling and analytical method for fungal spores. 

Endotoxin concentrations in these same areas were also an order of magnitude greater (ranging up to 97

endotoxin units per cubic meter of air [EU/m3

] in Stadium Hall 1) than background concentrations (geometric

mean of 3 EU/m3

). However, all of the endotoxin samples were below the criteria suggested by Rylander of

200 EU/m3

 for an 8-hour TWA. 

CO2 levels throughout the Hall of Education Complex (including the Expo Hall and Beef Palace) ranged from 

625 ppm up to 4450 ppm. Levels were consistently above 1000 ppm (a criteria sometimes used to indicate

ventilation efficiency) and averaged closer to 2000 ppm. The highest levels (4200-4450 ppm) were measured

on a Saturday in the center of the Hall of Education building, second floor, near the vendor’s exhibits. The

floors were often so crowded it was difficult to move, particularly on weekends. Another area where high

levels of CO2 were consistently observed was in the Beef Palace Auction Arena. During an auction,

concentrations of CO2 averaged between 2500 to 3500 ppm. CO2 levels in the Coliseum during the rodeos

averaged between 1145 to 1490 ppm with peaks up to 2000 ppm. Levels in the Event Center averaged

between 860 and 1700 ppm with most levels remaining below 1000 ppm. Average daily CO2 levels in the

Stadium were below 1000 ppm every day with only brief excursions above 1000 ppm. 

Additional ventilation is recommended to dilute the levels of CO2 and airborne biological material in the Hall

of Education complex and the promenade area in the Coliseum. Additional work practice recommendations to

help reduce exposures to airborne biological material are included in the Recommendation Section of this

report.

High levels of carbon dioxide and elevated levels of airborne biological material (as measured by spore

concentrations, ergosterol and endotoxin levels) were observed throughout the National Western Stock Show

Complex. It is difficult to assess the health hazard associated with the airborne biological material since there

are no established evaluation criteria for these compounds. However, the observed levels (for spore and

ergosterol concentrations) are consistent with those reported in the literature that are associated with specific

adverse health outcomes. Increased ventilation is recommended to reduce carbon dioxide and airborne

biological material. Other recommendations are included to help further reduce airborne biological material. 

Keywords: SIC 7999 (Amusement and Recreation Services, Not Elsewhere Classified), stock show, carbon

dioxide, carbon monoxide, total dust, respirable dust, silica, ergosterol, endotoxin, and spores 
TABLE OF CONTENTS

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii

Acknowledgments and Availability of Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii

Introduction ......................................................................... 2

Background ......................................................................... 2

Methods ........................................................................... 2

Evaluation Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Page 2 Health Hazard Evaluation Report No. 96-0052-2583

INTRODUCTION

On November 22, 1995 the National Institute for Occupational Safety and Health (NIOSH) received a letter

from the City and County of Denver’s Occupational Health/ Indoor Air Specialist requesting NIOSH’s

assistance in determining worker and spectator exposures during the National Western Stock Show held in

Denver, Colorado January 6-21, 1996. The exposures of concern were carbon monoxide (CO), carbon dioxide

(CO2) as an indicator of ventilation efficiency, total and respirable dust, free silica, and bioaerosols.

BACKGROUND

The National Western Stock Show (NWSS) is one of the top five stock shows and rodeos in the country. 

Approximately 500,000 visitors attend the two-week long NWSS each year. A general layout of the NWSS

grounds is shown in Figure 1. Twenty-two rodeos occur in the Denver Coliseum during the two-week period. 

Rodeo and associated stock are housed in the Horse Barn area west of the Coliseum. The stock show also

includes daily stock competition for numerous breeds of cows, sheep, and hogs. Most of the halter shows for

the cows are held in the Stadium while the sheep and hog classes are held in the Stadium Hall. Animals are

housed and groomed in stalls located on the ground floor of the Hall of Education (HOE), north of the Stadium. 

 Once the animal competitions are over, auctions are held to sell the stock. Some of the cattle auctions are held

in the Beef Palace auction area, located on the first floor of the HOE on the Northwestern corner. The

remaining auctions are held in a specially curtained off area on the western edge of the Stadium. Sheep and

hog auctions are generally held in the Stadium Hall, at the western edge of the HOE. 

The second floor of the HOE contains a wide variety of vendors selling products related to stock show animals

(e.g., farm equipment, veterinary products, cowboy hats, clothing, food, etc.). The small top floor of the HOE

contains a petting zoo, various small animals such as chickens, rabbits, and guinea pigs, and more vendors. 

The various horse shows, both halter and performance, occur in the Events Center. Horses used for these

events are stabled in the Event Center Horse Barn with an overflow area on the first floor, in the eastern part of

the HOE. During each day of the NWSS, a variety of events occur in each of the locations described. The

three main arenas of concern in the request were the Coliseum, Stadium, and Event Center. The Event Center

was constructed one year ago, while the Coliseum and Stadium were built over 40 years ago. Dirt used in these

arenas is stored in a parking lot west of the Coliseum and reused each year. The dirt, consisting mostly of sand,

is spread throughout the arenas prior to the NWSS; a few inches of new sand are added on the top each year. 

No attempt is made to remove or sterilize the animal feces that are deposited in the soil during the stock show.

Over the years, many of the Denver employees who work at the NWSS complained about feeling ill at the end

of the show. This illness, referred to by the workers as the “Stock Show Crud”, includes a variety of allergic

and flu-or cold-like symptoms, such as runny nose, congestion of the nose, throat and lungs, fever, and eye

irritation. During the 1995 NWSS, City and County of Denver employees conducted limited monitoring for

CO, CO2, and particulates. Based on this limited monitoring and the recurrence each year of the Stock Show

Crud, the city requested that NIOSH conduct more extensive monitoring to determine what may be causing

these symptoms. 
Health Hazard Evaluation Report No. 96-0052-2583 Page 3

METHODS

Carbon Monoxide

Carbon monoxide (CO) was monitored with Biosystems, Inc. Toxilog personal CO monitors equipped with

electrochemical sensors. These units were set to record CO levels every 10 seconds and store the results in a

data logger. At the end of the day, the data were downloaded to a computer and the results printed. The units

were calibrated before the survey and periodically during the two-week NWSS run. Each unit was zeroed on

outside air daily.

Carbon Dioxide

Carbon dioxide (CO2), CO (for one of the two units), temperature and relative humidity were monitored with

Metrosonics, Inc. Model AQ501 IAQ Monitors. These units were set in three main event centers (Coliseum,

Stadium, and Event Center), to continuously monitor during different events. The data were stored in an

internal data logger and later downloaded to a computer and printed. The units were calibrated prior to use and

the CO2 levels were checked against outside levels before use each day.

CO2 levels were monitored throughout the NWSS complex with portable Gas Tech, Inc. Model RI-411A CO2

Monitors. These units utilize infrared detectors for CO2. The units were calibrated daily to 350 parts per

million (ppm) of CO2 using outside air.

Particulates

Two different real-time monitors were used to sample for airborne particulates. The first was the Grimm

Model 1105 Dust Monitor (Labortechnik GmbH & CoKG, Ainring, Germany). The Grimm Dust Monitor is a

light scattering aerosol spectrometer designed for real-time particulate measurement with particle size

discrimination. Eight channels collect count information for particle sizes of 0.75, 1, 2, 3.5, 5, 7.5, 10, and 15

micrometers (:m). Data were collected during four separate rodeo shows to monitor the dust generated by

distinct rodeo events. The monitor was mounted on the railing next to the arena floor at an approximate height

of five feet. For each rodeo show, data was integrated for 1 minute (min) and stored sequentially on the Grimm

data card over the entire show time period. The collected particle count and size information was downloaded

to a laptop computer following the completion of the show. Start and stop times for significant rodeo events

were recorded during each sample collection period.

The second particle monitor used was the MET One Laser Particle Counter. The Met One Particle counter

stores the data in internal data loggers and may also be connected to printers to provide 2.5-minute averages of

the particle counts at different particle size distributions. Two different Met One units were used; one provided

particle counts at cut points of 0.3 :m and 5.0 :m. The other unit gave cut points of 0.5, 1.0, 2.0, 5.0, and 10.0

:m. These cut points provided counts of particles that were in the air with sizes in the range of 0.5-1.0 :m, 1.0-

2.0 :m, etc.

