What is male reproductive health?
Male reproductive health refers to a man’s sexual function and fertility. It is a broad concept which includes physical formation of the genitals, sperm count, erectile function, age at puberty and risk of testicular and other male reproductive cancers.
A number of male reproductive health disorders are increasing, including malformations of the penis, low sperm count, testicular cancer (which has roughly doubled since the 1970s) and undescended testicle. The rise has been so rapid and so recent that the environment has to be a causal factor, and there is growing evidence from laboratory research that chemicals are contributing to the problem (Sharpe & Skakkebaek 2008).
How might chemicals affect male reproductive health?
Male reproductive health is complex and there are many ways in which it can be affected by chemical exposure. One area of particular concern is how chemicals can either suppress production or block the action of the hormone testosterone. If this happens while the foetus is developing, it can have a number of serious consequences for later development of the male genitalia. These include an increased the risk of the testicles not descending properly, of the penis not developing properly (a condition known as hypospadias), of low sperm count as an adult, and increased risk of testicular cancer.
Chemicals which have been shown to potentially have these effects include dioxin, organochlorine pesticides, some sun screens, some phthalates, herbicides such as linuron and diuron, vinclozolin and other fungicides such as chlorpyrifos, PBDE flame retardants and PCBs. None of these on their own have a particularly dramatic effect; however, people are generally exposed to combinations of many of these and, since the chemicals all affect the same biological system, it is possible these individual chemicals have significant combined toxicity.
A number of oestrogenic chemicals have been connected with feminizing effects in the male, including BPA, phenols, and the phthalates DINP and DCHP. PCBs, PFCs (in particular PFOS and PFOA) have been implicated in delayed puberty in boys. Dioxin, BPA and phthalate exposure is suspected of reducing sperm count in adults, while exposure to organochlorines and butyl parabens may damage the genetic material in sperm. The antimicrobial agents triclosan and triclocarban, DDT, parabens and some phthalates have been shown to affect testosterone production, with DEHP having a particularly powerful suppressive effect during later stages of foetal development.
Out for the count: Why levels of sperm in men are falling. The UK newspaper The Independent looks at how levels of viable sperm in human males are falling, and how scientists believe the causes of infertility can begin in the womb.
Male Reproductive Health Disorders and the Potential Role of Exposure to Environmental Chemicals. Professor Richard Sharpe of the UK Medical Research Council describes the deterioration of male reproductive health and potential role of exposure to hormone disrupting chemicals.
Save the men – environmental toxicants affect fertility and development. Swedish Society of Nature Conservation report.
Selection of references
Sharpe RM, Skakkebaek NE. Testicular dysgenesis syndrome: mechanistic insights and potential new downstream effects. Fertil Steril. 2008 Feb;89(2 Suppl):e33-8. Review. PubMed PMID: 18308057.