Lead - Toxicology of Metals - page 615

2.11.2 Males cancers (Kristensen and Andersen, 1992) in the off-

spring of male lead workers.
In a recent review, it was concluded that effects on
male reproduction (endocrine function, sperm qual-
ity, and perhaps fertility) may occur at B-Pb of 1.5-
2.0

In lead workers, slight, lead-associated effects on the
hypothalamic-pituitary-testis axis (mainly luteinizing
and follicle-stimulating hormones) have been reported
(Braunstein et al ., 1978; Erfurth et al ., 2001; Gustafsson
et al ., 1989).
Lead is distributed to the testis (Barry, 1975). Also,
lead accumulates in other parts of the male reproduc-
tive tract (epididymis, seminal vesicles, and prostate;
Johansson and Wide, 1986). Furthermore, there is
incorporation into seminal fl uid.
Low levels of lead (a few

µ mol/L or higher (Table 3; Skerfving, 2005).

2.12 Overall Assessment of Risk
2.12.1 The Data Sets—Strengths and Limitations

In the last decades, the perspective of lead toxicity has
changed in several aspects: Large lead-worker groups
and general populations have been investigated. Some
effects have been reported in general population strata
with low exposures, in the range of the referent groups
in many studies of lead workers. This is a problem in
the interpretation of the occupational studies.
Also, explanations of the formerly intriguing dif-
ferences in sensitivity have begun to appear in terms
of gene-environment interactions, mainly as regards
ALAD genotype. ALAD 2 subjects seem to have a higher
B-Pb at the same exposure intensity (at least when it is
not low) and perhaps less toxic effects. Thus, despite
their higher B-Pb, they may be protected from at least
some adverse effects and may tolerate higher exposure.
These phenomena may induce selection at the work-
place. Hence, if B-Pb is surveyed, ALAD 2 subjects may
be more likely to be removed. On the other hand, if
there is no such surveillance, ALAD 1 subjects may quit
selectively because of early symptoms. Moreover, the
prevalences of the genes differ between races, which
may affect the risk patterns. Preemployment screening
for ALAD genotype has been proposed. However, this
seems premature.
One problem is that most studies do only allow con-
clusions about differences between groups with vary-
ing exposure; hence, it is not possible to defi ne a no
(NOAEL) or lowest (LOAEL) observed adverse effect
levels. Also, the number of workers have often been
low. On the other hand, when discrete exposure meas-
ures (B-Pb) are used in large populations, effects may
be shown at low exposures, but then at a low rate.
At the same time, sensitive methods have been
used. Then, the question whether the effects should
really be considered adverse (i.e., indicating a health
risk, and thus a basis for risk assessment) becomes
more complicated.
There is still far too little information on the relation-
ship between air lead and effects. Hence, biomarkers
have to be used. However, the choice of biomarkers to
defi ne the exposure may seem less obvious than earlier.
Hence, in the last decade, the use of in vivo determination
of skeletal lead has exploded. Thus, bone lead has some-
times shown relationships to effects, when B-Pb has not.

g/L) have been found in
the seminal plasma in males without particular expo-
sure (Chia et al ., 1992; Dawson et al ., 1998; Xu et al .,
1994; 2003). It seems that a signifi cant fraction of this
originates from the prostate or the seminal vesicles
(Butrimowitz et al ., 1983). Furthermore, lead work-
ers have increased lead levels in the seminal fl uid; the
levels were approximately one tenth of those in blood
(Bonde et al ., 2002; Kuo et al ., 1997). The level in sper-
matozoa is similar to that in blood (Bonde et al ., 2002).
In lead workers, there were associations between
exposure and sperm count, motility, and morphology
(Aribarg and Sukcharoen, 1996; Lerda, 1992; Telisman
et al ., 2000). In one study, the critical B-Pb seemed to be
440

µ

g/L (Bonde et al ., 2002). Signifi cant improvement
has been reported after reduction of exposure (Viskum
et al ., 1999). Even in subjects without occupational lead
exposure, there was an association between seminal
fl uid lead and sperm count (Xu et al ., 2003).
Decreased libido, erectile dysfunction, and ejacu-
lation problems have been reported in lead workers
(Lancranjan et al ., 1975), but there are methodological
problems that preclude fi rm conclusions. In a study of
Finnish lead workers, there was a blood-lead associated
decrease of the standardized fertility ratio; an effect
was seen at 0.5-0.9

µ

mol/L (Sallmén et al ., 1992; 2000).
Similar data have been reported from Belgium (Gennart
et al ., 1992b). However, other results have not been con-
sistent (Apostoli et al ., 2000; Lin et al ., 1996).
There are indications of a risk of spontaneous abor-
tion in wives of lead workers (Anttila and Sallmén,
1995). Such a risk was also suggested by a Finnish case-
referent study of hospital-treated spontaneous abor-
tion, although the data did not allow fi rm conclusions
(Lindbohm et al ., 1991).
Furthermore, preterm birth (Kristensen et al ., 1993)
and low birth weight in the offspring (Min et al ., 1996)
have been reported to be associated with occupational
lead exposure of the father, but the risk of confound-
ing by secondary exposure of the mother by lead dust
brought home, as well as lifestyle and other occu-
pational factors, is obvious. There is no conclusive
evidence as to malformations (Irgens et al ., 1998) or

µ