Respirable Dust and Crystalline Silica

Air samples for respirable dust and crystalline silica were collected at 1.7 liters per minute (Lpm) on preweighed PVC membrane filters. Prior to collection onto the filters, 10-mm nylon cyclones were used to

remove all airborne dust except the respirable fraction. Gilian Model HFS 113D personal sampling pumps

were used to collect the samples. Respirable dust levels were quantified by weighing the filters after sampling

to determine the amount of airborne dust that was in the respirable range. These same filters were then

analyzed for quartz and cristobalite (crystalline silica) content using X-ray diffraction according to NIOSH

Analytical Method #7500.1
Page 4 Health Hazard Evaluation Report No. 96-0052-2583

Microbiologic Aerosols

To determine area concentrations of airborne fungi and Gram-negative bacteria at various Coliseum locations,

air was drawn through filters, via flexible Tygon® tubing, with Gilian® Model HFS 513A high flow personal

sampling pumps. Two distinct methods of sampling and analysis were used for the collection of fungal

particles. In the first method, airborne fungal spores were collected on a 37-millimeter (mm) mixed cellulose

ester (MCE) filter at a calibrated flow rate of 2 Lpm with subsequent optical microscopic analysis. Each filter

sample was analyzed according to a modification of NIOSH Method 7400.1

 One quarter of each filter sample

was cleared with acetone vapor and mounted in a phloxine-alcohol-glycerin mounting medium. (Phloxine is a

biological dye that stains fungal spores pink.) The prepared slide was allowed to sit over night or was heated

gently to enhance staining before reading. Slide samples were scanned (200 fields per sample) at 400x

magnification using bright field or phased contrast illumination. Only particles greater than 2 :m in diameter

were considered as possible fungal spores. In the second method, samples for ergosterol were collected

through a 25-mm, 0.2-:m polytetrafluoroethylene (PTFE) filter at a calibrated flow rate of 1.5 Lpm. 

(Ergosterol is a component of fungal membranes and has been used as an indicator of biomass.2,3,4) The

recovery of ergosterol from each filter sample was facilitated with methylene chloride. Filter extracts were

analyzed by high performance liquid chromatography with an ultraviolet detector set at 282 mm. In an

analytical column of Adsorbosphere C18 (Alltech 28015) with octadecyl silane (C18) chemically bonded to 3

:m silica particles, ergosterol eluted at 3.3 minutes using a flow rate of 1 milliliter per minute (ml/min).

Samples for endotoxin (a cell wall constituent of Gram-negative bacteria) were collected on a 37-mm polyvinyl

chloride (PVC) filter at a calibrated flow rate of 2 liters per minute (Lpm). Each filter sample was analyzed

gravimetrically (NIOSH Method 05001

) and subsequently placed into 50 ml conical centrifuge tubes. Ten

milliliters (ml) of sterile, pyrogen-free water (LAL Reagent Water, BioWhittaker Inc., Walkerville MD) was

added to each tube. The filter samples were gently rocked at room temperature for approximately 60 minutes. 

Each supernate was then decanted in a 15 ml centrifuge tube and centrifuged for 10 min at 2200 revolutions per

minute (rpm) at 4/C. From each tube, 3 ml of the supernatant fluid was recovered, place in a sterile vial, and

stored at -85/C until analyzed. The samples were assayed for endotoxin content using the Kinetic-QCL Assay

Kit (BioWhittaker, Walkerville, MD) according to the manufacturer’s recommended procedure.

EVALUATION CRITERIA

As a guide to the evaluation of the hazards posed by workplace exposures, NIOSH field staff employ

environmental evaluation criteria for the assessment of a number of chemical and physical agents. These

criteria are intended to suggest levels of exposure to which most workers may be exposed up to 10 hours per

day, 40 hours per week for a working lifetime without experiencing adverse health effects. It is, however,

important to note that not all workers will be protected from adverse health effects even though their exposures

are maintained below these levels. A small percentage may experience adverse health effects because of

individual susceptibility, a pre-existing medical condition, and/or a hypersensitivity (allergy). In addition, some

hazardous substances may act in combination with other workplace exposures, the general environment, or

with medications or personal habits of the worker to produce adverse health effects even if the occupational

exposures are controlled at the level set by the criteria. These combined effects are often not considered in the

evaluation criteria. Also, some substances are absorbed by direct contact with the skin and mucous

membranes, and potentially increasing the overall exposure. Finally, evaluation criteria may change over the

years as new information on the toxic effects of an agent become available.
Health Hazard Evaluation Report No. 96-0052-2583 Page 5

The primary sources of environmental evaluation criteria for the workplace are: (1) NIOSH Recommended

Exposure Limits (RELs)5

 (2) the American Conference of Governmental Industrial Hygienists' (ACGIH)

Threshold Limit Values (TLVsTM)6

 and (3) the U.S. Department of Labor, OSHA Permissible Exposure Limits

(PELs)7

. In July 1992, the 11th Circuit Court of Appeals vacated the 1989 OSHA PEL Air Contaminants

Standard. OSHA is currently enforcing the 1971 standards which are listed as transitional values in the current

Code of Federal Regulations; however, some states operating their own OSHA approved job safety and health

programs continue to enforce the 1989 limits. NIOSH encourages employers to follow the 1989 OSHA limits,

the NIOSH RELs, the ACGIH TLVs, or whichever are the more protective criteria. The OSHA PELs reflect

the feasibility of controlling exposures in various industries where the agents are used, whereas NIOSH RELs

are based primarily on concerns relating to the prevention of occupational disease. It should be noted when

reviewing this report that employers are legally required to meet those levels specified by an OSHA standard

and that the OSHA PELs included in this report reflect the 1971 values.

A time-weighted average (TWA) exposure refers to the average airborne concentration of a substance during a

normal 8-to-10-hour workday. Some substances have recommended short-term exposure limits (STEL) or

ceiling values which are intended to supplement the TWA where there are recognized toxic effects from higher

exposures over the short-term.

1. Indoor Environmental Quality

Indoor environmental quality (IEQ) is affected by the interaction of a complex set of factors which are

constantly changing. Four elements involved in the development of IEQ problems are: 

! sources of odors or contaminants,

! problems with the design or operation of the HVAC system,

! pathways between contaminant sources and the location of complaints,

! and the activities of building occupants.

A basic understanding of these factors is critical to preventing, investigating, and resolving IEQ problems. 

The symptoms and health complaints reported to NIOSH by non-industrial building occupants have been

diverse and usually not suggestive of any particular medical diagnosis or readily associated with a

causative agent. A typical spectrum of symptoms has included headaches, unusual fatigue, varying

degrees of itching or burning eyes, irritation of the skin, nasal congestion, dry or irritated throats and other

respiratory irritations. Usually, the workplace environment has been implicated because workers report

that their symptoms lessen or resolve when they leave the building. 

A number of published studies have reported a high prevalence of symptoms among occupants of office

buildings.8-12 Scientists investigating indoor environmental problems believe that there are multiple factors

contributing to building-related occupant complaints.13,14 Among these factors are imprecisely defined

characteristics of HVAC systems, cumulative effects of exposure to low concentrations of multiple

chemical pollutants, odors, elevated concentrations of particulate matter, microbiological contamination,

and physical factors such as thermal comfort, lighting, and noise.15-20 Indoor environmental pollutants can

arise from either outdoor sources or indoor sources. 
Page 6 Health Hazard Evaluation Report No. 96-0052-2583

There are also reports describing results which show that occupant perceptions of the indoor environment

are more closely related to the occurrence of symptoms than to any measured indoor contaminant or

condition.21-23 Some studies have shown relationships between psychological, social, and organizational

factors in the workplace and the occurrence of symptoms and comfort complaints.23--26 

Less often, an illness may be found to be specifically related to something in the building environment. 

Some examples of potentially building-related illnesses are allergic rhinitis, allergic asthma,

hypersensitivity pneumonitis, Legionnaires' disease, Pontiac fever, carbon monoxide poisoning, and

reaction to boiler corrosion inhibitors. The first three conditions can be caused by various microorganisms

or other organic material. Legionnaires' disease and Pontiac fever are caused by Legionella bacteria. 

Sources of carbon monoxide include vehicle exhaust and inadequately ventilated kerosene heaters or other

fuel-burning appliances. Exposure to boiler additives can occur if boiler steam is used for humidification

or is released by accident.

