FMCSA-RRA-07-012

DOT-VNTSC-FMCSA-07-02
 

 

Human Factors Division (RTV-4G)
Office of Aviation Programs
John A. Volpe National Transportation Systems Center 


 

 

Emissions Impacts on Driver Safety

 


 

Prepared by:
Dr. Michelle Yeh, RITA/RTV-4G
John K. Pollard, RITA/RTV-4G  
U.S. Department of Transportation 
Research and Innovative Technology Administration 
John A. Volpe National Transportation Systems Center 
Cambridge, MA 02142 




Prepared for:
Michael Johnsen
Federal Motor Carrier Safety Administration
Washington, DC. 20590



July 2007

Final Report


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essential to the objective of this report.




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Final Report, July 2007


4. TITLE AND SUBTITLE
Emissions Impacts on Driver Safety

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6. AUTHOR(S)
Michelle Yeh and John K. Pollard 



7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)
U.S. Department of Transportation
John A. Volpe National Transportation Systems Center
Research and Innovative Technology Administration
Cambridge, MA 02142-1093


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DOT-VNTSC-FMCSA-07-02


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U.S. Department of Transportation
Federal Motor Carrier Safety Administration
Washington, DC. 20590


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FMCSA-RRA-07-012


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13. ABSTRACT (Maximum 200 words)
The Federal Motor Carriers Safety Administration (FMCSA) is concerned that truck 
drivers' exposure to high levels of air pollutants and mobile air toxics for 
potentially long periods of time, may lead to acute and/or long term cognitive 
impairments as a result. The goal of this project was to compile existing 
information addressing the following question: Does exposure to diesel exhaust 
at levels found in cabs affect driver safety performance by affecting driver 
sleep, alertness, reaction time, fatigue levels, or judgment-making abilities? 
To determine whether such an effect exists, the Volpe National Transportation 
Systems Center conducted expert interviews to obtain insight into the question 
and searched the environmental and medical literature. The results of these 
activities are reported here. 

The results of the expert interviews and literature search highlighted the fact 
that very little is known regarding the cognitive impact of exposure to diesel 
exhaust emissions. Certainly, the potential for an effect exists, but cognitive 
ability is generally confounded with other "lifestyle" factors for truck drivers 
(e.g., fatigue, shift work). Consequently, the question will be difficult to 
answer. Challenges for future research are identified.

14. SUBJECT TERMS
Diesel exhaust, emissions, driver safety, truck drivers, cognition, driver 
alertness, reaction time, fatigue, decision making

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59



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Unclassified


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PREFACE

This report was prepared by the Human Factors Division of the Office of Aviation 
Programs at the John A. Volpe National Transportation Systems Center, United 
States Department of Transportation. This research was conducted with funding 
from the Federal Motor Carriers Safety Administration (FMCSA); Michael Johnsen 
served as the project manager. The authors wish to thank Michael Johnsen, Jose 
Mantilla, and Paul Zebe for their direction and guidance in the development of 
this report. Special thanks also go to Christopher Zevitas for his help 
identifying experts to interview, to the researchers who participated in the 
interviews, and to Marilyn Gross for her assistance in conducting the literature 
review.

The views expressed herein are those of the authors and do not necessarily 
reflect the views of the Volpe National Transportation Systems Center, the 
Research and Innovative Technology Administration, or the United States 
Department of Transportation.

Feedback on this document can be sent to Michelle Yeh 
(Michelle.Yeh@volpe.dot.gov) or JK Pollard (John.K.Pollard@volpe.dot.gov). 





TABLE OF CONTENTS

1	Introduction	1

2	Expert Interviews	2

2.1	Participants	2

2.2	Method	2

2.3	Results	3

2.4	Conclusions	4

3	Literature Review	5

3.1	Method	5

3.2	Results	5

3.2.1	Diesel Emissions Exposure	6

3.2.2	Carbon Monoxide Exposure	7

3.2.3	Similar Substances	7

3.3	Summary	8

4	Summary and Challenges for Future Research	9

4.1	Summary	9

4.2	Research Challenges	9

4.3	Conclusion	10

References	12

Appendix A.	Notes from Expert Interviews	17

Appendix B.	Annotated Bibliography	24

B.1	Cognitive Effects of Diesel Exposure	25

B.2	Cognitive Effects of Carbon Monoxide Exposure	28

B.3	Cognitive Effects of Exposure to Jet Fuel Vapors	37

B.4	Other Health Effects of Diesel Exposure	43

B.5	Measuring Air Quality	47




EXECUTIVE SUMMARY

The goal of this project was to compile existing information regarding whether 
driver performance is affected by exposure to diesel exhaust emissions at levels 
found in cabs. The health effects of exposure on the cardiovascular and 
pulmonary systems are well documented, but there is a lack of understanding 
regarding the potential cognitive effects of diesel exhaust emissions exposure. 
The Federal Motor Carriers Safety Administration (FMCSA) is concerned that truck 
drivers' exposure to high levels of air pollutants and mobile air toxics for 
potentially long periods of time, could influence their safety and affect their 
sleep, alertness, or judgment. To address this issue, the Volpe National 
Transportation Systems Center conducted expert interviews to obtain insight into 
the issue and searched the environmental and medical literature for relevant 
research. The results of these two activities are reported here. Challenges to 
future research are also noted.

Expert Interviews

Ten researchers from the Environmental Protection Agency (EPA), Harvard School 
of Public Health, and Wright Patterson Air Force Base participated in the 
interviews. The researchers noted that there is a dearth of literature 
addressing the cognitive effects of diesel emissions. Instead, human studies 
have generally addressed the effects of diesel exhaust on pulmonary and 
cardiovascular health, and animal studies have typically focused on the 
neurotoxic effects of exposure. Most researchers acknowledged that there is a 
cause for concern; several studies have shown high concentrations of particles 
at hot spots such as truck stops and major freeways. However, little is known 
whether cognitive ability would be impaired as a consequence, and the consensus 
reached by the researchers interviewed was that such a question would be 
difficult to answer.

Literature Review

A review of the environmental and medical literature identified only three 
studies that directly examined the cognitive impacts of diesel exhaust exposure. 
Two of these studies focused on the chronic effects of exposure to diesel 
exhaust emissions and reported impairments in cognitive ability - as indicated 
by decrements in memory, problem solving, and reaction time - as a consequence. 
However, the level of exposure leading to the impairment was not measured, and 
the extent of the impairment (i.e., whether it is long-lasting or temporary) was 
not clear. Only one study measured and controlled for exposure, but its focus 
was on the health effects of acute, short-term exposure, particularly for those 
with sensitivity to chemicals. The results showed no effect on cognitive ability 
due to exposure between those who were chemically sensitive versus those who 
were not, although the former group reported more symptoms (e.g., dizziness, 
nausea, fatigue) than the latter group. However, performance differences within 
a group before, during, and after exposure were not compared as part of the 
study.

The literature search was expanded to include research that examined the 
cognitive impacts to chemicals in diesel exhaust or substances that could have 
similar cognitive effects as diesel exhaust, but no clear conclusions could be 
drawn from these studies. With respect to the literature on the cognitive 
effects of chemicals in diesel exhaust, the only studies found addressed the 
effects of carbon monoxide exposure. In these studies, exposure was generally 
acute and short-term. The cognitive impact of carbon monoxide exposure varied 
depending on the task; performance on vigilance and tracking tasks showed no 
effect of exposure and time estimation was impaired slightly, but performance on 
complex tasks requiring abstract thinking and manual dexterity or performing two 
tasks concurrently was impaired. Consequently, carbon monoxide could impair 
driver judgments at high levels of exposure, but it is not clear whether such 
levels are encountered in the typical driving environment. It is also important 
to consider that the level of carbon monoxide to which drivers are exposed 
fluctuates greatly due to weather and traffic. 

With respect to the literature for substances that could have similar cognitive 
consequences as diesel exhaust, a body of research addressing the cognitive 
effects of exposure to jet fuel vapors was considered potentially relevant, 
since both jet fuel and diesel are fuel oils and hence, closely related. Much of 
this research was the result of the military's concern that such exposure could 
lead to errors by pilots in navigation and communication. Studies addressing 
this issue focused on the chronic, long-term effects of exposure, i.e., over 
weeks in the case of animal studies and years for human studies. While animal 
studies examining the neurobehavioral consequences of jet fuel vapor exposure 
showed only short-term effects of exposure on behavior and brain development, 
the results of human studies examining the consequences of occupational exposure 
to jet fuel showed more lasting effects. Exposed workers had more variable 
performance on complex tasks compared to non-exposed workers and greater 
performance decrements on simple tasks. However, the degree to which exposure to 
diesel emissions has similar consequences as exposure to jet fuel vapors is 
unknown.

Challenges to Future Research

The results of the expert interviews and literature search highlight the fact 
that very little is known regarding the cognitive impact of exposure to diesel 
exhaust emissions. One reason for this is that the question is a difficult one 
to answer. 

First, cognitive ability is influenced by external stressors; for the truck 
driver, lifestyle factors (e.g., long hours, shift work) have significant 
impacts on cognitive functioning. Consequently, the specific impacts of diesel 
exhaust emissions exposure could be difficult to isolate and measure. Second, a 
good metric of cognitive ability that would be sensitive to the effects is 
needed. Results from the literature examining the effects of carbon monoxide 
exposure show varying levels of cognitive impairment depending on task 
complexity. 

Third, a dose-response effect of exposure on cognition would be difficult to 
determine. To measure the effects of acute, short-term exposure, cognitive tests 
would need to be administered at the time of exposure, but there are no easy 
methods to track drivers' exposure in real-time, and capturing drivers at the 
time of exposure would be methodologically challenging. To measure the chronic 
effects of long-term exposure, an estimate of the level of diesel exhaust 
emissions to which drivers are exposed over time would be needed. Developing a 
model to determine these estimates would require a large data collection effort 
to consider all factors that moderate exposure (e.g., commodity, length of 
haul).

One interesting approach is to examine whether there are any biological 
indicators (e.g., blood markers) of cognition. No such markers have yet been 
identified, and establishing the relationship between biological markers and 
cognitive ability would be a significant task. 

While controlled laboratory studies and animal studies offer an alternative to 
occupational studies in a complex real-world environment, it is not clear 
whether the results from these basic research studies would generalize to the 
truck driving population. The results of human laboratory studies would still 
need to be considered with other important lifestyle factors that influence 
cognitive ability, and animal studies would be limited to addressing the effects 
of diesel emissions exposure on basic cognition, whereas much of the skills 
required in driving in order to maintain safety require a high level of 
cognitive functioning.

Thus, any research to be conducted would be costly, difficult to implement, and 
any effects difficult to measure. Although the potential for an effect exists, 
it is important to note that the harmful effects of emissions are being 
addressed in other ways. The EPA is establishing a comprehensive national clean 
diesel initiative to reduce emissions from diesel engines in the heavy-duty 
commercial motor vehicle fleet through the use of high-efficiency catalytic 
exhaust emission control devices or comparably effective advanced technologies. 
It is hoped that when the program is fully implemented and the fleet of older 
engines has fully turned over (by 2030), the benefits of this initiative will be 
evidenced by the improved health and safety of all drivers.


1 INTRODUCTION
 
The Federal Motor Carriers Safety Administration (FMCSA) is concerned that truck 
drivers, who are exposed to diesel emissions for potentially long periods of 
time and over many years, may suffer acute and/or long term cognitive 
impairments as a result. Measurements of diesel exhaust in cabs of idling trucks 
and in "hot spots" where many trucks idle (e.g., overnight at truck stops or 
waiting at a border crossing) show levels of air pollutants and mobile air 
toxics that exceed federal health standards. The health impacts of diesel 
exhaust exposure have generally focused on its cancer-related effects and impact 
on cardiovascular and pulmonary function. Less is known regarding the impact of 
diesel exhaust exposure on cognition. Thus, FMCSA sponsored the Volpe National 
Transportation Systems Center (Volpe Center) to compile existing information 
that addressed the role (if any) of these pollutants in affecting 1) driver 
alertness, reaction time, and fatigue; and 2) the quality of sleep drivers 
experience in cabs with elevated levels of emissions. Specifically, the question 
of interest addressed was: Does exposure to diesel exhaust at levels found in 
cabs affect driver safety performance by affecting driver sleep, alertness, 
reaction time, fatigue levels, or judgment-making abilities?

The Volpe Center conducted two tasks. One task was a series of expert interviews 
to obtain insight into the question. The other task was a literature search of 
environmental and medical literature to determine whether any studies were 
conducted that examined the cognitive impacts of diesel exposure. The literature 
search included neurological studies, studies related to specific chemicals 
found in diesel exhaust, and studies examining the cognitive effects of 
substances that could have similar effects as diesel exhaust (e.g., jet fuel). 

This report presents the results of this effort. Section 2 provides a summary of 
the expert interviews and Section 3 presents an overview of the literature 
review findings. Detailed notes from each interview and an annotated 
bibliography of the literature identified in the review are provided in Appendix 
A and Appendix B, respectively. A summary of the findings and challenges for 
future research are identified in Section 4.



2 EXPERT INTERVIEWS

The Volpe Center conducted interviews with neurotoxicologists, engineers, and 
medical professionals for their insight regarding the cognitive effects of 
diesel exhaust exposure. This section describes the methodology for the 
interviews and presents a summary of the interview discussions. Notes from each 
interview are provided in Appendix A.

2.1 Participants
Ten subject matter experts participated in the interviews, as listed below: 

* EPA: Vernon Benignus, William Boyes, Ian Gilmour, Chad Bailey
* Harvard School of Public Health: Tom Smith, Eric Garshick, Jaime Hart
* United States (U.S.) Air Force, Wright Patterson Air Force Base/Science 
Applications International Corporation (SAIC): Gail Chapman, Palur Gunasekar, 
Shawn McInturf, and Haviland Steele
 
The participants were identified through recommendations from the Environmental 
Protection Agency (EPA), FMCSA, and the Volpe Center, as well as through a 
review of the relevant literature (see Section 3). 

The first interviews were conducted with researchers at the U.S. Environmental 
Protection Agency (EPA). FMCSA identified three experts as a starting point: 
Vernon Benignus, William Boyes, and Chad Bailey. Vernon Benignus and William 
Boyes are neurotoxicologists with knowledge regarding the neurobehavioral 
effects of organic compounds and solvents. They recruited Ian Gilmour, a 
research biologist, to participate in the discussion to provide input on the 
health effects of air pollutants. Chad Bailey is an environmental scientist with 
knowledge on the health effects of diesel emissions. 

During the course of the EPA interviews, it was recommended that the Volpe 
Center contact researchers at the Harvard School of Public Health to discuss 
their large-scale cohort study examining the occupational health effects of 
diesel exhaust emissions on truck drivers. It was not known whether the Harvard 
study addressed cognitive ability, however. Environmentalists at the Volpe 
Center also felt that researchers at Harvard would have insight into the problem 
and provided the initial contacts for Tom Smith, a Professor of Industrial 
Hygiene in the Department of Environmental Health, and Eric Garshick, an 
Assistant Professor at Harvard Medical School, both involved in the cohort 
study.

Finally, the results of the literature review, conducted concurrently with the 
interviews, indicated that research sponsored by the military might shed some 
light on the problem. In particular, the U.S. Air Force had conducted studies 
examining the neurobehavioral effects of exposure to jet fuel vapors. Because 
diesel exhaust and jet fuel are closely related, it was of interest to determine 
if the effects of exposure from jet fuel vapors might be similar to that 
expected from exposure to diesel exhaust emissions.

2.2 Method

To structure the interviews, six questions of interest were identified by the 
Volpe Center in conjunction with FMCSA:

1. Are you aware of any research on the effects of diesel emissions (preferably 
at levels a driver might be exposed to) on alertness, decision-making, or 
sleeping, or any other impacts that could affect a driver's ability to drive 
safely?

2. Do you think there is any chance that there could be an effect such as this?  

3. Some existing research suggests that there are elevated levels of emissions 
in truck cabs that exceed Federal agency standards. Are you aware of any 
research that has examined ambient air quality in 'hot spots' where trucks might 
park or inside truck cabs?

4. If primary research needs to be conducted (in the absence of existing 
research) what vehicle would be appropriate (Federal agency or organization with 
expertise in this field)?  

