The toxicity of lead has been known for millennia and has served as a template for toxicology studies.¹ According to some 45 000 measurements in European industrial settings spanning smelters, battery manufacturing, and foundries, the average concentration of lead in blood steadily declined from 68 μg/dl in 1970 to 35 μg/dl in 1995.² In parallel with this development the introduction of non-leaded gasoline in the late 1970s was followed by a dramatic decline in body burden of lead in the general population.³ However, unlike many other metals such as zinc, chromium, manganese, copper, and iron, lead has no known essential effects for living organisms, and current exposure levels are still high compared to pre-industrial populations. Therefore it is important to continue to control lead exposure and to unravel effects of the low and very low doses of the metal.

Lead has long been known to be toxic to male fertility. Several studies in rats and other rodents indicate that blood lead concentrations above 30–40 μg/dl are associated with impairment of spermatogenesis and reduced concentrations of androgens—although some rat species and strains seem quite resistant.⁴ The latter could be due to differences in tissue distribution. Contrary to findings in …