Problems NIOSH investigators have found in the non-industrial indoor environment have included poor air

quality due to ventilation system deficiencies, overcrowding, volatile organic chemicals from furnishings,

machines, structural components of the building and contents, tobacco smoke, microbiological

contamination, and outside air pollutants; comfort problems due to improper temperature and relative

humidity (RH) conditions, poor lighting, and unacceptable noise levels; adverse ergonomic conditions; and

job-related psychosocial stressors. In most cases, however, these problems could not be directly linked to

the reported health effects. 

Standards specifically for the non-industrial indoor environment do not exist. NIOSH, the Occupational

Safety and Health Administration (OSHA), and the American Conference of Governmental Industrial

Hygienists (ACGIH) have published regulatory standards or recommended limits for occupational

exposures.4-6 With few exceptions, pollutant concentrations observed in non-industrial indoor

environments fall well below these published occupational standards or recommended exposure limits. 

The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) has

published recommended building ventilation design criteria and thermal comfort guidelines.27,28 The

ACGIH has also developed a manual of guidelines for approaching investigations of building-related

complaints that might be caused by airborne living organisms or their effluents.29

Measurement of indoor environmental contaminants has rarely been helpful in determining the cause of

symptoms and complaints except where there are strong or unusual sources, or a proven relationship

between contaminants and specific building-related illnesses. The low-level concentrations of particles

and mixtures of organic materials commonly found are difficult to interpret and usually impossible to

causally link to observed and reported health symptoms. However, measuring ventilation and comfort

indicators such as CO2, temperature, and RH, has proven useful during the early stages of an investigation

in providing information relative to the proper functioning and control of HVAC systems. The basis for

measurements made during this evaluation are listed below. 

Carbon Dioxide 

Carbon dioxide (CO2) is a normal constituent of exhaled breath and, if monitored, may be useful as a

screening technique to evaluate whether adequate quantities of fresh air are being introduced into an

occupied space. The ASHRAE Standard 62-1989, Ventilation for Acceptable Indoor Air

Quality, recommends outdoor air supply rates of 20 cubic feet per minute per person (cfm/person) for
Health Hazard Evaluation Report No. 96-0052-2583 Page 7

office spaces and conference rooms, and 15 cfm/person for reception areas, and provides estimated

maximum occupancy figures for each area.27 

Indoor CO2 concentrations are normally higher than the generally constant ambient CO2 concentration

(range 300-350 ppm). When indoor CO2 concentrations exceed 1000 ppm in areas where the only

known source is exhaled breath, inadequate ventilation is suspected. Elevated CO2 concentrations

suggest that other indoor contaminants may also be increased. 

Temperature and Relative Humidity

The perception of comfort is related to one's metabolic heat production, the transfer of heat to the

environment, physiological adjustments, and body temperatures. Heat transfer from the body to the

environment is influenced by factors such as temperature, humidity, air movement, personal activities,

and clothing. ANSI/ASHRAE Standard 55-1981 specifies conditions in which 80% or more of the

occupants would be expected to find the environment thermally comfortable.28

2. Carbon Monoxide

Carbon monoxide (CO) is a colorless, odorless, tasteless gas produced by incomplete burning of

carbon-containing materials; e.g., natural gas. The initial symptoms of CO poisoning may include

headache, dizziness, drowsiness, and nausea. These initial symptoms may advance to vomiting, loss

of consciousness, and collapse if prolonged or high exposures are encountered. Coma or death may

occur if high exposures continue.30,31 

The NIOSH REL for CO is 35 ppm for an 8-hour TWA exposure, with a ceiling limit of 200 ppm

which should not been exceeded.5

 The NIOSH REL of 35 ppm is designed to protect workers from

health effects associated with carboxy-hemoglobin (COHb) levels in excess of 5%.5

 The ACGIH

recommends an eight-hour TWA TLV of 50 ppm, with a ceiling level of 400 ppm. Currently, the

ACGIH has published a notice of an intent to change the TLV to 25 ppm as an eight-hour TWA.6

 The

OSHA PEL for CO is 50 ppm for an 8-hour TWA exposure. In addition to these standards, the

National Research Council has developed a CO exposure standard of 15 ppm, based on a 24 hours per

day, 90-day TWA exposure.32

3. Microbial Contaminants

Microorganisms (including fungi and bacteria) are normal inhabitants of the environment. The

saprophytic varieties (those utilizing non-living organic matter as a food source) inhabit soil,

vegetation, water, or any reservoir that can provide an ample supply of a nutrient substrate. Under the

appropriate conditions (optimum temperature, pH, and with sufficient moisture and available

nutrients) saprophytic microorganism populations can be amplified. Through various mechanisms,

these organisms can then be disseminated as individual cells or in association with soil/dust or water

particles. In the outdoor environment, the levels of microbial aerosols will vary according to the

geographic location, climatic conditions, and surrounding activity. In a "normal" indoor environment,

the level of microorganisms may vary somewhat as a function of the cleanliness of the HVAC system

and the numbers and activity level of the occupants. Generally, the indoor levels are expected to be

below the outdoor levels (depending on HVAC system filter efficiency) with consistently similar

ranking among the microbial species.34,35
Page 8 Health Hazard Evaluation Report No. 96-0052-2583

Some individuals manifest increased immunologic responses to antigenic agents encountered in the

environment. These responses and the subsequent expression of allergic disease is based, partly, on a

genetic predisposition.36 Allergic diseases typically associated with exposures in indoor environments

include allergic rhinitis (nasal allergy), allergic asthma, allergic bronchopulmonary aspergillosis

(ABPA), and extrinsic allergic alveolitis (hypersensitivity pneumonitis).33 Allergic respiratory

diseases resulting from exposures to microbial agents have been documented in agricultural,

biotechnology, office, and home environments.37-44

Individual symptomatology varies with the disease. Allergic rhinitis is characterized by paroxysms of

sneezing; itching of the nose, eyes, palate, or pharynx; nasal stuffiness with partial or total airflow

obstruction; and rhinorrhea (runny nose) with postnasal drainage. Allergic asthma is characterized by

episodic or prolonged wheezing and shortness of breath in response to bronchial (airways) narrowing. 

Allergic bronchopulmonary aspergillosis is characterized by cough, lassitude, low-grade fever, and

wheezing.33,45 Heavy exposures to airborne microorganisms can cause an acute form of extrinsic

allergic alveolitis which is characterized by chills, fever, malaise, cough, and dyspnea (shortness of

breath) appearing four to eight hours after exposure. In the chronic form, thought to be induced by

continuous low-level exposure, onset occurs without chills, fever, or malaise and is characterized by

progressive shortness of breath with weight loss.46

Acceptable levels of airborne microorganisms have not been established, primarily because allergic

reactions can occur even with relatively low air concentrations of allergens, and individuals differ with

respect to immunogenic susceptibilities. The current strategy for on-site evaluation of environmental

microbial contamination involves an inspection to identify sources (reservoirs) of microbial growth

and potential routes of dissemination. In those locations where contamination is visibly evident or

suspected, bulk samples may be collected to identify the predominant species (fungi, bacteria, and

thermoactinomycetes). In limited situations, air samples may be collected to document the presence of

a suspected microbial contaminant. Air sample results can be evaluated epidemiologically by

comparing those from the "complaint areas" to those from non-complaint areas, or by relating

exposure to immunologic findings.

4. Bacterial Endotoxin

A bacterial endotoxin is a lipopolysaccharide compound from the outer cell wall of gram-negative

bacteria, which occur abundantly in organic dusts.47 It has been shown that the biological properties of

endotoxin vary depending upon the bacterial species from which they are derived, as well as upon the

state of the growth cycle of the bacteria.48 Endotoxins have a wide range of biological activities

involving inflammatory, hemodynamic, and immunological responses. Of most importance to

occupational exposures are the activities of endotoxin in the lung.49 The primary target cell

for endotoxin-induced damage by inhalation is the pulmonary macrophage. Human macrophages in

particular have been shown to be extremely sensitive to the effects of endotoxin in vitro.50 Endotoxin,

either soluble or associated with particulate matter, will activate the macrophage, causing the cell to

produce a host of mediators.49

Clinically, little is known about the response to inhaled endotoxins. Exposure of previously

unexposed persons to airborne endotoxin can result in acute fever, dyspnea, coughing, and small

reductions in forced expiratory volume in one second (FEV1), although some investigators have not

been able to demonstrate acute changes in FEV1.

