1192 VOLUME 115 | NUMBER 8 | August 2007 • Environmental Health Perspectives

Research

Population-based studies have related

exposure to fine particulate air pollution

(Dominici et al. 2006; Laden et al. 2006;

Pope et al. 2002, 2004), and specifically particulate matter (PM) from vehicle exhausts

(Dominici et al. 2006; Garshick et al. 2004;

Hoek et al. 2002; Laden et al. 2000; Le

Tertre et al. 2002; Nafstad et al. 2003,

2004; Nyberg et al. 2000; Peters et al.

2004) to cardiovascular diseases and lung

cancer. We have established a large retrospective cohort study of mortality in the

unionized U.S. trucking industry. Each job

category in this population has distinct

exposure patterns: drivers are exposed

directly to traffic; dockworkers are exposed

to trucks in the yard and propane and liquified natural gas exhaust from forklifts; shopworkers are exposed to short-term vehicle

exposures during repairs; and other terminal-based personnel have little exposure to

vehicle exhaust (Davis et al. 2006; Smith

et al. 2006). To provide insight into mortality patterns associated with these exposures

we examined rates of cause-specific mortality

by the different job categories in the trucking industry compared with the general U.S.

population.

Materials and Methods

The Trucking Industry Particle Study. The

Trucking Industry Particle Study was

designed to assess the risk of lung cancer mortality in trucking industry workers with exposures to diesel and other vehicle exhausts. The

study consists of three parts: a) a retrospective

cohort study of lung cancer mortality among

Teamsters Union members employed in

1985 in four participating companies; b) an

extensive national exposure assessment

designed to determine the factors influencing

exposure to diesel and other vehicle exhausts,

including job title, diesel vehicle use, and size

and location of assigned terminal (Davis et al.

2006; Smith et al. 2006); and c) a mailed

questionnaire sent to current workers to assess

the distribution of smoking habits by job title

and terminal characteristics (Jain et al. 2006).

The Brigham and Women’s Hospital,

Harvard School of Public Health, and VA

Boston Institutional Review Boards approved

the protocol. Cohort participants were not

contacted directly, and therefore could not

provide informed consent. Individuals completing the smoking questionnaire were sent a

cover letter describing the goals of the study

and other key aspects of informed consent,

and were assumed to have given consent by

completing the questionnaire.

We obtained detailed work history information for all 58,326 unionized trucking

industry employees (54,319 men and

4,007 women) who had worked for at least

1 day in 1985 at one of the participating companies. Information available on each individual included social security number, age, race,

sex, date of hire, last date of work, and daily

job title and terminal (i.e., workplace) location

through 2000. In one of the four companies,

computer files were only available for the

active workers starting in 1993. Therefore, we

included only workers at that company who

were working in 1985 and were still working

in 1993. 

Job titles. Job titles and duties were uniform across the four companies. Table 1

includes the description and work location for

each job title. An individual contributed person-time through 2000 in each job category

for which he or she had at least 1 day of work

experience. The time periods did not have to

be consecutive. Intercity long haul drivers, city

pick-up and delivery (P&D) drivers, and

combination drivers (loading dock workers

who also drive P&D trucks) were grouped

together into a “driver” category, and all other

job titles were considered “non-drivers.” 

Mortality follow-up. Vital status, date of

death, and cause-specific mortality from 1985

through 2000 was obtained through searching

the National Death Index [National Center

for Health Statistics (NCHS), Hyattsville,

MD]. Matching criteria included social security number; month and year (± 1) of birth;

and first name, middle initial, and last name.

From 1985 to 2000, there were a total of

4,950 deaths (4,875 men and 75 women).

Cause of death. Annual cause-specific

death rates by 10-year age group and race

Address correspondence to F. Laden, Channing

Laboratory, 181 Longwood Ave., Boston MA 02115

USA. Telephone: (617) 525-2271. Fax: (617) 525-

2578. E-mail: Francine.Laden@channing.harvard.edu

We thank M.J. Canner for programming assistance,

the Teamster Health and Safety Office, and the participating companies.

This study was supported by grant R01 CA90792

from the National Institutes of Health/National

Cancer Institute. 

The authors declare they have no competing

financial interests.

Received 21 December 2006; accepted 27 April

2007.

