Lead - Toxicology of Metals - page 611

Hence, there are indications that lead causes endo-
crine disruption. In a recent review, it was concluded
that there were some indications of such effects at
occupational lead exposure in the range of 1.5-
2.0

In a recent review, it was concluded that gastrointes-
tinal symptoms usually occur at B-Pb of 3 µ mol/L and

higher (Table 3; Skerfving, 2005).

mol/L and higher (Table 3; Skerfving, 2005).
There are associations between lead and serum lev-
els of vitamin D metabolites. In children, very high
B-Pb was associated with low concentrations of 1,25-
dihydroxycholecalciferol (1,25-(OH) 3 D 3 ; Mahaffey et al .,
1982), possibly because of defi cient hydroxylation in
the kidney tubuli, no such relationship was seen in chil-
dren with lower B-Pb (Koo et al ., 1991). However, the
picture is complicated. Hence, in lead workers, high
B-Pb was associated with high serum concentrations
of 1,25-(OH) 3 D 3 (Chalkley et al ., 1998; Kristal-Boneh
et al ., 1998; Mason et al ., 1990). The latter may be due
to compensatory increase of formation to compensate
for lead-inhibited intestinal lead absorption (Fullmer,
1990). 1,25-(OH) 3 D 3 may increase lead mobilization
from the skeleton. Interactions between genetics of
VDR and lead metabolism were discussed previously
(Section 2.5.6), effects of lead on the skeleton will be
treated later (Section 2.7.7).
Sex hormones will be discussed later (Section 2.11).

µ

2.7.7 Other Organs

Lead exposure is associated with a low skeletal
growth, even at levels of exposure in the general popu-
lation (Frisanch and Ryan, 1991; Schwartz et al ., 1986).
The mechanism is not known. However, there are pos-
sibilities of interaction with both calcium metabolism
and bone cell proteins (Sauk et al ., 1992).

2.8 Immunotoxicology
There is only limited information on immunotoxic
effects of lead (McCabe, 1994), and the picture is not
consistent. Some of the interstudy discrepancies may
be due to the variations in exposure intensity and
methodological differences. There is no evidence of a
marked immunotoxic effect of lead at the exposure lev-
els studied.
However, there are probably various effects on the
humoral immunity—immunoglobulin levels in serum
(Horiguchi et al ., 1992a; Pinkerton et al ., 1998; Queiroz
et al ., 1993; 1994; Undeger et al ., 1996) and saliva (Pink-
erton et al ., 1998; Queiroz et al ., 1994) in lead workers.
Moreover, in lead-exposed workers, varying effects on
leukocyte and lymphocyte subtypes and function have
been described (Fishbein et al ., 1993; Pinkerton et al .,
1998; Queiroz et al ., 1994; Sata et al ., 1997; Undeger
et al ., 1996; Valentino et al ., 1991). Their health impli-
cations are not clear, but there are some indications
of increased sensitivity to infections in Japanese lead-
refi nery workers (Horiguchi et al ., 1992b).
The information is not easy to interpret in terms of
exposure response. However, in a recent review it was
concluded that various effects have been reported in
groups of lead workers with mean B-Pb of approxi-
mately 2

2.7.6 Gastrointestinal Tract

Lead is excreted in the saliva (Koh et al ., 2003),
which may explain the gingival “lead line” (Burtonian
line) sometimes seen in lead workers (alternately, the
origin is lead in the gingival tissue). The greyish color
is due to precipitated lead sulfi de, which is formed by
sulfur produced by bacteria. Hence, the sign is most
prevalent in lead workers with bad oral hygiene and
bacterial paradentosis.
Gastrointestinal symptoms (lead colic) are often
the only clinical ones in lead poisoning. They appear in
the beginning, often remain during the entire course of
the disease and are often the reason why lead poisoning
is diagnosed. They are often not characteristic. They most
often start as protracted constipation, indigestion, and loss
of appetite, but only occasionally diarrhea. The abdomi-
nal cramps are intermittent, often with pain-free intervals,
most often localized in the hypogastrium (sometimes in
the epigastrium), sometimes radiating to the urinary blad-
der, scrotum, and kidney. They may be very intensive.
Vomiting is prevalent, as is tenesmus without defecation
and miction without much urine. The clinical picture may
be mistaken for obstructive ileus or appendicitis. The
patients often compress their abdomen because of the
pain, which excludes peritonitis as the cause. Probably,
the gastrointestinal effects are due to interaction with cal-
cium in the smooth muscle cells; calcium administration
intravenously will give temporary relief.

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

2.9 Mutagenicity
Lead has a clastogenic effect, inducing chromo-
some aberrations, micronuclei, and sister chromatid
exchanges (SCEs) in lead workers (Dönmez et al ., 1998;
Duydu et al ., 2001; Vaglenow et al ., 1998; 2001; Wu
et al ., 2002). In a recent review, it was concluded that
increased occurrences of such effects have been shown
in peripheral lymphocytes of lead workers exposed at
levels corresponding to average B-Pbs of approximately
1.5-2 mol/L and higher (Table 3; Skerfving, 2005).

All these effects may increase the risk of cancer
(Section 2.10). Indeed, it has now become clear that

µ