Lifestyle and environmental contribution to male infertility.
This chapter is an overview of recent developments in our understanding and thinking about the importance and nature of environmental effects on sperm counts and fertility in the human male. This area is plagued by imperfect studies, not necessarily because of imperfect design but because of other 'uncontrollable' constraints. The available data, therefore, need to be placed in context and account taken of the limitations of our understanding or, more correctly, our ignorance. As we enter the new millennium, one of the saddest scientific aspects of human reproduction and infertility is our persisting ignorance about the causes and treatment of male infertility. With one notable exception (Y chromosome microdeletions) there has been little advance in our understanding of the causes of male infertility and its direct treatment over the past 20 years. Although most infertile men can now be offered the chance of fertility via ICSI, it is largely ignored that this does not represent treatment of the patient's infertility (which will persist unchanged), but is a means of circumventing the problem and leaving it for the next generation to tackle. There are many reasons for our ignorance about the causes of infertility, and some of these are outlined below in order to emphasise how this limits our ability to establish whether or not specific lifestyle and environmental factors do, or do not, affect human male reproductive function.