Cause-Specific Mortality in the Unionized U.S. Trucking Industry

Francine Laden,1,2,3 Jaime E. Hart,1,2 Thomas J. Smith,2 Mary E. Davis,2,4 and Eric Garshick1,5

1Channing Laboratory, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts, USA; 2Exposure,

Epidemiology and Risk Program, Department of Environmental Health, and 3Department of Epidemiology, Harvard School of 

Public Health, Boston, Massachusetts, USA; 4Department of Resource Economics and Policy, University of Maine, Orono, 

Maine, USA; 5Pulmonary and Critical Care Medicine Section, Medical Service, VA Boston Healthcare System, West Roxbury,

Massachusetts, USA

BACKGROUND: Occupational and population-based studies have related exposure to fine particulate

air pollution, and specifically particulate matter from vehicle exhausts, to cardiovascular diseases

and lung cancer. 

OBJECTIVES: We have established a large retrospective cohort to assess mortality in the unionized

U.S. trucking industry. To provide insight into mortality patterns associated with job-specific exposures, we examined rates of cause-specific mortality compared with the general U.S. population.

METHODS: We used records from four national trucking companies to identify 54,319 male

employees employed in 1985. Cause-specific mortality was assessed through 2000 using the

National Death Index. Expected numbers of all and cause-specific deaths were calculated stratifying

by race, 10-year age group, and calendar period using U.S. national reference rates. Standardized

mortality ratios (SMRs) and 95% confidence intervals (CIs) were calculated for the entire cohort

and by job title. 

RESULTS: As expected in a working population, we found a deficit in overall and all-cancer mortality,

likely due to the healthy worker effect. In contrast, compared with the general U.S. population, we

observed elevated rates for lung cancer, ischemic heart disease, and transport-related accidents. Lung

cancer rates were elevated among all drivers (SMR = 1.10; 95% CI, 1.02–1.19) and dockworkers

(SMR = 1.10; 95% CI, 0.94–1.30); ischemic heart disease was also elevated among these groups of

workers [drivers, SMR = 1.49 (95% CI, 1.40–1.59); dockworkers, SMR = 1.32 (95% CI,

1.15–1.52)], as well as among shop workers (SMR = 1.34; 95% CI, 1.05–1.72). 

CONCLUSIONS: In this detailed assessment of specific job categories in the U.S. trucking industry,

we found an excess of mortality due to lung cancer and ischemic heart disease, particularly among

drivers. 

KEY WORDS: diesel, ischemic heart disease, lung cancer, mortality, occupation, traffic exposure,

trucking industry. Environ Health Perspect 115:1192–1196 (2007). doi:10.1289/ehp.10027 available via http://dx.doi.org/ [Online 27 April 2007]
were obtained from the CDC WONDER

database [Centers for Disease Control and

Prevention (CDC) 2005]. Due to the small

number of females, only males were used in

the analysis. We considered causes of death by

major disease classification, as well as additional causes potentially associated with fine

particulate air pollution and diesel and other

vehicle exhausts. These additional causes

included lung cancer (Bhatia et al. 1998;

Diesel Epidemiology Expert Panel 1999;

Lipsett and Campleman 1999), bladder cancer

(Boffetta and Silverman 2001), ischemic heart

disease (Pope et al. 2004), and obstructive

lung disease (defined as “chronic lower respiratory disease”) (Hart et al. 2006).

Statistical analysis. Expected numbers of

all and cause-specific deaths were calculated by

multiplying the person-years in each race-,

10-year-age-, and calendar period–specific

stratum by the national reference rates for the

entire cohort and stratified by driver versus

nondriver. Standardized mortality ratios

(SMRs) were calculated as the ratio of

observed to expected deaths. We calculated

95% confidence intervals (CIs) under the

assumption that the observed numbers of

deaths follow a Poisson distribution. 

To assess the potential impact of smoking

on our interpretation of comparisons of mortality rates in the trucking industry with the

general population, we calculated birth cohort–

specific smoking rates for both groups. Year of

birth and ever-smoking and current smoking

rates for the trucking industry were obtained

from the mailed questionnaire (Jain et al.

2006). Equivalent ever-smoking rates for the

male U.S. population in 1988 were obtained

from the 1997 Surgeon General’s report

(National Cancer Institute 1997). Because

rates were available by race only, we calculated

combined rates weighting by the racial

distribution of the trucking cohort. Current

smoking rates for 2003 were obtained from the

“Chartbook on Trends in Human Health” for

the male U.S. population, regardless of race

(NCHS 2006).