49 The effects of repeated exposure to aerosols of

endotoxins in humans are not known. Some animal studies have demonstrated a chronic inflammatory
Health Hazard Evaluation Report No. 96-0052-2583 Page 9

response characterized by goblet cell hyperplasia and increased mucous production. This suggests that

repeated exposure may cause a syndrome similar, if not identical, to chronic bronchitis.49

Occupational exposure criteria have not been established for bacterial endotoxin by either OSHA,

NIOSH, or ACGIH. However, Jacobs has reported that a sufficient toxicological data base is believed

to exist for establishing an occupational limit for endotoxin based on acute changes in pulmonary

function.49 Eight-hour (8-hr) TWA concentrations have been suggested for over-shift decline in FEV1

(100 - 200 ng/m3), for chest tightness (300 - 500 g/m3), and for fever (500 - 1,000 ng/m3).48

An 8-hr TWA threshold for airborne endotoxin of 10 ng/m3 has also been suggested based on a decline

in FEV1 for individuals sensitized to cotton dust.51 The exposure system for the study from which this

recommendation was made consisted of a commercial carding machine in a cardroom, an exposure

room, and connecting duct work. Airborne dust concentrations were determined in the exposure room

using four vertical elutriators.51 The vertical elutriator has traditionally been the instrument of choice

for cotton dust sampling because it will not collect cotton fly lint fibers and dust particles with an

aerodynamic mass medial diameter larger than 15 μm.52

5. Silica (Quartz, Cristobalite)

Crystalline silica (quartz) and cristobalite have been associated with silicosis, a fibrotic disease of the

lung caused by the deposition of fine particles of crystalline silica in the lungs. Symptoms usually

develop insidiously, with cough, shortness of breath, chest pain, weakness, wheezing, and non-specific

chest illnesses. Silicosis usually occurs after years of exposure, but may appear in a shorter period of

time if exposure concentrations are very high.53 The NIOSH RELs for respirable quartz and

cristobalite, published in 1974, are 50 μg/m3

, as TWAs, for up to 10 hours per day during a 40-hour

work week.54 These RELs are intended to prevent silicosis. However, evidence indicates that

crystalline silica is a potential occupational carcinogen and NIOSH is currently reviewing the data on

carcinogenicity.55-57 The OSHA PELs and the ACGIH TLVsTM for respirable quartz and cristobalite

are 100 and 50 μg/m3

, as 8-hour TWAs, respectively.5,6

RESULTS

1. Respirable and Total Dust; Free Silica

Air samples collected in the Stadium, Coliseum, and Event Center for respirable and total dust were all

very low, with over fifty percent of the samples below the limit of detection (0.02 milligrams/sample). 

The highest level measured for respirable dust was 0.27 mg/m3

. All samples were well below the OSHA

PEL of 5 mg/m3

 as a TWA for respirable dust. All but one of the samples for total dust were below 1

mg/m3

. One sample, collected in the Hall of Education 1 East, was 1.5 mg/m3. All samples were well

below the ACGIH TLV of 10 mg/m3

 and the OSHA PEL of 15 mg/m3 for total dust.

Air samples for respirable free silica were all below the limit of detection for quartz (0.01 mg/sample) and

cristobalite (0.02 mg/sample). In fact, 70% of the air samples did not have enough collected mass to

conduct the analysis. Bulk analysis of sand from the various arenas had previously been analyzed and

found to contain 49% (Coliseum), 45% (Stadium), and 61% (Event Center) crystalline quartz. 
Page 10 Health Hazard Evaluation Report No. 96-0052-2583

2. Carbon Dioxide (CO2)

Tables I-IV contain summaries of CO2 levels measured throughout the NWSS grounds. Table I contains a

summary of levels in the Hall of Education building; Table II summarizes CO2 levels in the Event Center;

Table III in the Stadium; and Table IV the Coliseum. Additional CO2 data are summarized in Figures 2-4

which contain selected printouts of the Metrosonic datalogger results of fixed point sampling during

specific events. Table V contains a summary of these fixed point CO2 measurements.

CO2 levels throughout the Hall of Education Complex (including the Expo Hall and Beef Palace) ranged

from 575 ppm up to 4450 ppm (Table I). Levels were consistently above 1000 ppm and averaged closer

to 2000 ppm. The highest levels (4200-4450 ppm) were measured on a Saturday in the center of the Hall

of Education building, second floor, near the vendor’s exhibits. The floors were often so crowded that it

was difficult to move. This was particularly true on weekends. Another area where high levels of CO2

were consistently observed was in the Beef Palace Auction Arena. Levels of CO2 during an auction

averaged 2500 to 3500 ppm.

The fixed point monitoring data (Table V and Figures 2-4) shows that CO2 levels in the different arenas

were lower than those found throughout the Hall of Education building. CO2 levels during the rodeos

averaged between 1145 to 1490 ppm with peaks up to 2000 ppm. Levels in the Event Center averaged

between 860 and 1700 ppm. For most days, levels remained below 1000 ppm with the exception of 1-19-

96 (see Figure 4). On this day, the weather was mild and there was little demand for heating or cooling. 

Around noon on this day, the ventilation system came on and the CO2 levels quickly dropped below 1000

ppm. CO2 levels in the Stadium averaged below 1000 ppm every day with only brief excursions above

1000 ppm. 

3. Carbon Monoxide (CO)

In general, CO levels were very low, with most areas recording 1-3 ppm of CO at the most. Occasionally,

gas-powered vehicles were encountered and brief CO spikes would be recorded. For example, during the

rodeo and after events in the other arenas, trucks or tractors would be driven into the arena to drag the

grounds or to bring in or remove equipment. Some of the tractors were diesel powered and had very little

or no CO emissions. If the vehicles were gas-powered, a brief CO spike was recorded. The highest level

was a peak of 125 ppm which lasted for only a minute. The peak was noted when the person carrying the

monitor walked behind an operating gas powered car in the food area between the Stadium and the

Coliseum.

Table V contains summaries of CO monitoring data collected at fixed sampling locations in the Coliseum,

Stadium, and Event Center. During most of the events, short-term peak concentrations of CO up to 33

ppm were measured. However, the average levels over the entire performance were all below 8 ppm. The

brief peaks were all related to gas-powered vehicles entering the arenas. The STEL values are the highest

15-minute average over the monitoring period. The STELs ranged from 0 to 12 ppm.

Figure 5 shows a graph of CO levels measured in the breathing zone of a worker who drove a propanepowered sweeper during the evenings throughout the Hall of Education. The average CO reading for the

entire evening period (4:30 pm to 9:30 am) was 5 ppm with a peak of 75 ppm. This was the only personal

sample collected for CO.

 
Health Hazard Evaluation Report No. 96-0052-2583 Page 11

All of the TWA, STEL and Ceiling levels of CO measured were below the applicable OSHA, NIOSH and

ACGIH limits.

4. Bioaerosols

Graphical summaries of the sampling results for spores, ergosterol, and endotoxins are presented in Figures

6-8. Sampling results are presented as geometric means calculated over four survey days with I-bars

indicating minimum and maximum values. Observed trends for each analyte appear consistent across

sample locations. The lowest concentrations for spores, ergosterol, and endotoxins were found in the Hall

of Education (3rd Floor), the Horse Event Center, and the Security Office in the Coliseum. (The Security

Office was selected as a control location with which to compare to other sampled areas.) The highest

concentrations for all three analytes were found in Expo Hall 1, Hall of Education 1 West, and Stadium

Hall 1. Expo Hall 1 served as a horse paddock area; the Hall of Education 1 West stabled cattle; and

Stadium Hall 1 was used for various competitions for small animals such as hog shows, sheep shearing,

and miniature horse shows. The relative concentrations were consistent with factors such as level of

activity, quantity of animals per area, and level and type of ventilation.

5. Particle Counts

Graphical summaries of the sampling results from real-time particulate measurements from the Grimm

monitors are presented in Figures 9-12. Graphical summaries from the MetOne particle counters are

presented in Figures 13-19 and are very similar to the data in Figures 9 and 10. Particle counts varied

considerably during a specific event. Overall counts were higher than those reported in indoor studies but

still low when compared with industrial exposures.

