BIOMONITORING OF LEAD-CONTAMINATED MISSOURI STREAMS WITH AN ASSAY FORERYTHROCYTE DELTA-AMINOLEVULINIC-ACID DEHYDRATASE ACTIVITY IN FISH BLOOD

The activity of the enzyme 8-aminolevulinic acid dehydratase (ALA-D) i n erythrocytes has long been used as a biomarker of lead exposure in h umans and waterfowl and, more recently, in fishes. The assay was teste d for ALA-D activity in fishes from streams affected by lead in combin ation with other metals from lead-zinc mining and related activities. Fishes (mostly catostomids) were collected from sites affected by hist oric and current mining activities, and from sites considered to be un affected by mining (reference sites). A group of potentially toxic ele ments was measured in blood and carcass samples of individual fish, as were ALA-D activity, total protein (TP), and hemoglobin (Hb) in blood . Concentrations of mining-related metals (lead, zinc, and cadmium) we re significantly greater (P < 0.05) in fish blood and carcass at sites affected by historic mining activities than at reference and active m ining sites. When analyzed by multiple regression, ALA-D activity, Hb, and TP accounted for 66% of blood-lead and 69% of carcass-lead variab ility. Differences among species were small. ALA-D activity as a bioma rker adequately distinguished sites affected by bioavailable environme ntal lead. Zinc was the only other metal that affected ALA-D activity; it appeared to ameliorate the inactivation of ALA-D by lead.