Chemistry Reference
In-Depth Information
Alexandersson and Lidums (1979) measured the
urinary excretion of cobalt in workers occupation-
ally exposed to hard metal dusts. During one work-
ing week, these workers displayed urinary excretion
of cobalt more than 100 times higher than that found
in controls. Urinary levels of cobalt increased during
the working week and were approximately twice as
high in the afternoon after an 8-hour working shift as
morning values. The workers were also given a follow-
up for a period of 4 weeks after vacation (i.e., during
a nonexposure period). During this time, the average
urinary concentration decreased from approximately
60-5
media, which may also be infl uenced by the concomi-
tant presence of other substances, and this is likely to
affect the interpretation of biomarkers of exposure. The
importance of the chemical nature of the exposure has
been pointed out by Christensen and Poulsen (1994),
who observed increased concentrations of cobalt in
blood (0.2-24
g/L) of pot-
tery plate painters who used a soluble cobalt pigment,
whereas only slightly increased values were measured
in those using an insoluble cobalt pigment (0.05-0.6
and 0.05-7.7
µ
g/L) and urine (0.4- 848
µ
g/L in blood and urine, respectively).
The relationships between environmental and bio-
logical (blood and urine) parameters of exposure for
different chemical forms of cobalt have been investi-
gated in a cross-sectional study in workers exposed
to cobalt metal, oxides, and salts in a refi nery or to
a mixture of cobalt and tungsten carbide in a hard
metal producing plant (Lison
et al
., 1994). The main
conclusion of this study was that although biologi-
cal monitoring of workers exposed to cobalt oxides
revealed increased blood and urine levels compared
with nonexposed subjects, these parameters poorly
refl ected recent exposure level (23-7772
µ
g/L. This latter value was, however, approxi-
mately 10 times higher than that found in urine
obtained from men without previous cobalt exposure.
In a later study, Alexandersson (1988) compared blood
and urinary values in 70 cobalt-exposed workers from
the hard metal industry. He found that variations of
cobalt in blood were smaller than for urine, but both
parameters were shown to follow ambient exposure
(5-150
µ
g/m
3
). On the Friday afternoon samples, the
average exposure to cobalt for the entire work week
was correlated (
n
= 10), with the concentration of the
element in urine (0.79) and in blood (0.87).
Studying 10 groups of hard metal workers (air-
borne cobalt concentration, 28-367
µ
g/m
3
). In
contrast, when exposure was to soluble cobalt com-
pounds (metal, 17-10,767
µ
µ
g/m
3
; salts, 1-4690
µ
g/
g/m
3
), Ichikawa
et al
. (1985) found a good correlation between cobalt
concentration in blood and cobalt in air on the basis
of the mean values observed in the different groups.
On the basis of the correlation analyses, an airborne
exposure to 100
µ
m
3
; and hard metals, 1-203
g/m
3
), the measurement
of urine and/or blood cobalt at the end of the work-
week could be recommended for the monitoring of
workers. It was calculated that an 8-hour exposure
to 20 or 50
µ
g/m
3
of a soluble form of cobalt would
lead to an average urinary concentration of 18.2 and
32.4
µ
g/m
3
was associated with a cobalt
concentration of 5.7-7.9
µ
g/L
in urine (95% confi dence intervals). In a survey involv-
ing similar groups of workers (airborne cobalt concen-
tration, 120-284
µ
g/L in blood and 59-78
µ
g of cobalt/g creatinine, respectively (postshift
urine sample collected at the end of the workweek).
In workers from the hard metal industry, it has been
shown that concentrations of cobalt in urine rapidly
increase in the hours that follow cessation of exposure,
with a peak of elimination approximately 2-4 hours
after exposure, and a subsequent decrease (more rapid
for the fi rst 24 hours) in the following days (Apostoli
et al
., 1994).
There is no biological marker of effect that would be
specifi c for cobalt or hard metal exposure.
The determination of the HLA-DP genotype may
have some relevance in terms of individual suscepti-
bility to hard metal disease (see Section 7.2.3.2).
µ
g/m
3
), Perdrix
et al
. (1983) suggested
that the difference between the end and the beginning
of the shift urinary cobalt concentration refl ected the
day exposure. The concentration in the Friday evening
urine was indicative of the cumulative exposure dur-
ing the week, and the level of cobalt in urine collected
on Monday morning mainly refl ected long-term expo-
sure. In another group of hard metal workers exposed
to cobalt airborne concentrations <100
µ
g/m
3
, it has
been shown that there was an increase of urinary
cobalt concentration as the workweek proceeded
(Scansetti
et al
. 1985). In a study in diamond polishers
who used cobalt-containing disks, the measurement of
urinary cobalt concentration (0.03-75
µ
g/g creatinine),
when considered on a workshop basis, was found to
refl ect the level of exposure to the metal (<50
µ
7 EFFECTS AND DOSE-RESPONSE
RELATIONSHIPS
µ
g/m
3
)
(Nemery
et al
., 1992).
Limited comparative data are available for other
forms of cobalt to which workers may be exposed. Their
absorption rate depends on their solubility in biological
7.1 Local Effects
The existence of cobalt allergy is well documented;
it generally causes an erythematous and/or papular
