COMPARISON OF LEAD BIOAVAILABILITY IN F344 RATS FED LEAD ACETATE, LEAD-OXIDE, LEAD SULFIDE, OR LEAD ORE CONCENTRATE FROM SKAGWAY, ALASKA

An animal model using rats was developed to initiate investigations on the bioavailability of different sources of environmental lead. Lead must be absorbed and transported to target organs like brain, liver, k idney, and bone, before susceptible cells can be harmed. The bioavaila bility and therefore the toxicity of lead are dependent upon the route of exposure, dose, chemical structure, solubility, particle size, mat rix incorporation, and other physiological and physicochemical factors . In the present study male F344 rats were fed less-than-or-equal-to 3 8 mum size particles of lead sulfide, lead oxide, lead acetate, and a lead ore concentrate from Skagway, Alaska, mixed into the diet at dose s of 0, 10, 30, and 100 ppm as lead for 30 d. No mortality or overt sy mptoms of lead toxicity were observed during the course of the study. Maximum blood lead concentrations attained in the 100 ppm groups were approximately 80 mug/dl in rats fed lead acetate and lead oxide, and w ere approximately 10 mug/dl in those fed lead sulfide and lead ore con centrate. Maximum bone lead levels in rats fed soluble lead oxide and lead acetate were much higher (approximately 200 mug/g) than those see n in rats fed the less soluble lead sulfide and lead ore (approximatel y 10 mug); kidney lead concentrations were also about 10-fold greater in rats fed the more soluble compared to the less soluble lead compoun ds. However, strong correlations between dose and tissue lead concentr ations were observed in rats fed each of the four different lead compo unds. Kidney lesions graded as minimal occurred in 7/10 rats fed 30 pp m and in 10/10 rats fed 100 ppm lead acetate, but not at lower doses o r from other lead compounds. Similarly, urinary aminolevulinic acid ex cretion, a biomarker for lead toxicity, was increased in rats fed 100 ppm lead acetate or lead oxide, but was unaffected at lower doses or b y the less soluble lead compounds. Although the histological and bioch emical responses to lead toxicity were restricted to the more soluble lead compounds in this study, lead from Skagway lead ore concentrate a nd lead sulfide was also bioavailable, and accumulated in proportion t o dose in vulnerable target organs such as bone and kidney Longer-term studies with different mining materials are being conducted to determ ine if tissue lead continues to increase, and whether the levels attai ned are toxic. Data from such studies can be used to compare the toxic ity and bioavailability of lead from different sources in the environm ent.