Lead in blood and tissues of mice after administration of low lead doses

Lead levels in whole blood could be determined reliably up to a lower limit of 2 micrograms/100 ml blood, using a modified micromethod of the graphite tube furnace technique. Lead contents of various tissues were also determined by using the automated graphite tube furnace after wet ashing of the organs with nitric acid in autoclaves. Animal experiments with mice showed no measurable increase in blood lead level after a single, 10- or 30-days oral administration of lead in doses of 10--1000 micrograms lead acetate/kg body weight/day. However, these doses led to a rise in tissue lead content. There was a clear dependence of tissue lead content on type of organ examined, lead dose and duration of lead exposure. According to our experiments, the threshold dose which leads to a long-term increase in tissue lead content is assumed to be about 100 micrograms lead acetate/kg body weight/day, orally administered.