5. What factors should be considered in this research?

6. Can you recommend anyone else we should contact regarding this research?

The interviews were generally conducted as informal discussions. During the 
interview, experts were asked to discuss their research examining the health 
effects of diesel exhaust or similar substances or to discuss their interest in 
the topic. 

2.3 Results

The researchers interviewed noted that there is a paucity of literature 
examining the cognitive effects of diesel emissions. Only two studies were known 
to be of potential relevance: one that examined the neurobehavioral effects of 
occupational exposure by railroad workers and electricians to diesel exhaust 
(see Kilburn, 2000; note that this study was identified by FMCSA in their 
earlier review) and one that considered the likelihood of reporting Gulf War 
syndrome symptoms after exposure to diesel fuel vapors (see Fiedler, et al., 
2004). A third study noted by some researchers to be of interest, although not 
directly relevant to cognitive functioning, was a recent finding that 
particulate matter can migrate from nasal passages to the brain when it is 
inhaled (in particular, manganese). However, it was not clear from the research 
whether these particulates would have any impact on neurological functions.

Other research examining the health effects of diesel exhaust emissions has 
tended to focus on the cardiovascular or pulmonary effects. In the laboratory 
setting, these studies are conducted with healthy young adults or mild 
asthmatics, who inhale low levels of diesel exhaust fumes and then perform 
physical tasks. In the field, several occupational studies have measured the 
level of diesel emissions in vehicles and examined its effect on drivers. In one 
study, for example, the level of diesel emissions in patrol cars of North 
Carolina state troopers was measured and the health effects were evaluated with 
respect to the state troopers' blood profiles, blood pressure and heart rate. 
The results of the study identified cardiac consequences of the troopers' 
occupational exposure to diesel emissions (see Riediker, et al., 2003, 2004). 

With respect to the trucking industry, the Harvard School of Public Health is 
conducting a large study addressing the health effects of occupational exposure 
to diesel emissions. Specifically, the study examines the relationship between 
lung cancer and diesel and vehicle emissions exposure. Researchers have 
collected measurements for particulates at various trucking terminals, and a 
database is being developed so that exposure can be estimated based on workers' 
job title, work location, and terminal site. The results of the study so far 
have shown that there is an increased risk of lung cancer, cardiac mortality, 
and accidental death.

The discussions highlighted the fact that exposure to diesel emissions can occur 
in several ways. Of particular concern to FMCSA is the air quality in "hot 
spots", where trucks may park for an extended period of time with their engines 
idling. Several research studies have focused on one interchange in Tennessee 
along Interstate-40 and Watt Road, where there are three truck stops with an 
overall capacity for 700 overnight trucks. As part of the studies, the air 
quality at these truck stops and in cabs have been measured and modeled. The 
measurements showed high concentrations of particulate matter during the 
nighttime hours when there were more diesel trucks idling and the atmosphere was 
at its meteorological low, and during the winter months. Models of air quality 
show that truck stops represent islands of high concentration among low 
background areas. There is also a consistent finding showing that the 
concentration of very fine particles coming out of exhaust tailpipes is ten 
times higher along major freeways compared to urban background air. Other 
studies examining the levels of different particulate mixture components (i.e., 
soot, carbon) also show a steep gradient along major freeways.

Researchers were divided regarding whether there could be a cognitive effect of 
diesel emissions. Neurotoxicologists interviewed generally thought that an 
effect was possible; in fact, the EPA is proposing a series of animal studies to 
examine the neurophysiological and cognitive effects of diesel exposure. Animal 
studies provide a means for drawing clear conclusions between a neurotoxin and 
behavior, without influences by external sources. However, medical researchers 
were more cautious, acknowledging that cognitive issues are generally confounded 
with "lifestyle" factors for truck drivers (e.g., poor sleep). As a result, if 
cognitive impairments were found, it would not be clear whether the impairment 
was the result of exposure to diesel exhaust emissions or other external 
stressors.

2.4 Conclusions

If any research were to be conducted for FMCSA on the cognitive impact of diesel 
emissions, it would be important to consider factors that could be measured 
empirically and variables that could moderate the results. Both real-time 
exposure and cognitive ability are difficult to measure. A series of studies 
would be needed to identify markers of exposure and biological indicators of 
neurocognitive functioning. Additionally, it would be important to consider the 
method of exposure; inhalation is only one form and drivers may absorb diesel 
through the hands. The dose and level of exposure could vary depending on the 
source, magnitude and length of time of exposure. 

Several agencies are interested and in a position to conduct this kind of 
research should new studies be proposed by FMCSA. The EPA and military are best 
suited for conducting animal studies. For human studies, the Harvard School of 
Public Health has established relationships with trucking companies, unions, and 
management, and could expand their current study to measure the cognitive 
impacts of diesel exhaust exposure. 

 

3 LITERATURE REVIEW

A literature review was conducted on neurological studies and studies relating 
to the specific chemicals found in diesel exhaust that examined the cognitive 
impacts of diesel exhaust exposure (e.g., driver alertness, reaction time, 
fatigue levels, sleep-disruption, or judgment-making abilities). Literature 
addressing the potential cancer risks of diesel exhaust emissions exposure or 
its cardiovascular or pulmonary effects was not included in the scope of the 
review. The methodology for the literature search and a summary of the findings 
are presented in this section. An annotated bibliography, providing details for 
each of the studies discussed, is included as Appendix B. Note that while the 
literature review focused only on the those studies that addressed the cognitive 
effects of diesel exhaust emissions exposure, Appendix B presents a larger view 
of the problem and includes references for studies that addressed the non-
cognitive health effects of diesel exhaust exposure and for studies that 
measured air quality in general traffic and "hot spots" since it was expected 
that this research might also be of interest to the reader.

3.1 Method
 
The review searched the environmental and medical literature and included the 
following nine sources:

1) Transportation Research Information Service (TRIS)/National Transportation 
Library (NTL)
2) Defense Technical Information Center (DTIC)
3) Center for Disease Control (CDC)/National Institute of Occupational Safety & 
Health (NIOSH)
4) Medline
5) National Institute of Environmental Health Sciences
6) EPA
7) EbscoHost and InfoTrac (indexes to a variety of journals)
8) Health Effects Institute
9) Assorted links from Internet search engines (e.g., Google)
 
The focus was on those studies examining the cognitive effects of diesel 
exposure rather than examination of cancer risks or cardiovascular or pulmonary 
functions.

3.2 Results

The results of the literature search consisted of neurological studies and 
research related to chemicals found in diesel exhaust and similar substances. An 
overview of the findings is presented in the three following sections. Section 
3.2.1 addresses research on diesel exhaust exposure. Because so little 
literature specifically addressing the cognitive impact of diesel exhaust 
exposure was found, the literature search was expanded to consider research 
examining the cognitive impacts of exposure to chemicals found in diesel 
exhaust, based on the "Partial List of Chemicals Associated with Diesel Exhaust" 
specified by the U.S. Department of Labor (see 
www.osha.gov/SLTC/dieselexhaust/chemical.html). Of these chemicals, only studies 
were found addressing the cognitive effects of carbon monoxide exposure, and an 
overview of these findings are provided in Section 3.2.2. Finally, the 
literature search also considered the cognitive effects of substances that could 
have similar effects to diesel exhaust. In particular, the literature review 
identified a body of research addressing the cognitive effects of exposure to 
jet fuel vapors. Both jet fuel and diesel are fuel oils, so the two were 
considered to be closely related. Additionally, because diesel vapors from 
unburned fuel can be a component of diesel exhaust, findings from the literature 
regarding the cognitive impairments due to jet fuel vapors were expected to be 
potentially relevant. This is discussed in Section 3.3.3.

3.2.1 Diesel Emissions Exposure

The literature review identified only three studies that directly examined the 
cognitive impacts of diesel exhaust exposure, none of which were focused 
specifically on truck drivers. Two of these studies addressed the chronic 
effects of long-term exposure and reported impairments in cognitive ability. In 
the first study, Kilburn (2000) examined whether diesel exhaust-exposed workers 
had more impairment in central nervous system functions than non-exposed 
workers. Performance on neurophysiological and neuropsychological tests for 10 
railroad workers and six electricians (the chemically-exposed workers) was 
compared to a control group with no known history of exposure. The results 
showed impairments in neurobehavioral functions for the diesel-exposed workers 
relative to the control group and suggested that a link between diesel-exhaust 
exposure and impairment to the central nervous system (including cognitive 
functioning) may be present. Specifically, diesel-exhaust exposure led to 
cognitive decrements in memory, problem solving, reaction time and neurological 
impairments in vision and balance.

In the other study, Maruff, et al. (1998) addressed the neurological and 
cognitive consequences of chronic petrol sniffing. Blood tests, neurological 
tests, and psychological tests were performed on 34 non-sniffers who had never 
sniffed petrol, 33 current sniffers who had sniffed petrol for at least six 
months and were currently and actively sniffing; and 30 ex-sniffers, who had 
sniffed petrol for at least six months but had not sniffed petrol in the six -
month period prior to the study. The psychological test results showed better 
performance for non-sniffers on pattern and spatial recognition and paired 
association learning, particularly as the number of patterns increased, relative 
to current sniffers and ex-sniffers. Additionally, non-sniffers showed higher 
performance than current sniffers on visual search as the number of distractors 
increased. The findings suggest that petrol sniffing may compromise neurological 
and cognitive functions but that their effects may be reduced over time with 
abstinence.

While chronic exposure to diesel exhaust emissions has been found to impair 
cognitive functioning, less known are the effects of acute, short-term exposure. 
This was the focus of a study by Fiedler, et al. (2004), which assessed the 
health effects of acute exposure to diesel vapors with acetaldehyde on Gulf War 
veterans under stressful and non-stressful conditions. Participants were 
classified as being ill, based on criteria for chronic fatigue syndrome and 
self-reported chemical sensitivity, or healthy. They were exposed for 50 minutes 
in a controlled environment facility to 5 parts per million (ppm) diesel vapor, 
simulating typical exposure concentrations in garages where diesel and other 
fuels are used, with 0.5 ppm concentration of acetaldehyde added to simulate the 
soldiers' environmental conditions. Subjective reports of symptoms and 
performance on a dual-task driving task, with and without stressors, were 
compared for the two groups of Gulf War veterans before, during, and after 
exposure. The results indicated that although ill Gulf War veterans reported 
more severe symptoms than healthy Gulf War veterans as a result of the exposure 
(e.g., difficulty concentrating, disorientation, dizziness, and headaches), 
there was no performance difference attributable to cognitive ability between 
the two groups, as measured by the dual-task driving simulation test. However, 
it is important to note that there was no control group (i.e., a "no exposure" 
condition), nor was performance within a group compared before, during, or after 
exposure. 

Thus, the results of the literature review suggest that cognitive impairment may 
result from chronic exposure to diesel exhaust emissions (Kilburn, 2000 and 
Maruff, et al., 1998), but the level of exposure leading to the impairment was 
not known, and the extent of the impairment (i.e., whether it is temporary or 
not) is not clear. The one study that did measure and control for exposure 
showed that chemically-sensitive participants were more likely to report 
symptoms than healthy participants after acute exposure, but reported no 
difference attributable to cognitive ability between the two groups (Fiedler, et 
al., 2004). However, it was not clear whether there were performance differences 
within a group as a consequence of exposure.

3.2.2 Carbon Monoxide Exposure

Studies addressing the cognitive effects of carbon monoxide exposure were 
primarily conducted in controlled laboratory environments. In the studies, 
exposure was considered with respect to its short-term, acute effects and 
measured as a function of the concentration level (in parts per million, ppm) 
and/or via participants' carboxyhemoglobin (COHb) levels, a measure of the 
amount of carbon monoxide and hemoglobin in red blood cells when carbon monoxide 
is inhaled. The concentration levels tested vary from 0 ppm to 200 ppm, with 
COHb levels ranging from less than 1% (with no exposure) to 10% and higher. 
Subjectively, participants reported symptoms such as headaches at high levels of 
exposure (Stewart, et al., 1970; Stewart, et al., 1973). Objectively, the 
results of these studies generally showed no effects on monitoring (Horvath, 
Dahms, and O'Hanlon, 1971) and tracking (Hanks, 1970; Mikulka, et al., 1970; 
O'Donnell, et al., 1971) tasks and small effects on time estimation abilities 
(Beard and Wertheim, 1967; Bunnell and Horvath, 1988). Of concern, however, are 
studies that show the potential for memory deficits and impaired cognitive 
functioning on more complex tasks such as abstract thinking and manual dexterity 
(Amitai, et al., 1998; Ryan, 1990; Stewart, et al., 1970) and dual task 
performance (Milhevic, Gliner, and Horvath, 1983). 

With respect to driving performance, the effects of carbon monoxide exposure are 
not as clear. Wright, Randell, and Shephard (1973) showed that a 3.4% increase 
in COHb levels (achieved through carbon monoxide exposure at levels of 100 ppm 
for 2 hours) could impair judgments while driving. Additionally, COHb levels 
upwards of 11% created some "tunnel vision", with drivers focusing more on 
information in the forward field of view and less on information at the 
periphery (McFarland, 1973). However, it is not clear whether the levels of 
carbon monoxide to which drivers are exposed while on the road are equivalent to 
those used in the studies. In fact, one report that noted the carbon monoxide 
level in cars indicated levels of less than 25 ppm (Mayron and Winterhaller, 
1976), although the level of exposure fluctuates due to weather and traffic. 

It is worth noting that there were no negative consequences of carbon monoxide 
exposure on sleep (O'Donnell, Chikos, and Theodore, 1971); participants exposed 
to carbon monoxide experienced more "deep sleep" than those who were not 
exposed, with no impact on cognitive functioning.

3.2.3 Other Substances

Anecdotal reports by pilots complaining of nausea, poor coordination, short-term 
memory loss, and "slow thinking" after short-term acute exposure to jet fuel led 
to concerns that exposure to jet fuel vapors could result in pilot errors in 
navigation and communication (Davies, 1964; Porter, 1990; Smith, et al., 1997). 
Basic research investigating the consequences of exposure to jet-fuel vapors has 
generally focused on the consequences of chronic exposure, measured in weeks for 
controlled animal studies and years for human studies. The results of animal 
studies indicated short-term neurological and behavioral effects (e.g., during 
exposure or initially during postnatal development) without any long-term 
consequences (Mattie, et al., 2001; Nordholm, 1998). However, human studies 
suggest more permanent neurological effects. Three studies directly examined the 
prevalence of cognitive deficits on aircraft factory workers with long-term 
exposure to jet fuel (Knave, Mindus, and Struwe, 1979; Knave, Persson, Goldberg, 
and Westerholm, 1976; Knave, et al., 1978), the results of which suggest a link 
between exposure and cerebellar functioning (Ritchie, et al., 2001). The results 
show more symptoms of exposure (e.g., dizziness, headache, nausea, respiratory 
tract inflammation, chest palpitations) reported by workers with high exposure 
compared to workers with lower levels or no exposure. Exposed workers showed 
greater variability in performance on psychological tests of complex reaction 
time and greater performance decrements on tasks of simple reaction time and 
perceptual speed (Knave, Mindus, and Struwe, 1979; Knave, et al., 1978). 
Neurological tests on workers with high and low levels of exposure showed no 
differences due to level of exposure (Knave, Persson, Goldberg, and Westerholm, 
1976). The extent to which jet fuel vapors and diesel exhaust have similar 
effects is not known, however.

3.3 Summary

The review of the environmental and medical literature identified only three 
studies that directly examined the cognitive impacts of diesel exhaust exposure. 
Two of the three studies reported impairments in cognitive ability as a result 
of chronic exposure, but the level of exposure resulting in the impairment was 
not measurable, and whether the impairment was temporary or long lasting is not 
clear. Only one study controlled for exposure, but its focus was on determining 
the effects of acute diesel emissions exposure, particularly for those with 
chemical sensitivity. The results of the study showed no difference in cognitive 
ability due to exposure between chemically-sensitive participants and healthy 
participants, but no comparison of cognitive performance before, during, or 
after exposure within a group was conducted.

