NIOSH HEALTH HAZARD EVALUATION REPORT 

HETA #2003-0364-3012 

Mesaba Airlines, Inc. 

Minneapolis, MN 

August 2006 

DEPARTMENT OF HEALTH AND HUMAN SERVICES 

Centers for Disease Control and Prevention 

National Institute for Occupational Safety and Health
ii 

PREFACE

The Hazard Evaluation and Technical Assistance Branch (HETAB) of the National Institute for 

Occupational Safety and Health (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 (OSHA) 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 employers 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. 

HETAB 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 NIOSH. 

ACKNOWLEDGMENTS AND AVAILABILITY OF REPORT

This report was prepared by Randy L. Tubbs of HETAB, Division of Surveillance, Hazard Evaluations 

and Field Studies (DSHEFS). Analytical support was provided by Ardith Grote of the Chemical 

Exposure Monitoring Branch, NIOSH. Desktop publishing was performed by Robin Smith. Editorial 

assistance was provided by Ellen Galloway. 

Copies of this report have been sent to employee and management representatives at Mesaba Airlines, the 

Association of Flight Attendants (AFA) AFL-CIO, and the FAA Regional Office. This report is not 

copyrighted and may be freely reproduced. The report may be viewed and printed from the following 

internet address: http://www.cdc.gov/niosh/hhe. Copies may be purchased from the National Technical 

Information Service (NTIS) at 5825 Port Royal Road, Springfield, Virginia 22161. 

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 

Highlights of Health Hazard Evaluation 

Highlights of the NIOSH Health Hazard Evaluation

The National Institute for Occupational Safety and Health (NIOSH) received a confidential union request 

for a health hazard evaluation (HHE) at Mesaba Airlines in Minneapolis, Minnesota. The union submitted 

the HHE request because of concerns by flight attendants about noise and air contaminants in the 

passenger cabins of the aircraft flown by Mesaba. NIOSH investigators conducted an investigation in 

November 2004. 

What NIOSH Did

 We measured personal noise exposures for 

20 flight attendants. 

 We sampled the air in the aft passenger 

compartment for chemicals. 

 We measured area noise in the back of the 

passenger cabin during take-off and landing 

and at cruise altitude. 

What NIOSH Found

 Some chemicals were found in very low 

concentrations. These were presumed to be 

from cleaning products, jet fuel, deicing 

fluid, and engine operations. 

 The personal noise measurements for a few 

flight attendants were above or near the 

recommended limits of NIOSH. 

 The area noise measurements were slightly 

louder in aircraft that the flight attendants 

had identified as “noisy.” 

 Continue to measure personal noise 

exposures in the aircraft on a periodic basis. 

 Begin a hearing testing program to insure 

that flight attendants are not showing 

changes in their hearing. 

 Be active in a health and safety committee 

with employees to discuss workplace 

concerns and make sure that correct and upto-date information is being passed on to all 

employees. 

What the Mesaba Airlines Employees Can Do

 Report changes in the aircrafts’ passenger 

compartments. 

 Keep current on all information that the 

union and management provide about 

workplace conditions. 

 Participate on the Mesaba Airline’s health 

and safety committee. 

What To Do For More Information:

We encourage you to read the full report. If you 

would like a copy, either ask your health and 

safety representative to make you a copy or call 

1-513-841-4252 and ask for 

HETA Report #2003-0364-3012

What Mesaba Airlines Managers Can Do
iv 

Health Hazard Evaluation Report 2003-0364-3012 

Mesaba Airlines, Inc. 

Minneapolis, MN 

August 2006 

Randy L. Tubbs, Ph.D. 

SUMMARY

On September 8, 2003, the National Institute for Occupational Safety and Health (NIOSH) received a 

confidential union request from Mesaba Airlines in Minneapolis, Minnesota about the work conditions 

inside the aircraft passenger cabin. Specifically, the request identified concerns about noise levels and air 

contaminants in the aft vestibule of the cabin during aircraft operations. 

An onsite evaluation was conducted November 8-12, 2004, out of the Minneapolis/St. Paul International 

Airport. Twenty flight attendants volunteered to wear a noise dosimeter for most of their work shift. 

Additionally, area samples for noise and air contaminants were taken in 10 aircraft flown by Mesaba 

Airlines. The results of the noise and air sampling revealed that the flight attendants had exposures that 

were generally below applicable occupational exposure limits. The air contaminants were all below the 

criteria, and only 1 of 20 noise dosimeter measurements exceeded the NIOSH recommended exposure 

limit for occupational noise. 

Exposures found in the passenger cabins during the NIOSH investigation were 

consistently below the relevant occupational limits. Air contaminants were identified, 

but in concentrations that are not considered to pose an increased risk for health effects. 

The noise levels were generally also below evaluation criteria, but a few of the personal 

samples approached or exceeded the limits. Based on these results, the NIOSH 

investigator recommended periodic monitoring of the occupational noise exposures and 

their effects on the flight attendants’ hearing. 

Keywords: NAICS 481111 (Air passenger carriers, scheduled), commercial airline, flight attendants, 

noise, carbon monoxide, aircraft cabin air pollution, noise dosimetry, volatile organic compounds 
Table of Contents 

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

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

Highlights of Health Hazard Evaluation .................................................................................................iii

Summary.....................................................................................................................................................iv

Introduction.................................................................................................................................................1

Background .................................................................................................................................................1

Methods........................................................................................................................................................1

Noise .........................................................................................................................................................2

Air Contaminants....................................................................................................................................2

Evaluation Criteria .....................................................................................................................................3

Noise .........................................................................................................................................................3

Air Contaminants....................................................................................................................................4

Carbon Monoxide ...............................................................................................................................4

Volatile Organic Compounds.............................................................................................................4

Results ..........................................................................................................................................................5

Noise .........................................................................................................................................................5

Air Contaminants....................................................................................................................................6

Discussion ....................................................................................................................................................7

Conclusions..................................................................................................................................................8

Recommendations.......................................................................................................................................9

References....................................................................................................................................................9
Health Hazard Evaluation Report No. 2003-0364-3012 Page 1 

INTRODUCTION

On September 8, 2003, the National Institute for 

Occupational Safety and Health (NIOSH) 

received a confidential union request from 

Mesaba Airlines in Minneapolis, Minnesota. 

The requesters were concerned about the 

conditions inside the aircraft passenger cabin to 

which the flight attendants were exposed during 

their work shift. Specifically, the request 

identified concerns about noise levels and air 

contaminants in the aft vestibule of the cabin 

during aircraft operations. The auxiliary power 

unit (APU) was suspected as a source for some 

of the exposures. 

An initial site visit was made by a NIOSH 

investigator to Mesaba Airlines headquarters on 

April 30, 2004, to meet with Mesaba Airline 

safety and inflight managers and a Mesaba 

Association of Flight Attendants (AFA) union 

representative. The purpose of this visit was to 

discuss the proposed protocol for the health 

hazard evaluation (HHE). A Principal Avionics 

Inspector with the Federal Aviation 

Administration’s Minneapolis Flight Standards 

District Office was identified to review the 

equipment NIOSH planned to use on the aircraft 

during flight operations and certify that it did not 

interfere with any navigational equipment on the 

aircraft. The technical specifications of the air 

and noise measuring instruments planned for the 

survey were forwarded to this individual for 

approval. It was decided at the initial site visit 

to perform the survey in November after the 

busy summer vacation period, but before the 

holiday travel period. November 8-12, 2004, 

was chosen to conduct the evaluation of Mesaba 

Airlines. 

BACKGROUND

Mesaba Airlines operates as a Northwest Airlink 

affiliate under code-sharing agreements with 

Northwest Airlines. Mesaba Airlines is the 12th 

largest regional airline in the United States and 

currently provides service to more than 100 

cities and 31 states and Canada from Northwest 

Airline’s three major hubs in Minneapolis/St. 

Paul, Minnesota; Detroit, Michigan; and 

Memphis, Tennessee. Mesaba Airlines operates 

a fleet of 77 regional jet and jet-prop aircraft, 

consisting of the 69-passenger Avro RJ-85, the 

50-passenger CRJ-200, and the 30-34 passenger 

Saab 340. In 2005, Mesaba Airlines carried 

more than 5.7 million passengers.1

NIOSH had previously investigated noise levels 

at a regional airline that flew turboprop aircraft 

and found that the exposures in the passenger 

cabin were not sufficient to increase the risk of 

occupational hearing loss for the flight 

attendants.2

 NIOSH has also investigated the 

low levels of air contamination found in 

transcontinental flights.3

 This investigation was 

planned to add to the body of knowledge 

concerning working conditions for flight 

attendants. 