DISCUSSION

Respirable and total dust and silica exposures were below the established criteria levels. Particle counts

reflected a wide range of particle levels at different size distributions, mostly correlating with specific events in

the arenas. For example, elevated particle counts at all size distributions were measured when the Westernaire

performance group had 30-40 horses galloping around the arena. During the bull riding or horse (bareback and

saddle) riding, levels spiked considerably whenever the animals came close to the measurement area on the

fence. However, the overall dust levels remained below established criteria. 

CO levels were consistently below the most stringent evaluation criteria (25 ppm as a TWA). Occasional high

levels of CO were measured when gas-powered vehicles were driven into one of the arenas. Prior to the start

of the NWSS, while walking through the Stadium area, consistent levels of 40 ppm CO with spikes over 150

ppm were measured while two trucks were preparing the sand. During the NWSS, gas-powered vehicles were

not driven inside the arenas for long periods of time. Consequently, high levels of CO were not observed. The

only sustained exposure to CO was to the worker who drove a propane-powered sweeper throughout the Hall

of Education every evening (Figure 5). However, this worker’s average full-shift exposure was only 5 ppm of

CO. 

The spore concentrations observed in Expo Hall 1, Hall of Education 1 West, and Stadium Hall 1 were 1-11⁄2

orders of magnitude greater (ranging as high as 1,430,000 spores per cubic meter of air [spores/m3

] in Expo

Hall 1) than those observed in the Security Office (geometric mean of 30,000 spores/m3

). This difference
Page 12 Health Hazard Evaluation Report No. 96-0052-2583

indicates a significant increase in the exposure potential in areas that house animal populations. These values

are consistent with a Swedish study of farm workers in 28 swine confinement houses that reported a mean

concentration of 20,000 spores/m3

.

58 In another study of Finnish farmers (diagnosed with farmer’s lung)

handling hay, straw, or grain, mean spore concentrations ranging from 50,000 to 2,700,000 spores/m3

 were

reported.59

Ergosterol (an indicator of fungi) concentrations in these areas were an order of magnitude greater (ranging up

to 258 nanograms per cubic meter of air [ng/m3

] in Stadium Hall 1) than the levels in the Security Office

(geometric mean of 7 ng/m3

). This correlates with the spore sampling results, although larger differences were

observed with the spore data. The greater disparity for spores between the high concentration areas and the

Security Office may in large part be due to the increased sensitivity of the sampling and analytical method for

fungal spores. Endotoxin concentrations in these areas were also an order of magnitude greater (ranging up to

97 endotoxin units per cubic meter of air [EU/m3

] in Stadium Hall 1) than the levels measured in the Security

Office (geometric mean of 3 EU/m3

). However, all of the endotoxin samples were below the criteria suggested

by Rylander of 200 EU/m3

 for an 8-hour TWA.48 The activities that contributed to these elevated levels

included washing and blow drying the animals in preparation for being shown; using large fans throughout the

first floor of the Hall of Education to keep the animals cool; large numbers of people moving through the area

disturbing the highly biologically active dust on the floor; and constant cleaning of old straw and animal feces

from the area. The Expo Hall 1 area is on the first floor of the Hall of Education (HOE) building and was used

to stable horses. This area had some of the highest spore counts, ergosterol and endotoxin levels. The level of

activity was less in this area as compared to the HOE 1 East and West, yet the measures of biological activity

were higher. This may be due to the presence of a concrete floor in this area as compared to a dirt floor in the

rest of the building. The hard surface of the concrete floors and the high volume of foot traffic across the

surface could result in more dust being caused to be airborne than in the dirt floor areas. The dirt floors were

also kept moist in order to reduce dust. Another point of concern regarding the very high levels of biological

agents in the Hall of Education complex is that most of the area samples were collected high off the ground (6-

7 feet) for sample security reasons. These samples were well above the breathing zone of people in these areas. 

Therefore, the actual exposures may be even higher than the samples indicate.

The areas with the highest levels of biological agents contained much stronger odors. While the odors

themselves may not cause health problems, they are indicators of a lack of good general ventilation. One high

odor area that was frequently mentioned by city workers was near the Clydesdale area in the Coliseum. The

Budweiser Clydesdale team was stabled on the ground floor on the northeast portion of the Coliseum at the

foot of a stairway. Ammonia odors were quite strong in the stairway area approaching the Clydesdale stables

where public viewing was allowed. There was little air movement in this area. Air flow in general in this area

came from the Coliseum horse barn into the paddock area and then into the Coliseum itself. On windy days,

when the western most doors into the horse barn were left open, air flow was quite gusty from the horse barn

into the Coliseum. The horse barn area contained relatively high levels of biological agents (see samples

labeled Coliseum Horse Paddock in Figures 6-8) and strong odors and air from this area was blown into the

Coliseum itself. An odor control system had been installed in the bay door area between the horse barn and the

paddock. The odor control agent was called Get the Odor Out and was automatically misted into the air. The

only hazardous ingredient listed in the MSDS was a stabilized chlorine peroxide. No health problems were

reported from the use of this material. Workers who had been in the areas prior to the odor control system

being installed (prior to the 95-96 show) thought the system helped.

Employees in the First Aid station in the Coliseum were interviewed to determine what types of health

problems were being reported during the NWSS. Most of the reports were for allergy problems (eye irritation

and redness or watering of the eyes, runny nose, sneezing, etc.) or asthma. Fourteen people with asthma
Health Hazard Evaluation Report No. 96-0052-2583 Page 13

reported to the First Aid station on one Saturday. These were individuals with pre-existing asthma conditions

who had an attack during the stock show. Many of these people reported allergies to animals. The high

biological activity documented with the spore counts, ergosterol, and endotoxin may have contributed to these

problems. 

The CO2 levels in many places in the NWSS complex indicate the need for additional ventilation to handle the

large numbers of people and animals. This is especially true in the Hall of Education complex. The areas with

the highest levels of CO2 were the Beef Palace Auction Arena and most of the Expo Hall during weekend

crowding. At any area where large numbers of people gathered, such as the main second floor entrance to the

Expo Hall from the Stadium, high levels of CO2 (>2000 ppm) were consistently measured. Areas where high

levels of ergosterol, spore counts, and endotoxin were found were also areas where elevated CO2 levels were

measured. On most days during the NWSS, the outside bay doors were open into the first floor of the Hall of

Education (where cattle are stabled). However, if the outside doors could not be opened due to weather, which

often occurs in January, the air quality conditions would worsened appreciably. Another area that consistently

had high levels of CO2 was in the promenade area of the Coliseum. This area was crowded with vendors and

people most of the time. Most of the ventilation in the Coliseum was concentrated on the arena itself, not the

promenade.

The effectiveness of ventilation in reducing CO2 levels, and concurrently lowering temperature, relative

humidity, particulate levels and CO, is illustrated in Figures 4 and 16. These data were collected in the Event

Center on Jan 19. Levels of CO2, CO and particle counts (see Figure 16) rose slowly throughout the morning. 

At approximately 11:00 am, the ventilation system started operating (as reported by the person watching the

equipment in the Event Center), and levels of all these contaminants dropped. CO2 levels decreased from a

high of 2800 ppm to below 1000 ppm in about 2 hours. Similar trends were observed for the other

contaminants such as particle counts (Figure 12). This was also observed on January 12 in the Event Center

(Figure 3) when CO2 levels reached a high of 1500 ppm at 11:00 am and dropped to a level of approximately 

850 ppm where it remained for the rest of the day.

CONCLUSIONS

Respirable and total dust levels, silica levels and CO concentrations were observed to be below the

recommended criteria levels. Biological activity, as measured by ergosterol, spore counts and endotoxin levels,

was elevated on the first floor of the Hall of Education and in the Stadium Hall. These are areas where high

numbers of animals were housed and cleaned for show. Strong odors of animals, molds, etc. were associated

with these areas. It is difficult to draw specific conclusions about the health implications of elevated levels of

the ergosterol, spore counts, and endotoxin. There are no specific evaluation criteria against which to measure

these levels other than the research studies quoted. However, the observed levels of spore counts and

ergosterol were significantly above background levels and were at levels that are consistent with those seen in

other studies where adverse health effects were observed. 

