Inability to become pregnant is prevalent throughout Europe. Large European surveys of representative population samples indicate that some 15% of couples do not achieve a pregnancy within 1 year of trying.1 Although there are no good indications that couple fecundity or semen quality has deteriorated during past decades,2 ,3 we have witnessed a dramatic increase in use of assisted reproduction techniques.4 In Denmark about 5% of all live-born babies are now conceived by in vitro fertilisation or other assisted reproduction techniques. On this background efforts to unravel preventable causes of infertility are welcomed. The paper by Cherry et al5 addresses semen quality and occupational exposure is an excellent example.

According to clinical series, male factors are contributing to infertility in almost half of couples attending infertility examinations. Semen quantity and quality has for decades been used as a biological marker of male fecundity at the population as well as at the individual level.6 The access to this simple and inexpensive biomarker of male fecundity may be part of the explanation that much more knowledge on environmental and in …