The literature search was expanded to include research that examined the 
cognitive effects to chemicals in diesel exhaust or substances that could have 
similar cognitive effects as diesel exhaust. With respect to the former, only 
studies addressing the cognitive effects of carbon monoxide exposure were 
identified. While carbon monoxide may impair driver judgments, it is not clear 
whether the level of carbon monoxide to which drivers are exposed is significant 
enough to cause such impairments. With respect to the latter, research examining 
the cognitive effects of exposure to jet fuel vapors was considered to be 
potentially relevant since both jet fuel and diesel are components and fuel oil 
and diesel exhaust emissions also contain a mixture of gases and vapors. The 
results of these studies showed no long-term neurobehavioral consequences of 
chronic exposure to jet fuel vapors in animals but more lasting effects in 
humans. However, the degree to which jet fuel vapors and diesel exhaust vapors 
have similar effects is not known.

4 SUMMARY AND CHALLENGES FOR FUTURE RESEARCH

The goal of this project was to determine whether truck drivers' exposure to 
diesel exhaust emissions at levels found in cabs affects cognitive ability. A 
series of expert interviews was conducted and the environmental and medical 
literature was reviewed to answer this question. Unfortunately, no conclusive 
answer was found; the potential for an effect exists, but the question is 
difficult to answer empirically. The results are summarized below and challenges 
to future research are discussed.

4.1 Summary

The consensus of the experts interviewed was that the effects of diesel exhaust 
emissions exposure on the cardiovascular and pulmonary system are well-known, 
but it is not clear whether a cognitive impact exists. While an effect is 
possible, a clear link between the two would be difficult to measure 
empirically. This may account for the lack of literature that directly addressed 
the cognitive effects of diesel emissions exposure. The literature review 
identified only three studies. While the results of those studies suggested that 
chronic exposure to diesel exhaust could affect memory, problem solving, and 
reaction time, the level of exposure resulting in the impairment and the 
severity of the impairment, was not defined. 

Research examining the cognitive effects of exposure to chemical components of 
diesel exhaust (i.e., carbon monoxide) and to substances that could have similar 
effects as diesel exhaust emissions (i.e., jet fuel vapors) was also considered. 
The literature addressing the cognitive-related health effects of chemical 
components in diesel exhaust was limited to research on carbon monoxide 
exposure. Carbon monoxide impaired performance only slightly on simple tasks 
(e.g., vigilance and tracking tasks), but more significantly on complex tasks, 
such as abstract thinking. However, the studies addressing carbon monoxide 
exposure were generally conducted in controlled laboratory environments, and 
whether levels of exposure in the typical driving environment are as high as 
those used was not clear. The literature examining the cognitive effects of 
exposure to jet fuel vapors was considered to be potentially relevant since 
diesel and jet fuel are closely related. Controlled animal studies and 
occupational studies on human participants showed contradictory results; the 
effect of exposure on animals had only short-term neurological effects, which 
dissipated once exposure ceased, but the results of human research studies 
showed long-term impairments.

4.2 Research Challenges

The expert interviews and literature search highlighted the fact that little is 
known regarding the cognitive effects of diesel exhaust emissions exposure. The 
results identified several challenges to conducting further research. 
Specifically, any research to address this issue would be costly and difficult 
to implement and any effects difficult to measure for a number of reasons.

First, it is difficult to isolate the cognitive effects due to diesel emissions 
exposure from the cognitive effects of other stressors, such as lifestyle (e.g., 
long hours, shift work). Second, a good metric of cognitive ability that would 
be sensitive to the effects is needed. Research addressing the cognitive impacts 
of carbon monoxide exposure showed varying results depending on the difficulty 
of the task. 

Third, a good dose-response effect of diesel emissions exposure on cognition 
would be methodologically difficult to collect. To measure the effects of acute, 
high-dosage exposure, cognitive tests would need to be administered at times of 
exposure, but the level of exposure is variable due to factors such as the 
traffic, weather, and time of day. There are no easy methods to track drivers' 
exposure to concentration of particles over time, and capturing drivers at the 
time of exposure to evaluate their cognitive ability would be a challenge. To 
measure the chronic effects of long-term exposure, an estimate of the level of 
diesel exhaust emissions to which drivers are exposed over time would be needed. 
Developing a model to determine these estimates would require a large data 
collection effort to consider factors that moderate exposure (e.g., commodity, 
length of haul).

One interesting approach for future research is to examine whether there are any 
biological indicators (e.g., blood markers) of cognition. That is, inflammatory 
markers in the blood that might indicate cognitive impairments. The Harvard 
School of Public Health is currently collecting biological data from truck 
drivers as part of a cohort study examining the non-cognitive health effects of 
diesel emissions exposure on the population. Although no biological markers for 
cognition have yet been identified, the Harvard School of Public Health could 
begin to examine whether such a marker exists and establish a relationship 
between a specific inflammatory marker and cognitive ability. This would be a 
significant task, however.

Additionally, the results from the cohort study conducted by the Harvard School 
of Public Health could be used to estimate drivers' level of exposure over time. 
Researchers are measuring concentrations of particulate matter at trucking 
terminals and in cabs (with body worn monitors). This data could be used to 
develop a model of exposure, and the model considered with respect to the 
overall cognitive effects of the truck driver lifestyle. Further refinements to 
the model could examine the contribution of other moderating variables; for 
example, the combined effects of aging and exposure by comparing data on 
cognitive ability collected from truck drivers with cognitive data collected 
from gerontology studies. Similar to the previous proposal, developing such a 
model and deriving any valuable data would be a long-term effort.

Several other options for basic research should be noted, although it is also 
important to consider that results from these controlled laboratory studies may 
not generalize to the truck driving population. A laboratory study is feasible; 
healthy participants can be exposed to diesel exhaust emissions at levels that 
would be representative of that encountered at truck stops and complete a series 
of tasks. The level of impairment and the extent of the impairments (i.e., how 
long it lasts) could be measured. However, the results would still need to be 
considered with respect to other important lifestyle factors that influence 
cognitive ability. Animal studies are also possible and could serve as a 
starting point for determining whether a clear link between cognition and diesel 
exposure exists. However, animal studies could measure only performance on 
simple tasks, and much of the skills required in driving in order to maintain 
safety require a high level of cognitive functioning. Consequently, the question 
of whether or not the results would generalize remains. It is possible that 
these basic human and animal studies could provide the basis for a model that 
examines the contribution of acute and chronic exposure to diesel exhaust to 
cognitive ability. 

If FMCSA determines that additional research is needed, several organizations 
would be interested in assisting in the effort. The Harvard School of Public 
Health could expand their current occupational study to address whether a 
cognitive effect of diesel exhaust emissions exposure exists. Harvard 
researchers have established relationships with several trucking companies and 
are traveling to terminals to collect information on exposure levels and 
biological data from truck drivers. As noted above, they could begin to examine 
whether a biological marker for cognitive ability exists and determine what 
tasks to administer to measure neurocognitive functioning. For basic research, 
the EPA is well suited to conducted animal studies; in fact, the EPA's 5-year 
plan proposes animal studies to examine the effect of diesel emissions exposure.

4.3 Conclusion

Unfortunately, the question regarding whether diesel exhaust emissions exposure 
affects cognition will remain unanswered for a while to come. The potential for 
an effect exists, but a clear answer is difficult to obtain. The harmful effects 
of emissions are being addressed in other ways, however. The EPA is establishing 
a comprehensive national clean diesel initiative to reduce emissions from the 
over 11 million diesel engines in the heavy-duty commercial motor vehicle fleet. 
Standards set forth by this initiative are anticipated to reduce nitrous oxide 
(NOX) and particulate matter emissions from heavy duty engines by 90% and 95% 
below current standard levels, respectively, through the use of high-efficiency 
catalytic exhaust emission control devices or comparably effective advanced 
technologies. These new standards will significantly reduce drivers' exposure to 
emissions as they are phased in between 2007-2010. The public health and 
environmental benefits of the program will come at an average cost increase of 
about $2,000 to $3,200 per new vehicle in the near term and about $1,200 to 
$1,900 per new vehicle in the long term.  

However, these standards may only offer a short-term solution. Estimates show an 
increasing trend of truck vehicle miles traveled (TVMT). In 2005, the Energy 
Information Administration estimated that truck drivers traveled an average of 
230 million miles, with an annual growth rate of 2.2%. Consequently, it is not 
known whether the benefits from the EPA's clean diesel initiative will be offset 
by an increase in the number of heavy-duty commercial motor vehicles in the 
long-term. It is hoped that when the program is fully implemented and the fleet 
of older engines has fully turned over (by 2030), the reduction in NOX, non-
methane hydrocarbon and particulate matter emissions will be evidenced through 
the improved health and safety of all drivers.




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Dumschat, R.E., and Mulligan, S.J.P. (2004). A simultaneous job- and task-based 
exposure evaluation of petroleum tanker drivers to benzene and total 
hydrocarbons. Applied Occupational and Environmental Hygiene, 1, 725-737.

[B.5]
Verma, D.K., Finkelstein, M.M., Kurtz, L., Smolynec, K., and Eyre, S. (2003). 
Diesel exhaust exposure in the Canadian railroad work environment. Applied 
Occupational and Environmental Hygiene, 18(1), 25-34.

[B.5]
Verma, D.K., Shaw, L., Julian, J., Smolynek, K., Wood, C., and Shaw, D. (1999). 
A comparison of sampling and analytical methods for assessing occupational 
exposure to diesel exhaust in a railroad work environment. Applied Occupational 
and Environmental Hygiene, 14(10), 701-714.

[B.4]
Wade III, J.F. and Newman, L.S. (1993). Diesel asthma: Reactive airways disease 
following overexposure to locomotive exhaust. Journal of Occupational Medicine, 
35(2), 149-154.

[B.2]
Wright, G., Randell, P., and Shephard, R.J. (1973). Carbon monoxide and driving 
skills. Archives of Environmental Health, 27, 349-354.

[B.5]
Zhu, Y., Kuhn, T., Mayo, P., and Hinds, W.C. (2006). Comparison of daytime and 
nighttime concentration profiles and size distribution of ultrafine particles 
near a major highway. Environmental Science and Technology, 40(8), 2531-2536.

[B.5]
Ziskind, R., Carlin, T., Axelrod, M., Allen, R.W., and Schwartz, S.H. (1977). 
Toxic Gases In Heavy Duty Diesel Truck Cabs (Report No FHWA-RD-77-139). U.S. 
Department of Transportation: Washington, D.C.


Appendix A. NOTES FROM EXPERT INTERVIEWS

Interviewee(s): Vernon Benignus, William Boyes, Ian Gilmour
Date: March 6, 2007

1. Are you aware of any research on the effects of diesel emissions (preferably 
at levels a driver might be exposed to) on alertness, decision-making, or 
sleeping, or any other impacts that could affect a driver's ability to drive 
safely?

No. Will Boyes has examined the effects of air pollution on animals with 
particular focus on the effects of the organic compounds. He is aware of 
primarily animal studies looking at the neurotoxic effects of diesel, rather 
than the cognitive effects. Recent studies looking at the effects of exposure on 
humans have included a meta-analysis examining the neurological effects of 
exposure to specific organic compounds. While these studies have not 
specifically examined the effect of diesel, the hydrocarbons in the fluids 
tested may have similar effects on the central nervous system (CNS) as the 
hydrocarbons in diesel exhaust, e.g., CNS-depressant properties. A recent 
finding is that particulate matter may be able to migrate from nasal passages 
(when inhaled) into the brain. This research has been done primarily on specific 
metals, e.g., manganese.

Ian Gilmour discussed new research that has examined the specific effects of the 
different chemical components in diesel exhaust on pulmonary health 
(specifically, asthma). He noted that there are eight labs that are conducting 
human-diesel inhalation studies but these studies are focused on the effects of 
diesel on the pulmonary and cardiovascular systems. These studies are conducted 
with healthy young adults or with mild asthmatics who are asked to inhale diesel 
(in the amount that may be typical of daily exposure) and asked to perform 
physical tasks. Researchers then examine lung function, cardiac output, heart 
rate, etc. No studies have specifically looked at the cognitive effects on 
sleep.

Other studies: Monitoring of North Carolina state troopers and air pollution 
levels in the patrol cars and associated the two with cardiac and respiratory 
functions.



2. Do you think there is any chance that there could be an effect such as this?  

Yes. In the EPA's 5-year research plan, there is an item to conduct animal 
studies to examine the neurophysiology or cognitive deficits with exposure to 
diesel, e.g., by placing trained rats into Skinner boxes in inhalation chambers 
where volatiles are trapped and testing their cognitive and neurological 
functions.


3. Some existing research suggests that there are elevated levels of emissions 
in truck cabs that exceed Federal agency standards. Are you aware of any 
research that has examined ambient air quality in 'hot spots' where trucks might 
park or inside truck cabs?

There are several initiatives underway to look at "hot spots" at or near 
roadways and highways and to look at children's exposure to diesel exhaust as a 
cause of asthma.


4. If primary research needs to be conducted (in the absence of existing 
research) what vehicle would be appropriate (Federal agency or organization with 
expertise in this field)?  

Federal agencies should conduct the programs to leverage with existing research 
programs. The Health Effects Institute was noted. This organization receives 
funding from EPA and automotive and trucking industries.


5. What factors should be considered in this research?

Research may be conducted using a controlled exposure (i.e., a laboratory study 
including control groups) to determine the specific effect of chemicals or a 
field study in which occupational participants are monitored in their work 
environments and compared with workers in similar occupations who have only 
normal exposure to diesel exhaust. 


6. Can you recommend anyone else we should contact regarding this research?
 
* For information on human studies: Bob Devlin (devlin.robert@epa.gov, 
919.966.6255); Michael Madden (919.966.6257)  
* Eric Garshick, Harvard School of Public Health. Epidemiological studies 
examining whether there is a link between diesel exposure and cancer.




Interviewee(s): Chad Bailey
Date: March 6, 2007

1. Are you aware of any research on the effects of diesel emissions (preferably 
at levels a driver might be exposed to) on alertness, decision-making, or 
sleeping, or any other impacts that could affect a driver's ability to drive 
safely?

No, but there have been several other studies looking at the cardiac and 
pulmonary effects of diesel exposure (e.g., lung cancer, asthma) in trucking 
terminals, truck yards, truck stops and in the railroad industry examining 
exposure in locomotive cabs.

* The Harvard University School of Public Health conducted an epidemiological 
study systematically evaluating emissions exposure of truck drivers at the five 
largest unionized trucking firms and the rate of lung cancer. A similar study 
was conducted looking at the exposure risk to rail workers.
 
* A study conducted in the state of North Carolina examined the effects of 
diesel exposure on state troopers. Researchers measured the troopers' blood 
pressure and heart rhythm and collected blood draws before and after their 
shifts and found increased heart rate variability in young police officers, and 
in cars with higher concentration of higher particulate matter. Additionally, 
the blood profile showed signs of inflammation, suggesting that there were 
cardiac consequences.

* Kilburn conducted a small study examining the effects of diesel exposure on 10 
railroad workers and six electricians and suggested that there may be 
neurobehavioral impairments resulting from diesel exposure. 

* Another study looked at the likelihood of Gulf War syndrome resulting from 
breathing fuel vapors.

* NIOSH has conducted worksite health hazard evaluations, e.g., a long-term 
miner study looking at lung cancer. 

* Vernon Benignus and Will Boyes published a paper addressing toluene exposure. 
Although toluene is not in diesel exhaust, if a fuel truck operator is routinely 
unloading fuel from a tank truck, it's possible that s/he could be exposed early 
on, and this could influence choice reaction time. 

* Other studies have examined the chemicals to which people in petroleum 
distribution chain are exposed, e.g., Dave Verma at McMaster University looked 
at tank truck drivers' exposure to vapors.
 

2. Do you think there is any chance that there could be an effect such as this?  

Yes.


3. Some existing research suggests that there are elevated levels of emissions 
in truck cabs that exceed Federal agency standards. Are you aware of any 
research that has examined ambient air quality in 'hot spots' where trucks might 
park or inside truck cabs?

Exposure to diesel emissions can occur in a variety of scenarios. For example, 
for a less-than-truckload company, exposure can occur at the truck terminals at 
the origin and destination points where there is lots of diesel activity in the 
truck yard or from engines on the dock. Once the truck is moving, exposure can 
occur on secondary roads, freeways, etc., with the most direct exposure at 
overnight locations (e.g., a truck stop). 

