Chemistry Reference
In-Depth Information
had worked in asbestos processing. Smoking habits
were reported to be similar in platers and referents.
Results were reported on the mortality among
952 Cr platers in Tokyo (Okubo and Tsuchiya, 1979)
where workers had been recruited from 1970 to 1976
records of the Tokyo Health Insurance Society of the
Plating Industry and comprised workers born before
May 31, 1937, with 6 months or more experience with
Cr plating. Expected deaths were based on SMRs of
the general Tokyo population. No lung cancer deaths
had occurred in males versus 1.2 expected (not sig-
nifi cant).
A study on cancer mortality among 178 Italian Cr
platers was reported on by Franchini
et al
. (1983), 62
of whom were “bright” and 116 were “hard” platers.
Seven cancer deaths had occurred in hard platers ver-
sus 2.7 expected on the basis of national rates. Three
deaths were from lung cancer (E = 0.7) (
P
= 0.03); abso-
lute risk = 182 × 10
−5
/year. When excluding 10 years
presumed latency, six cancer deaths (E = 2.2) and
three lung cancer deaths (E = 0.6) (
P
= 0.02) remained.
Exposure to Cr(VI) in hard plating in 1980 averaged
7
7.3.2.5.2 Stainless Steel Welding
Stainless steel (SS)
generally contains 8-10% nickel (Ni) and 18-20% Cr, and
the electrodes applied during welding on SS generally
contain more Ni and Cr than the base material. The
fume generated during welding on SS contains Cr and
Ni along with other toxic gases and fumes (i.e., CO,
NO
x
and O
3
). Although the Cr in the base materials
is present in the inert 0 valency form, it oxidizes to
Cr(VI) resulting from the high temperatures (i.e.,
6000°C+) during the welding process. Consequently,
unprotected welders may be exposed to Cr(VI) at
various air levels; the exposure levels depend largely
on which method of welding is being used, generally
with highest levels during manual metal arc (MMA)
welding. Because welders frequently weld on different
materials, they may also be exposed to oxides of other
metals (i.e., oxides of Mn, Fe, Al, and others) (Karlsen
et al
., 1996; Stern, 1981).
Given the mixed exposure among welders, epidemi-
ological studies on SS welders are diffi cult to perform,
but few studies are carried out among welders who
have welded SS only. Some studies indicate that there
is an excess cancer of the respiratory organs among SS
welders. Sjögren (1980) studied a group of 234 subjects
who had welded SS only for 5 years+ between 1950 and
1965. Dilution was avoided by excluding subjects from
the study with <5 years of welding. Sjögren found that
smoking habits of the study group were similar to the
general male population used as reference entity. There
were three cases of lung cancer in the group versus 0.8
expected. Sjögren
et al
. (1987) subsequently studied
the same cohort through an additional period until
1984 and observed fi ve cases of lung cancer versus 2.0
expected. Compared with other studies, exposure to
welding fumes was well characterized, and latencies
for possible exposure-related cancer were accounted.
Becker
et al
. (1985) performed a cohort study in
1224 SS welders who had used different methods.
The only subgroup with excess lung cancers was that
performing MMA with 20-29 years since fi rst expo-
sure; fi ve observed versus 2.1 expected, whereas the
entire MMA subgroup showed fi ve cases versus 5.1
expected. A short observation time was an inherent
weakness of the study. In a later follow-up through
1995 (Becker, 1999), it seemed that the excess lung
cancer was confounded by previous exposure to
asbestos (i.e., there were 7 deaths from mesotheli-
oma versus 0 expected), indicating that a signifi cant
number of the previously observed excess lung can-
cer deaths are likely to be due to exposure to asbes-
tos fi bers.
A major study was carried out by the IARC includ-
ing both mild steel (MS) as well as SS welding in 11,092
welders (Simonato
et al
., 1991). Welders from nine
g/m
3
, but it was assumed that exposure had been
higher in the early exposure years.
Sorahan
et al
. (1987) reported on the mortality
experience among 2689 (males/females = 1288/1401)
Cr electroplaters from the period 1946-1983 per-
forming primarily bright (thin) plating of bumpers
and overriders. The cohort included workers fi rst
employed during 1946-1975 with 6 months+ experi-
ence as Cr platers. Air measurements of Cr had been
taken before 1973, measuring the concentration of
Cr
2
O
3
as high as 8.0 mg/m
3
, 1.6 mg/m
3
, and 0.4 mg/
m
3
, respectively. From 1973 onward, the air levels
were generally <50
µ
g Cr/m
3
. All participants had at
least some period of work associated with Cr expo-
sure, but concomitant exposure to nickel chloride and
nickel sulfate had taken place. Death rates were com-
pared with that of the general population of England
and Wales, and there were 213 cancer deaths from all
sites versus 164.2 expected, when combining genders.
Sixty-three of 72 lung cancer deaths were in males
(E = 40;
P
< 0.001), and nine in females (E = 8.1). The
highest O/E ratios were 13/3.8 (
P
< 0.001) after 10-14
years and 12/4.9 (
P
< 0.01) after 15-19 years of work
at chrome baths in combined genders. There were 25
deaths from stomach cancer (E = 16.2), but excess in
males only.
In a study among 176 consecutive hospital-based
male lung cancer cases in Norway, Kjuus
et al
., (1986)
found that seven cases and six referents had been
exposed for 3 years or more to Cr and nickel com-
pounds (welding excluded). The odds ratio adjusted
for smoking was 1.4(CI = 0.4-4.4).
µ