METHODS

A flight schedule arranged by Mesaba Airlines 

allowed the NIOSH investigator to be on two 

outbound/inbound flights originating at the 

Minneapolis St. Paul (MSP) airport each day of 

the five survey days so that 10 different Avro 

RJ-85 aircraft were sampled in this manner. On 

each aircraft tested, the NIOSH investigator was 

seated in a back location in the cabin near the aft 

vestibule during the entire flight collecting 

spectral noise measurements during takeoff and 

landing, and at cruising altitude. Also, on the 

flights on which the NIOSH investigator flew, 

air monitors were attached on the back wall of 

the aft vestibule with duct tape. The air 

monitors were turned on at the beginning of the 

flight out and turned off when the aircraft 

returned to MSP. Finally, two groups of flight 

attendants, two per aircraft, were identified by 

the airline to ask if they would volunteer to wear 

a noise dosimeter throughout the work day. The 

flight attendants either started their day at MSP 

or flew into the airport early in their shift when a 

dosimeter was placed on them. They either 

ended their day in or flew into MSP near the end 

of their assigned daily itinerary so that the 

dosimeters could be collected from them. 

Mesaba’s inflight department provided NIOSH 
Page 2 Health Hazard Evaluation Report No. 2003-0364-3012 

with the scheduled itinerary for the flight 

attendants along with the Avro RJ-85 tail 

numbers for identification. The 10 aircraft 

tested with dosimeters on the flight attendants 

were different than the 10 airplanes that the 

NIOSH investigator sampled. 

Noise 

Quest® Electronics Model Q-300 Noise 

Dosimeters were used to collect the daily noise 

exposure measurements from the flight 

attendants who volunteered to be in the NIOSH 

evaluation. The dosimeters were secured on the 

employees’ belts and the dosimeter microphones 

attached to their shirts, halfway between the 

collar and the point of the shoulder. A 

windscreen provided by the dosimeter 

manufacturer was placed over the microphone 

during recordings. The dosimeters were worn for 

the entire time that the flight attendants were on 

their assigned aircraft. The noise information 

was downloaded to a personal computer for 

interpretation with QuestSuite® Professional 

computer software and the dosimeters reset for 

the next day. The dosimeters were calibrated 

before and after the work shift according to the 

manufacturer’s instructions. 

The spectral noise measurements were made 

with a Larson-Davis Laboratory Model 2800 

Real-Time Analyzer and a Larson-Davis 

Laboratory Model 2559 1⁄2" random incidence 

response microphone. The microphone was 

connected to the analyzer with a 6-ft. cable. The 

analyzer allows for the analysis of noise into its 

spectral components in a real-time mode. The 

1⁄2"-diameter microphone has a frequency 

response range (± 2 decibels [dB]) from 4 Hertz 

(Hz) to 21 kilohertz (kHz) that allows for the 

analysis of sounds in the region of concern. 

One-third octave bands consisting of center 

frequencies from 25 Hz to 20 kHz were 

integrated for 15 seconds and stored in the 

analyzer. The analyzer was set in the auto-store 

mode so that a 15-second sample was 

automatically stored at the end of the period and 

the analyzer reset to instantly begin the next 15-

second sample period. The series of sample 

periods was continued for a total of 5 minutes, 

thus yielding 20 samples for each of the aircraft 

activities. Take-off sampling was started when 

the aircraft first began to move on the runway 

and ended 5 minutes later. Samples taken at 

cruise altitude were collected for a period of 5 

minutes once the aircraft had leveled off in the 

sky. Finally, landing samples began when the 

pilot lowered the landing gear or the wing flaps 

and continued for 5 minutes or, in some cases, 

until the aircraft came to a stop at the gate. 

Air Contaminants 

Carbon Monoxide (CO) 

Carbon monoxide exposures were evaluated 

with the Biosystems Toxi Ultra, a real-time, 

data-logging, passive CO monitor that logs, in 

parts per million (ppm), average exposures, 8-

hour time-weighted averages (TWA), maximum 

15-minute short-term exposures, and maximum 

peak exposures. These instruments were 

operated in a passive diffusion mode with a 1-

minute sampling interval. One area sample was 

collected on each airplane ridden by the NIOSH 

investigator by attaching the instrument to the 

aft cabin wall with duct tape, making sure the 

sensor was open to the environment. The CO 

monitor was turned on at the beginning of the 

outbound flight and left on until the aircraft 

returned to MSP. 

Volatile Organic Compounds (VOCs) 

Area air samples that screen for VOCs were 

collected on each aircraft ridden by the NIOSH 

investigator. The samples were collected on 

thermal desorption tubes attached by Tygon® 

tubing to SKC® Pocket Pumps® calibrated at a 

flow rate of 0.05 liters per minute (Lpm). The 

thermal desorption tubes used for qualitative 

identification of VOCs contain three beds of 

sorbent material: a front layer of Carbopack 

YTM, a middle layer of Carbopack BTM, and a 

back section of Carboxen 1003TM. The tubes 

were analyzed by the NIOSH laboratory in a 

Perkins-Elmer ATD 400 automatic thermal 

desorption system. The thermal unit was 

interfaced directly to an HP5890A gas 

chromatograph with an HP5970 mass selective 

detector according to the NIOSH Manual of 

Analytical Methods (NMAM) Method 2549.4 
Health Hazard Evaluation Report No. 2003-0364-3012 Page 3 

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 health effects 

even if the occupational exposures are controlled 

at the level set by the criterion. 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 thus potentially increases the 

overall exposure. Finally, evaluation criteria 

may change over the years as new information 

on the toxic effects of an agent become 

available. 

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 (TLVs®),6

 and (3) the 

U.S. Department of Labor, Occupational Safety 

and Health Administration (OSHA) Permissible 

Exposure Limits (PELs).7

 Employers are 

encouraged to follow the OSHA limits, the 

NIOSH RELs, the ACGIH TLVs®, or 

whichever are the more protective criteria. 

OSHA requires an employer to furnish 

employees a place of employment that is free 

from recognized hazards that are causing or are 

likely to cause death or serious physical harm 

[Occupational Safety and Health Act of 1970, 

Public Law 91–596, sec. 5(a)(1)]. Thus, 

employers should understand that not all 

hazardous chemicals have specific OSHA 

exposure limits such as PELs and short-term 

exposure limits (STELs). An employer is still 

required by OSHA to protect their employees 

from hazards, even in the absence of a specific 

OSHA PEL. 

TWA exposure refers to the average airborne 

concentration of a substance during a normal 8- 

to 10-hour workday. Some substances have 

recommended STEL or ceiling values which are 

intended to supplement the TWA where there 

are recognized toxic effects from higher 

exposures over the short-term. 

Noise 

Noise-induced loss of hearing is an irreversible, 

sensorineural condition that progresses with 

exposure. Although hearing ability declines with 

age (presbycusis) in all populations, exposure to 

noise produces hearing loss greater than that 

resulting from the natural aging process. This 

noise-induced loss is caused by damage to nerve 

cells of the inner ear (cochlea) and, unlike some 

conductive hearing disorders, cannot be treated 

medically.8

 While loss of hearing may result 

from a single exposure to a very brief impulse 

noise or explosion, such traumatic losses are 

rare. In most cases, noise-induced hearing loss is 

insidious. Typically, it begins to develop at 4000 

or 6000 Hz (the hearing range is 20 Hz to 20000 

Hz) and spreads to lower and higher frequencies. 

Often, material impairment has occurred before 

the condition is clearly recognized. Such 

impairment is usually severe enough to 

permanently affect a person's ability to hear and 

understand speech under everyday conditions. 

Although the primary frequencies of human 

speech range from 200 Hz to 2000 Hz, research 

has shown that the consonant sounds, which 

enable people to distinguish words such as "fish" 

from "fist," have still higher frequency 

components.9

The A-weighted decibel (dBA) is the preferred 

unit for measuring sound levels to assess worker 
Page 4 Health Hazard Evaluation Report No. 2003-0364-3012 

noise exposures. The dBA scale is weighted to 

approximate the sensory response of the human 

ear to sound frequencies near the threshold of 

hearing. The decibel unit is dimensionless, and 

represents the logarithmic relationship of the 

measured sound pressure level to an arbitrary 

reference sound pressure (20 micropascals, the 

normal threshold of human hearing at a 

frequency of 1000 Hz). Decibel units are used 

because of the very large range of sound 

pressure levels which are audible to the human 

ear. Because the dBA scale is logarithmic, 

increases of 3 dBA, 10 dBA, and 20 dBA 

represent a doubling, tenfold increase, and 

hundredfold increase of sound energy, 

respectively. It should be noted that noise 

exposures expressed in decibels cannot be 

averaged by taking the simple arithmetic mean. 