Several studies have measured exposure to diesel in Tennessee along Interstate-
40 and Watt Road. There are three truck stops here with a capacity for 700 
overnight trucks. As part of the Watt Road Environmental Laboratory Initiative, 
the air quality at this truck stop and in truck cabs has been measured. The 
results of these studies indicate that high concentration of particulate matter 
was found during the nighttime hours, when there were more diesel trucks idling 
and the atmosphere was at its meteorological low, and during the winter months, 
when more trucks are idling.

Additionally, researchers from Oak Ridge National Labs (John Storey, Jim Parks) 
collected a wide range of emissions measurements, which Chad Bailey is modeling. 
The modeling results show that truck stops represent islands of high 
concentration among low background areas. Other studies have looked at typical 
concentrations of air pollutants found on freeways and roadsides; data is being 
collected in California by USC and UCLA, and in the New York area by the 
University of Rochester, Albany. There is a consistent finding showing that 
along freeways, the concentration of very fine particles coming out of exhaust 
tailpipes is a tenfold higher along major freeways compared to urban background 
air. Studies that have looked at other component of particulate mixture (soot, 
carbon) also show a steep gradient along major freeway.



4. If primary research needs to be conducted (in the absence of existing 
research) what vehicle would be appropriate (Federal agency or organization with 
expertise in this field)?  

Academia would be well-equipped to conduct some of the research, e.g., through 
Industrial Hygiene and Occupational Health departments at Harvard University, 
University of Michigan, UCLA, and UC-Berkeley. Other organizations who might be 
able to assist are the Health Effects Institute (HEI) and NIOSH-CDC. Other 
experts in the field are Vern Benignus and Will Boyes. 



5. What factors should be considered in this research?


6. Can you recommend anyone else we should contact regarding this research?

* Eric Garshick, Harvard School of Public Health. Epidemiological studies 
examining whether there is a link between diesel exposure and cancer.
* Byron Bunker (emissions engineer): 734.214.4155


Other discussion topics

What is the impact of regulations that may be enacted? The concentration of 
particulate mass and the numbers of particles will decrease as a result of these 
standards. Reducing the sulfur in the base fuel will reduce ultrafine matter. 
With respect to soot, the new standards are expected to require manufacturers to 
use particle traps, so that emissions may not be an issue. 



	
Interviewee(s): Thomas Smith, Harvard University
Date: April 4, 2007

The Harvard School of Public Health is conducting a cohort study to examine the 
relationship between lung cancer and diesel and vehicle emissions exposure in 
the trucking industry. The cohort contains drivers, dock workers, mechanics, 
hostlers, and clerks from four large trucking companies. As part of the study, 
over 4,000 measurements of particulates were collected at various trucking 
terminals with different levels of operations. This data is being used to create 
a database of exposure to estimate exposure based on job title, work location, 
and terminal site. The results of the study so far have shown that there is an 
increased risk of lung cancer, cardiac mortality, and accidental death in this 
population.

1. Are you aware of any research on the effects of diesel emissions (preferably 
at levels a driver might be exposed to) on alertness, decision-making, or 
sleeping, or any other impacts that could affect a driver's ability to drive 
safely?

No, much of their work has focused on measuring exposure at different work 
locations for different types of workers at various terminal sites.


2. Do you think there is any chance that there could be an effect such as this?  

There could be an effect, but it is much more difficult to quantify than 
disease.


3. Some existing research suggests that there are elevated levels of emissions 
in truck cabs that exceed Federal agency standards. Are you aware of any 
research that has examined ambient air quality in 'hot spots' where trucks might 
park or inside truck cabs?

Measurements of air quality in truck cabs have been collected as part of their 
study. No "hot spots" were found, per se, but measurements suggest that truck 
drivers' exposure is primarily the result of traffic emissions from other cars. 
That is, addressing the effects of exposure to traffic emissions may be more 
feasible than addressing the effects of exposure to diesel, specifically. 
However, exposure levels are sporadic, e.g., occurring only if the driver is 
following close to another car or truck. Note that most of the drivers in their 
study are not long-haul drivers and do not sleep in their trucks.


4. If primary research needs to be conducted (in the absence of existing 
research) what vehicle would be appropriate (Federal agency or organization with 
expertise in this field)?  

The Harvard School of Public Health has a good working relationship with 
trucking companies and Teamsters, with whom they have current partnerships. A 
study to address the cognitive effects of diesel emissions exposure could be 
developed in conjunction with these organizations.


5. What factors should be considered in this research?
. 
* Symptoms of exposure
* Genetic responses/blood markers
* The development of tasks that are sensitive enough to measure differences in 
cognitive performance


11. Can you recommend anyone else we should contact regarding this research?
 
* Eric Garshick, Harvard School of Public Health
* Mark Weiskopf, Harvard School of Public Health (neurophysiologist who could 
help generate tasks for measuring cognition at terminals)



Interviewee(s): Eric Garshick and Jaime Hart, Harvard School of Public Health
Date: April 6, 2007


1. Are you aware of any research on the effects of diesel emissions (preferably 
at levels a driver might be exposed to) on alertness, decision-making, or 
sleeping, or any other impacts that could affect a driver's ability to drive 
safely?

There are organic compounds in exhaust that with enough exposure could have 
effects. There is literature addressing emissions exposure from school buses, 
and a birth cohort study in the New York area that examined the effect of PAH 
(polycyclic aromatic hydrocarbons) exposure on neurocognitive performance in 
schools. No one has yet looked at the neurocognitive effects of emissions on 
truck drivers. 


2. Do you think there is any chance that there could be an effect such as this?  

It is hard to tell. The cognitive issues may be confounded with other 
"lifestyle" factors (e.g., poor sleep, obesity), and it will be necessary to 
disentangle the various neurocognitive effects. Additionally there are many ways 
to measure cognition. 


3. Some existing research suggests that there are elevated levels of emissions 
in truck cabs that exceed Federal agency standards. Are you aware of any 
research that has examined ambient air quality in 'hot spots' where trucks might 
park or inside truck cabs?


4. If primary research needs to be conducted (in the absence of existing 
research) what vehicle would be appropriate (Federal agency or organization with 
expertise in this field)?  

The Harvard School of Public Health has established relationships with trucking 
companies, unions, and management. Most truck drivers in their study are willing 
to participate in research studies, particularly if they are paid to do so. Most 
of their truckers in their study are not long-haul drivers and do not sleep at 
truck stops. Instead, the drivers' companies often pay for a hotel on overnight 
trips.


5. What factors should be considered in this research?

The question currently asked is too broad and needs to be focused by determining 
what can be measured empirically. First, exposure can be measured in several 
ways. A pilot study may be needed in which several markers are collected (e.g., 
elemental carbons, organic vapors) to determine which markers to use and which 
might have the most impact on cognition. $200k is a reasonable budget for such 
pilot study. Second, a method for measuring the neurocognitive impact will need 
to be devised. A pilot study could be conducted to test the protocol at local 
terminals before expanding it to larger terminals.  Collecting blood samples to 
determine the presence of "inflammatory markers" may also be useful, especially 
if a correlation can be demonstrated between these markers and impaired 
cognitive response.

It may also be interesting to examine the effects of exposure versus lifestyle, 
or to rephrase the question to consider the risk factors of neurocognitive 
effects.


6. Can you recommend anyone else we should contact regarding this research?



Interviewee(s): Haviland Steele, SAIC; Dr. Gail Chapman, Dr. Palur Gunasekar, 
Dr. Shawn McInturf, Wright Patterson Air Force Base
Date: April 12, 2007


1. Are you aware of any research on the effects of diesel emissions (preferably 
at levels a driver might be exposed to) on alertness, decision-making, or 
sleeping, or any other impacts that could affect a driver's ability to drive 
safely?
 
The military has extensively examined the effects of exposure to jet fuel vapors 
because the potential for neurobehavioral effects was noticed. Shawn McInturf 
assisted in the data collection of eye-blink conditioning data on rats in one 
study that examined whether exposure to jet fuel resulted in any cerebellum 
deficits. The results showed differences in eye-blink responses among rats with 
high exposure to jet fuel vapors versus those with low exposure. A subsequent 
study examined the effect of jet fuel exposure on the rats' circadian rhythms, 
but the data collected showed no overall effect. With respect to diesel 
exposure, animal models have shown cardiovascular effects.


2. Do you think there is any chance that there could be an effect such as this?  

It is not clear; it would be important to measure the concentration levels at 
hot spots to determine what levels are inhaled. If these numbers are 
significant, then additional research may be needed to determine the cognitive 
impact.


3. Some existing research suggests that there are elevated levels of emissions 
in truck cabs that exceed Federal agency standards. Are you aware of any 
research that has examined ambient air quality in 'hot spots' where trucks might 
park or inside truck cabs?



4. If primary research needs to be conducted (in the absence of existing 
research) what vehicle would be appropriate (Federal agency or organization with 
expertise in this field)?  

Most of the toxicology research conducted at Wright Patterson Air Force Base 
consists of animal studies. These animal studies could be used to develop clear 
conclusions regarding a link between diesel exposure and cognition. Stressors 
could also be introduced to examine their effects.

Human body exposure studies, if needed, would be better conducted by the EPA. 
Wright Patterson AFB has not conducted toxicology studies on humans, and if they 
are needed, IRB approval could take up to a year to obtain.


5. What factors should be considered in this research?

Driver exposure may occur in various ways (e.g., inhaled from the air, absorbed 
from the hands). The dose and effects of exposure may vary depending on the 
source and length of time of exposure. Also, consider whether there are any 
biomarkers (e.g., blood markers) that could be indicative of cognitive deficits.

6. Can you recommend anyone else we should contact regarding this research?

* John Hinz, U.S. Air Force
* Laurie Roszell, U.S. Army
* Dave Mattie, U.S. Air Force
Appendix B. 



ANNOTATED BIBLIOGRAPHY
Appendix C. 
The annotated bibliography is organized into five sections. The first three 
references the literature addressing the cognitive effects of exposure to diesel 
exhaust (B.1), carbon monoxide (B.2), and jet fuel vapors (B.3) respectively. 
Each of the studies in these sections is described in a table that highlights 
the following:

* the purpose of the study, 
* the number of participants, 
* the method and level of exposure, 
* the task participants performed, 
* the results of the study, and 
* implications of the research.

Because the literature review identified research that addressed other aspects 
of diesel exhaust exposure, two additional sections in the annotated 
bibliography are included. Section B.4 lists literature identified in this 
search and in the Project Plan Agreement (PPA) that addresses other health 
effects of diesel exhaust exposure, e.g., on cardiovascular and pulmonary 
functions. The purpose of each study and an overview of the findings are 
provided for each article in Section B.4. Finally, Section B.5 contains 
literature addressing measurements of air quality in general traffic and in "hot 
spots." Because these studies do not address any health effects, only the 
purpose is noted.


B.1 Cognitive Effects of Diesel Exposure

Title:  Responses to controlled diesel vapor exposure among chemically sensitive 
Gulf War Veterans

Author(s):  Fiedler, N., Giardino, N., Natelson, B., Oteenweller, J.E., Weisel, 
C., Lioy, P., Lehrer, P., Ohman-Strickland, P., Kelly-McNeil, K., and Kipen, H.

Journal:  Psychosomatic Medicine, 66, 588-598

Year:   2004

Purpose:  To evaluate the health effects of exposure to diesel vapors with 
acetaldehyde on Gulf War veterans under stressful and non-stressful conditions

Participants:  19 healthy Gulf War veterans and 12 ill Gulf War veterans (based 
on criteria for chronic fatigue syndrome and self-reported chemical sensitivity, 
as indicated by sensitivity to 5 or more of 8 chemicals and 1 or more lifestyle 
change due to chemical sensitivities)

Exposure:  Participants were seated in a controlled environment facility (CEF; a 
7.3'x 9'x13.6' stainless steel chamber) and exposed to 5 ppm diesel vapor, 
simulating typical exposure concentrations in garages where diesel and other 
fuels are used, with 0.5 ppm concentration of acetaldehyde added to simulate the 
soldiers' environmental conditions. 

Task:  The experiment was divided into four phases: pre-exposure, exposure, 30-
minutes post-exposure, and 1-hour post exposure.
* In the pre-exposure phase, participants performed tasks to collect baseline 
data in a "clean air" environment. Participants completed a questionnaire 
indicating whether they experienced specific symptoms related to eye irritation, 
anxiety, somatic health (e.g., numbness/tingling, back pain, muscle aches), 
respiration, and cognition (disorientation, dizziness, ability to concentrate) 
and general symptoms related to exposure volatile organic compounds (e.g., 
headache, fatigue, lightheadedness, drowsiness, nausea), and provided ratings on 
the environmental quality, odor intensity, and odor irritation. Participants 
also performed a dual-task driving simulation test, in which they responded to a 
central task when a "safe" condition was present (e.g., white head lights in the 
left lane) and a peripheral task when a critical stimulus appeared (e.g., a stop 
sign). These tasks took approximately 50 minutes.
* In the exposure phase, participants were exposed to diesel vapors. After 25 
minutes, participants performed a Stroop task, which was used as a psychological 
stressor. Participants then completed the symptom and environmental 
questionnaires and the dual-task driving simulation test.
* Thirty minutes post-exposure, participants completed the symptom and 
environmental questionnaires and performed the dual-task driving simulation 
test. 
* One hour post-exposure, participants completed the symptom and environmental 
questionnaire.

Results
Ill Gulf War veterans indicated more severe symptoms, e.g., difficulty 
concentrating, disorientation, dizziness, and headaches, than healthy Gulf War 
veterans. These symptoms are consistent with physiological data showing reduced 
end-tidal CO2 levels and hyperventilation. Other symptoms experienced by ill 
Gulf War veterans included increased drowsiness and increased fatigue with 
prolonged exposure relative to the healthy veterans. However, despite these 
differences in the subjective ratings, there was no performance difference on 
the dual-task driving simulation test between the two groups. It is important to 
note that the veterans were given only a single exposure and that there was no 
control group that did not experience no exposure, apart from the baseline data 
collected before the exposure to diesel, so the results could reflect a stress 
resulting from anticipating the odor.

Implications: Persons with chemical intolerances are more likely than those 
without those same intolerances to hyperventilate as a result of exposure to 
general chemicals. The authors hypothesize that the ill Gulf War veterans may 
have exhibited a conditioned response (e.g., hyperventilating) to the odor of 
diesel fumes, possibly the result of associating the odors with the Gulf War. 
Thus, veterans' anxiety about chemical exposures due to previous illness may 
lead to chronic anxiety and contribute to the occurrence of general somatic 
symptoms such as fatigue when exposed to these chemicals.



Title:  Effects of diesel exhaust on neurobehavioral and pulmonary functions

Author(s):  Kilburn, K.H.

Journal:  Archives of Environmental Health, 55(1), 11-17

Year:   2000

Purpose:  To examine whether diesel exhaust exposure causes impairment in 
central nervous system functions

Participants:  16 chemically-exposed workers: 10 railroad workers (between 43 - 
60 years old) and 6 electricians (between 42 - 56 years old). A control group 
consisted of 159 males with no known exposure to chemicals.

Exposure:  Exposure level varied. The 10 railroad workers had a range of 15-40 
years of experience as diesel mechanics or train crewmen. The 6 electricians 
were working in a contained space with exhaust from idling diesel engines 
pouring into the space

Task:  Participants completed a self-administered questionnaire and a set of 
neurophysiological and neuropsychological tests measuring reaction time, 
balance, visual functioning, memory, dexterity, coordination, decision making, 
and peripheral sensation and discrimination.

Results
The group of diesel-exposed workers showed impairments on neurobehavioral 
functions relative to the control group, with abnormalities slightly higher in 
the railroad workers with longer-term exposures. Specifically, the tests showed 
decrements in balance, reaction time, blink reflex latency, problem solving, 
perceptual motor functions, and verbal and visual memory recall. Pulmonary test 
also showed that 10 of the diesel-exposed participants had airway obstructions, 
and 10 had chronic bronchitis, chest pain, tightness, and hyper reactive 
airways.

Implications: There may be a link between diesel-exhaust exposure and impairment 
to the central nervous system (including cognitive functioning). Specifically, 
diesel-exhaust exposure led to cognitive decrements in memory, problem solving, 
reaction time and neurological impairments with respect to vision and balance. 
Similar impairments were noted regardless of exposure time (i.e., exposure for 1 
year versus 25 years).



