Environmental xenobiotics and male reproductive health

toxicants.3 Following the Seveso disaster in northern Italy in 1976, a remarkable increase in the proportion of girls was reported among offspring of heavily dioxin exposed men.4 Thus, the overarching question is not whether environmental chemicals may represent a hazard to male reproductive health, but how important this hazard at exposure levels found in the general population is in comparison with other risk factors and causes. Alarming reports from the 1880’s and 1990’s including the Danish 1992 report on a global major decline in sperm count5 have fuelled speculations that the environmental impact may be substantial because only changing environmental factors can explain dramatic changes in health outcomes across short time period. With one notable exception, testicular cancer, there is, however, no scientific consensus that sperm counts and various testicular disorders have changed markedly over past 50–100 years,6,7 and some researchers doubt that there ever will be provided valid data to corroborate or refute alleged changes in male reproductive health.8 The only long-term prospective study of semen quality with repeated yearly examinations in Denmark do not indicate that changes of sperm count has taken place during past 15 years.9 There is more reliable, but yet limited evidence indicating regional differences in sperm counts,10,11 but other comparative studies of semen quality have shown remarkable similar sperm count distributions in different regions including remote populations.12,13 In this special issue of the Asian Journal of Andrology, the environmental xenobiotic impact on male reproductive health is highlighted through a series of invited papers by authors who have advanced knowledge in this field during past 20–30 years. First thing to notice is the current strong evidence that L from the occupational arena demonstrate the potential of industrial chemicals to damage human testicular function. An important but still unresolved question is whether low‐level xenobiotic exposure of the general population poses a hazard. In this volume of the Asian Journal of Andrology, this issue is addressed by a series of reviews on xenobiotic exposure profiles, possible biological mechanisms, research methods and knowledge on impact of specific exposures. Interdisciplinary research fields as gene‐environment interaction and male‐mediated developmental toxicity is also addressed. Papers are cross‐linked by answers to questions mutually put forward by the authors. Several undisputed lessons from the past demonstrate how xenobiotics in the environment may have profound impact on male reproductive health. The most known cases are from the occupational arena and following environmental disasters. More than 30 years ago it was almost concomitantly reported from the United States and from Israel that the nematocide dibromochloropropane (DBCP) causes severely reduced sperm counts and even sterility in workers manufacturing or applying this pesticide.1,2 Since this discovery numerous occupational semen studies have provided considerable although less compelling evidence that some heavy metals, some halogenated organic solvents, some fungicides and other compounds are male reproductive INVITED EDITORIAL