The OSHA standard for occupational exposure 

to noise (29 CFR 1910.95)10 specifies a 

maximum PEL of 90 dBA for a duration of 8 

hours per day. The regulation, in calculating the 

PEL, uses a 5 dB time/intensity trading 

relationship, or exchange rate. This means that a 

person may be exposed to noise levels of 95 

dBA for no more than 4 hours, to 100 dBA for 2 

hours, etc. Conversely, up to 16 hours exposure 

to 85 dBA is allowed by this exchange rate. The 

duration and sound level intensities can be 

combined in order to calculate a worker's daily 

noise dose according to the formula: 

Dose = 100 X (C1/T1 + C2/T2 + ... + Cn/Tn ), 

where Cn indicates the total time of exposure at a 

specific noise level and Tn indicates the 

reference duration for that level as given in 

Table G-16a of the OSHA noise regulation. 

During any 24-hour period, a worker is allowed 

up to 100% of his daily noise dose. Doses 

greater than 100% are in excess of the OSHA 

PEL. 

The OSHA regulation has an additional action 

level (AL) of 85 dBA; an employer shall 

administer a continuing, effective hearing 

conservation program when the 8-hour TWA 

value exceeds the AL. The program must 

include monitoring, employee notification, 

observation, audiometric testing, hearing 

protectors, training, and record keeping. All of 

these requirements are included in 29 CFR 

1910.95, paragraphs (c) through (o). Finally, the 

OSHA noise standard states that when workers 

are exposed to noise levels in excess of the 

OSHA PEL of 90 dBA, feasible engineering or 

administrative controls shall be implemented to 

reduce the workers' exposure levels. 

NIOSH, in its Criteria for a Recommended 

Standard,11 and the ACGIH6

 propose exposure 

criteria of 85 dBA as a TWA for 8 hours, 5 dB 

less than the OSHA standard. The criteria also 

use a more conservative 3 dB time/intensity 

trading relationship in calculating exposure 

limits. Thus, a worker can be exposed to 85 dBA 

for 8 hours, but to no more than 88 dBA for 4 

hours or 91 dBA for 2 hours. Twelve-hour 

exposures have to be 83 dBA or less according 

to the NIOSH REL. 

Air Contaminants 

Carbon Monoxide 

Carbon monoxide (CO) is a colorless, odorless, 

tasteless gas which can be a product of the 

incomplete combustion of organic compounds. 

CO combines with hemoglobin and interferes 

with the oxygen carrying capacity of blood. 

Symptoms include headache, drowsiness, 

dizziness, nausea, vomiting, collapse, 

myocardial ischemia, and death.12 The NIOSH 

REL for carbon monoxide is 35 ppm for an 8-

hour TWA, with an additional recommendation 

for a ceiling limit of 200 ppm which should not 

be exceeded at any time during the workday.5

 

The OSHA PEL for carbon monoxide is 50 ppm 

for an 8-hour TWA.7

 The ACGIH TLV for 

carbon monoxide is 25 ppm as an 8-hour TWA.6

Volatile Organic Compounds 

Volatile organic compounds describe a large 

class of chemicals which are organic 

(i.e., containing carbon) and have a sufficiently 

high vapor pressure to allow some of the 

compound to exist in the gaseous state at room 

temperature. These compounds are emitted in 

varying concentrations from numerous indoor 
Health Hazard Evaluation Report No. 2003-0364-3012 Page 5 

sources including, but not limited to, carpeting, 

fabrics, adhesives, solvents, paints, cleaners, 

waxes, cigarettes, and combustion sources. Two 

major compounds were identified in this 

evaluation that have published occupational 

exposure limits: toluene and 2-butoxyenthanol 

(Butyl Cellosolve®). 

Toluene 

Toluene is a colorless, aromatic organic liquid 

containing a six carbon ring (a benzene ring) 

with a methyl group (CH3) substitution. It is a 

typical solvent found in paints and other 

coatings, and used as a raw material in the 

synthesis of organic chemicals, dyes, detergents, 

and pharmaceuticals. Inhalation and skin 

absorption are the major occupational routes of 

exposure. Toluene can cause acute irritation of 

the eyes, respiratory tract, and skin. Since it is a 

defatting solvent, repeated or prolonged skin 

contact will remove the natural lipids from the 

skin which can cause drying, fissuring, and 

dermatitis.12

The NIOSH REL for toluene is 375 milligrams 

per cubic meter (mg/m3

) for up to a 10-hour 

TWA.5

 NIOSH has also set a recommended 

STEL of 560 mg/m3 for a 15-minute sampling 

period. The OSHA PEL for toluene is 754 

mg/m3

 for an 8-hour TWA.7 The ACGIH TLV 

is 188 mg/m3

 for an 8-hour TWA, but a notice of 

intended change has been published to reduce 

this level down to 75 mg/m3

.

6

 This ACGIH 

TLV carries a skin notation, indicating that 

cutaneous exposure contributes to the overall 

absorbed inhalation dose and potential systemic 

effects. 

2-Butoxyethanol 

2-Butoxyethanol, also known as ethylene glycol 

monobutyl ether, or Butyl Cellosolve®, is a 

colorless liquid solvent with a mild ether odor.12 

2-Butoxyethanol is a widely used solvent and 

cleaning agent. The low vapor pressure of 2-

butoxyethanol is such that high air 

concentrations are unlikely; however, the 

material can be absorbed through the skin. The 

NIOSH REL for 2-butoxyethanol is 24 mg/m3

for up to a 10-hour TWA.5 While intended to 

prevent hematotoxicity, the REL should also 

prevent eye and mucous membrane irritation.13 

The OSHA PEL is 240 mg/m3

 as an 8-hour 

TWA.7 

RESULTS

Noise 

The Quest dosimeters collect data so that one 

can directly compare the information with the 

three different noise criteria used in this survey, 

the OSHA PEL and AL, and the NIOSH REL. 

The OSHA criteria use a 90 dBA criterion and 

5-dB exchange rate for the PEL and AL. The 

difference between the two is the threshold level 

employed, with a 90 dBA threshold for the PEL 

and an 80 dBA threshold for the AL. The 

threshold level is the lower limit of noise values 

included in the calculation of the criteria; values 

less than the threshold are ignored by the 

dosimeter. The NIOSH criterion differs from 

OSHA in that the criterion is 85 dBA, the 

threshold is 80 dBA, and it uses a 3-dB 

exchange rate. 

Twenty flight attendants flying in 10 Avro RJ-85 

airplanes wore noise dosimeters for a majority of 

their scheduled daily itinerary, usually four 

flight legs, over the five survey days. One pair 

of attendants was sampled over only two flight 

legs because of scheduling difficulties. The 

individual flight attendants’ noise dosimeter data 

are presented in Figures 1-20. Each figure 

shows the minute-by-minute dBA levels over 

the sampled work shift. Included in each figure 

are the scheduled departure times (D) and the 

scheduled arrival times (A) for each flight leg as 

well as the equivalent noise levels (TWA) for 

the total sampled period calculated according the 

OSHA AL and NIOSH REL criteria. These data 

are also summarized in Table 1, which shows 

the total sampling time and the percent dose 

accumulations calculated according to the three 

evaluation criteria for each flight attendant. 

Only one flight attendant was found to have a 

daily noise dose in excess of the NIOSH REL 

(attendant 1 - #507 Figure 17). All others were 

below the criterion for the time that they were 

wearing the dosimeter. No flight attendant 
Page 6 Health Hazard Evaluation Report No. 2003-0364-3012 

exceeded the OSHA criteria. As noted earlier, 

the flight attendants generally had one additional 

flight the day on which they wore the noise 

dosimeter that was not included in the measured 

daily noise dose. To see the effect of this 

additional flight leg, the average noise levels 

calculated according to the NIOSH REL and 

OSHA AL criteria were determined for each of 

the scheduled times between departure and 

arrival given on the flight attendant’s itinerary 

furnished by Mesaba Airlines to find an average 

noise level for the time the aircraft was flying. 

The reference duration for the average level was 

calculated and the remaining flight time for each 

attendant was put into the Cn/Tn formula to 

estimate the added noise dose from the 

unmeasured portion of the flight attendant’s day. 

These estimated noise dose values are presented 

in Table 2. Only the OSHA AL criterion was 

calculated because the PEL dose measurements 

were so far below the 100% allowable dose. 

None of the extrapolated noise doses exceeded 

the OSHA AL criterion. However, two more 

flight attendants were found to have extrapolated 

daily noise doses above the NIOSH REL. 