Title:  Neurological and cognitive abnormalities associated with chronic petrol 
sniffing

Author(s):  Maruff, P., Burns, C.B., Tyler, P., Currie, B.J., and Currie, J.

Journal:  Brain, 121, 1903-1917

Year:   1998

Purpose:  To examine the effects of chronic petrol sniffing on neurological and 
cognitive performance

Participants:  34 non-sniffers, 33 current-sniffers, and 30 ex-sniffers

Exposure:  Non-sniffers had never sniffed petrol; current sniffers had sniffed 
petrol for at least 6 months and were currently and actively sniffing; and ex-
sniffers had sniffed petrol for at least 6 months but had not sniffed petrol in 
a 6-month period prior to the study

Task:  Blood tests; neurological examination; psychological testing of motor 
function, simple and choice reaction time, visual search pattern recognition, 
spatial recognition, pattern-location paired-associate learning, visual 
attention, drawing and copying

Results
Results of the psychological testing indicated that current-sniffers performed 
poorer than non-sniffers on tasks of visual search as the number of distractors 
increased, pattern and spatial recognition, and paired association learning and 
memory tasks (particularly as the number of patterns increased). Ex-sniffers 
showed poorer performance on pattern and spatial recognition and paired 
associate learning tasks (similar to current-sniffers, this deficit was seen as 
the number of patterns increased) relative to non-sniffers. Performance speed 
did not vary among the three groups, suggesting that the cognitive deficits 
found were not due to an inability to perform the tasks.

Implications: Neurological and cognitive function is compromised with petrol 
sniffing but their effects may be reduced with abstinence.


B.2 Cognitive Effects of Carbon Monoxide Exposure

Title:  Neuropsychological impairment from acute low-level exposure to carbon 
monoxide

Author(s):  Amitai, Y., Zlotogorski, Z., Golan-Katzav, V., Wexler, A., and 
Gross, D.

Journal:  Archives of Neurology, 55, 845-848.

Year:   1998

Purpose:  To examine the effect of acute low-level carbon monoxide exposure on 
cognitive functioning

Participants:  92 students; 45 in the experimental group (6 of which were 
smokers) and 47 in the control group (8 smokers)

Exposure:  Participants in the experimental group were exposed to carbon 
monoxide from kerosene stoves in their dormitory rooms for a period of 1.5 to 
2.5 hours. The exposure level ranged from 17-100 ppm resulting in COHb levels 
ranging from 1% to 11%. 

Task:  Participants completed five tests measuring short-term and long-term 
semantic and figural memory; visuomotor coordination; visuospatial organization 
and constructional skills; auditory memory, attention, and concentration; 
spatial planning; and verbal memory and learning abilities. 

Results
Low level exposure to carbon monoxide impaired short- and long-term memory, 
visuomotor coordination, visuospatial planning and construction, and 
temporospatial orientation.

Implications: Carbon monoxide exposure was linked to cognitive decrements in 
memory, learning, attention, tracking, abstract thinking, and visuospatial 
planning and processing. 



Title:  Carbon monoxide exposure and cerebral function

Author(s):  Beard, R.R. and Grandstaff, N.

Journal:  Annals of the New York Academy of Sciences, 174(1), 385-395

Year:   1970

Purpose:  Summarize the literature regarding the effects of carbon monoxide on 
cerebral function

Results and Implications: Many studies have examined the effects of carbon 
monoxide on cerebral brain function without clear results. Testing in different 
environments can modify behavioral patterns, and the minimal dose needed to 
produce a demonstrable effect has varied.



Title:  Behavioral impairment associated with small doses of carbon monoxide

Author(s):  Beard, R.R. and Wertheim, G.A.

Journal:  American Journal of Public Health and the Nation's Health, 57 (11), 
2012-2022

Year:   1967

Purpose:  Examine the effects of carbon monoxide on rats, monkeys, and humans to 
determine behavioral changes

Experiment 1

Participants:  18 young adult, non-smoking, university students

Exposure:  Carbon monoxide was administered in concentrations of 0, 50, 100, 
175, and 200 parts per million

Task:  Participants were presented with two tones; the first was one second long 
and the second varied between 0.675 seconds and 1.325 seconds. Participants 
judged whether the length of the second tone was the same as, shorter, or 
longer, than the first by pressing one of three levers.

Results
Participants showed no overt changes in motor behavior, but judgments of time 
intervals, as measured by the ability to discriminate the length of two 
successively presented auditory tones, were impaired as a result of exposure to 
all carbon monoxide concentrations. Accuracy decreased as the carbon monoxide 
concentration exposure increased, and this performance decrement in judgment 
precision was similar for small and large differences in tone duration. Ninety 
minutes of exposure was sufficient to cause significant decrement with 50ppm, 
with shorter times needed for higher concentrations.

Experiment 2

Participants:  Rats

Exposure:  0, 250, 500, 750, 1000 ppm

Task:  Rats were trained to press levers to obtain food pellets or water 
(reinforcement) at fixed time intervals, e.g., the rat was rewarded with a food 
pellet three minutes after the previous pellet was delivered. Rats learn that 
pressing the level soon after the reinforcement is delivered is useless but 
increases the rate of lever pressing as the end of the fixed time interval 
approaches.

Results
Ninety minutes of exposure to carbon monoxide at a concentration level of 50 ppm 
led to decrements in discriminating the relative length of auditory tones. 
Recovery from carbon monoxide exposure was quick, however, suggesting that the 
performance decrement was not related to the amount of carbon monoxide 
hemoglobin in the blood. Additionally, carbon monoxide exposure impacted the 
rats' ability to discriminate time.

Implications: Low levels of carbon monoxide exposure may impact complex tasks 
such as time estimation, with performance decrements occurring faster for higher 
levels of carbon monoxide. Studies with rats showed similar effects of carbon 
monoxide exposure on time judgments. It is possible that these decrements in 
time estimation may lead to errors in speed estimation. However, this hypothesis 
is based on intuition rather than empirical evidence and needs testing.



Title:  Interactive effects of physical work and carbon monoxide on cognitive 
task performance

Author(s):  Bunnell, D.E. and Horvath, S.M.

Journal:  Aviation, Space, and Environmental Medicine, December, 1133-1138

Year:   1988

Purpose:  To evaluate the effects of carbon monoxide exposure and physical work 
on cognitive performance

Participants:  11 men and 7 women ranging in age from 18-29 years old

Exposure:  ~0.7-1%, 7%, and 10% COHb

Blood samples were collected prior to the study to determine the amount of 
carbon monoxide required to reach the target COHb levels. Participants breathed 
oxygen for 3 min, and then breathed a mixture of carbon monoxide and oxygen for 
5 min. Participants were then taken to an experimental chamber, with 45 ppm 
carbon monoxide in the 7% COHb condition and 65 ppm in the 10% COHb condition.

Task:  Participants sat or exercised in the experimental chamber for 50 minutes. 
In the exercise condition, participants walked on a treadmill at either 35% or 
60% of their maximum aerobic capacity. Participants then set for 5 min before 
completing five cognitive tasks measuring spatial processing, psychomotor 
tracking, short-term memory, arithmetic reasoning, visual search, and response 
inhibition. Participants then completed the Environmental Systems Questionnaire 
in which they indicated the extent to which they felt specific somatic systems 
during exposure.

Results
Participants reported no increase in symptoms with increasing levels of COHb, 
suggesting that participants could not tell when they were exposed to carbon 
monoxide. A cognitive effect of carbon monoxide exposure was reported in 
participants' responses to the second of two sequentially presented Stroop 
tasks, such that participants were hindered in their ability to learn a new 
response set. There was also an interaction of COHb level and exercise on visual 
search performance, with high levels of work (i.e., 60% exertion) at elevated 
COHb levels resulting in poorer performance.

Implications: COHb levels as high as 10% can be tolerated, even with physical 
work, with minor performance decrements in cognitive function



Title:  Human performance of a psychomotor test as a function of exposure to 
carbon monoxide

Author(s):  Hanks, T.G.

Journal:  Annals of the New York Academy of Sciences, 174(1), 421-424

Year:   1970

Purpose:  Determine whether carbon monoxide exposure in traffic affects driving 
judgment and control

Participants:  Nonsmoking, healthy young male university students (Note: the 
number of participants was not specified)

Exposure:  0, 25, 50, 75, and 100ppm carbon monoxide. Breath samples measured 
for carbon monoxide content before exposure and every 30 minutes during 
exposure, which lasted 41/2 hours.

Task:  Critical tracking task

Results
There was no effect of carbon monoxide exposure on tracking performance.

Implications: Exposure to carbon monoxide at levels up to 100 ppm (14.6% CoHB) 
did not result in decrements in tracking performance



Title:  Neurorimaging, cognitive, and neurobehavioral outcomes following carbon 
monoxide poisoning

Author(s):  Hopkins, R.O. and Moon. F.L.M.

Journal:  Behavioral and Cognitive Neuroscience Reviews, 5, 141-155

Year:   2006

Purpose:  To report on neurological and cognitive impairments resulting from 
carbon monoxide poisoning

Results and Implications: The focus of this review was on the effects of carbon 
monoxide-poisoning. The literature shows that carbon monoxide-poisoning leads to 
impairments in memory, executive function, mental processing speed, intellectual 
function, and attention, but the onset and severity of the impairments vary from 
individual to individual. Thus, a consistent pattern of cognitive deficits due 
to carbon monoxide-poisoning has not been found. 

There is no consistent criterion for characterizing less severe carbon monoxide 
poisoning, e.g., carbon monoxide exposure. COHb levels range from 1% to 15%, 
with few studies assessing the cognitive effects.



Title:  Carbon monoxide and human vigilance

Author(s):  Horvath, S.M., Dahms, T.E., and O'Hanlon, J.F.

Journal:  Archives of Environmental Health, 23, 343-347

Year:   1971

Purpose:  To determine whether the levels of carbon monoxide found in the urban 
atmosphere affect visual vigilance

Participants:  10 healthy males between 21 and 34 years old

Exposure:  The experiment consisted of three test sessions, one week apart. 
Participants inhaled a different gas mixture in each session, containing 0, 26, 
or 111 ppm carbon monoxide. During exposure, participants breathed the gas 
mixture for one hour before performing a monitoring task. Participants were also 
exposed to the gas while performing the task. COHb levels approached 0.8% in the 
control condition, 2.3% with 26 ppm exposure, and 6.6% in the 111 ppm condition.

Task:  Participants were asked to perform a monitoring task that required them 
to judge and discriminate between visual light signals and nonsignals. In the 
first part, participants were shown 10 signals interspersed among 50 nonsignals. 
In the second part, they were shown 10 signals within 290 nonsignals for four 
15-minute periods.

Results
There was no effect of carbon monoxide exposure in monitoring task performance 
at when the exposure level was 26 ppm relative to the control condition (0 ppm). 
Carbon monoxide exposure at 111 ppm (COHb levels of 6.6%) increased the effects 
of monotony and led to accuracy decrements in detecting signals over the two-
hour period. Heart rates and respiratory functioning was not affected.

Implications: Carbon monoxide exposure combined with monotony during driving 
could lead to less efficient performance of routine tasks and inability to cope 
with unexpected events. 

 

Title:  Carbon monoxide: A danger to the driver?

Author(s):  Mayron, L.W. and Winterhalter, J.J.

Journal:  Journal of the Air Pollution Control Association, 26(11), 1085-1088

Year:   1976

Purpose:  To determine carbon monoxide levels at intersections, busy streets and 
expressways, and in cars 

Method:  Measured carbon monoxide levels in the inside of an idling car from the 
driver's seat, in ventilating air entering the car, and in the ambient air at 
busy traffic locations and intersections

Results
Measurements of carbon monoxide, collected in Southern California under standard 
driving conditions generally show levels less than 25ppm carbon monoxide. The 
highest concentration of carbon monoxide measured was 45ppm for a 3-minute 
period. High concentrations (3-5%) of carboxyhemoglobin (resulting from exposure 
to 18-32 ppm carbon monoxide) may have adverse effects on the detection of small 
environmental changes. However, the impact on driving performance is not clear. 

The effect of carbon monoxide levels found in cars is dependent on how much time 
the driver spends in his/her car at one time and cumulatively. Carbon monoxide 
levels were measured in 51 cars; two were extremely high (70ppm and over 
100ppm), and 9 had levels higher than the 8-hour standard of 9ppm. This ambient 
air standard may be exceeded regularly, depending upon wind direction, wind 
strength, and traffic density. Readings of carbon monoxide levels in ventilating 
air ranged from 2 to 36 ppm. In traffic, the carbon monoxide level varied from 
25ppm to a high enough level to produce nausea and dizziness when traffic was 
stop-and-go. At busy intersections, the values of carbon monoxide ranged from 3-
60 ppm.

The main predictor of carbon monoxide levels is traffic delay. The actual amount 
of exposure to the driver is unknown.

Implications: It is not clear whether carbon monoxide exposure leads to car 
accidents, but measurements of carbon monoxide levels in cars suggest that it 
may be a contributing factor.



Title:  Low level exposure to carbon monoxide and driving performance

Author(s):  McFarland, R.A.

Journal:  Archives of Environmental Health, 27, 355-359

Year:   1973

Purpose:  Examine the effects of low levels of carbon monoxide on human 
performance and on driving

Participants:  27 participants ranging in age from 20-50 years old

Exposure:  17% COHb, 11% COHb, and no carbon monoxide exposure

A blood sample and alveolar sample were collected at the start of the experiment 
to determine initial COHb levels. Participants were then given normal room air 
or a mixture of 700 ppm carbon monoxide using a 500-liter gasometer; 
participants exhaled into a second gasometer to measure the amount retained. 
Each participant was exposed to carbon monoxide until one of the three levels 
was reached.

Task:  In the first phase of the study, participants completed laboratory tests 
measuring psychomotor reactions in dual-task performance, dark adaptation and 
glare recovery, peripheral vision, and depth perception. In the second phase, 
participants drove an automobile on an unopened, divided highway. 

Results
The psychomotor task required participants to respond to concurrent tasks 
appearing in the central field of vision and in the periphery. Performance on 
the central task showed no effect of carbon monoxide exposure, but performance 
on the peripheral task showed evidence of attentional lapses; participants 
failed to respond to the peripheral task if it appeared close in time to the 
central task more frequently at COHb levels of 17% and less so at 11%. There was 
no clear effect of carbon monoxide exposure on dark adaptation or glare 
recovery. The peripheral vision task required participants to look directly at a 
point while responding to lights in different patterns presented at 10, 20, 
and 30 from the center field of view. The results showed that participants 
missed more lights that appeared at a 20 point from the line of sight at a 17% 
COHb level than under control conditions. There was no difference at other 
levels or at other points. There was no difference in depth perception as a 
function of COHb levels.

Participants' visual information processing while driving was measured using a 
visual interruption apparatus that consisted of a helmet with a translucent face 
shield which moved up and down. While participants generally required more 
visual information at higher speeds (i.e., 50 mph) than lower speeds (i.e., 30 
mph), under conditions of carbon monoxide exposure, participants required more 
roadway viewing at higher speeds than without carbon monoxide.

Implications: COHb levels of 11% and 17% have slight effects on visual 
information processing, leading drivers to focus more attention on information 
in the forward field of view and consequently, miss information in peripheral 
vision.



Title:  Carbon monoxide exposure and information processing during perceptual-
motor performance

Author(s):  Mihevic, P.M., Gliner, J.A., and Horvath, S.M.

Journal:  International Archives of Occupational and Environmental Health, 51, 
353-363

Year:   1983

Purpose:  Examine the effects of carbon monoxide exposure on dual-task motor 
performance

Participants:  16 participants between 20 to 36 years old

Exposure:  Participants were seated in an 1.85 m x 1.85 m x 2.46 m chamber with 
clear walls. Carbon monoxide was mixed into the air stream from a tank 
containing 10% carbon monoxide in nitrogen (approximately 100 ppm).