Results

Among the 54,319 male employees, there were

756,311.7 person-years of follow-up time.

Demographics of the study population by driver status at the end of follow-up are presented

in Table 2. The mean age of the full cohort in

1985 (± SD) was 42.2 ± 10.0, and the drivers

were slightly older than the nondrivers. The

median age of death was 61.9 years, lower than

the national median for all males (73.2 years of

age in 1992; NCHS 1994). The majority of

the deaths occurred among the individuals

who were at least 40 years of age in 1985.

The majority of the population was white

(83.1%). The mean duration of work for drivers and nondrivers was 20.3 ± 8.1 years and

17.1 ± 10.0 years, respectively. Of the cohort,

82% did not switch driver/nondriver status.

The majority of the switching was between the

dockworker (nondriver) and combination

worker/P&D driver job titles. 

The SMRs for all-cause and cause-specific

mortality by major disease classification are

presented in Table 3. As expected in a working

cohort, there was evidence of a healthy worker

effect; the SMR for all-cause mortality was

0.72 (95% CI, 0.70–0.74), and most of the

cause-specific SMRs are < 1, including malignant neoplasms as a group and diseases of the

circulatory system. However, the specific

SMRs for lung cancer (SMR = 1.04; 95% CI,

0.97–1.12) and ischemic heart disease (SMR =

1.41; 95% CI, 1.33–1.49) were elevated. 

When assessed by specific job title, we

observed elevated SMRs for lung cancer

among the long-haul drivers, P&D drivers,

combination workers, and dockworkers, with

SMRs ranging from 1.08 for the combination

workers to 1.16 for the P&D drivers

(Figure 1). Among all drivers and dockworkers, the SMRs were 1.10 (95% CI,

1.02–1.19) and 1.10 (95% CI, 0.94–1.30),

Mortality in the unionized U.S. trucking industry

Environmental Health Perspectives • VOLUME 115 | NUMBER 8 | August 2007 1193

Table 1. Job titles, duties, and job location in the unionized trucking industry.

Job group Duties Location

Long-haul driver Drive heavy-duty tractor–trailer trucks between cities Highway truck cab

P&D driver Drive tractors and smaller single-bodied trucks within cities or rural In and out of truck 

areas; pick-up and deliver cargo between terminal docks and consumers cab

Dockworker Load and unload cargo; may operate forklifts Loading dock

P&D/dockworker Combination job: performs activities of either P&D driver or dockworker; As noted above for

(combination) more likely at smaller terminals each job

Mechanic Repair and maintain tractors; job may include fueling Truck repair shop

Hostler Drive small tractor units that do not comply with emissions standards, Terminal yard

moving trailers between the freight dock and the terminal yard

Clerks Cashiers, dock clerks, dispatchers, customer service representatives, Offices, occasionally 

and others not regularly near diesel vehicles dock

Table 2. Characteristics of the males in the cohort by driver/nondriver status.

Drivers Nondrivers Total

Total no. 36,299 18,020 54,319

No. of deaths 3,693 1,182 4,875

Race (no.)

White 30,668 14,489 45,157

Black 3,359 1,575 4,934

Other 2,272 1,956 4,228

Age in 1985 (years, mean ± SD) 44.0 ± 9.1 38.6 ± 10.6 42.2 ± 10.0

Age at death (years, mean ± SD) 61.3 ± 8.6 59.2 ± 10.6 60.8 ± 9.2

Year of hire (mean ± SD) 1974 ± 8.0 1976 ± 7.9 1975 ± 8.0

Total years of work (mean ± SD) 20.3 ± 8.1 17.1 ± 10.0 19.2 ± 8.9

Table 3. Cause-specific mortality in the Trucking Industry Particle Study cohort (n = 54,319 men),

1985–2000.