CO2 levels throughout the Hall of Education complex were well above 1000 ppm (a criteria sometimes used to

indicate ventilation efficiency), averaging above 2000 ppm and ranging up to 4300 ppm. These levels of CO2

indicate the need for additional outside air ventilation throughout the complex to help lower the levels of

airborne bioaerosols and control odors. CO2 levels in the promenade area around the Coliseum were also

consistently high. Additional outside air ventilation is therefore indicated around the promenade. The
Page 14 Health Hazard Evaluation Report No. 96-0052-2583

2. Gardner RM, Tindall GW, Cline SM, Brown KL [1993]. Ergosterol determination in activated

sludge and its application as a biochemical marker for monitoring fungal biomass. J Microb

Methods 17:49-60.

ventilation system in the Event Center should be adjusted to introduce outside air (outside air dampers set at a

minimum setting of 20%) for dilution prior to a certain preset time. 

RECOMMENDATIONS

1. Although elevated CO levels were not documented during the NWSS, levels monitored prior to the

show were high. Likewise, it is anticipated that CO levels during the dismantling of the show will also

be high. Therefore, electric or natural gas-powered vehicles are recommended when such vehicles are

required to be inside any of the buildings, particularly the Hall of Education building. Propanepowered vehicles can emit significant CO levels if they are not properly maintained, so they are not

generally recommended for use inside buildings. 

2. Increased outside air ventilation is recommended for the Hall of Education complex, which includes

the Expo Hall, the Beef Palace, and the Stadium Hall. Evaporative coolers, equipped with fans, exist

throughout the Hall of Education and could be used (without the cooling cycle on) to bring outside air

into the building. This may not be sufficient to provide the amount of air needed to correct the

problem. It is recommended that the buildings be engineered to meet the ASHRAE Guidelines 62-

1989.27

3. The ventilation system in the Event Center should be adjusted to also meet the ASHRAE Guidelines. 

The system is relatively new and has demonstrated that it can effectively control contaminants if

working properly. 

4. The high levels of spore counts, ergosterol and endotoxin are of concern but represent an unknown

health hazard. Increased dilution ventilation should lower the exposure potential. Steps should be

taken to reduce the source of these contaminants. Frequent cleaning of animal stalls and contaminated

bedding is recommended. Most areas on the first floor of the Hall of Education were kept fairly clean

to keep the animals clean for show. However, animal stalls in the horse barn in the Coliseum appeared

to be cleaned less frequently. Light application of moisture, particularly in areas with concrete floors,

should help reduce the dust in these areas. This would be especially effective if performed just before

the floors are swept. If drains are present, rinsing these areas with water would be a preferred method

of floor cleaning. The promenade area of the Coliseum had been cleaned in the past with an oiltreated cleaning compound (usually sawdust). This practice had been discontinued and only dry

sweeping was done. Use of the sweeping compound would help reduce dust during cleaning. 

5. The effectiveness of any ventilation changes and the general air quality in the various buildings, should

be monitored periodically with CO2

 meters.

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 42. Hodgson MJ, Morey PR, Attfield M, Sorenson W, Fink JN, Rhodes WW, Visvesvara GS [1985]. 

Pulmonary disease associated with cafeteria flooding. Archives of Environmental Health 40(2):96-

101.

 43. Fink JN, Banaszak EF, Thiede WH, Barboriak JJ [1971]. Interstitial pneumonitis due to

hypersensitivity to an organism contaminating a heating system. Annals of Internal Medicine 74:80-

83.

 44. Banazak EF, Barboriak J, Fink J, Scanlon G, Schlueter EP, Sosman A, Thiede W, Unger G [1974]. 

Epidemiologic studies relating thermophilic fungi and hypersensitivity lung syndrome. American

Review of Respiratory Disease 110:585-591.

 45. Kaliner M, Eggleston PA, Mathews KP [1987]. Rhinitis and asthma. Journal of the American

Medical Association 258(20):2851-2873.
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 46. Jordan FN, deShazo R [1987]. Immunologic aspects of granulomatous and interstitial lung diseases. 

Journal of the American Medical Association 258(20):2938-2944.

 47. Hagmar L, Schütz A, Hallberg T, Sjöholm A [1990]. Health effects of exposure to endotoxins and

organic dust in poultry slaughter-house workers. Int Arch Occup Environ Health 62:159-164.

 48. Rylander R [1987]. The role of endotoxin for reactions after exposure to cotton dust. Am J Ind Med

12:687-697.

 49. Jacobs RR [1989]. Airborne endotoxins: an association with occupational lung disease. Appl Occup

Environ Hyg 4:50-56.

 50. Olenchock SA [1985]. Endotoxins in occupationally related airborne dusts. Govern Lab 1:28-30.

 51. Castellan RM, Olenchock SA, Kinsley KB, Hankinson JL [1987]. Inhaled endotoxin and decreased

spirometric values, an exposure-response relation for cotton dust. N Engl J Med 317:605-610.

 52. Corn M [1987]. Methods to assess airborne concentrations of cotton dust. Am J Ind Med 12:677-686.

 53. NIOSH [1986]. Occupational respiratory diseases. Cincinnati, OH: U.S. Department of Health and

Human Services, Public Health Service, Centers for Disease Control, National Institute for

Occupational Safety and Health, DHHS (NIOSH) Publication No. 86-102.

 54. NIOSH [1974]. Abrasive blasting respiratory protective practices. Washington, DC: U.S.

Department of Health, Education, and Welfare, Public Health Service, Center for Disease Control,

National Institute for Occupational Safety and Health, DHEW (NIOSH) Publication No. 74-104, p

106.

 55. IARC [1987]. IARC monographs on the evaluation of the carcinogenic risk of chemicals to humans: 

silica and some silicates. Vol. 42. Lyons, France: World Health Organization, International Agency

for Research on Cancer, pp 49, 51, 73-111.

 56. NIOSH [1988]. NIOSH testimony to the U.S. Department of Labor: statement of the National

Institute for Occupational Safety and Health. Presented at the public hearing on OSHA

PELS/Crystalline Silica, July 1988. NIOSH policy statements. Cincinnati, OH: U.S. Department of

Health and Human Services, Public Health Service, Center for Disease Control, National Institute for

Occupational Safety and Health.

 57. DHHS [1991]. Sixth annual report on carcinogens: summary 1991. Research Triangle Park, NC: 

U.S. Department of Health and Human Services, Public Health Service, National Institute of

Environmental Health Sciences, pp 357-364.

 58. Donham K, Haglind P, Peterson Y, Rylander R, Belin L [1989]. Environmental and health studies of

farm workers in Swedish swine confinement buildings. British J Ind Med 46:31-37.

 59. Kotimaa MH, Husman KH, Terho EO, Mustonen MH [1984]. Airborne molds and actinomycetes in

the work environment of farmer’s lung patients in Finland. Scand J Work Environ Health 10:115-119.
Health Hazard Evaluation Report No. 96-0052-2583 Page 19

Table I

Summary of Carbon Dioxide Levels

National Western Stock Show

HALL OF EDUCATION COMPLEX

HETA 96-0052

DATE LOCATION TIME CONCENTRATION

(ppm)

Jan. 10 EH2-Entry 1200 1300

Jan. 10 EH2-Center 1205 1875

Jan. 10 EH1-Aisle 12 1210 850

Jan. 10 EH1-Aisle 8 1240 1000

Jan. 10 EH1-Aisle 5 1245 1100

Jan. 10 EH1-BP-Entry 1250 2400

Jan. 10 BP-NW Entry 1300 1500

Jan. 10 BPAA-NE Entry 1305 2800

Jan. 10 BPAA-SE Entry 1315 2650

Jan. 10 EH2-Food Area 1420 1425

Jan. 10 EH2-Aisle 1900 1422 1400

Jan. 10 EH2-Restaurant

West Door

1430 2000

Jan. 10 EH2-Restroom 1435 1750

Jan. 10 EH2-Southside Aisle 1000 1445 1875

Jan. 10 EH1-West 1512 2150

Jan. 10 EH-BP-top 1515 3350

Jan. 10 EH-BP-top 1517 3475

Jan. 10 EH3-Aisle 700 1528 1425
DATE LOCATION TIME CONCENTRATION

(ppm)