Task:  Participants were seated in the environmental chamber for 2 1/2 hours. In 
the first 11/2-hour, participants sat in the chamber. In the last hour, 
participants completed a reciprocal tapping task, the reciprocal tapping task in 
conjunction with a digit identification task, and the reciprocal tapping task in 
conjunction with a digit subtraction task. In the reciprocal tapping task, 
participants tapped a stylus alternatively between two metal targets on a board. 
The task difficulty was manipulated by varying the width of the target (0.35 or 
0.75cm) and the distance between the targets (5.2, 10.2, 20.5, or 41.0 cm). In 
the digit identification task, participants were asked to verbally identify the 
digit (from 0 - 9) that appeared on a circular display, mounted on the board 
used for the tapping task, showed digits from 0 - 9. In the digit subtraction 
task, participants subtracted the digit that appeared from 100. 

Participants completed the tasks in room air and carbon monoxide conditions, the 
order of which was counterbalanced).

Results
Performance on the primary tapping task did not vary as a function of whether it 
was performed alone or in conjunction with the secondary digit manipulation task 
(digit identification or digit subtraction). However, performance on the 
secondary digit manipulation task was higher when it was performed alone than 
performed in conjunction with the primary task. Carbon monoxide exposure served 
as a stressor which led to performance decrements on the digit manipulation task 
at moderate levels of difficulty on the primary tapping task relative to regular 
room air exposure. There was no difference in primary task performance as a 
function of carbon monoxide exposure during the digit identification task.

Implications: Carbon monoxide exposure had minimal effects on motor performance. 
However, there is some evidence to suggest that as task difficulty increases - 
hence increasing the attentional demands, carbon monoxide exposure may 
contribute to deficits if other tasks are performed concurrently.



Title:  The effect of carbon monoxide on human performance

Author(s):  Mikulka, P., O'Donnell, R., Heinig, P., and Theodore, J.

Journal:  Annals of the New York Academy of Sciences, 174(1), 409-420

Year:   1970

Title:  Low level carbon monoxide exposure and human psychomotor performance

Author(s):  O'Donnell, R.D., Mikulka, P., Heinig, P., and Theodore, J.

Journal:  Toxicology and Applied Pharmacology, 18, 593-602

Year:   1971

Purpose:  Determine the effects of carbon monoxide exposure on time estimation, 
tracking, and ataxia

Participants:  9 male students between 19 and 22 years old

Exposure:  Experiments were conducted in the Thomas Domes at Wright-Patterson 
Air Force Base. The domes are enclosed environments, in which air flow at a rate 
of 40 ft3/min allows the atmosphere to change completely in a 20-minute time 
period. 

There were five exposure levels - 0, 50, 125, 200, and 250 ppm carbon monoxide, 
resulting in mean COHb levels of 0.96% at no exposure, 2.98% at 50 ppm, 6.64% at 
125 ppm, 10.35% at 200 ppm, and 12.37% at 250 ppm.

Task:  Participants completed 3 3-hour sessions at carbon monoxide-levels of 0, 
50, and 125 ppm. Participants were given a 15-minute rest period and then asked 
to complete a series of tracking and time estimation tasks. In the tracking 
task, participants manipulated a control stick to keep a needle on a display 
dial from going off scale. In the time estimation task, participants estimated 
10 second time-intervals for a 3-minute time period by tapping on an electric 
switch.

At the end of the exposure period, blood samples were collected, and 
participants completed the Pensacola Ataxia battery, which comprises of a set of 
balancing tasks.

Results
The results showed no effect of carbon monoxide exposure on tracking performance 
or time estimation ability; rather performance on the tasks improved over time. 
Additionally, carbon monoxide exposure did not affect participants' balance.

Implications: Low levels of carbon monoxide exposure do not lead to a 
performance decrement



Title:  Effect of carbon monoxide exposure on human sleep and psychomotor 
performance

Author(s):  O'Donnell, R.D., Chikos, P., and Theodore, J.

Journal:  Journal of Applied Physiology, 31(4), 513-518

Year:   1971

Purpose:  To analyze the effects of carbon monoxide exposure on sleep patterns 
and subsequent performance

Participants:  4 non-smoking, male Air Force personnel with altitude training

Exposure:  Exposure was conducted in the Thomas Domes at Wright-Patterson Air 
Force Base. Participants slept for nine nights in the Thomas dome. The first 
four nights were used to adapt the participant to the dome. Over the next five 
nights, participants were presented with two exposures, either to 75 of 150 ppm 
carbon monoxide. Each "exposure" night was followed by one night of "clean air", 
and the final night served as a control condition where no carbon monoxide was 
given. Carboxyhemoglobin levels reflected a relationship with the level of 
carbon monoxide exposure; 0.6% in the control condition, 5.9% in the 75-ppm 
condition, and 12.7% at 150 ppm.

Task:  Electrophysiological measures were collected each night. In the mornings, 
participants performed a series of performance tasks to measure visual function 
(e.g., critical flicker fusion), mental arithmetic, tracking performance, and 
time estimation.

Results
There was no effect on sleep. In fact, participants experience more periods of 
"deep sleep" and less light sleep under carbon monoxide exposure than in the 
control condition. Performance measurements also showed no effect of carbon 
monoxide exposure. 

Implications: Carbon monoxide did affect sleep, increasing the amount of deep 
sleep, but these changes did not affect subsequent cognitive functioning.




Title:  Memory disturbances following chronic, low-level carbon monoxide 
exposure

Author(s):  Ryan, C.M.

Journal:  Archives of Clinical Neuropscyhology, 5, 59-67

Year:   1990

Purpose:  Demonstrate transient decrements in cognitive function may occur with 
carbon monoxide exposure

Participants:  48-year old right-handed married female with a 3-year history of 
headaches, lethargy, and memory problems

Exposure:  Approximately 180 ppm carbon monoxide, possibly due to exposure from 
her furnace

Task:  Pittsburgh Occupational Exposures Test Battery, which consisted of a set 
of cognitive tests including incidental memory (requiring recall of digit-symbol 
pairs), recognition of recurring words, verbal learning (requiring learning 
pairs of unrelated words), word association, symbol digit learning, short- and 
long-term memory (copy a design and recall it 30 minutes later)

Results
Prior to exposure, the subject held a job that required heavy concentration and 
memory skills, but following exposure, the subject was not able to track verbal 
information and visual information presented within 30 minutes. While it cannot 
be ruled out that the subject is suffering from a medical disease that disrupts 
memory, it is more likely that this memory deficit is due to a three-year low-
level carbon monoxide exposure.

Implications: Long duration exposure to low-levels of carbon monoxide could lead 
to decrements in concentration and memory. 



Title:  Experimental human exposure to high concentrations of carbon monoxide

Author(s):  Stewart, R.D., Fisher, T.N., Baretta, E.D., and Herrmann, A.A.

Journal:  Archives of Environmental Health, 26, 1-7

Year:   1973

Participants:  6 healthy male volunteers

Exposure:  13 carbon monoxide exposure levels ranging from 1,000 ppm for 10 min 
to 30,400 ppm for 1 min. COHb levels ranged from 3.2% to 15.2%.

Task:  A physical examination was performed to collect baseline information 
including cardiovascular data (ECG) at rest and after 3-minutes of exercise on a 
stationary bicycle and blood samples. During exposure, participants sat in a 
slightly reclined position, and their heart rate, respiratory rate, brain 
activity (EEG), and visual evoked response (VER) were monitored. Following 
exposure, participants were given 100% oxygen for 20 minutes. A physical 
examination was performed again 16 hours after exposure and one week following 
exposure.

Results
Two participants reported headaches following high levels of exposure (15,000 
ppm for 2 min and 30,000 ppm for 1 min resulting in COHb levels of 11.6% and 
9.1%) and one noted a pounding sensation (35,600 ppm for 45 seconds). There was 
no change in participants' cardiovascular function (ECGs), blood pressure, heart 
rate, or brain activity (EEG) following exposure.

Implications: Carbon monoxide was rapidly absorbed during exposure, and this 
abrupt increase (as measured by the COHb concentration) led to headaches in 
three participants. There was no change in cardiovascular, respiratory, or brain 
activity.



Title:  Experimental human exposure to carbon monoxide

Author(s):  Stewart, R.D., Peterson, J.E., Baretta, E.D., Bachand, R.T., Hosco, 
M.J., and Herrmann, A.A.

Journal:  Archives of Environmental Health, 21, 154-164

Year:   1970

Participants:  18 healthy males ranging from 24 - 42 years old

Exposure:  < 1, 25, 50, 100, 200, 500, and 1,000 ppm for 30 minutes to 24 hours

Task:  Blood samples were collected, and participants completed tasks to measure 
time estimation, reaction time, hand steadiness, manual dexterity, brain 
activity, visual activity, and cardiovascular activity.

Results
The data showed no subjective symptoms or objective evidence of decrements in 
task performance during exposure levels less than 100 ppm of carbon monoxide 
over an 8-hour period (a COHb saturation of 11% to 13%). Carbon monoxide 
exposure at a level of 200 ppm for four hours (leading to a COHb level of 15% to 
20%) led to reports of headaches in the final hour, but there was no change in 
task performance. Exposure to higher carbon monoxide-levels (500 and 1,000 ppm, 
COHb saturation close to 30%) also led to subjective reports of headaches, the 
onset of which typically occurred within 1-2 hours of exposure, with minimal 
levels of exertion increasing the pain. At these higher levels of carbon 
monoxide exposure, changes in participants' visual evoked response (VER) and 
poorer manual dexterity were noted.

Implications: Poorer dexterity at high levels of carbon monoxide exposure (i.e., 
1,000 ppm) could potentially lead to mechanical driving errors (e.g., shifting 
gears).



Title:  Carbon monoxide and driving skills

Author(s):  Wright, G., Randell, P., and Shephard, R.J.

Journal:  Archives of Environmental Health, 27, 349-354

Year:   1973

Purpose:  To examine the effect of carbon monoxide exposure on tasks of driving 
skill

Participants:  50 adult volunteers

Exposure:  Half the participants breathed in 80 ml of carbon monoxide, added to 
a rebreathing system at a 2% concentration level, and the other half received no 
exposure (control group)

Task:  Before exposure, the level of carboxyhemoglobin in the blood was measured 
using a rebreathing method. Participants then completed a set of driving tests 
evaluating brake reaction time, night vision, glare vision, glare vision 
recovery, hand steadiness, and depth perception followed by a period on the 
driving simulator. 

Participants were then randomly distributed into two groups, with some receiving 
carbon monoxide (experimental condition) and some clean air (control condition). 
Participants then repeated the driving tests and simulation task.

Results
Carbon monoxide exposure increased COHb levels by 3.4% relative to initial 
values. This difference led to significant performance decrements in the driving 
simulator for participants in the experimental condition post-exposure. When 
comparing performance pre-and post-exposure, the control group (no exposure) 
exhibited more careful driving habits (e.g., releasing the parking break, using 
the turn signals). The exposure group, however, showed less improvements with 
respect to their previous performance and when compared to the performance of 
the control group. These performance decrements are attributed to impaired 
judgment due to a lack of cerebral oxygen. There was no effect on performance on 
the driving tests due to carbon monoxide exposure. 

Implications: A 3.4% increase in carboxyhemoglobin levels may be expected 
through carbon monoxide exposure to 100 ppm for two hours or 50 ppm for five 
hours. Truck drivers, regularly exposed to exhaust fumes, may experience these 
high carbon monoxide concentrations, which may impair safe driving habits.



B.3 Cognitive Effects of Exposure to Jet Fuel Vapors

Title:  Jet Fuel Intoxication

Author(s):  Davies, N.E.

Journal:  Aerospace Medicine, May, 481-482

Year:   1964

Purpose:  To report a case of in-flight intoxication due to jet fuel

Participants:  32-year old male Air Force pilot

Exposure:  Pilot flying a T-33A (two seated jet trainer) was exposed to what was 
estimated to be 3000 to 7000 ppm JP-4 fuel vapors for approximately 7 minutes

Task:  Flight from Craig Air Force Base, Alabama, to Dover Air Force Base, 
Delaware, with an emergency landing at Dobbins Air Force Base, Georgia

Results
At 15,000 feet, pilot began to feel groggy and switched regulator to 100% 
oxygen. At 20,000 feet, he felt weak and decided to land as quickly as possible. 
Symptoms showed a slight stagger in his gait, mild headache, slurred speech, and 
mild muscle weakness.

Implications: There are large individual differences with respect to hydrocarbon 
intoxication. Mild symptoms include giddiness, slurred speech, poor 
coordination, nausea, and mild euphoria. These may be followed by a headache, 
mild depression, throat irritation, or staggering. Severe cases lead to dyspnea, 
cyanosis, and coma.



Title:  Long-term exposure to jet fuel

An investigation on occupationally exposed workers with special reference to the 
nervous system.

Author(s):  Knave, B., Persson, H.E., Goldberg, J.M., and Westerholm, P.

Journal:  Scandinavian Journal of Work Environment and Health, 3, 152-164

Year:   1976

Purpose:  To examine the effects of long-term exposure to jet fuel on the 
nervous system

Participants:  29 aircraft factory workers, of which 13 were considered "heavily 
exposed" and 16 were considered "less heavily exposed"

Exposure:  All had been exposed for at least 5 years of employment. The "heavily 
exposed" group experienced continuous exposure to high concentrations of jet 
fuel fumes for several hours every day, for at least 20-30 minutes each time. 
The "less heavily exposed" group reported a more intermittent pattern of 
exposure than the heavily exposed group, with several days of heavy exposure 
followed by weeks or months without exposure.

Task:  Participants provided a personal history (heredity, previous health, 
occupational history, smoking, symptoms, etc.) and completed a neurological 
examination.

Results
All participants in the heavily exposed group reported symptoms of exposure 
consisting of dizziness (77%), headache (23%), nausea (31%), respiratory tract 
irritation (46%), and palpitations and pressure on the chest (23%). In the less 
heavily exposed group, 44% of the participants reported symptoms, ranging from 
dizziness (31%), headache (31%), nausea (13%), respiratory tract irritation 
(19%), and palpitations and pressure on the chest (13%). There were no 
significant differences found between the two groups from the neurological 
tests, but it is likely that there current sample was too small to show such an 
effect. A comparison of the jet fuel exposed workers to several other 
occupational groups (workers in a storage battery factory, workers in heavy 
metals industry) showed an increase in symptoms of neurasthenia (a lack of the 
central nervous system's energy reserves) and polyneuropathy (a neurological 
disorder in which the peripheral nerves throughout the body malfunction). 

Implications: Heavily exposed workers were more likely to report symptoms of 
exposure than less heavily exposed workers. Additionally, jet fuel exposed 
workers were more likely to report symptoms of potential neurological disorders 
than a reference group of non-jet fuel exposed workers. However, information 
regarding the fuel concentrations in the air when the symptoms occurred was not 
available.



Title:  Neurasthenic symptoms in workers occupationally exposed to jet fuel

Author(s):  Knave, B., Mindus, P., and Struwe, G.

Journal:  Acta Psychiatry Scandinavia, 60, 39-49

Year:   1979

Title:  Long-term exposure to jet fuel

II. A cross-sectional epidemiologic investigation on occupationally exposed 
industrial workers with special reference to the nervous system.

Author(s):  Knave, B., Olson, B.A., Elofsson, S., Gamberale, F., Isaksson, A., 
Mindus, P., Persson, H.E., Struwe, G., Wennberg, A., and Westerholm, P.

Journal:  Scandinavian Journal of Work Environment and Health, 4, 19-45

Year:   1978

Purpose:  To examine the effects of long-term exposure to jet fuel on the 
nervous system

Participants:  30 jet fuel exposed workers and 30 nonexposed workers (control)

Exposure:  Mean exposure time for experimental group was 17.7 years and control 
group was 19.8 years. Measured by time of employment, analysis of work 
practices, and measurements of airborne fuel contents during exposure

Task:  Interviews; psychological tests of reaction time addition, simple 
reaction time, memory, manual dexterity, and perceptual speed; and 
neurophysiological measurements (EEGs)

Results
Only four participants in the exposure group did not indicate any symptoms on 
exposure. Twenty-one of the 30 participants in the exposure group indicated they 
had experienced symptoms such as dizziness, headache, nausea, respiratory tract 
symptoms, palpitations, and thoracic oppression. Thirteen of the participants 
indicated feeling fatigued while working with jet fuel and in the evenings. A 
comparison of symptoms reported between the two groups also showed that those in 
the exposed group reported more depression, lack of initiative, palpitations, 
and sleep disturbances. The psychological test results showed participants in 
the exposure group had poorer performance on reaction time and perceptual speed 
tasks (i.e., those tasks with high attentional demand) but no difference 
attributable to exposure on memory or manual dexterity.