In addition to the noise dosimeter data collected 

on flight attendants, spectral noise data were 

collected on 10 different aircraft during an 

outbound flight from MSP and the subsequent 

return flight to MSP on the same airplane. For 

each flight, the NIOSH investigator sat near the 

back of the aircraft in a passenger seat collecting 

noise data with the real-time analyzer during 

take-off and landing, and while the aircraft was 

at cruise altitude. The data were stored as onethird octave bands over the frequency range of 

20 – 20,000 Hz. These data are presented 

graphically in an appendix to this report. 

The flight attendants’ local union identified five 

of Mesaba’s Avro RJ-85 aircraft as being 

particularly noisy. The list included aircraft 

#508, #511, #513, #521, and #527. Scheduling 

difficulties did not allow for each of the 

identified aircraft to be investigated during this 

evaluation. However, aircraft #511 and #513 

were included in the spectral noise evaluation. 

The median dBA levels measured during takeoff, cruise, and landing were calculated for the 

10 aircraft included in the survey. For aircraft 

#511, the median levels were 82.7 dBA for takeoff, 84.0 dBA for cruise, and 82.7 dBA for 

landing. For aircraft #513, the median levels 

were 82.1 dBA, 84.0 dBA, and 80.8 dBA for the 

three flight conditions. The median noise levels 

for the remaining eight aircraft tested during the 

evaluation were 82.2 dBA for take-off, 81.7 

dBA for cruise, and 78.7 dBA for landing. 

Thus, for aircraft operations during cruise 

altitude and landing, the two “noisy” aircraft 

were louder than the rest of the measured fleet, 

by 2 – 4 dBA. There was little difference in 

noise levels emitted during take-off for the 10 

aircraft. 

Air Contaminants 

Carbon Monoxide 

The monitors continuously measured the levels 

of CO in the rear portion of the passenger 

compartment from the time the NIOSH 

investigator boarded the aircraft at MSP until it 

returned. The results for the 10 individual Avro 

RJ-85 aircraft are shown in Table 3. The flight 

durations were generally 3-4 hours in length. 

All of the measured CO levels were minimal, 

with most TWAs found to be 0 ppm and STELs 

much less than the ceiling limit. Aircraft #516 

was found to have the highest concentrations of 

CO, showing a peak level of 13 ppm and a 

STEL of 6 ppm. A review of the time when 

peak CO levels occurred revealed that they 

usually happened during the first time the 

airplane took-off from MSP. This is seen in 

Figure 21 for aircraft #516 where take-off began 

at 5:32 pm. The second recorded take-off began 

at 7:32 pm. A second aircraft with one of the 

higher measured peak CO levels was #511, 

exhibiting a 6 ppm concentration. For this 

aircraft, the highest peak occurred during the 

first take-off operation as seen for aircraft #516, 

but a second smaller peak happened during the 

second take-off. This is shown graphically in 

Figure 22. 

Volatile Organic Compounds 

Total ion chromatograms were generated for the 

thermal desorption tube samples collected on 10 

Avro RJ-85 aircraft. The major components 
Health Hazard Evaluation Report No. 2003-0364-3012 Page 7 

identified on many of the samples were 

limonene, toluene, propylene glycol, and 2-

butoxyethanol (Butyl Cellosolve®). The 

samples were quantified for these major 

components. However, since the sampling and 

analytical techniques used in these analyses have 

not been validated, all of these results should be 

considered as estimates. With the exception of 

aircraft #532, at least one of the major 

compounds was detected on each of the aircraft 

during the two scheduled flight legs that were 

sampled. Concentrations for all of the estimated 

contaminants were 2.0 μg/m3

 or less. 

DISCUSSION

The results of the noise and air sampling in 

Mesaba’s aircraft revealed that the flight 

attendants had exposures that are generally 

below all relevant evaluation criteria. The VOC 

and CO air contaminants were all below the 

criteria, and only 1 of 20 flight attendants’ noise 

dosimeter measurements exceeded the NIOSH 

REL for occupational noise. 

The CO meter readouts showed that the levels 

were generally 0 ppm in the aft vestibule of the 

aircraft. The only time that detectable levels of 

this air contaminant were noted was during takeoff on a majority of the sampled fleet. The 

highest recorded peak of 13 ppm in aircraft #516 

is much lower than the NIOSH ceiling level of 

200 ppm. The major VOCs identified on the 10 

aircraft were also at very low concentrations. 

The four major components identified on the 

thermal desorption tubes, limonene, toluene, 

propylene glycol, and 2-butoxyethanol, are 

readily explainable as to their origin. Both 

limonene and 2-butoxyethanol are found in 

common cleaning agents. Toluene is a 

component of jet A fuel and propylene glycol is 

listed as one of the ingredients in the deicing 

fluid used by Mesaba Airlines. The CO could 

be a combustion byproduct from the aircraft’s 

engines. 

These chemical contaminants were a concern of 

the Mesaba flight attendants and their union 

representatives. A Department of 

Transportation, Federal Aviation Administration 

(FAA) Final Rule was published in 2004 where 

a new airworthiness directive, applicable to 

certain BAE Systems (Operations) Limited 

Model BAe 146 and Avro 146-RJ series 

airplanes, required replacing the existing 

bellows inlet duct of the APU system with a 

new, improved rectangular metallic bellows inlet 

duct.14 The directive stated that this action is 

necessary to prevent air from the APU bay being 

ingested into the flight deck and passenger 

cabin, resulting in poor air quality and, if the air 

is contaminated, possible incapacitation of the 

flightcrew and passengers. Because the 

airworthiness directive does not address the 

Avro RJ-85, the NIOSH investigator contacted 

the technical support section of BAE Systems to 

clarify the aircraft covered by the directive. A 

BAE Systems Technical Support Engineer 

responded that the original design of the AVRO 

RJ-85 incorporated the modifications specified 

in the directive and therefore there is no reason 

to apply the airworthiness directive to these 

aircraft.15 

Measured noise levels were almost always 

below the most conservative evaluation 

criterion. Only one dosimeter measured noise in 

excess of the NIOSH REL for the portion of the 

flight attendant’s shift that was sampled. The 

extrapolated exposures that attempt to account 

for the flight legs that were not actually 

measured only put two additional flight 

attendants in a category where their noise levels 

exceed the criterion. However, three more 

attendants were found to have daily noise doses 

greater than 90% of the allowable amount 

according to the NIOSH REL after the 

extrapolation. Also, the median noise levels 

during cruising in the two aircraft identified as 

being noisier than the rest of the fleet were 

calculated to be 84 dBA, a value near the limit 

of 85 dBA for an 8-hour work shift. Because of 

the closeness of the noise exposures to the 

NIOSH criterion, Mesaba airlines should 

monitor flightcrews’ occupational noise 

exposures and their hearing ability more closely. 

For most industries in the U.S., OSHA is the 

agency that oversees worker health and safety. 

However, the FAA published a Federal Register 
Page 8 Health Hazard Evaluation Report No. 2003-0364-3012 

notice in 1975 asserting its complete and 

exclusive responsibility for the regulation of 

occupational safety and health standards of 

employees engaged in civil aircraft operations.16 

Because OSHA has statutory authority 

governing the occupational safety and health of 

most employees, the FAA and OSHA entered 

into a Memorandum of Understanding in August 

2000 to establish a procedure for coordinating 

and supporting enforcement of the Occupational 

Safety and Health Act with respect to the 

working conditions of employees on aircraft in 

operation (other than flight deck crew) and for 

resolving jurisdictional questions. A 

FAA/OSHA Aviation Safety and Health Team 

was formed, and a report was issued in 

December 2000. Included in this report was a 

section on occupational exposure to noise where 

the team looked at the application of OSHA’s 

general industry standards on occupational noise 

to employees on aircraft in operation. Although 

the team reports that they have no data as to the 

levels of noise encountered by employees during 

operation, they felt that many of the OSHA 

provisions, such as training and testing, could be 

applied without any effect on aviation safety. 

However, the team felt that engineering and 

administrative controls and the use of hearing 

protection devices (HPDs) would affect aviation 

safety and would therefore require FAA 

approval. On June 18, 2002, the Aviation Safety 

and Health Team released an Action Plan 

proposing an Aviation Safety and Health 

Partnership Program which would expand the 

FAA’s role in worker safety and health issues. 