Page 20 Health Hazard Evaluation Report No. 96-0052-2583

Jan. 10 EH2-Aisle 1000 1700 1763

Jan. 10 EH3-NE 1710 2325

Jan. 10 EH1 1710-1725 2250

Jan. 10 EH3-center 1712 2000

Jan. 10 EH3-South 1715 1675

Jan. 10 EH2-East 1750 2175

Jan. 10 EH3-Rabbits 1755 2350

Jan. 10 EH2-Aisle 1300 1800 2450

Jan.10 HE2- Walkway 1800-1820 2500

Jan. 10 EH1-West 1810 2850

Jan. 10 EH2-various 1820-1835 2500

Jan. 11 HE2-Entry from Stadium 1230 1575

Jan. 11 EH3-SE Corner-Petting Zoo 1235 1575

Jan. 11 EH3-NE Corner-Rabbits 1237 2050

Jan. 11 EH3-NE Top Stairs 1240 2500

Jan. 11 EH2-NE Bottom Stairs 1245 1575

Jan. 11 EH2- restroom, N. Center 1247 2100

Jan. 11 EH2-NW Corner Near EXIT 1250 2100

Jan. 11 HE1-BP 1300 2400

Jan. 11 HE2-Entry from Stadium 1310 1750

Jan. 12 HE2-Aisle 500 South 1340 2650

Jan. 12 HE-East 1341 2625

Jan. 13 HE1-NE Entry - 2850

Jan. 13 HE2-Aisle 600 North - 2100
DATE LOCATION TIME CONCENTRATION

(ppm)

Health Hazard Evaluation Report No. 96-0052-2583 Page 21

Jan. 13 HE2-Aisle 700 Center - 2850

Jan. 13 HE2-Aisle 900 North - 3350

Jan. 13 HE2-Aisle 1200 Center - 4200

Jan. 13 EH2-Aisle 1400-N - 4450

Jan. 13 EH1-North - 1075

Jan. 13 EH1-Center - 2000

Jan. 13 EH1- S. Center - 2100

Jan. 13 EH1-Horse area - 1250

Jan. 16 EH1-South 1058 650

Jan. 16 EH1-SE Corner 1101 925

Jan. 16 EH1-Eastside 1102 875

Jan. 16 EH1-North doors 1104 650

Jan. 16 EH1-Men’s Restroom 1105 625

Jan. 16 EH1-Aisle 12 1110 750

Jan. 16 EH1-Aisle 10 1112 1075

Jan. 16 EH1-Aisle 8 1115 1500

Jan. 16 EH1-Aisle 6 1117 1750

Jan. 16 EH1-Aisle 4 1120 2150

Jan. 16 EH1-Aisle 2 1123 1500

Jan. 16 EH1-South Aisle 2 1125 2575

Jan. 16 EH1-South Aisle 4 1127 2825

Jan. 16 EH1-South Aisle 6 1130 1875

Jan. 16 EH1-South Aisle 8 1133 1500

Jan. 16 EH1-South Aisle 10 1135 800
DATE LOCATION TIME CONCENTRATION

(ppm)

Page 22 Health Hazard Evaluation Report No. 96-0052-2583

Jan. 16 EH1-South Aisle 12 1137 575

Jan. 16 EH1-North Aisle 12 1140 575

Jan. 16 EH1-North Aisle 8 1143 1600

Jan. 16 EH1-North Aisle 4 1145 875

Jan. 16 EH1-North Aisle 2 1155 1025

Jan. 18 EH2-Entry from Stadium - 675

Jan. 18 EH2-Overhead Door

Aisle 1400

- 750

Jan. 18 EH2-Restaurant

Aisle 1400

- 1050

Jan. 18 EH2-N. Entry Aisle 1300 - 1150

Jan. 18 EH2-N. Entry Aisle 1200 - 1075

Jan. 18 EH2-Middle Aisle 1100 - 1100

Jan. 18 EH2-Middle Aisle 900 - 975

Jan. 18 EH2-Middle Aisle 600 - 1025

Jan. 18 EH2-South Aisle 500 - 975

Jan. 18 EH2-South Aisle 100 - 775

Jan. 18 EH2-Middle Aisle 300 - 875

Jan. 18 EH2-North Aisle 100 - 775

Jan. 18 EH2-North Aisle 400 - 800

Jan. 18 EH2-North Aisle 500 - 875

Jan. 18 EH2-North Aisle 700 - 875

Jan. 18 EH2-North Aisle 800 - 1000

Jan. 18 EH2-North Aisle 1200 - 1225

Jan. 18 EH2-North Aisle 1300 - 1200
DATE LOCATION TIME CONCENTRATION

(ppm)

Health Hazard Evaluation Report No. 96-0052-2583 Page 23

Jan. 19 EH3- Petting Zoo 1100-1330 3200

SA - Stadium Arena HE - Hall of Education

SAA - Stadium Auction Arena SH - Stadium Hall

BP - Beef Palace EH1 - Expo Hall (level 1)

BPAA - Beef Palace Auction Arena EH2 - Expo Hall (level 2)

EC - Events Center EH3 - Expo Hall (level 3)
Page 24 Health Hazard Evaluation Report No. 96-0052-2583

Table II

Summary of Carbon Dioxide Levels

National Western Stock Show

EVENT CENTER

HETA 96-0052

DATE LOCATION TIME CONCENTRATION

(ppm)

Jan. 10 Entry 1220 1125

Jan. 10 Entry, Near Shoe Shine 1225 955

Jan. 10 Paddock - center 1230 750

Jan. 10 Paddock - west 1235 550

Jan. 10 SW Entry, Top Stairs 1732 1150

Jan. 10 SW Entry, Top Stairs 1736 1200

Jan. 10 Paddock 1745 775

Jan. 11 Entry 1315 1275

Jan. 11 S. Center, Top Row 1320 1225

Jan. 11 Eastend, Top Row 1330 1300

Jan. 11 Paddock, Westend 1350 1075

Jan. 13 Entry - 675

Jan. 19 S. Seat. 1100-1330 975
Health Hazard Evaluation Report No. 96-0052-2583 Page 25

Table III

Summary of Carbon Dioxide Levels

National Western Stock Show

STADIUM ARENA

HETA 96-0052

DATE LOCATION TIME CONCENTRATION

(ppm)

Jan. 10 SA 1350 950

Jan. 10 SA-Southside Top Row 1410 950

Jan. 10 SA-Eastside

Top Row

1410 875

Jan. 10 SA-Eastside Top Row 1415 775

Jan. 10 SA-Door 1507 1450

Jan. 10 SH-1 1510 1850

Jan. 10 Walk way 1630-1645 1000

Jan. 10 SH 1645-1655 2625

Jan. 10 SA-2nd level East 1647 1050

Jan. 10 SAA 1700-1710 3000

Jan. 10 SH-Aisle 1600 1805 1600

Jan. 12 SH-2 Top Stairs 950 950

Jan. 12 SH-1 955 2200

Jan. 12 SH-North Sheep Shearing 1010 2800

Jan. 12 SH-2 West 1020 1700

Jan. 13 SA-Westend - 1800

Jan. 13 Livestock Arena - 2100

Jan.19 SA - S. Center 1100-1330 950

SA - Stadium Arena SAA - Stadium Auction Arena

SH - Stadium Hall
Page 26 Health Hazard Evaluation Report No. 96-0052-2583

Table IV

Summary of Carbon Dioxide Levels

National Western Stock Show

COLISEUM ARENA

HETA 96-0052

DATE LOCATION TIME CONCENTRATION

(ppm)

Jan. 10 West lower 1627 1225

Jan. 10 Portal 10 1820 1100

Jan. 10 West 1827 1625

Jan. 10 Vendor Area 1835-1900 1750

Jan. 11 N. Center (RR1) 1415 1075

Jan. 12 Entry to Ped. Walkway 1350 1350

Jan. 13 Paddock - 825

Jan. 13 Upper Floor - 2400

Jan. 19 Center - North 1100-1330 1200
Health Hazard Evaluation Report No. 96-0052-2583 Page 27

Table V

Summary of Carbon Dioxide and Carbon Monoxide Concentrations for Specific Events

Fixed Location Monitoring

National Western Stock Show

January 10-19, 1996

HETA 96-0052

Date Time Carbon Dioxide (ppm) Carbon Monoxide (ppm)*

Average Minimum Peak Average Minimu

m

Peak STEL

Coliseum (Rodeo)

