Chromium - Toxicology of Metals - page 490

European countries participated, recruited mainly
during the 1960s and the 1970s. There were 116 lung
cancer deaths versus 86.8 expected. In the subgroup of
primarily SS welders, there were 39 lung cancer deaths
versus 30.45 expected, whereas in the subgroup of
SS welders with more than 10 years of welding and
accounting or 20 years of “latency” the fi gures were 13
deaths versus 9.1 expected.
Danielsen et al . (1996) studied a recruitment cohort
of 2957 boiler welders recruited in 1942-1981 in a his-
torical, prospective cohort study with observation
from 1953 through 1992, including a subcohort of 606
certifi ed SS welders. Observed and expected outcomes
were derived from the Norwegian cancer register, and
there was a 4.9% loss at follow-up.
There were 50 lung cancers versus 37.5 expected
in the entire cohort (SIR = 133; CI, 99-176) and six
lung cancers versus 5.8 expected in the SS steel
subgroup. When accounting for the 15 years pre-
sumed latent period, the slight excess was reduced
to a deficiency of 2 observed versus 3.4 expected,
suggesting that there was no excess. Hence, this
study's results did not lend support to the view that
SS welding results in a higher risk of lung cancer
than MS welding.

A study was performed that included residents of the
villages: Ketleman, Hinkley, and Topack in the south-
ern part of San Bernadino County in California (Fryzek
et al ., 2001). In these villages, soluble Cr(VI) was added
to water used for cooling of pipes from gas compres-
sor plants. Wastewater from these towers was trans-
ferred to ponds possibly leaking into the groundwater.
The presumed exposed population was observed for
10 years only (1989-1998). The control of migration
over the decades of interest, 1950s and onward, was
not fully controlled, which may have contributed to
the signifi cant defi cit of the total cancer mortality and
lung cancer mortality over the study period. Despite
the low rates of cancer, the results of the study may be
considered nonconclusive.

7.3.2.5.4 Cancer at Other Sites Teleky (1936) drew
attention to a possible connection between exposure
to chromates and enhanced risk of cancer of the
intestines after observing fi ve digestive tract cancer
cases among 44 deceased chromate workers. Results
in some epidemiological studies suggest elevated
risks of cancer of the stomach and digestive tract.
In the large body of literature published on the
relationship between exposure to Cr(VI) compounds
and occurrence of cancer (Costa, 1997; De Flora, 2000;
IARC, 1990; Langård, 1990), studies that may help
resolve this question are likely to be found in well-
designed epidemiological studies with high accesses
of lung cancer, in particular in studies showing a dose-
response relationship between Cr(VI) exposure and
lung cancer. The heavier the exposure to Cr(VI) by
inhalation, the more Cr(VI) is likely to be ingested.
Thus, epidemiological studies that do not demonstrate
a strong association between heavy exposure to Cr(VI)
compounds and cancer of the respiratory organs are
unlikely to present valid information on the possible
relationship between exposure to Cr(VI) compounds
and cancer for the digestive tract.
Most epidemiological studies of cancers are done in
cohorts inhaling Cr(VI). There were some hints that Cr
by inhalation exposure could enhance cancers at other
sites such as stomach (Costa, 1997; Langård, 1990).
There are no epidemiological studies on the ingestion
of Cr(VI) compounds. However, exposure to chromates
by inhalation also results in ingestion of some Cr(VI).
Therefore, information on cancer possibly resulting
from ingestion of Cr(VI) could be derived from some
epidemiological studies on populations exposed to
Cr(VI) by inhalation.
Enterline (1974) reanalyzed the mortality data
reported by Taylor (1966) and derived from workers
employed between 1930 and 1947 in three U.S. plants
manufacturing Cr(VI)-compounds. The study covered

7.3.2.5.3 Chromium Compounds in the Environment
At Tokushima University in Japan (Kondo et al ., 1971),
a study was carried out among residents close to a
newly started chromate manufacturing plant. The con-
clusion was: “no defi nite signs exist for health injury
caused by the chromate.”
Environmental exposure to Cr(VI) and its pos-
sible relationship to the development of cancer was
examined in Sweden (Axelsson and Rylander, 1980)
in a population living near a ferrochromium smelter.
No difference was observed between cancer mortality
among the local population living close to the smelter
compared with that of the population living farther
away. In this study, the exposure levels to Cr com-
pounds was not measured and must have been quite
low compared with levels experienced by Cr manufac-
turing workers.
A study carried out in the People's Republic of
China (Ziang and Li , 1997) was hampered by insuffi -
cient characterization of the alleged exposure to Cr(VI)
compounds, poorly defi ned exposed study popula-
tion, and a too short observation period to reveal
a possible relationship that might be present between
Cr(VI) exposure and occurrence of cancers of the res-
piratory organs. Therefore, the nonpositive result from
the study permits conclusions either on a possible rela-
tionship or on absence of relationship between Cr(VI)
exposure and the cancer outcome.