Implications: Exposure in the work context studied here was relatively stable. 
87% of the participants in the experimental group reported recurrent symptoms 
due to exposure (depression, fatigue, lack of initiative, dizziness were most 
common). Additionally, psychological testing showed greater variability in 
performance for participants in the experimental group relative to the control 
group for complex reaction time, greater decrement in performance over time on 
tasks of simple reaction time, and poorer perceptual speed performance.



Title:  Developmental neurobehavioral effects on JP-8 jet fuel on pups from 
female Sprague-Dawley rats exposed by oral gavage

Author(s):  Mattie, D.R., Cooper, J.R., Sterner, T.R., Schimmel, B.D., Bekkedal, 
M.Y.V., Bausman, T.A., and Young, S.M.

Journal:  United States Air Force Research Laboratory

Year:   2001

Purpose:  To examine the effects of prenatal JP-8 exposure on central nervous 
system development

Participants:  140+ female rats

Exposure:  0, 325, 750, 1500 mg/kg JP-8 daily by gavage (minimum of 35 female 
rats in each condition)

Task:  Tests of neurobehavioral development were conducted on the 68 litters 
consisting of 4 male and 4 female pups. Pups performed tasks requiring them to 
turn over, raise their head, swim, and complete a water maze.

Results
The results showed no difference in neurobehavioral development on simple tasks 
(e.g., turning over and raising one's head) or in completing the water maze. 
However, dose-related effects were found for swimming ability, such that pups 
exposed to jet fuel showed poorer performance initially than non-exposed pups 
although performance between the two groups equalized over time. This result 
suggests that exposure to jet fuel may delay brain development in areas of motor 
coordination, but that these effects disappear at later ages.

Implications: Exposure to JP-8 jet fuel may delay cerebellum development in pups 
but this effect is not lasting.



Title:  Cognitive neurobehavioral toxicity assessment of three hydrocarbon fuels

Author(s):  Nordholm, A.F.

Journal:  U.S. Army Medical Research and Materiel Command: Fort Detrick, 
Maryland

Year:   1998

Purpose:  Examine the effects of jet fuel exposure (JP-8, JP-4, and JP-5) on 
rats to determine neurobehavioral changes

Participants:  32 Sprague-Dawley rats

Exposure:  Whole-body inhalation of JP-8 (1.0 mg/L +/- 10%) or JP-5 (1.2 mg/L 
+/- 10%) vapor for 6 hours/day, 5 days/week for 6 weeks; to JP-4 (2.0 mg/L +/- 
10%) vapor for 6 hours/day for 14 days; or to a control condition. 
Concentrations were representative of real world vapor exposures experienced by 
operational military. Rats were rested 14-65 days after exposure to minimize the 
neurobehavioral effects resulting from physiological irritance or stress during 
exposure and to examine the presence of neurobehavioral deficits resulting 
several weeks post-exposure.

Task:  Neurobehavioral Toxicity Assessment Battery (NTAB), which consisted of 10 
tests that evaluated muscle strength, locomotion, physical fatigue, nociception 
(i.e., pain perception), auditory brainstem function, short-term memory, 
emotional depression, spatial localization, short-term memory, central nervous 
system sensitization, and social behavior.

Results
In the "long-term" (i.e., 60 days), exposure to the vapors led to no changes in 
neurology or behavior. However, 14-days post-exposure to JP-4 vapor for 6 
hours/day led to a significant decrease in the rats' response to pain, their 
acoustic startle response, and locomotion, and a significant increase in 
approaching "novel" food stimulus; this finding is consistent with an increase 
in dopamine and/or serotonin levels in the brain. Exposure to JP-8 also resulted 
in a significant increase in approaching "novel" food stimulus and significant 
increase in muscle strength, consistent with changes in the dopamine and DOPAC 
levels in several brain regions. JP-5 exposure led to no significant deficits on 
the NTAB tests. Exposure to the vapors reduced weight gains relative to rats in 
the control group; during exposure, rats in the experimental conditions weighed 
less than the control groups, but recovered their weight rapidly once the 
exposure period ended. 

Implications: Exposure (of rats) to JP-4, JP-6, or JP-8 vapors from 14-30 days 
may cause neurological and behavioral changes. Increased dopamine and/or 
serotonin levels due to JP-4 and JP-8 exposure have cognitive implications 
although it is not clear what that effect is. The results suggest that JP-4 has 
the greatest risk on neurological functioning and behavior, with the effect of 
JP-8 being greater than or equal to that of JP-5. Additional research is needed 
to determine if these humans will experience these same effects.



Title:  Audiological and vestibulo-oculomotor findings in workers exposed to 
solvents and jet fuel

Author(s):  dkvist, L.M., Arlinger, S.D., Edling, C., Larsby, B., and 
Bergoltz., L.M.

Journal:  Scandinavian Audiology, 16, 75-91

Year:   1987

Title:  Audiological findings in solvent-exposed workers

Author(s):  Bergoltz., L.M. and dkvist, L.M.

Journal:  Acta Otolaryngologica Supplementum, 412, 109-110

Year:   1984

Purpose:  Examine the effects of occupational exposure to solvents/jet fuel on 
the central and peripheral nervous systems

Participants:  3 participant groups: 

(A) 16 participants with diagnosis of solvent-induced psychoorganic syndrome 
based on neurophysiological and psychological testing
(B) 7 participants with suspected psychoorganic syndrome (neurasthenic symptoms) 
but normal findings on psychological tests
(C) 8 participants with significant exposure to jet fuel but free from 
psychoorganic syndrome

Exposure:  
(a) Participants were paint mixers, construction painters, spray painters, 
printers, and truck drivers with a range of exposure from 9 - 40 years. All 
participants had been free from exposure for at least 2 years 
(b) House painters, spray painters, and tanker drivers with a range of exposure 
time from 5 - 30 years
(c) Aircraft mechanics with a range of exposure from 15 - 41 years

Task:  Audiological and vestibular tests 

Results
The test results suggest potential disturbances in the central nervous system as 
a consequence of exposure to solvents. In particular, participants' performance 
on the test suggest that greater exposure increases the likelihood of lesions in 
the auditory cortex and brainstem. Decrements in performance were found on those 
tests evaluating the functional state of the cerebellum rather than tests of 
simple reflexes.

Implications: The results suggests a dose-effect relationship with greater 
levels of exposure resulting in an increased likelihood of psychoorganic 
syndrome and neurasthenic symptoms. 



Title:  Aviators intoxicated by inhalation of JP-5 fuel vapors

Author(s):  Porter, H.O.

Journal:  Aviation, Space, and Environmental Medicine, July, 654 - 656

Year:   1990

Purpose:  To report two cases of inhalation of JP-5 fuel vapors

Participants:  Two pilots (instructor and student)

Exposure:  Two pilots were exposed to jet fuel vapors  in a T-34C, unpressurized 
aircraft

Task:  Radio instrument night-training flight

Results
Pilots reported irritation to the eyes and euphoria (even after the instructor 
pilot notified the student pilot of the emergency), and experienced difficulty 
walking after exiting the aircraft and filling out familiar forms. Both appeared 
fatigued but a physical examination indicated that they were normal.

Implications: Pilots have reported JP-5 exposure-related symptoms such as 
transient memory loss (e.g., difficulty remembering emergency procedures), 
lightheadedness, and "slow thinking". Jet fuel exposure has led to errors by 
experienced pilots in navigation and communication.



Title:  Biological and Health Effects of JP-8 Exposure

Author(s):  Ritchie, G.D., Bekkedal, M.Y.V., Bobb, A.J., and Still, K.R.

Journal:  Naval Health Research Center Detachment Toxicology: Wright Patterson 
Air Force Base, OH

Year:   2001

Purpose:  To summarize the human, animal, and in vitro studies examining the 
biological and neurological health effects due to acute or long-term exposure to 
JP-8 and its chemical constituents

Implications: Long-term occupational exposure to JP-8 jet fuel vapors could lead 
to deficits in cerebellar functioning (e.g., eye-blink responses, balance).



Title:  Effect of chronic low-level exposure to jet fuel on postural balance of 
U.S. Air Force Personnel

Author(s):  Smith, L.B., Bhattacharya, A., Lemasters, G., Succop, P., Puhala II, 
E., Medvedovic, M., and Joyce, J.

Journal:  Journal of Occupational and Environmental Medicine, 39(7), 623-632 

Year:   1997

Purpose:  To examine the effect of low-level exposure to JP-8 jet fuel vapors on 
postural stability

Participants:  27 United States Air Force aircraft maintenance personnel (20 
male, 7 female) served in the experimental group; 25 unexposed participants (14 
male, 11 female) from the military, university, and other sources served as the 
control group

Exposure:  8-hour breathing zone samples were collected from each participant in 
the occupational group

Task:  Postural sway, measured on a force platform, to determine the effects of 
the proprioceptive, visual, and vestibular systems on balance. Participants 
stood on the platform with their eyes open and closed and then stood on a 4-inch 
foam over the platform with their eyes open and closed.

Results
Participants balance decreased (i.e., sway increased) as exposure level 
increased. The neurotoxic effect of jet fuel vapor exposure could be seen at 
low-levels of exposure (e.g., the level received when opening a storage tank).

Implications: The effect of jet fuel vapor inhalation on proprioception has 
safety consequences, e.g., for workers in dark areas and slippery surfaces. 
Long-term exposure could lead to degraded neurological functions.



B.4 Other Health Effects of Diesel Exposure

Title:  Environmental and clinical investigation of workmen exposed to diesel 
exhaust in railroad engine houses

Author(s):  Battigelli, M.C., Mannella, R.J., and Hatch, T.F.

Journal:  Industrial Medicine and Surgery, March, 121-124

Year:   1964

Purpose:  To investigate the clinical and physiological effects of diesel 
exhaust exposure on railroad workers

Notes:  Physical examination, chest x-rays, ECGs, spirometry, and medical 
histories were collected for 364 railroad workers (210 exposed engine repairmen, 
154 railroad workers). The results showed no differences in pulmonary functions 
or chest abnormalities due to exposure.



Title:  Health problems resulting from prolonged exposure to air pollution in 
diesel bus garages

Author(s):  El Batawi, M.A. and Noweir, M.H.

Journal:  Industrial Health, 4, 1-10

Year:   1966

Purpose:  To evaluate environmental conditions in two bus garages and to examine 
the effect on workers' health

Notes:  Measurements of gases and vapors in the garages were below the known 
threshold levels. 161 workers were examined to determine the health effects. 
Workers complained of irritation of the eyes (42%) and throat (19%) from gases 
and fumes, dyspepsia (25.5%), and cough and sputum (10.6%). Clinical examination 
indicated that 13.7% of the workers showed signs of upper respiratory tract 
disease, 8.7% had chronic bronchitis, and 4.3% had asthma. These levels are 
higher than those found in similar working groups without diesel exposure (8.9% 
for URT, 5.6% chronic bronchitis, and 1.1% asthma). The number of cases of 
gastritis and peptic ulcer was also higher than expected (14.3%). Finally, 29.8% 
of workers had high blood pressure (over 150 mmHG systolic and 80mmHG 
diastolic); for those working night shifts, the rate was 39.6%.



Title:  Acute changes in pulmonary function in salt miners

Author(s):  Gamble, J., Jones, W., Hudak, J., and Merchant, J.

Journal:  Industrial Hygiene for Mining and Tunneling - Proceedings of an ACGIH 
Topical Symposium (11/6-7/78), 119-128

Year:   1978

Purpose:  To examine dose-response relationship of particulate and/or NO2 
exposure over work shifts

Notes:  There was no relationship found between pulmonary function due to 
particulate and/or NO2 exposure



Title:  Epidemiological-environmental study of diesel bus garage workers: 
Chronic effects of diesel exhaust on the respiratory system

Author(s):  Gamble, J., Jones, W., and Minshall, S.

Journal:  Environmental Research, 44, 6-17

Year:   1987

Purpose:  To determine the relationship between diesel exposure and respiratory 
symptoms, cardiac function, and pulmonary function in diesel bus garage workers

Notes:  Diesel-exposed workers had a higher prevalence of coughing, phlegm, and 
wheezing than a comparison group, but there was no association with length of 
time in the occupation. Pulmonary function decreased as tenure increased. There 
was no effect found on cardiac function.



Title:  Diesel Exhaust: A Critical Analysis of Emissions, Exposure, and Health 
Effects

Author(s):  Health Effects Institute

Year:   1995

Purpose:  To evaluate the evidence examining the potential that diesel emissions 
cause cancer and to identify information gaps in the literature

Notes:  Epidemiologic data suggests a weak association between diesel exposure 
and lung cancer, but it is not clear what the relative risk of diesel exposure 
is with respect to other lifestyle factors (e.g., smoking, asbestos, diet). 
Additionally, no studies provide exposure information, i.e., a measurement of 
exposure for the time period most relevant to the development of lung cancer. 
Developing markers to measure diesel emissions exposure would help establish a 
risk assessment for lung cancer.



Title:  Acute overexposure to diesel exhaust: Report of 13 cases

Author(s):  Kahn, G., Orris, P., and Weeks, J.

Journal:  American Journal of Industrial Medicine, 13, 405-406

Year:   1988

Purpose:  To determine the risk of overexposure and its health effects

Notes:  13 incidents of overexposure at five underground coal mines were 
identified. Twelve miners reported mucous membrane irritation, headaches, and 
feeling light-headed. Eight miners indicated feelings of nausea; 4 reported 
feeling "high" and experiencing heartburn; 3 reported weakness, numbness and 
tingling in extremities; 2 reported chest tightness; and 2 reported wheezing. 
These symptoms were resolved within 1-2 days.



Title:  Historical estimation of diesel exhaust exposure in a cohort study of 
U.S. railroad workers and lung cancer

Author(s):  Laden, F., Hart, J.E., Eschenroeder, A., Smith, T.J., and Garshick, 
E.

Journal:  Cancer Causes Control, 17(7), 911-919

Year:   2006

Purpose:  To develop a profile of exposure in the railroad industry and to 
estimate lung cancer risk associated with the exposures 

Notes:  After adjusting for time and differences in the probability and 
intensity of exposure, the data showed an increased risk of lung cancer deaths 
for diesel-exposed railroad workers than non-exposed workers



Title:  Diesel exhaust inhalation causes vascular dysfunction and impaired 
endogenous fibrinolysis

Author(s):  Mills, N.L., Trnqvist, H., Robinson, S.D., Gonzalez, M., Darnley, 
K., MacNee, W., Boon, N.A., Donaldson, K., Blomberg, A., Sandstrom, T., and 
Newby, D.E.

Journal:  Circulation, December 20/27, 3930-3936.

Year:   2005

Purpose:  Examine the effects of diesel exhaust inhalation on cardiovascular 
function (endothelial vasomotor and fibrinolytic function)

Notes:  30 healthy, male nonsmokers, aged 20-38 years old, were exposed to 
diesel exhaust generated by an idling Volvo diesel engine. Inhalation of diluted 
diesel exhaust led to impairments in human vascular functioning, with as little 
as 1 hour of exposure.



Title:  Airway inflammation following exposure to diesel exhaust: a study of 
time kinetics using induced sputum

Author(s):  Nordenhll, C., Pourazar, J., Blomberg, A., Levin, J-O., Sandstrm, 
T., and delroth, E.

Journal:  European Respiratory Journal, 15, 1046-1051

Year:   2000

Purpose:  Examine the time kinetics of airway inflammation following exposure to 
diesel fuel

Notes:  15 healthy nonsmoking volunteers were exposed to diesel exhaust 
generated by an idling Volvo diesel engine. Participants alternated between 
moderate levels of exercise and rest periods for 15-minute intervals. Sputum 
induction, performed 6 hours and 24 hours after each exposure, showed that 
diesel exposure led to a time-dependent inflammatory response in the airways.



Title:  Urbanization and traffic related exposures as risk factors for 
schizophrenia

Author(s):  Pedersen, C.B. and Mortensen, P.B.