OSHA’s role in this program would be advisory 

only. On May 15, 2003, the FAA issued a 

Departmental Order (1110.134) describing a 

voluntary Aviation Safety and Health 

Partnership Program (ASHPP) with a 

rulemaking committee consisting of members 

from the FAA, air carriers, and air carrier 

employee unions. This action led to a suit filed 

in District Court on September 19, 2005, by the 

Association of Flight Attendants against OSHA 

and the FAA for their failure to ensure the health 

and safety of flight attendants and other 

employees working in the airline industry.17

Because the oversight of occupational noise 

exposure in flight attendants is not detailed in 

such a manner as the OSHA Occupational Noise 

Standard, it should be possible to institute many 

of the components of an effective hearing loss 

prevention program and be in compliance with 

FAA regulations and approvals. Because the 

noise exposures measured in the NIOSH 

evaluation approached or exceeded the REL in a 

number of instances, additional periodic 

assessments of flight attendants’ noise levels 

should be put into Mesaba Airline’s operating 

procedures. This will verify that the noise has 

not begun to routinely exceed levels where there 

is a risk of occupational hearing loss. Along 

with noise exposure measurements, an 

audiometric testing program should be 

implemented to check to see that the employees 

are not exhibiting gradual losses of hearing 

which would affect their ability to perform their 

work activities, which could be classified as 

“hearing critical.” Early identification of 

hearing loss will allow Mesaba management to 

intervene with additional actions, such as 

maintenance or engineering controls on the 

aircraft, reduced time in the aircraft, or hearing 

protection devices for the flightcrew that meet 

FAA approval. 

CONCLUSIONS

Conditions found in the passenger cabins during 

the NIOSH investigation were consistently 

below the relevant occupational exposure 

standards. Air contaminants were identified, but 

in concentrations that are not considered to pose 

an increased risk for health effects. The likely 

sources of the major components are cleaning 

products, deicing fluids, jet fuel, and combustion 

products emitted by the engines. 

The noise exposures experienced by the flight 

attendants were usually below the most 

conservative evaluation criterion. However, the 

measured levels did approach the NIOSH REL 

and should be checked periodically to assure 

management officials and employees that the 

noise conditions are not increasing to levels that 

may put the flight attendants at risk for 

occupational hearing loss. Also, in striving to 
Health Hazard Evaluation Report No. 2003-0364-3012 Page 9 

keep the noise levels low in the passenger 

cabins, the auditory experience of Mesaba 

employees and their customers will be better. 

Communications between and among employees 

and the passengers will improve as the 

background noise levels from engines and other 

aircraft components are reduced. 

Finally, incorporating a periodic audiometric 

examination as part of the flight attendants’ 

medical or wellness program will insure that 

their hearing levels are not deteriorating over 

time. If there should be a change in the 

schedules of the flight attendants that increases 

their daily time on aircraft or should the type of 

aircraft flown by Mesaba change to one that has 

higher noise exposures, then there will be 

historical data on the hearing levels of the 

employees that may be necessary to meet the 

regulatory requirements of a hearing 

conservation program. 

RECOMMENDATIONS

Based on the findings and observations of this 

evaluation, the following recommendations are 

offered to Mesaba Airlines and its flight 

attendants to improve the work environment on 

the AVRO RJ-85 aircraft. 

1. Mesaba Airlines should institute a noise 

monitoring program which includes both 

personal noise dosimetry to document the flight 

attendants’ exposures and general area noise 

samples of the passenger cabins. The noise 

monitoring should be conducted on a periodic 

basis, e.g., annually or biennially, or whenever 

flight attendants notice that the noise levels of a 

particular aircraft seem to be getting louder. 

2. An audiometric testing program should 

be instituted by Mesaba Airlines for their flight 

attendants. The program should minimally use 

pure-tone threshold testing. The Council for 

Accreditation in Occupational Hearing 

Conservation (CAOHC) has guidelines for such 

a program.18

3. If the flight attendants feel that the use 

of HPDs would help them in performing 

communication tasks during flights, FAA 

approval would first have to be secured by the 

airline. If allowed, there are HPDs on the 

market that are characterized as flat spectrum, 

moderate attenuation devices, sometimes 

referred to as “musician earplugs.”19 They offer 

levels of attenuation from 9 – 25 dB and tend to 

lower sound equally over the entire spectrum. 

Thus, they do not have the characteristic shape 

of increasingly higher attenuation of sound in 

the high frequencies, which tends to be 

detrimental to detecting speech signals in a 

background of noise. 

4. A health and safety committee with 

representatives from management and the union 

should be active at Mesaba Airlines. The 

concern over the FAA airworthiness directive 

about the replacement of the bellows inlet 

appears to be based on faulty information. This 

committee could work on obtaining the most upto-date information about employees’ concerns 

and communicating this information to all 

workers. 

REFERENCES

 1. Mesaba Airlines [2006]. Mesaba Info. 

World Wide Web [URL=http://www.mesaba. 

com/mescom/home.nsf/main?openframeset&Fra

me=main&Src=/mescom/home.nsf/splash/infor

mation?opendocument]. Date accessed: June 

2006. 

 2. Tubbs RL [2004]. Health hazard 

evaluation: Horizon Air, Seattle, Washington, 

Cincinnati, OH: U.S. Department of Health and 

Human Services, Public Health Service, Centers 

for Disease Control and Prevention, National 

Institute for Occupational Safety and Health, 

HETA Report No. 2003-0094-2931. 

 3. Waters MA, Bloom TF, Grajewski B, 

Deddens J [2002]. Measurements of Indoor Air 

Quality on Commercial Transport Aircraft. In 

Indoor Air 2002: Proceedings of the 9th 

International Conference on Indoor Air Quality 

and Climate, Vol. 4, H Levin, ed., Santa Cruz, 

California, pp. 782-787 
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 4. NIOSH [2006]. NIOSH manual of 

analytical methods (NMAM®). 4th ed. Schlecht 

PC, O’Connor PF, eds. Cincinnati, OH: U.S. 

Department of Health and Human Services, 

Public Health Service, Centers for Disease 

Control and Prevention, National Institute for 

Occupational Safety and Health, DHHS 

(NIOSH) Publication 94–113 (August, 1994); 

1st Supplement Publication 96–135, 2nd 

Supplement Publication 98–119; 3rd 

Supplement 2003–154. 

[http://www.cdc.gov/niosh/nmam/] 

 5. NIOSH [1992]. Recommendations for 

occupational safety and health: compendium of 

policy documents and statements. Cincinnati, 

OH: U.S. Department of Health and Human 

Services, Public Health Service, Centers for 

Disease Control and Prevention, National 

Institute for Occupational Safety and Health, 

DHHS (NIOSH) Publication No. 92-100. 

 6. ACGIH® [2006]. 2006 TLVs® and 

BEIs®: threshold limit values for chemical 

substances and physical agents. Cincinnati, OH: 

American Conference of Governmental 

Industrial Hygienists. 

 7. CFR [2003]. 29 CFR 1910.1000. Code of 

Federal Regulations. Washington, DC: U.S. 

Government Printing Office, Office of the 

Federal Register. 

 8. Ward WD, Royster LH, Royster JD 

[2000]. Anatomy & physiology of the ear: 

normal and damaged hearing. Chapter 4. In: 

Berger EH, Royster LH, Royster JD, Driscoll 

DP, & Layne M, eds. The noise manual. 5th ed. 

Fairfax, VA: American Industrial Hygiene 

Association, pp 101-122. 

 9. Suter AH [1978]. The ability of mildlyimpaired individuals to discriminate speech in 

noise. Washington, DC: U.S. Environmental 

Protection Agency, Joint EPA/USAF study, 

EPA 550/9-78-100, AMRL-TR-78-4. 

 10. CFR [2003]. 29 CFR 1910.95. Code of 

Federal Regulations. Washington, DC: U.S. 

Government Printing Office, Office of the 

Federal Register. 

 11. NIOSH [1998]. Criteria for a 

recommended standard: Occupational noise 

exposure (revised criteria 1998). Cincinnati, OH: 

U.S. Department of Health and Human Services, 

Public Health Service, Centers for Disease 

Control and Prevention, National Institute for 

Occupational Safety and Health, DHHS 

(NIOSH) Publication No. 98-126. 

 12. Proctor NH, Hughes JP, Fischman ML 

[1988]. Chemical hazards of the workplace, 2nd 

ed. Philadelphia, PA: J.B. Lippincott Company. 

 13. NIOSH [1990]. Criteria for a 

recommended standard: occupational exposure 

to ethylene glycol monobutyl ether and ethylene 

glycol monobutyl ether acetate. 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. 90–118. 

 14. 69 Fed. Reg. 44594 [2004]. Federal 

Aviation Administration: Airworthiness 

Directives; BAE Systems (Operations) Limited 

Model BAe 146 and Avro 146-RJ Series 

Airplanes; final rule. 

 15. King M (martyn.king@baesystems.com) 

[2005]. Clarification of Airworthiness 

Directive. Private e-mail message to Randy L. 

Tubbs (rlt2@cdc.gov), December 1. 

