home edit2 whole TSD November 2002 PDF format - OEHHA

The three largest - and therefore potentially most sensitive - industrial cohort studies reported elevated
rates of lung cancer. The largest, Blair et al. (1986) with 26,561 U.S. workers, reported a statistically
elevated death rate due to lung cancer, equivalent to 35% above the national average. The other two
studies reporting elevated death rates due to lung cancer were Acheson et al. (1984a, b) with 7,680
British male workers, mostly young, and Stayner et al. (1988) with 11,030 U.S. workers, predominantly
female. Some of the categories in the Acheson study showed statistically significant increases of lung
cancer. The Stayner study found lung cancer to be elevated 14% overall, which was not statistically
significant, but the exposures were well below those of the other two studies.
In the Blair et al. (1986) study the investigators concluded that a causal relationship between
formaldehyde exposure and lung cancer was unlikely because of a lack of dose gradient for those
tumors. Sterling and Weinkam (1988, 1989a, b) performed a reanalysis on the basis that Blair et al.
(1986) failed to account for a “healthy-worker” effect in the original report. These corrected results
showed that lung cancer was related to formaldehyde exposure in a dose-dependent manner, which
was statistically significant. In a subsequent analysis of the same workers Blair et al. (1990) concluded
that exposure to phenol, melamine, urea, and wood dust and other substances might account for some
or all of the excess lung cancer observed.
Table 1: Cohort study on industrial exposure to formaldehyde (Blair et al., 1986).
Exposure Cancer Site Number
Observed
Number
Exposed
SMR
90% Confidence
Interval
Lower Upper
0.1 - > 2.0 ppm brain 17 21 0.81 0.52 1.21
time weighted leukemia 19 24 0.80 0.52 1.16
average buccal/pharynx 18 19 0.96 0.61 1.41
lung 201 182 1.11 0.98 1.24
larynx 12 8 1.42 0.87 2.43
nasal 2 2.2 0.91 0.16 2.86
> 0 - 5.5 ppm-yr lung, 20 yr latency 146 108 1.35 1.17 1.55
hypopharynx 1 1.7 0.59 0.02 2.78
nasopharynx 6 2.0 3.00 1.30 5.92
oropharynx 5 2.6 1.92 0.76 4.04
Source: OEHHA (1992)
Recent epidemiological studies contribute to the conclusions only marginally. Gerin et al. (1989)
presented the results of a large case control study with 3,726 cancer patients. The odds ratio for the
highest exposure group with adenocarcinoma of the lung was nearly significant at the 95% confidence
level, and there was an apparent trend of incidence of this cancer with exposure. Nevertheless, the
authors concluded that there was no persuasive evidence of an increased risk of any type of cancer
among men exposed to the exposure levels of formaldehyde cited by Blair et al. (1986) (Table 1). The
study did not consider cancers of the nasal cavity, of the brain, or of leukemia. Bertazzi et al. (1989)
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