1-10-96 1930-2230 1160 635 2000 8 3 22 -

1-13-96 1100-1400 1145 870 1510 7 5 33 9

1-16-96 1100-1700 - - - 1 0 24 6

1-19-96 1400-1730 1490 1230 1700 7 4 9 -

Event Center

1-10-96 1300-1600 995 830 1065 - - - -

1-12-96 1000-1500 1050 815 1550 1 0 32 9

1-16-96 1050-1620 860 630 1100 - - - -

1-19-96 0920-1600 1705 860 2830 5 2 19 12

Stadium

1-10-96 1300-1600 840 655 1250 8 5 8 -

1-12-96 0950 810 585 1390 4 3 17 -

1-16-96 1030-1415 725 555 885 0 0 1 0

*Peak values represent the highest level measured . STEL is the highest 15-minute average CO concentration

during the entire sampling period.
Page 28 Health Hazard Evaluation Report No. 96-0052-2583

Figures
Health Hazard Evaluation Report No. 96-0052-2583 Page 29

Figure 1. Layout of the National Western Stock Show Grounds 
Page 30 Health Hazard Evaluation Report No. 96-0052-2583

600 

800 

1000 

1200 

1400 

1600 

1800 

2000 

Carbon Dioxide (ppm)

06:44 PM07:29 PM08:14 PM08:59 PM09:44 PM10:29 PM

TIME

RODEO

January 10

Figure 2. Carbon Dioxide Concentrations During Rodeo, Jan. 10 

800 

1000 

1200 

1400 

1600 

Carbon Dioxide (ppm)

10:03 AM 11:13 AM 12:23 PM 01:33 PM 02:43 PM

TIME 

EVENT CENTER

January 12

Figure 3. Carbon Dioxide Concentrations in Event Center, Jan 12
Health Hazard Evaluation Report No. 96-0052-2583 Page 31

500 

1000 

1500 

2000 

2500 

3000 

Carbon Dioxide (ppm)

09:22 AM 10:42 AM 12:02 PM 01:22 PM 02:42 PM

TIME

EVENT CENTER

January 19

Figure 4. Carbon Dioxide Concentration in Event Center, Jan 19

0 

20 

40 

60 

80 

CO Concentration (ppm)

0 200 400 600 800 1000 1200 

TIME (minutes)

SWEEPER

CO

Figure 5. Carbon Monoxide Concentrations on Floor Sweeper in Hall

of Education, January 18, 1996
Page 32 Health Hazard Evaluation Report No. 96-0052-2583

0 

200,000 

400,000 

600,000 

800,000 

1,000,000 

1,200,000 

1,400,000 

1,600,000 

Spore Concentration (spores/m3)

A B C D E F G H I J K L

A - Coliseum Horse Paddock

B - Event Center Paddock

C - Expo Hall 1

D - Hall of Education 1 East

E - Hall of Education 1 West

F - Hall of Education 3rd Floor

G - Horse Event Center

H - Office

I - Rodeo

J - Stadium Arena

K - Stadium Hall 1

L - Coliseum (west wall)

Figure 6. Total Spore Sampling Results, NWSS, January 1996

0 

50 

100 

150 

200 

250 

300 

Ergosterol Concentration (ng/m3)

A B C D E F G H I J K

A - Coliseum Horse Paddock

B - Event Center Paddock

C - Expo Hall 1

D - Hall of Education 1 East

E - Hall of Education 1 West

F - Hall of Education 3rd Floor

G - Horse Event Center

H - Office

I - Rodeo

J - Stadium Arena

K - Stadium Hall 1

Figure 7. Ergosterol Sampling Results, NWSS January, 1996
Health Hazard Evaluation Report No. 96-0052-2583 Page 33

0 

20 

40 

60 

80 

100 

Endotoxin Concentration (EU/m3)

A B C D E F G H I J K

A - Coliseum Horse Paddock

B - Event Center Paddock

C - Expo Hall 1

D - Hall of Education 1 East

E - Hall of Education 1 West

F - Hall of Education 3rd Floor

G - Horse Event Center

H - Office

I - Rodeo

J - Stadium Arena

K - Stadium Hall 1

Figure 8. Endotoxin Sampling Results, NWSS, January 1996

5000 

10000 

15000 

20000 

25000 

30000 Concentration (particles/L)

01:45 PM 02:15 PM 02:45 PM 03:15 PM 03:45 PM 04:15 PM 04:45 PM 

Figure 9. Real-time Particle Concentration (>0.7 um) for Rodeo, January 12,

1996 
Page 34 Health Hazard Evaluation Report No. 96-0052-2583

0 

50000 

100000 

150000 

200000 

250000 

300000 Concentration (particles/L)

11:00 AM 11:30 AM 12:00 PM 12:30 PM 01:00 PM 01:30 PM 

Figure 10. Real-time Particle Concentrations (>0.7 micron) for January 13 Rodeo (early

show)
Health Hazard Evaluation Report No. 96-0052-2583 Page 35

10,000 

15,000 

20,000 

25,000 

30,000 

35,000 

Particle Concentration (part/l)

01:30 PM 02:00 PM 02:30 PM 03:00 PM 03:30 PM 04:00 PM 04:30 PM 

Figure 11. Real-time Particulate Measurement Results for January 16 Rodeo (late show)

0 

50,000 

100,000 

150,000 

200,000 

250,000 

300,000 

Particle Concentration (part/l)

03:00 PM 03:30 PM 04:00 PM 04:30 PM 05:00 PM 05:30 PM 06:00 PM 

Figure 12. Real-time Particle Concentration Results for Rodeo (early show), January 16 
Page 36 Health Hazard Evaluation Report No. 96-0052-2583

0 

10 

20 

30 

40 

Particle Counts

(Thousands)

09:36 10:48 12:00 13:12 14:24 

TIME

5.0um 0.3um/10

STADIUM

JAN. 12

Figure 13: Real-time Particle Counts Over Time, at Two Size Distributions (>0.3μ and

>0.5μ) in the Stadium, January 12, 1996

0 

5 

10 

15 

20 

Particle Counts 

(Thousands)

10:33 11:02 11:31 12:00 12:28 12:57 13:26 13:55 14:24 

TIME

5.0um 0.3um/10

STADIUM

JAN. 16

Figure 14: Real-time Particle Measurements at two Size Distributions (>0.3μ and

>0.5 μ), at Stadium, January 16
Health Hazard Evaluation Report No. 96-0052-2583 Page 37

0 

20 

40 

60 

80 

100 

Particle Counts

(Thousands)

09:59 AM 10:49 AM 11:39 AM 12:29 PM

TIME

0.5u 1.0u 2.0u 5.0u 10.u

STADIUM

JAN. 19

Figure 15: Real-time Particulate Measurements in the Stadium, Jan 19

0 

10 

20 

30 

40 

50 

60 

Particle Counts

(Thousands)

09:20 AM 10:37 AM 11:54 AM 01:11 PM 02:28 PM 03:45 PM

TIME

5.0um 0.3um/10

EVENT CENTER

JAN. 19

Figure 16: Real-time Particle Measurement in Event Center, Jan 19
Page 38 Health Hazard Evaluation Report No. 96-0052-2583

0 

20 

40 

60 

80 

100 

Particle Counts

(Thousands)

08:04 PM 08:54 PM 09:44 PM 10:24 PM

TIME

0.5u 1.0u 2.0u 5.0u 10.u

RODEO

JAN. 10

Figure 17: Real-time Particle Measurement during Rodeo, Jan 10 

0 

10 

20 

30 

40 

50 

Particle Counts

(Thousands)

10:56 AM11:59 AM01:01 PM01:54 PM02:56 PM

TIME

0.5u 1.0u 2.0u 5.0u 10.u

EVENT CENTER

JAN. 16

Figure 18: Real-time Particle Measurement, Event Center Jan 16
Health Hazard Evaluation Report No. 96-0052-2583 Page 39

0 

10 

20 

30 

40 

50 

60 

Particle Counts

(Thousands)

01:30 PM 02:17 PM 03:07 PM 03:57 PM

TIME

0.5u 1.0u 2.0u 5.0u 10.u

RODEO

JAN. 19

Figure 19: Real-time Particle Measurement, Rodeo on Jan. 19, 1996