 16. 40 Fed. Reg. 29114 [1975]. Federal 

Aviation Administration: Occupational Safety 

or Health Standards for Aircraft Crewmembers. 

 17. Association of Flight Attendants - CWA 

[2006]. AFA Files Suit Against OSHA, FAA. 

World Wide Web 

[URL=http://ashsd.afacwa.org/index.cfm?zone=

/unionactive/view_article.cfm&HoneID=25835]. 

Date accessed: March 2006. 

 18. Suter AH [2002]. Hearing conservation 

manual. 4th ed. Milwaukee, WI: Council for 
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Accreditation in Occupational Hearing 

Conservation. 

 19. Hager LD [2003]. Hearing conservation - 

Encouraging compliance. Advance for 

Audiologists, Merion Publications, Inc.: King 

of Prussia, PA, November/December, 32-34. 
Page 12 Health Hazard Evaluation Report No. 2003-0364-3012

Table 1 

Noise Dosimeter Results 

Percent Dose for Actual Time Sampled 

Mesaba Airlines 

Minneapolis, MN 

HETA 2003-0364-3012 

November 8-12, 2004 

Flight Attendant – 

Aircraft Tail # 

Time Sampled 

[hh:mm] 

Percent Dose 

OSHA PEL 

Percent Dose 

OSHA AL 

Percent Dose 

NIOSH REL 

Attendant 1 - #522 08:39 1% 14% 35% 

Attendant 2 - #522 08:37 1% 18% 43% 

Attendant 1 - #514 & #504 09:46 3% 20% 52% 

Attendant 2 - #514 & #504 09:47 3% 23% 66% 

Attendant 1 - #527 & #524 11:04 1% 31% 80% 

Attendant 2 - #527 & #524 11:04 3% 28% 70% 

Attendant 1 - #522 08:54 4% 24% 63% 

Attendant 2 - #522 08:59 6% 27% 75% 

Attendant 1 - #510 & #515 10:36 4% 26% 62% 

Attendant 2 - #510 & #515 10:39 1% 19% 52% 

Attendant 1 - #522 & #520 09:22 3% 24% 61% 

Attendant 2 - #522 & #520 09:29 5% 28% 81% 

Attendant 1 - #520 & #532 08:59 4% 23% 58% 

Attendant 2 - #520 & #532 09:01 3% 19% 54% 

Attendant 1 - #521 & #522 07:21 6% 21% 75% 

Attendant 2 - #521 & #522 07:20 2% 15% 41% 

Attendant 1 - #507 10:33 9% 49% 128% 

Attendant 2 - #507 10:36 7% 34% 94% 

Attendant 1 - #520 03:41 1% 9% 25% 

Attendant 2 - #520 03:43 0% 6% 15% 
Health Hazard Evaluation Report No. 2003-0364-3012 Page 13 

Table 2 

Extrapolated Percent Dose for Additional Scheduled Flight Time 

Mesaba Airlines 

Minneapolis, MN 

HETA 2003-0364-3012 

November 8-12, 2004 

Flight Attendant – 

Aircraft Tail # 

Remaining Flight 

Time 

[hh:mm] 

Extrapolated 

Percent Dose 

OSHA AL 

Extrapolated 

Percent Dose 

NIOSH REL 

Attendant 1 - #522 02:09 20% 47% 

Attendant 2 - #522 02:09 25% 58% 

Attendant 1 - #514 & #504 01:52 26% 67% 

Attendant 2 - #514 & #504 01:52 29% 81% 

Attendant 1 - #527 & #524 01:08 36% 93% 

Attendant 2 - #527 & #524 01:08 32% 80% 

Attendant 1 - #522 02:09 31% 84% 

Attendant 2 - #522 02:09 35% 97% 

Attendant 1 - #510 & #515 01:28 32% 76% 

Attendant 2 - #510 & #515 01:28 23% 60% 

Attendant 1 - #522 & #520 01:57 29% 75% 

Attendant 2 - #522 & #520 01:57 35% 103% 

Attendant 1 - #520 & #532 01:09 28% 71% 

Attendant 2 - #520 & #532 01:09 22% 62% 

Attendant 1 - #521 & #522 03:31 34% 111% 

Attendant 2 - #521 & #522 03:31 25% 67% 

Attendant 1 - #507 00:00 49% 128% 

Attendant 2 - #507 00:00 34% 94% 

Attendant 1 - #520 02:51 18% 44% 

Attendant 2 - #520 02:51 13% 30% 
Page 14 Health Hazard Evaluation Report No. 2003-0364-3012

Table 3 

Aircraft Carbon Monoxide Levels 

Mesaba Airlines 

Minneapolis, MN 

HETA 2003-0364-3012 

November 8-12, 2004 

Aircraft 

Tail # 

Sample 

Duration [Min]

8-hr. 

TWA 

[ppm] 

TWA 

For 

Sample 

Duration 

Max. 

STEL 

[ppm] 

Max. Peak 

[ppm] 

506 184 0 0 1 1 

532 199 0 1 2 4 

513 223 0 1 3 7 

511 209 0 1 3 6 

514 204 0 0 2 3 

522 227 1 1 3 3 

509 179 0 1 2 2 

516 199 1 1 6 13 

533 198 0 1 3 3 

529 193 1 2 4 4 
Health Hazard Evaluation Report No. 2003-0364-3012 Page 15 

Figure 1

Avro RJ-85 (#522) Flight Attendant 1

Mesaba Airlines

Minneapolis, MN

HETA 2003-0364

November 08, 2004

9:02 A

M

9:30 A

M

10:00 A

M

10:30 A

M

11:00 A

M

11:30 A

M

12:00 PM

12:30 PM

1:00 PM

1:30 PM

2:00 PM

2:30 PM

3:00 PM

3:30 PM

4:00 PM

4:30 PM

5:00 PM

5:40 PM

Time of Day

60

70

80

90

100

Noise Level [dB

A]

OSHA TWA = 76 dBA

NIOSH TWA = 81 dBA

D A D A D D A A

D - Scheduled Departure

A - Scheduled Arrival

Figure 2

Avro RJ-85 (#522) Flight Attendant 2

Mesaba Airlines

Minneapolis, MN

HETA 2003-0364

November 08, 2004

9:04 A

M

9:30 A

M

10:00 A

M

10:30 A

M

11:00 A

M

11:30 A

M

12:00 PM

12:30 PM

1:00 PM

1:30 PM

2:00 PM

2:30 PM

3:00 PM

3:30 PM

4:00 PM

4:30 PM

5:00 PM

5:40 PM

Time of Day

60

70

80

90

100

Noise Level [dB

A]

OSHA TWA = 78 dBA

NIOSH TWA = 81 dBA

D A D A D D A A

D - Scheduled Departure

A - Scheduled Arrival

 
Page 16 Health Hazard Evaluation Report No. 2003-0364-3012

Figure 3

Avro RJ-85 (#514 & #504) Flight Attendant 1

Mesaba Airlines

Minneapolis, MN

HETA 2003-0364

November 08, 2004

9:30 A

M

10:00 A

M

10:30 A

M

11:00 A

M

11:30 A

M

12:00 PM12:30 PM

1:00 PM

1:30 PM

2:00 PM

2:30 PM

3:00 PM

3:30 PM

4:00 PM

4:30 PM

5:00 PM

5:30 PM

6:00 PM

6:30 PM

7:16 PM

Time of Day

60

70

80

90

100

110

Noise Level [dB

A]

OSHA TWA = 79 dBA

NIOSH TWA = 83 dBA

D A D A D D A A

D - Scheduled Departure

A - Scheduled Arrival

Figure 4

Avro RJ-85 (#514 & #504) Flight Attendant 2

Mesaba Airlines

Minneapolis, MN

HETA 2003-0364

November 08, 2004

9:33 A

M

10:00 A

M

10:30 A

M

11:00 A

M

11:30 A

M

12:00 PM

12:30 PM

1:00 PM

1:30 PM

2:00 PM

2:30 PM

3:00 PM

3:30 PM

4:00 PM

4:30 PM

5:00 PM

5:30 PM

6:00 PM

6:30 PM

7:18 PM

Time of Day

60

70

80

90

100

Noise Level [dB

A]

OSHA TWA = 78 dBA

NIOSH TWA = 82 dBA

D A D A D D A A

D - Scheduled Departure

A - Scheduled Arrival
Health Hazard Evaluation Report No. 2003-0364-3012 Page 17 

Figure 5

Avro RJ-85 (#527 & #524) Aft Cabin Flight Attendant

Mesaba Airlines

Minneapolis, MN

HETA 2003-0364

November 09, 2004

8:09 A

M

9:00 A

M

9:30 A

M

10:00 A

M

10:30 A

M

11:00 A

M

11:30 A

M

12:00 PM

12:30 PM

1:00 PM

1:30 PM

2:00 PM

2:30 PM

3:00 PM

3:30 PM

4:00 PM

4:30 PM

5:00 PM

5:30 PM

6:00 PM

6:30 PM

7:12 PM

Time of Day

60

70

80

90

100

Noise Level [dB

A]

