Chromium - Toxicology of Metals - page 492

There is some evidence (Alderson, 1981; Baetjer,
1950; Hayes, 1979) that work in the high-lime process
could be associated with a greater lung cancer haz-
ard than the low-lime process. The high-lime process
seems to generate more calcium chromate than the
low-lime process. However, the evidence as of today is
insuffi cient to confi rm that exposure to calcium chro-
mate poses a higher lung cancer hazard than other
Cr(VI) compounds present in the work atmospheres.
Mancuso (1975) suggested that “carcinogenic potential
extends to all forms of chromium.” Although the results
from his study suggest that both soluble and insolu-
ble Cr(VI) compounds are involved in enhanced risk of
Cr(VI)-related cancers, the results also seem to suggest
a stronger relationship between exposure to soluble
Cr(VI) and lung cancer than between insoluble Cr(VI)
and lung cancer. Hence, the results seem to support
the view that soluble Cr compounds are more potent
lung carcinogens than are the insoluble ones. Because
exposure to Cr(VI) seems to have occurred in all sub-
groups in the study and could thus have accounted for
the enhanced cancer risk, it seems unjustifi ed to infer
that compounds other than Cr(VI) be regarded to cause
lung cancer in the study.
There are case reports (Brochard et al ., 1983; Kim
et al ., 1985; Korallus et al ., 1974; Michel-Briand and
Simonin, 1977; Pfeil, 1935; Takemoto et al ., 1977; Zober,
1979) presenting some evidence in support of an asso-
ciation between Cr(VI) exposure in electroplating and
lung cancer, possibly also strengthened by the fact
that some of these case subjects were very young at
diagnosis.
Studies among Cr electroplaters could lend support
to the view that fumes from Cr 2 O 3 exert a carcinogenic
potency. The results presented by Sorahan (1987) may
be considered weak but seem to be in favor of a rela-
tionship between work at the Cr electroplating baths
and enhanced risk of lung cancer. Air measurements
suggested that the participants' exposure to Cr had
been intensive, even later than the time period when
enhanced cancer risk must have been accumulated.
The study presented no association between work in
nickel electroplating and lung cancer. In Royle's study
(1975a,b) an unusual short latent period for lung can-
cers was observed (mean 13.6 years), suggesting that
work exposures before plating and smoking could
have infl uenced the results. In a small Italian study
(Franchini et al ., 1983), exposure to Cr(VI) was well
documented, and later follow-up may provide addi-
tional information.
Hence, epidemiological studies present some evi-
dence in favor of a relationship between exposure to
fumes from the quite water-soluble Cr 2 O 3 and can-
cer of the respiratory organs. The exposure-response

relationship is, however, shown to be signifi cantly
weaker than among workers in dichromate and Cr
pigment manufacture.

7.3.2.5.7 CarcinogenicPotency Some reports (Gross
and Kölsch, 1943; Letterer et al ., 1944; Newman, 1890)
strongly suggest zinc chromate as the prime causative
agent among some young workers with lung cancer.
Among studies presenting data necessary to calculate
absolute risk, the study by Langård and Vigander (1983)
presents the highest absolute risk, approximately 1500
cases per 100,000 observation years in a subgroup of 24
workers primarily exposed to zinc chromate. Five case
subjects had been exposed solely to zinc chromate,
whereas one case subject had also been in contact with
some lead chromate. In Davies' study (1984a), excess
lung cancer deaths were observed primarily in workers
of the study plants where workers had been exposed
both to zinc and lead chromate, whereas excess lung
cancer deaths were nonsignifi cant in those who were
stated to manufacture lead chromate only, making the
author suggest that zinc chromate was the most likely
cause of lung cancer among workers exposed to both
compounds. A nonsignifi cant excess of lung cancer
deaths was also observed in a subgroup exposed only
to lead chromate (Davies, 1984a) and in a study of
a small group of previously lead-intoxicated chromate
workers (Davies, 1984b). These results suggest that
zinc chromate is a more potent human carcinogen
when inhaled than are other chromate pigments like
lead chromate.
In the study by Hayes et al . (1989), much lower rela-
tive risks were reported despite higher air concentra-
tions than in the study group by Langård and Vigander
(1983). Given that the measurements are comparable in
the two studies and the airborne Cr in the U.S. study
was primarily lead chromate, the results are not con-
fl icting. No epidemiological studies have included
exposure to strontium chromate.
The current evidence from epidemiological data
seems to point out chromates of zinc and calcium as
the most potent carcinogenic chromates. However,
there are only few data on other Cr(VI) compounds.

7.3.2.5.8 Levels of Cancer Risk Absolute risk of
lung cancer experienced by workers in some of the
early study cohorts seems to be lower than in some of
the Cr pigment studies. However, the reference risks
in the 1940s and 1950s were much lower than in the
1970s and 1980s. Therefore, although the absolute
risk was lower in the early study by Gafafer (1953),
the RRs varied between 14 and 80, refl ecting an even
higher cancer hazard than in more recent studies
with highest absolute risks. Imprescia (1952) gave no