1990
How the Study was Done
The NIOSH study compared the number of bladder cancers among workers
at a tire and rubber manufacturing plant from 1973 to 1988
with the number that would be expected in a similar population
of New York State residents. This fact sheet will explain how
the study was done.
How Work Records Were Used
Work records contained the department and the general job title
for each worker. NIOSH used the work records to identify who
had worked in departments where exposure to o-toluidine
and aniline may have occurred. We also recorded the
dates each worker held jobs in these areas.
How a Worker's Exposure Was Determined
NIOSH classified all workers who worked in exposed departments between
1957 and 1988 as definitely exposed to aniline
and o-toluidine. NIOSH does not have enough information
to know how much exposure to o-toluidine and aniline individual
workers had in the past. Therefore, NIOSH used the number
of years of employment to estimate how much exposure individual
workers had.
NIOSH believes that some workers in maintenance, janitorial/yard,
and shipping jobs also may have been exposed. If an individual
worked in any of these departments, NIOSH identified that
individual as being possibly exposed to
these chemicals.
If an individual did not work in either certain exposed departments
or maintenance, janitorial/yard, or in the shipping departments
the worker was identified as probably unexposed
to either chemical.
Determining the Number of Workers Who Developed Bladder Cancer
NIOSH determined the number of bladder cancer cases from company
and union records and from death certificates. NIOSH also
matched the records of the workers with cases of bladder cancer
listed in the New York State Cancer Registry.
How the Expected Number of Bladder Cancer Cases Was Determined
The number of bladder cancer cases expected in each group was
calculated using the rate of bladder cancer in New York State
for individuals of similar age and sex.
Results
In this study, 8 cases of bladder cancer were found among workers
definitely exposed to o-toluidine and aniline,
while only 1.2 were expected.
Among workers who were possibly exposed to these
chemicals there were 4 bladder cancer cases observed and 1.05
expected.
Among workers who were probably exposed to these
chemicals there were 2 cases of bladder cancer, and 1.29 expected.
What Was the Likely Cause?
To try to determine the cause of an apparent increase in bladder
cancer, NIOSH first identified all the chemicals used in exposed
departments since 1957.
One of those chemicals, o-toluidine, is known to cause
bladder cancer in animals. Therefore, this chemical is thought
to be the most likely cause of bladder cancer in workers.
Another chemical, aniline, which causes cancer in rats
cannot be ruled out as a cause of bladder cancer in these
workers.
Both o-toluidine and aniline are used to make Wingstay 100.
Wingstay 100 has been manufactured since 1957. Aniline is
used to make Morfax which has been manufactured since
1970. The two chemicals were used only in certain departments
at the plant.
Determining Your Risk
The chart at the right shows the estimated bladder cancer risk
for each exposure group. The number above each bar is the
estimate of risk. The normal value for New York State residents
is 1.0 and is indicated by the heavy, solid line across the
chart.
Here is how to interpret the chart. Above the bar called All
Workers you will see the number 3.95. That Number means
that all the workers at the plant have a 3.95 times greater
risk of developing bladder cancer than other residents of
the state.
Workers with definite and possible
exposure to aniline and o-toluidine appear to have a serious
risk of developing bladder cancer.
Though workers in the probably unexposed group
had an elevated risk of bladder cancer, the increase was small.
Some workers in this group may have been exposed to aniline
and o-toluidine which would increase their risk of bladder
cancer. The increase in that group may also have occurred
solely by chance.
For more information please call the NIOSH toll-free number at 1-800-356-4674.