Cause of death ICD-9 ICD-10 Observed Expected SMR 95% CI

All causes 4,875 6791.9 0.72 0.70–0.74

Infectious and parasitic diseases 1–139 A0–99, B0–99 86 278.4 0.31 0.25–0.38

Malignant neoplasms 140–208 C0–97, D0–9 1,735 2003.86 0.87 0.83–0.91

Bladder cancer 188 C67 29 36.3 0.80 0.56–1.15

Lung cancer 162 I33–34 769 737.8 1.04 0.97–1.12

Diabetes 250 E10–14 103 173.5 0.59 0.49–0.72

Blood diseases 280–289 D50–89 15 21.5 0.70 0.42–1.17

Mental disorders 290–319 F1–99 30 86.0 0.35 0.24–0.50

Nervous system diseases 320–389 G0–98 59 99.6 0.59 0.46–0.76

Circulatory system diseases 390–459 I0–99 1,793 2472.1 0.73 0.69–0.76

Ischemic heart disease 410–414 I20–25 1,133 803.8 1.41 1.33–1.49

Cerebrovascular disease 430–438 I60–69 167 242.9 0.69 0.59–0.80

Respiratory system diseases 480–519 J10–18, J40–98 322 437.4 0.74 0.66–0.82

Chronic lower respiratory disease 490–494, 496, J40–47 212 253.1 0.84 0.73–0.96

519.9

Digestive system diseases 520–579 K0–92 143 321.9 0.44 0.38–0.52

Skin diseases 680–709 L0–98 3 5.1 0.59 0.19–1.84

Musculoskeletal system diseases 710–739 M0–99 4 15.5 0.26 0.10–0.69

Symptoms of congenital anomalies 780–799 Q0–99 47 63.5 0.74 0.56–0.99

Accidents, homicide, suicide 800–999 V0–99, W0–98 431 645.2 0.67 0.61–0.73

X0–98, Y0–98

Transport-related accidents 800–848 V0–99 178 189.4 0.94 0.81–1.09

Abbreviations: ICD-9, International Classification of Diseases, Ninth Revision (WHO 1977); ICD-10, International

Classification of Diseases, Tenth Revision (WHO 1993).
respectively. Although there was an overall

deficit of deaths caused by circulatory system

disease, ischemic heart disease mortality was

elevated among these same job titles [all drivers SMR = 1.49 (95% CI, 1.40–1.59); dockworker SMR = 1.32 (95% CI, 1.15–1.52)], as

well as among the shop workers (SMR = 1.34;

95% CI, 1.05–1.72). In Figure 2, we also present the SMRs for the remaining causes of

death by driver status. Transport-related accidents were elevated in drivers only (SMR =

1.15; 95% CI, 0.97–1.37). We found no evidence of increased bladder cancer, obstructive

lung disease, or cerebrovascular mortality. All

results were similar in analyses that removed

the company with information available only

on workers who were still working in 1993.

Figure 3 shows the comparison of the

ever-smoking and current smoking rates in

the surveyed trucking population with the

birth cohort–specific rates in the general U.S.

male population. For both drivers and nondrivers, the ever-smoking rates were similar to

the general population. Current smoking

rates among the drivers track with the U.S.

population, except for the two youngest birth

cohorts, and the rate of current smoking is

highest among the nondrivers.

Discussion

As expected in a working population, there was

a deficit in overall and all-cancer mortality and

in most other causes of death, likely due to the

healthy worker effect. In contrast, there were

31 excess deaths due to lung cancer and 329

due to ischemic heart disease—a 41% excess—

in this “healthy worker” population compared

with the general U.S. population. Lung cancer

rates were elevated among all drivers and dockworkers; ischemic heart disease was also elevated among these jobs, as well as among shop

workers. Transport accidents were only elevated in the driver categories. 

Because this was a retrospective cohort

study using company records to identify the

cohort, no information was available on potential confounders such as smoking or diet.

However, smoking histories were available from

a representative survey of currently employed

and recently retired workers (Jain et al. 2006).

Birth cohort–specific ever-smoking rates were

similar to the male U.S. general population

rates available in 1988. These data were limited

in that there were proportionally fewer older

workers included in the mail survey compared

with the retrospective cohort study, and recent

information on birth cohort–specific eversmoking rates were not available. However,

current smoking rates based on the mail survey

were similar to U.S. birth cohort–specific rates

in 2003; among the nondrivers, who had the

lowest risks, rates were actually slightly higher

than the U.S. population for most birth

cohorts. For the drivers, however, differences

from the general population were evident only

in the younger birth cohorts who contributed

< 1% of the total deaths. Therefore, excess

smoking in this population compared with the

general U.S. population is unlikely to explain

the elevated lung cancer and ischemic heart

disease rates. Chronic obstructive pulmonary

disease and other diseases of the respiratory

system, which are predominantly related to

smoking, were not elevated, providing further

support for this conclusion. In contrast, diet

and other lifestyle information were not available and may partially explain the elevated

rates of ischemic heart disease (Pearson et al.

