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Using the statistical tests (one-tailed and two-tailed test of significance) employed by investigators, no
cancer site displayed a significantly elevated death rate. Nevertheless, eight deaths from pancreatic
cancer were observed compared to 3.0 expected based on the New York data or 2.6 based on the
other employees’ data. Although this finding was not considered significant based on the two-tailed test
described above, an exact one-sided Poisson test using the other Kodak employees as the control
group yields a p-value of 0.0053 and suggests a possible relationship between the exposure to MC and
pancreatic cancer mortality. Somewhat smaller-than-expected death rates were observed for certain
tumor sites, including the colon, and the genital and urinary organs; these observations did not reach
statistical significance.
In the subset of the cohort which had been exposed for a minimum of 20 years by 1964 (N = 252),
fewer cancer deaths were observed than expected when compared to the New York State data (23 vs.
33.8) or to the data from other Kodak employees (23 versus 27.0). A slight excess of deaths from
pancreatic neoplasms was observed here (4 compared to 1.9 or 1.6 expected). None of these
differences were statistically significant.
Hearne et al. (1987) presented estimates of exposure and expanded the exposed cohort to 1,013 men
who had at least one year of experience in the methylene chloride operation between January 1964 and
December 1970. The 1985 report analyzed approximately 14,000 person-years of follow-up in the
exposed cohort; this 1987 report presented data from 19,465 person-years, with a follow-up of 99%
for the exposed cohort. Again, compared to either control group, no statistically significant difference
was found between observed and expected deaths for respiratory or hepatic cancer mortality, based on
a one-sided test, (p < 0.05). Among the nonhypothesized outcomes, workers exposed to methylene
chloride still experienced more than a two-fold greater rate of mortality from pancreatic cancer (8
observed vs. 3.2 or 3.1 expected [New York State or Kodak controls]). The SMR for this site was
2.5 with 95% confidence limits of 1.1 to 4.9. DHS staff calculations indicate an exact one-sided
Poisson test using the New York State data as a control yields a p-value of 0.017. Thus, the results still
suggest a possible relationship between exposure to methylene chloride and pancreatic cancer mortality.
Exposure estimates were based on over 1,200 area and task-specific air samples collected between
1945 and 1986 and more than 900 full-shift personal samples collected between 1980 and 1986. The
majority of the cohort was exposed to peak concentrations of 500 ppm, an average of three times per
day, 10 or 40 days per year (depending on occupational classification). Other solvents, including 1,2-
dichloropropane and 1,2-dichloroethane, were present at lower levels in the workroom.
In a series of reports, Ott and colleagues (Ott et al., 1983a-e) evaluated the health of employees
working at a fiber production plant in Rock Hill, South Carolina, where methylene chloride was used as
a part of a solvent system. Workers in this plant were exposed to a mixture of methylene chloride and
methanol from one process and to acetone from a second process. Median 8-hr TWA methylene
chloride concentrations in the plant’s two main work areas were 140 and 475 ppm. Health evaluations
of these employees were compared to those of employees at a similar fiber production plant in
Narrows, Virginia, where only acetone was used. One of the reports (Ott et al., 1983b) evaluated
whether exposure to methylene chloride was associated with cancer deaths. Smoking habits were not
considered in the analyses, although age was controlled for. Compared with United States death rates,
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