Journal:  BMC Psychiatry, 6(2)

Year:   2006

Purpose:  To explore the urban-rural difference in schizophrenia by examining 
whether traffic-related exposure increases the risk of the disease

Notes:  Initial examination of the data suggested that geographical proximity to 
the nearest major road and degree of urbanization had significant effects on the 
risk of developing schizophrenia. With respect to the former, higher risk levels 
were found in children living 500-1000 meters from the nearest major road; with 
respect to the latter, children living in the capital city at the time of their 
15th birthday had a greater risk of schizophrenia compared to children living in 
rural areas. However, further analysis indicated that the degree of urbanization 
accounted for the effect of geographical distance. That is, traffic-related 
exposure (e.g., to carbon monoxide, benzene) does not explain urban-rural 
differences in schizophrenia risk



Title:  Effect of prenatal exposure to airborne polycyclic aromatic hydrocarbons 
on neurodevelopment in the first three years of life among inner-city children

Author(s):  Perera, F.P., Rauh, V., Whyatt, R.M., Tsai, W.Y., Tang, D., Diaz, 
D., Hopener, L., Barr, D., Tu, Y.H., Camann, D., and Kinney, P.

Journal:  Environmental Health Perspectives

Year:   2006

Purpose:  To evaluate the effects of prenatal exposure to urban air pollutants 
on child mental and psychomotor development

Notes:  Three-year olds with high levels of prenatal exposure to polycyclic 
aromatic hydrocarbons (PAHs) received lower scores on tests of their mental 
development than those with lower levels of exposure. This exposure could lead 
to performance deficits in language, reading, and math in early school years. 
There was no effect of PAH-exposure on cognitive development observed for 
children under 3 years of age, nor were there any effects seen with respect to 
psychomotor development and behavioral issues.



Title:  An experimental investigation in animals of the functional and 
morphologic effects of single and repeated exposures to high and low 
concentrations of carbon monoxide

Author(s):  Preziosi, T.J., Lindenberg, R., Levy, D., and Christenson, M. 

Journal:  Annals of the New York Academy of Sciences, 174(1), 369-384

Year:   1970

Purpose:  To examine the pathological effects of carbon monoxide and to 
determine what levels of carbon monoxide in the atmosphere are safe if 
continuously exposed using animals (dogs)



Title:  Coal miners exposed to diesel exhaust emissions

Author(s):  Reger, R., Hancock, J., Hankinson, J., Hearl, F., and Merchant, J.

Journal:  American Occupational Hygiene, 26 (1-4), 799-815

Year:   1982

Purpose:  To examine differences in respiratory symptoms and pulmonary function 
between diesel-exposed and non-diesel exposed coal miners. 

Notes:  Underground miners and surface workers at diesel-use mines reported more 
coughing and phlegm than the control group of non-diesel exposed workers and 
showed patterns consistent with small airways disease. However, because miners' 
exposure time and exposure level to diesel emissions is low, no clear link 
between the health effects and diesel emissions could be made.



Title:  Particulate matter exposure in cars is associated with cardiovascular 
effects in healthy young men

Author(s):  Riediker, M., Cascio, W.E., Griggs, T.R., Herbst, M.C., Bromberg, 
P.A., Neas, L., Williams, R.W., and Devlin, R.B.

Journal:  American Journal of Respiratory Critical Care Medicine, 169, 934-940

Year:   2004

Purpose:  To understand the cardiovascular effects of occupational exposure to 
particulates (PM2.5)

Notes:  Nine young (23 to 30 years old), nonsmoking, North Carolina State 
Highway Patrol troopers were monitored over 4 days, while working a 3pm to 12am 
shift. Blood samples were collected before the first shift and 10 to 14 hours 
after each shift, and the troopers wore electrocardiogram monitors throughout 
their shift. Air-quality monitors were installed in their vehicles to measure 
PM2.5 levels. The results showed that PM2.5 exposure was associated with changes 
in heart rate variability and inflammatory and coagulatory responses in blood 
markers.



Title:  Diesel Asthma: Reactive airways disease following overexposure to 
locomotive exhaust

Author(s):  Wade III, J.F. and Newman, L.S.

Journal:  Journal of Occupational Medicine, 35(2), 149-154

Year:   1993

Purpose:  Report of three cases of railroad workers who developed asthma from 
diesel exhaust inhalation





B.5 Measuring Air Quality

Title:  Heavy-Duty Vehicle Idle Activity and Emissions Characterization Study

Author(s):  Baker, R., Ahanotou, D., and Allen, J.D.

Journal:  N/A

Year:   2004

Purpose:  To refine the Texas Commission on Environmental Quality's statewide 
On-Road Heavy-Duty Vehicle (HDV) Extended Idling Activity Database and Emissions 
Inventory for different source generators. Truck idling was characterized at 
different time scales and annual emissions projected through 2030



Title:  Methodology for evaluating mobile source air toxic emissions: 
Transportation project alternatives

Author(s):  Claggett, M. and Miller, T.L.

Journal:  Transportation Research Record: Journal of the Transportation Research 
Board, 1987, 32-41.

Year:   2006

Purpose:  To present a method for computing and evaluating mobile source air 
toxics (MSATs) emissions among a group of transportation project alternatives



Title:  Variability of mobile air toxic emissions factors with MOBILE6.2

Author(s):  Claggett, M. and Miller. T.L.

Journal:  Transportation Research Record: Journal of the Transportation Research 
Board, 1987, 103-109

Year:   2006

Purpose:  To discuss the range of mobile source air toxic (MSAT) emissions 
factors produced by the MOBILE6.2 model as a function of calendar year, ambient 
temperature, fuel (gasoline), Reid vapor pressure, and vehicle speed



Title:  Air quality measurements inside diesel truck cabs during long term 
idling

Author(s):  Doraiswamy, P., Davis, W.T., Miller, T.L., Lam, N., and Bubbosh, P.

Journal:  Transportation Research Record: Journal of the Transportation Research 
Board, 1987, 82-91

Year:   2006

Purpose:  To measure air quality inside and outside diesel truck cabs for 
different truck types in extended idling conditions



Title:  Integrating geographic information systems for transportation and air 
quality models for microscale analysis

Author(s):  Hallmark, S. and O'Neill, W.

Journal:  Transportation Research Record: Journal of the Transportation Research 
Board, 1551, 133-140

Year:   1996

Purpose:  To apply geographic information system (GIS) tools to microscale air 
quality analysis





Title:  Patterns of Drivers' Exposure to Particulate Matter

Author(s):  Krausse, B. and Mardaljevic, J.

Journal:  Spatial Planning, Urban Form, and Sustainable Transport. In K. 
Williams, Ed., (pp. 151-167). Ashgate: Burlington, VT.

Year:   2005

Purpose:  To evaluate drivers' exposure to particle emissions in urban traffic 
conditions



Title:  Exposure of trucking company workers to particulate matter during the 
winter

Author(s):  Lee, N.K., Smith, T.J., Garshick, E., Natkin, J., Reaser, P., Lane, 
K., Lee, H.K.

Journal:  Chemosphere, 61, 1677-1690

Year:   2005

Purpose:  To analyze air pollutant concentrations in the workplaces of various 
trucking companies during the winter

       
       
Title:  Study of exhaust emissions from idling heavy-duty diesel trucks and 
commercially available idle-reducing devices

Author(s):  Lim, H.

Journal:  United States Environmental Protection Agency (EPA420-R-02-025)

Year:   2002

Purpose:  To understand exhaust emissions and fuel consumption due to long-
duration idling in different weather conditions and accessory loads



Title:  Project level carbon monoxide hot-spot analysis for level of service D 
intersections

Author(s):  Meng, Y. and Niemeier, D.

Journal:  Transportation Research Record: Journal of the Transportation Research 
Board, 1641, 73-80.

Year:   1998

Purpose:  To present a screening methodology for modeling carbon monoxide 
concentrations at level of service D intersections using meteorological 
situation-orientated reference charts 



Title:  Characteristics and emissions of heavy-duty vehicles in Tennessee under 
the MOBILES model

Author(s):  Miller, T.L., Davis, W.T., Reed, G.D., Doraiswamy, P., and Fu, J.S.

Journal:  Transportation Research Record: Journal of the Transportation Research 
Board, 1842/2003, 99-108

Year:   2003

Purpose:  To compare characteristics of heavy-duty vehicles in the state of 
Tennessee with that described by national data in the MOBILE6 model and to 
propose a new method for classifying vehicles



Title:  Corrections to mileage accumulation rates for older vehicles and the 
effect on air pollution emissions

Author(s):  Miller, T.L., Davis, W.T., Reed, G.D., Doraiswamy, P., Tang, A., and 
Sanhueza, P.

Journal:  Transportation Research Record: Journal of the Transportation Research 
Board, 1750, 49-55

Year:   2001

Purpose:  To present a model for predicting average cumulative mileage for older 
vehicles to be used in estimating emissions levels 





Title:  Effect of county-level income on vehicle age distribution and emissions

Author(s):  Miller, T.L., Davis, W.T., Reed, G.D., Doraiswamy, P., and Tang, A.

Journal:  Transportation Research Record: Journal of the Transportation Research 
Board, 1815, 47-53.

Year:   2002

Purpose:  To analyze trends in the types and ages of vehicles driven in 
Tennessee relative to national data and to average personal income 



Title:  Diesel truck idling emissions - measurements at a PM2.5 hot spot

Author(s):  Miller, T.L., Fu, J.S., Hromis, B., Storey, J.M.E., and Parks, J.E.

Journal:  Proceedings of the Transportation Research Board 86th Annual Meeting

Year:   2007

Purpose:  To measure ambient concentrations of PM1.0, PM2.5, and PM10 at the 
Watt Road interchange on I-40 in Knoxville, TN. There are three large truck 
stops at this interchange, with up to 400 trucks idling at night and 20,000 
trucks traveling by day.



Title:  Diesel truck idling emissions - mobile source air toxics measured at a 
hot spot

Author(s):  Parks, J.E., Storey, J.M.E., Miller, T.L., Fu, J.S., and Hromis, B.

Journal:  Proceedings of the Transportation Research Board 86th Annual Meeting

Year:   2007

Purpose:  To measure mobile source air toxics (MSATs) emissions (e.g., 
formaldehyde, acetaldehyde, acrolein, and other species collected on di-
nitrophenyl hydrazine (DNPH) filters) at the Watt Road interchange on I-40 in 
Knoxville, TN. 



Title:  Travel characteristics of urban freight vehicles and their effects on 
emission factors

Author(s):  Protopapas, A., Chatterjee, A., Miller, T.L., and Everett, J.

Journal:  Transportation Research Record: Journal of the Transportation Research 
Board, 1941, 89-98

Year:   2005

Purpose:  To analyze and compare data for different commercial vehicle usage 
classes to develop input parameters for the MOBILE6 model



Title:  Mass, surface area and number metrics in diesel occupational exposure 
assessment

Author(s):  Ramachandran, G., Paulsen, D., Watts, W., and Kittelson, D.

Journal:  Journal of Environmental Monitoring, 7, 728-735

Year:   2005

Purpose:  To evaluate diesel exposure using three different metrics (aerosol 
mass, surface area, and number concentration) using three different occupational 
groups (bus drivers, parking garage attendants, and mechanics)



Title:  Exposure to particulate matter, volatile organic compounds, and other 
air pollutants inside patrol cars

Author(s):  Riediker, M., Williams, R., Devlin, R., Griggs, T., and Bromberg, P.

Journal:  Environmental Science and Technology, 37(1), 2084-2093

Year:   2003

Purpose:  To understand the potential occupational exposure of North Carolina 
Highway State troopers to air pollutants by measuring the average pollutant 
levels inside patrol cars 



Title:  The mobile source effect on curbside 1,3-butadiene, benzene, and 
particle-bound polycyclic aromatic hydrocarbons assessed at a tollbooth

Author(s):  Sapkota, A. and Buckley, T.J.

Journal:  Journal of the Air and Waste Management Association, 53, 740-748

Year:   2003

Purpose:  To measure human exposure (to benzene and 1,3-butadiene) with respect 
to vehicle volume and class

Notes:  Vehicles with more 2 axles produced higher levels of air pollutants than 
2-axle vehicles (9 times more benzene, 32 times more 1,3-butadiene, and 60 times 
more particle-bound PAH)



Title:  Exposure to Diesel Exhaust Emissions on Board Locomotives

Author(s):  Seshagiri, B.

Journal:  American Industrial Hygiene Association Journal, 64, 678-683

Year:   2003

Purpose:  To measure elemental carbon concentrations of diesel exhaust emissions 
in train cabs



Title:  Overview of particulate exposure in the U.S. trucking industry

Author(s):  Smith, T.J., Davis, M.E., Reaser, P., Natkin, J., Hart, J.E., Laden, 
F., Heff, A., and Garshick, E.

Journal:  Journal of Environmental Monitoring, 8, 711-720

Year:   2006

Purpose:  To measure occupational exposure to diesel exhaust and other common 
environmental pollutants at various work sites (e.g., terminal sites, office, 
dock area, shop areas)



Title:  Mobile source air toxics from idling trucks - A report from the Mexican 
Border

Author(s):  Storey, J.M.E., Lewis Sr., S.A., Zietsman, J., Villa, J.C., and 
Forrest, T.L.

Journal:  Proceedings of the Transportation Research Board 86th Annual Meeting

Year:   2007

Purpose:  To estimate idling emissions (in particular MSATs and diesel PM) from 
trucks crossing at the El Paso - Ciudad Juarez border



Title:  Particulate matter and aldehyde emissions from idling heavy-duty diesel 
trucks

Author(s):  Storey, J.M.E., Thomas, J.F., Lewis Sr., S.A., Dam, T.Q., Edwards, 
K.D., DeVault, G.L., and Retrossa, D.J.

Journal:  2003 SAE World Congress (SAE Technical Paper Series 2003-01-0289), 
Detroit, MI, March 3-6, 2003

Year:   2003

Purpose:  To measure diesel emissions from in-use idling trucks at the Aberdeen 
Test Center and to examine the impact of idle reduction technologies on emission 
levels



Title:  A simultaneous job- and task-based exposure evaluation of petroleum 
tanker drivers to benzene and total hydrocarbons

Author(s):  Verma, D.K., Cheng, W.K., Shaw, D.S., Shaw, M.L., Verma, P., Julian, 
J.A., Dumschat, R.E., and Mulligan, S.J.P.

Journal:  Applied Occupational and Environmental Hygiene, 1, 725-737

Year:   2004

Purpose:  To evaluate petroleum tanker drivers' exposure to benzene per task 
(e.g., loading, unloading, and travel) and on a full-shift basis




Title: Diesel exhaust exposure in the Canadian railroad work environment 

Author(s): Verma, D.K., Finkelstein, M.M., Kurtz, L., Smolynec, K., and Eyre, S. 

Journal: Applied Occupational and Environmental Hygiene, 18(1), 25-34 

Year:2003

 
Purpose: 
To investigate occupational exposure to diesel exhaust in the railroad industry. 
Specifically, to collect and measure elemental carbon levels in diesel exhaust 
and compare it to other industries 



Title: A comparison of sampling and analytical methods for assessing 
occupational exposure to diesel exhaust in a railroad work environment 

Author(s): Verma, D.K., Shaw, L., Julian, J., Smolynek, K., Wood, C., and Shaw, 
D. 

Journal: Applied Occupational and Environmental Hygiene, 14(10), 701-714

Year:1999 

Purpose: 
To evaluate sampling methods for measuring diesel exhaust in the railroad 
environment 



Title: Comparison of daytime and nighttime concentration profiles and size 
distribution of ultrafine particles near a major highway 

Author(s): Zhu, Y., Kuhn, T., Mayo, P., and Hinds, W.C. 

Journal: Environmental Science and Technology, 40(8), 2531-2536 

Year: 2006 

Purpose: To measure the concentration and size distribution of ultrafine 
particles near major highways during the day and at night

 

Title: Toxic Gases In Heavy Duty Diesel Truck Cabs 

Author(s): Ziskind, R., Carlin, T., Axelrod, M., Allen, R.W., and Schwartz, S.H. 

Journal: FHWA-RD-77-139 

Year: 1977 

Purpose: 
To measure in-cab concentrations of carbon monoxide, nitric oxide, and nitrogen 
dioxide.