2002). Other factors that may also contribute

to lung cancer risk, including family history

and history of obstructive lung disease, are also

not known, but these are not likely to be associated with exposure and are unlikely to be

confounders.

Another potential limitation is the representativeness of these unionized workers to the

rest of the U.S. trucking industry. Work practices among unionized companies are welldefined and the workforce is stable. It is

possible that equipment-maintenance practices

in these companies are more stringent than in

the general trucking industry. However, there

is wide variation even among our included

companies, which has not been an important

Laden et al.

1194 VOLUME 115 | NUMBER 8 | August 2007 • Environmental Health Perspectives

2.0

1.5

1.0

0.5

0

SMR 2.0

1.5

1.0

0.5

0

SMR

Job title

Long-haul

Long-haul

P&D

P&D

Combination

Combination

Dockworker

Dockworker

Shopworker

Shopworker

Hostler

Hostler

Clerk

Clerk

Job title

A

B

Figure 1. SMRs of lung cancer (A) and ischemic heart disease (B) by job title in the U.S. trucking industry

compared with the general U.S. population. Error bars indicate 95% CIs.

2.0

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

SMR

All causes

Malignant neoplasms

Bladder cancer

Diabetes

Circulatory system diseases

Cerebrovascular disease

Respiratory system diseases

Chronic obstructive lung disease

Digestive system diseases

Musculoskeletal system diseases

Accidents, homicide, suicide

Transport-related accidents

Drivers

Nondrivers

Figure 2. SMRs for selected causes of death by driver/nondriver status in the U.S. trucking industry compared with the general U.S. population. Error bars indicate 95% CIs.
determinant of exposure in our exposure

assessment studies (Smith et al. 2006). Finally,

there is no reason to believe that these findings

by job title would not be applicable to equivalent jobs in other nonunionized companies.

The observed elevations in lung cancer

mortality are consistent with results from previous occupational and general population

studies. Results from > 30 studies in a variety

of occupational groups with diesel and vehicle

exhaust exposures, including truck and other

professional drivers, have been quite consistent

with relative risks for lung cancer ranging

from 1.2 to 1.4 (Bhatia et al. 1998; Diesel

Epidemiology Expert Panel 1999; Lipsett and

Campleman 1999). In a case–control study of

lung cancer mortality in the U.S. unionized

trucking industry, Steenland et al. (1990)

observed age- and smoking-adjusted odds

ratios of 1.27 for long-haul truck drivers, 1.31

for P&D drivers, 1.69 for shopworkers, and

0.92 for dockworkers, compared with workers

in the same union but not in trucking-related

jobs. Nyberg et al. (2000) in Stockholm

County, Sweden, and Nafstad et al. (2003) in

Oslo, Norway, reported an association

between lung cancer risk and historical exposures to traffic after adjustment for smoking.

The American Cancer Society (Pope et al.

1995, 2002) and the Harvard Six Cities Study

(Dockery et al. 1993; Laden et al. 2006), two

population-based prospective cohort studies in

the United States, also observed elevated lung

cancer mortality with increasing levels of PM

from combustion sources. Nevertheless, the

association of lung cancer with exposure to

diesel exhaust is still being questioned

(Hesterberg et al. 2006; Stober et al. 1998). 

Exhaust exposures in the trucking industry

are from diesel, gasoline, and propane sources.

Trucking industry employees who drive trucks

are mainly exposed to combustion particles

attributable to gasoline and diesel traffic in the

cities and on the highways where they work

and drive. Loading-dock workers are currently

exposed to exhaust from propane forklifts.

Diesel forklifts were used during the 1980s

and 1990s, and gasoline forklifts were used

before that time. Historically there has been

concern about lung cancer risk from diesel

exhaust since older diesel engines produced

more PM on a mass basis than other emission

sources. These particles are mainly < 1.0 μm

in diameter and contain mutagenic and carcinogenic organic carbons, including polycyclic aromatic hydrocarbons (Diesel Working

Group 1995). Despite extensive efforts, the

specific mechanisms and dose whereby diesel

exhaust might cause lung cancer in humans

remain uncertain, and there is no animal

model relevant to human exposures (U.S.

Environmental Protection Agency 2002).

