Methods for evaluating the effects of environmental chemicals on human sperm production.

Sperm tests provide a direct and effective way of identifying chemical agents that induce spermatogenic damage in man. Four human sperm tests are available: sperm count, motility, morphology (seminal cytology) and the Y-body test. These sperm tests have numerous advantages over other approaches for assessing spermatogenic damage, and they have already been used to assess the effects of at least 85 different occupational, environmental, and drug-related chemical exposures. When carefully controlled, seminal cytology appears to be statistically more sensitive than the other human sperm tests and should be considered an integral part of semen analysis when assessing induced spermatogenic damage. Human sperm studies have complex requirements and, before sampling, careful consideration should be given to exposure details, group size and makeup, as well as animal and human data that indicate spermatogenic effects. Several study designs are possible and should include questionnaires covering medical and reproductive histories as well as known confounding factors. Animal sperm tests, such as the mouse morphology test, may be used to identify the toxic components of a complex mixture. Animal tests may also help assess the chemical effects on fertility and reproductive outcome in cases when human data are incomplete. Further efforts are needed in these areas to develop improved human sperm tests sensitive to induced spermatogenic damage, to develop improved animal models of induced spermatogenic damage, to understand the relationships among sperm changes, fertility, and reproductive outcome, and to develop sperm tests with express mutational end points.