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Table 1 (continued):
Epidemiological Studies of Exposure to Diesel Exhaust and Lung Cancer Studies
Among Railroad Workers
Reference
Study Design,
Population, and
Exposures
Cases
or
deaths
Effect
Measure
Confidence
Interval a or
P-Value
Comments
Howe et al.
1983
Canada
Cohort
Entire cohort
Retired after 1950
Exposure to DE
“nonexposed”
“possibly” exposed
“probably” exposed
933
897
239
407
279
SMR
1.06
1.00
1.20
1.35
0.99-1.13
p = 0.13
p < 0.001
Study consisted of 43,826 males of the Canadian
National Railway Co. retired and alive in 1965 and
followed until 1977. No data on smoking.
However, authors note that this may not be crucial
since conclusions were based on internal comparisons
where no large variation in smoking habits was likely.
It was also noted that certain smoking-related deaths
were elevated. The results remained unchanged when
individuals likely to have been exposed to asbestos
were excluded from the analysis.
Garshick et al.
1987a
USA
Case-control
Age (years)
65
DE Exposure:
Diesel-years < 64
worker
5-19
>20
Diesel-years > 65
worker
5-19
>20
Minus
shopworkers*
>20 years of
exposure
Years of cumulative
DE exposure:**
5-14
>15
1256
335
921
OR
1.41
0.91
1.02
1.64
0.95
0.94
1.55
1.07
1.43
1.06-1.88
0.71-1.17
0.72-1.4
1.18-2.2
0.79-1.13
0.56-1.59
1.09-2.21
0.69-1.66
1.06-1.94
Study consisted of Railroad Retirement Board
registrants (1,256 cases and 2,385 matched controls)
who died between March 1981 and February
1982. Subjects were active and retired workers with
at least 10 years work experience. Persons who died
from cancer, suicide, accidents or unknown causes
were excluded as controls. Results were adjusted for
smoking and asbestos exposure. The baseline study
year was 1959, when diesel engines had nearly
replaced all steam engines. Consequently, few
of these workers were exposed to asbestos. Personal
exposure was assessed by industrial hygiene sampling
in 39 job categories. Job titles were used
to dichotomize subjects into exposed and unexposed
groups (Woskie et al., 1988a,b). See also Garshick et
al. (1988).
*Shopworkers had the highest levels of asbestos
exposure.
**These results excluded exposure occurring within 5
years before death. The shortest exposure category, 0
to 4 years, was used as a reference group.
a 95% Confidence intervals unless noted. N.S.= Not significant. No confidence intervals or p-values
reported in original study. DE = Diesel Exhaust, OR = Odds Ratio, RR = Relative Risk, SIR =
Standardized Incidence Ratio, SMR = Standardized Mortality Ratio
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