Lead Toxicity in Mute Swans

DISCUSSION
Tissue lead levels have been used by many workers as an indication
of levels of lead exposure in bi"rds. J h (
o nson et al., 1982) and Hutton
and Goodman (1980) for example, have recorded increased lead levels in
Feral pigeons Columba livia (L) exposed to different lead levels.
Levels of lead in tissues were correlated with increased urbanisation,
(Johnson, et al., 1982).
Tissue lead levels have also been used as a
diagnostic tool for lead poisoning in birds.
The liver is the most
widely used organ in diagnosing lead poisoning.
It should be borne in
mind that lead in the body is not static in most tissues and levels are
in flux .
Rabinwits et al., (1974) and Anders et al., (1982) have
proposed models for predicting lead levels in humans and birds exposed
to lead with a view to interpreting lead levels in experimental
studies.
O'Halloran et al., [(B) in press] found good agreement
between blood lead levels in Mute swans in the field and experimental
models.
To test the model in wild birds is more difficult since
usually tissues from dead birds only are examined.
In the present
study, six tissues were examined (Tables 1-2).
Kidney, liver and
pancreas lead levels were generally high in lead poisoned birds.
In
lead poisoned swans, however, the median liver lead level was higher
than in the kidney.
This is not unexpected, based on the model of
Anders et al., (1982), since liver lead is very labile. In pigeons
exposed to lead, the concentration of lead in the liver reaches its
maximum in seven weeks and reaches a lower steady-state level in a
about 18 weeks (Anders et al., 1982).
In contrast, levels of lead in
the kidney -were found to rise to a value greater than that for other
1 1982) In the Present study, maximum lead
tissues (Anders et~., ·
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