Any need to revisit the male reproductive toxicity of lead?

The toxicity of lead has been known for millennia and has served as a template for toxicology studies. 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. In parallel with this development, the introduction of non-leaded gasoline in the late 1970s was followed by a remarkable decline in body burden of lead in the general population. However, unlike many other metals, e.g., Zn, Cr, Mn, Cu, and Fe, Pb has no known essential effects for living organisms, and current exposure levels are still high compared to pre-industrial populations. 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 rate species and strains seem quite resistant. Male reproductive toxicity studies in humans have addressed effects on hormone levels, birth rates, time taken to conceive in couples not using contraception, and semen characteristics. This view on male reproductive toxicity of lead is challenged by the findings on decreased fecundity among male lead workers published by Shiau et al. (Occupational and Environmental Medicine, November 2004). Using the time to pregnancy methodology, an astonishing clear exposure response relation between current blood lead level and time taken to conceive among male battery workers in Taiwan is observed.