Although the size distribution of particles in

gasoline emissions is similar to that in diesel

emissions (Allen et al. 2001; Fraser et al. 2003;

Geller et al. 2005; Kittelson et al. 2003;

Kleeman et al. 2000; Zielinska et al. 2004)

and the particles include mutagenic compounds, lung cancer risk as a result of gasoline

particle exposure has not been extensively

studied. Propane forklift emissions include

ultrafine PM (Guo et al. 2004; Rundell 2003),

but the composition of these particles has not

been well characterized. 

There have been fewer studies investigating the relationship between occupational

exposure to vehicle exhaust and ischemic heart

disease risk. In Danish bus, taxi, and truck drivers, rates of hospital admissions for ischemic

heart disease were elevated 20–80% compared

with other employed Danish men (Hannerz

and Tuchsen 2001). Gustavsson et al. (1996)

found a significantly elevated risk of myocardial infarction among long-distance truck

drivers in Sweden [relative risk (RR) = 1.31].

The risk was not elevated among short-distance truck drivers, but relatively few were

included in the study. In a case–control study

assessing cardiovascular risk factors in survivors of first-time myocardial infarction, male

bus and taxi drivers who worked for > 1 year

had a nonsignificantly elevated risk (RR =

1.49; 95% CI, 0.90–2.45; and RR = 1.34;

95% CI, 0.82–2.19, respectively). The risk

among truck drivers was 1.10 (95% CI,

0.79–1.53) (Bigert et al. 2003). However, the

literature shows that there is growing evidence

of an association of exposures to vehicle

exhaust with ischemic heart disease in the general population. In Sweden, Nafstad et al.

(2004) also observed an association with

ischemic heart disease. In the Netherlands,

Hoek et al. (2002) observed an RR of cardiopulmonary deaths of 1.71 (95% CI,

1.10–2.67) for each 10 μg/m3 of black smoke,

a marker of traffic. Peters et al. (2004) found

that exposure to traffic was associated with the

time of onset of myocardial infarction. Finally,

an analysis based on specific elements from

particles in six U.S. cities found greater effects

on daily mortality rates (particularly for cardiovascular deaths) attributable to particles

from mobile sources than to particles from

other sources (Laden et al. 2000).

The association between ischemic heart

disease and combustion-related PM is supported by animal experiments (Sun et al. 2005;

Suwa et al. 2002). A potential mechanism

appears to be related to systemic inflammation

in which the inhalation of PM provokes a low

grade systemic inflammatory response and

changes in blood coagulability (Peters et al.

2001; Riediker et al. 2004; Schwartz 2001; van

Eeden et al. 2001). ST segment depression

during exercise has also been associated with

fine particulate air pollution (Pekkanen et al.

2002) and exposure to black carbon, suggesting a specific association with traffic (Gold

et al. 2005; Lanki et al. 2006). Taken together,

these results suggest an adverse effect of traffic

and other combustion-related PM on ischemic

heart disease mortality. 

There are workplace conditions, work

practices, and lifestyle choices associated with

the trucking industry that may have an

impact on life expectancy and mortality from

Mortality in the unionized U.S. trucking industry

Environmental Health Perspectives • VOLUME 115 | NUMBER 8 | August 2007 1195

100

90

80

70

60

50

40

30

20

10

0

Percent smoking

1925–1929 1930–1934 1935–1939 1940–1944 1945–1949 1950–1954 1955–1959 1960–1964 1965–1969

Birth year

U.S.-ever

Driver-ever

Nondriver-ever

U.S. current

Driver current

Nondriver current

Figure 3. Comparison of birth cohort–specific U.S. ever-smoking and current smoking rates with rates of

drivers and nondrivers in the trucking population.
Laden et al.

1196 VOLUME 115 | NUMBER 8 | August 2007 • Environmental Health Perspectives

specific causes independent of exposures to

traffic and other sources of vehicle exhaust. As

in any occupational SMR analysis, we were

unable to control for known risk factors of

the diseases of interest other than age, sex,

and race. However, our mail survey demonstrates that at least one factor—smoking—

was unlikely to explain our results. In this

detailed assessment of specific job groupings,

we conclude that there is an excess of mortality due to lung cancer and ischemic heart disease in the U.S. trucking industry, particularly

among drivers. Further research is required to

assess the contribution of lifestyle and personal habits to these health risks in trucking

industry workers. However, our findings are

consistent with previous occupational and

general population studies relating PM exposures to lung cancer and cardiovascular disease

and suggest that vehicle exhaust from a variety

of sources contributes to this risk. 

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