OSHA TWA = 82 dBA

NIOSH TWA = 84 dBA

D AD A D A D A

D - Scheduled Departure

A - Scheduled Arrival

Figure 6

Avro RJ-85 (#527 & #524) Forward Cabin Flight Attendant

Mesaba Airlines

Minneapolis, MN

HETA 2003-0364

November 09, 2004

8:10 A

M

9:00 A

M

9:30 A

M

10:00 A

M

10:30 A

M

11:00 A

M

11:30 A

M

12:00 PM

12:30 PM

1:00 PM

1:30 PM

2:00 PM

2:30 PM

3:00 PM

3:30 PM

4:00 PM

4:30 PM

5:00 PM

5:30 PM

6:00 PM

6:30 PM

7:13 PM

Time of Day

60

70

80

90

100

Noise Level [dB

A]

OSHA TWA = 81 dBA

NIOSH TWA = 84 dBA

D AD A D A D A

D - Scheduled Departure

A - Scheduled Arrival
Page 18 Health Hazard Evaluation Report No. 2003-0364-3012

Figure 7

Avro RJ-85 (#522) Flight Attendant 1

Mesaba Airlines

Minneapolis, MN

HETA 2003-0364

November 09, 2004

8:51 A

M

9:30 A

M

10:00 A

M

10:30 A

M

11:00 A

M

11:30 A

M

12:00 PM

12:30 PM

1:00 PM

1:30 PM

2:00 PM

2:30 PM

3:00 PM

3:30 PM

4:00 PM

4:30 PM

5:00 PM

5:35 PM

Time of Day

60

70

80

90

100

Noise Level [dB

A]

OSHA TWA = 80 dBA

NIOSH TWA = 83 dBA

D AD A D A D

D - Scheduled Departure

A - Scheduled Arrival

 

Figure 8

Avro RJ-85 (#522) Flight Attendant 2

Mesaba Airlines

Minneapolis, MN

HETA 2003-0364

November 09, 2004

8:46 A

M

9:30 A

M

10:00 A

M

10:30 A

M

11:00 A

M

11:30 A

M

12:00 PM

12:30 PM

1:00 PM

1:30 PM

2:00 PM

2:30 PM

3:00 PM

3:30 PM

4:00 PM

4:30 PM

5:00 PM

5:35 PM

Time of Day

60

70

80

90

100

Noise Level [dB

A]

OSHA TWA = 81 dBA

NIOSH TWA = 84 dBA

D AD A D A D

D - Scheduled Departure

A - Scheduled Arrival
Health Hazard Evaluation Report No. 2003-0364-3012 Page 19 

Figure 9

Avro RJ-85 (#510 & #515) Aft Cabin Flight Attendant

Mesaba Airlines

Minneapolis, MN

HETA 2003-0364

November 10, 2004

8:32 A

M

9:00 A

M

9:30 A

M

10:00 A

M

10:30 A

M

11:00 A

M

11:30 A

M

12:00 PM

12:30 PM

1:00 PM

1:30 PM

2:00 PM

2:30 PM

3:00 PM

3:30 PM

4:00 PM

4:30 PM

5:00 PM

5:30 PM

6:00 PM

6:30 PM

7:07 PM

Time of Day

60

70

80

90

100

Noise Level [dB

A]

OSHA TWA = 80 dBA

NIOSH TWA = 83 dBA

D A D A D A D

D - Scheduled Departure

A - Scheduled Arrival

 

Figure 10

Avro RJ-85 (#510 & #515) Forward Cabin Flight Attendant

Mesaba Airlines

Minneapolis, MN

HETA 2003-0364

November 10, 2004

8:30 A

M

9:00 A

M

9:30 A

M

10:00 A

M

10:30 A

M

11:00 A

M

11:30 A

M

12:00 PM

12:30 PM

1:00 PM

1:30 PM

2:00 PM

2:30 PM

3:00 PM

3:30 PM

4:00 PM

4:30 PM

5:00 PM

5:30 PM

6:00 PM

6:30 PM

7:08 PM

Time of Day

60

70

80

90

100

Noise Level [dB

A]

OSHA TWA = 78 dBA

NIOSH TWA = 82 dBA

D A D A D A D

D - Scheduled Departure

A - Scheduled Arrival
Page 20 Health Hazard Evaluation Report No. 2003-0364-3012

Figure 11

Avro RJ-85 (#522 & #520) Flight Attendant 1

Mesaba Airlines

Minneapolis, MN

HETA 2003-0364

November 10, 2004

8:49 A

M

9:30 A

M

10:00 A

M

10:30 A

M

11:00 A

M

11:30 A

M

12:00 PM

12:30 PM

1:00 PM

1:30 PM

2:00 PM

2:30 PM

3:00 PM

3:30 PM

4:00 PM

4:30 PM

5:00 PM

5:30 PM6:10 PM

Time of Day

60

70

80

90

100

Noise Level [dB

A]

OSHA TWA = 80 dBA

NIOSH TWA = 83 dBA

D A D A D A D

D - Scheduled Departure

A - Scheduled Arrival

 

Figure 12

Avro RJ-85 (#522 & #520) Flight Attendant 2

Mesaba Airlines

Minneapolis, MN

HETA 2003-0364

November 10, 2004

8:42 A

M

9:30 A

M

10:00 A

M

10:30 A

M

11:00 A

M

11:30 A

M

12:00 PM

12:30 PM

1:00 PM

1:30 PM

2:00 PM

2:30 PM

3:00 PM

3:30 PM

4:00 PM

4:30 PM

5:00 PM

5:30 PM

6:10 PM

Time of Day

60

70

80

90

100

Noise Level [dB

A]

OSHA TWA = 81 dBA

NIOSH TWA = 84 dBA

D A D A D A D

D - Scheduled Departure

A - Scheduled Arrival

 
Health Hazard Evaluation Report No. 2003-0364-3012 Page 21 

Figure 13

Avro RJ-85 (#520 & #532) Flight Attendant 1

Mesaba Airlines

Minneapolis, MN

HETA 2003-0364

November 11, 2004

8:23 A

M

9:00 A

M

9:30 A

M

10:00 A

M

10:30 A

M

11:00 A

M

11:30 A

M

12:00 PM

12:30 PM

1:00 PM

1:30 PM

2:00 PM

2:30 PM

3:00 PM

3:30 PM

4:00 PM

4:30 PM

5:00 PM

5:22 PM

Time of Day

60

70

80

90

100

Noise Level [dB

A]

OSHA TWA = 79 dBA

NIOSH TWA = 83 dBA

D A D A D A D

D - Scheduled Departure

A - Scheduled Arrival

 

Figure 14

Avro RJ-85 (#520 & #532) Flight Attendant 2

Mesaba Airlines

Minneapolis, MN

HETA 2003-0364

November 11, 2004

8:21 A

M

9:00 A

M

9:30 A

M

10:00 A

M

10:30 A

M

11:00 A

M

11:30 A

M

12:00 PM

12:30 PM

1:00 PM

1:30 PM

2:00 PM

2:30 PM

3:00 PM

3:30 PM

4:00 PM

4:30 PM

5:00 PM

5:22 PM

Time of Day

60

70

80

90

100

Noise Level [dB

A]

OSHA TWA = 78 dBA

NIOSH TWA = 82 dBA

D A D A D A D

D - Scheduled Departure

A - Scheduled Arrival
Page 22 Health Hazard Evaluation Report No. 2003-0364-3012

Figure 15

Avro RJ-85 (#521 & #522) Flight Attendant 1

Mesaba Airlines

Minneapolis, MN

HETA 2003-0364

November 11, 2004

12:30 PM

1:00 PM

1:30 PM

2:00 PM

2:30 PM

3:00 PM

3:30 PM

4:00 PM

4:30 PM

5:00 PM

5:30 PM

6:00 PM

6:30 PM

7:00 PM

7:30 PM

7:50 PM

Time of Day

60

70

80

90

100

Noise Level [dB

A]

OSHA TWA = 79 dBA

NIOSH TWA = 84 dBA

D A D A

A

D D

D - Scheduled Departure

A - Scheduled Arrival

 

