Air Quality Criteria for Lead Volume II of II - (NEPIS)(EPA) - US ...

AX6-163
Table AX6-5.3 (cont’d). Effects of Lead on Cardiovascular Mortality
Reference, Study
Location, and
Period Study Description Pb Measurement Findings, Interpretation
United States (cont’d)
Michaels et al.
(1991)
U.S.-New York
City
1961-1984
1261 males, avg age (range) at the
beginning of study 49.6 yrs (19-83),
representing 24,473 person-yrs were
followed. 498 died in the interval.
Subjects belonged to the International
Typographical Union and worked at two
large city newspapers. Hot Pb linotyping
was discontinued at the newspapers
during 1974-1978, providing the primary
source of occupational exposure. Last
exposure for all subjects still employed
was at the end of 1976.
Standardized mortality ratios (SMR)
were calculated using the LTAS program
developed by NIOSH, calculating the
expected number of deaths of the cohort
referenced to a comparison population, in
this case disease-specific mortality rates
from New York City. Cohort was
stratified based on yrs of employment.
Causes of death were based on ICD-8
codes.
Exposure was estimated
based on yrs of linotype
employment before the
end of 1976. Authors
note that, based on
measurements at other
print shops using hot Pb
linotype, air Pb levels
probably did not exceed
20 µg/m 3 .
Standardized mortality ratio was significant (SMR = 1.68 [95% CI: 1.18, 2.31])
only for cerebrovascular disease in those working, and thus exposed, for 30 yrs
or more. Neither arteriosclerotic heart disease (ICD-8 410-414) nor vascular
lesions of the central nervous system (ICD-8 430-438) had significant SMR in
the total cohort not stratified by yrs of exposure.
No direct measurement of Pb exposure. Many groupings of ICD codes were
explored in stratified and unstratified analyses, with the only significantly
elevated SMR found for cerebrovascular disease. No a priori hypotheses.
General weakness of all studies relying on a comparison population is that the
cohort belongs to the comparison population and can influence the comparison
mortality rates in direct proportion to the ratio between cohort and comparison
population size.