Air Quality Criteria for Lead Volume II of II - (NEPIS)(EPA) - US ...

Studies have identified ALAD in fish and amphibians as a useful indicator of Pb exposure
(Gill et al., 1991; Nakagawa et al., 1995a,b). ALAD catalyzes the formation of hemoglobin and
early steps in the synthesis of protoporphyrin (Gill et al., 1991; Nakagawa et al., 1995b). The
absence of an inhibitory effect on this enzyme following exposure to cadmium, copper, zinc, and
mercury suggests that this enzyme reacts specifically to Pb (Johansson-Sjöbeck and Larsson,
1979; Gill et al., 1991). A 0% decrease in ALAD activity was reported in common carp
(Cyprinus carpio) exposed to a Pb concentration of 10 µg/L for 20 days (Nakagawa et al.,
1995b). The recovery of ALAD activity after exposure to Pb has also been examined in carp
(Nakagawa et al., 1995a). After 2-week exposure to 200 µg Pb/L, ALAD activity decreased to
approximately 25% of value reported for controls (Nakagawa et al., 1995a). Fish removed from
the test concentration after 2 weeks and placed in a Pb-free environment recovered slightly, but
ALAD activity was only 50% of the controls even after 4 weeks (Nakagawa et al., 1995a).
Vogiatzis and Loumbourdis (1999) exposed the frog (Rana ridibunda) to a Pb concentration of
14,000 µg/L over 30 days and a 90% decrease in ALAD activity was observed in the frogs.
Blood Chemistry
Numerous studies have examined the effects of Pb exposure on blood chemistry in aquatic
biota. These studies have primarily used fish in acute and chronic exposures to Pb
concentrations ranging from 100 to 10,000 µg/L. Decreased erythrocyte, hemoglobin, and
hemocrit levels were observed in rosy barb (Barbus puntius) during an 8-week exposure to
126 µg/L of Pb-nitrate (Gill et al., 1991).
No difference was found in red blood cell counts and blood hemoglobin in yellow eels
(Anguilla anguilla) exposed to 0 and 300 µg/L of Pb for 30 days (Santos and Hall, 1990). The
number of white blood cells, in the form of lymphocytes, increased in the exposed eels. The
authors concluded this demonstrates the lasting action of Pb as a toxicant on the immune system
(Santos and Hall, 1990). Significant decreases in red blood cell counts and volume was reported
in blue tilapia (Oreochromis aureus) exposed to Pb-chloride at a concentration of 10,000 µg/L
for 1 week (Allen, 1993).
Blood components, such as plasma glucose, total plasma protein, and total plasma
cholesterol, were unaffected in yellow eels exposed to 300 µg/L of Pb for 30 days (Santos and
Hall, 1990). Effects on plasma chemistry were observed in Oreochromis mossambicus exposed
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