Figure 16

Avro RJ-85 (#521 & #522) Flight Attendant 2

Mesaba Airlines

Minneapolis, MN

HETA 2003-0364

November 11, 2004

12:30 PM

1:00 PM

1:30 PM

2:00 PM

2:30 PM

3:00 PM

3:30 PM

4:00 PM

4:30 PM

5:00 PM

5:30 PM

6:00 PM

6:30 PM

7:00 PM

7:30 PM

7:50 PM

Time of Day

60

70

80

90

100

Noise Level [dB

A]

OSHA TWA = 76 dBA

NIOSH TWA = 81 dBA

D A D A D A D

D - Scheduled Departure

A - Scheduled Arrival
Health Hazard Evaluation Report No. 2003-0364-3012 Page 23 

Figure 17

Avro RJ-85 (#507) Flight Attendant 1

Mesaba Airlines

Minneapolis, MN

HETA 2003-0364

November 12, 2004

6:22 A

M

7:00 A

M

7:30 A

M

8:00 A

M

8:30 A

M

9:00 A

M

9:30 A

M

10:00 A

M

10:30 A

M

11:00 A

M

11:30 A

M

12:00 PM

12:30 PM

1:00 PM

1:30 PM

2:00 PM

2:30 PM

3:00 PM

3:30 PM

4:00 PM

4:30 PM

4:55 PM

Time of Day

60

70

80

90

100

Noise Level [dB

A]

OSHA TWA = 85 dBA

NIOSH TWA = 86 dBA

D A D A D

D - Scheduled Departure

A - Scheduled Arrival

D

 

Figure 18

Avro RJ-85 (#507) Flight Attendant 2

Mesaba Airlines

Minneapolis, MN

HETA 2003-0364

November 12, 2004

6:20 A

M

7:00 A

M

7:30 A

M

8:00 A

M

8:30 A

M

9:00 A

M

9:30 A

M

10:00 A

M

10:30 A

M

11:00 A

M

11:30 A

M

12:00 PM

12:30 PM

1:00 PM

1:30 PM

2:00 PM

2:30 PM

3:00 PM

3:30 PM

4:00 PM

4:30 PM

4:55 PM

Time of Day

60

70

80

90

100

Noise Level [dB

A]

OSHA TWA = 82 dBA

NIOSH TWA = 85 dBA

D A D A D

D - Scheduled Departure

A - Scheduled Arrival

D
Page 24 Health Hazard Evaluation Report No. 2003-0364-3012

Figure 19

Avro RJ-85 (#520) Flight Attendant 1

Mesaba Airlines

Minneapolis, MN

HETA 2003-0364

November 12, 2004

9:47 A

M

10:30 A

M

11:00 A

M

11:30 A

M

12:00 PM

12:30 PM

1:00 PM

1:27 PM

Time of Day

60

70

80

90

100

Noise Level [dB

A]

OSHA TWA = 72 dBA

NIOSH TWA = 79 dBA

D A

D - Scheduled Departure

A - Scheduled Arrival

D

Figure 20

Avro RJ-85 (#520) Flight Attendant 2

Mesaba Airlines

Minneapolis, MN

HETA 2003-0364

November 12, 2004

9:46 A

M

10:30 A

M

11:00 A

M

11:30 A

M

12:00 PM

12:30 PM

1:00 PM

1:28 PM

Time of Day

60

70

80

90

100

Noise Level [dB

A]

OSHA TWA = 70 dBA

NIOSH TWA = 77 dBA

D A

D - Scheduled Departure

A - Scheduled Arrival

D
Health Hazard Evaluation Report No. 2003-0364-3012 Page 25 

Figure 21 

Peak CO Levels for Avro RJ-85 #516 

Mesaba Airlines 

Minneapolis, MN 

HETA 2003-0364 

November 11, 2004 

0

5

10

15

16:5217:0417:1617:2817:4017:5218:0418:1618:2818:4018:5219:0419:1619:2819:4019:5220:04

Time of Day [miltary time - hh:mm]

CO Levels [ppm]

Figure 22 

Peak CO Levels for Avro RJ-85 #511 

Mesaba Airlines 

Minneapolis, MN 

HETA 2003-0364 

November 9, 2004 

0

5

10

15

14:2214:3414:4614:5815:1015:2215:3415:4615:5816:1016:2216:3416:4616:5817:1017:2217:3417:46

Time of Day [military time - hh:mm]

CO Levels [ppm]
Page 26 Health Hazard Evaluation Report No. 2003-0364-3012

APPENDIX 

Noise Spectra for the 10 AVRO RJ-85 Aircraft Tested During the NIOSH Investigation 

The noise levels presented in the graphs are the average of two maximum noise levels measured on two 

different flights during take-off and landing and at cruise altitude. The bars on the graphs represent these 

three flight conditions for each of the measured one-third octave center frequencies sampled. 
Health Hazard Evaluation Report No. 2003-0364-3012 Page 27 

Avro RJ-85 Tail #506

40

50

60

70

80

90

100

254063

100160250400630

1k

1.6k2.5k

4k

6.3k

10k16k

1/3 Octave Band Center Frequency [Hz]

Average MAX Noise Level

[dB SPL]

Take-off

Cruise

Landing

Avro RJ-85 Tail #509

40

50

60

70

80

90

100

254063

100160250400630

1k

1.6k2.5k

4k

6.3k

10k16k

1/3 Octave Band Center Frequency [Hz]

Average MAX Noise Level

[dB SPL]

Take-off

Cruise

Landing
Page 28 Health Hazard Evaluation Report No. 2003-0364-3012

Avro RJ-85 Tail #511

40

50

60

70

80

90

100

254063

100160250400630

1k

1.6k2.5k

4k

6.3k

10k16k

1/3 Octave Band Center Frequency [Hz]

Average MAX Noise Level

[dB SPL]

Take-off

Cruise

Landing

Avro RJ-85 Tail #513

40

50

60

70

80

90

100

254063

100160250400630

1k

1.6k2.5k

4k

6.3k

10k16k

1/3 Octave Band Center Frequency [Hz]

Average MAX Noise Level

[dB SPL]

Take-off

Cruise

Landing
Health Hazard Evaluation Report No. 2003-0364-3012 Page 29 

Avro RJ-85 Tail #514

40

50

60

70

80

90

100

254063

100160250400630

1k

1.6k2.5k

4k

6.3k

10k16k

1/3 Octave Band Center Frequency [Hz]

Average MAX Noise Level

[dB SPL]

Take-off

Cruise

Landing

Avro RJ-85 Tail #516

40

50

60

70

80

90

100

254063

100160250400630

1k

1.6k2.5k

4k

6.3k

10k16k

1/3 Octave Band Center Frequency [Hz]

Average MAX Noise Level

[dB SPL]

Take-off

Cruise

Landing
Page 30 Health Hazard Evaluation Report No. 2003-0364-3012

Avro RJ-85 Tail #522

40

50

60

70

80

90

100

254063

100160250400630

1k

1.6k2.5k

4k

6.3k

10k16k

1/3 Octave Band Center Frequency [Hz]

Average MAX Noise Level

[dB SPL]

Take-off

Cruise

Landing

Avro RJ-85 Tail #529

40

50

60

70

80

90

100

254063

100160250400630

1k

1.6k2.5k

4k

6.3k

10k16k

1/3 Octave Band Center Frequency [Hz]

Average MAX Noise Level

[dB SPL]

Take-off

Cruise

Landing
Health Hazard Evaluation Report No. 2003-0364-3012 Page 31 

Avro RJ-85 Tail #532

40

50

60

70

80

90

100

254063

100160250400630

1k

1.6k2.5k

4k

6.3k

10k16k

1/3 Octave Band Center Frequency [Hz]

Average MAX Noise Level

[dB SPL]

Take-off

Cruise

Landing

Avro RJ-85 Tail #533

40

50

60

70

80

90

100

254063

100160250400630

1k

1.6k2.5k

4k

6.3k

10k16k

1/3 Octave Band Center Frequency [Hz]

Average MAX Noise Level

[dB SPL]

Take-off

Cruise

Landing
Page 32 Health Hazard Evaluation Report No. 2003-0364-3012

DEPARTMENT OF HEALTH AND HUMAN SERVICES 

Centers for Disease Control and Prevention 

National Institute for Occupational Safety and Health 

4676 Columbia Parkway 

Cincinnati, OH 45226-1998 

OFFICIAL BUSINESS 

Penalty for private use $300 

Delivering on the Nation's promise: 

Safety and Health at work for all people 

through research and prevention

To receive NIOSH documents or information 

about occupational safety and health topics 

contact NIOSH at: 

1-800-35-NIOSH (356-4674) 

Fax: 1-513-533-8573 

E-mail: pubstaft@cdc.gov 

or visit the NIOSH web site at: 

http://www.cdc.gov/niosh 

S A F E R • H E A L T H I E R • P E O P L ETM