Teratology Symposium Examines Male-Mediated Developmental Toxicity

Speakers at a symposium on "Male-Mediated Developmental Toxicity" presented compelling evidence that human exposure to ionizing radiation or certain chemicals can diminish sperm production and therefore, reduce fertility.

The symposium was presented during the 41st Annual Meeting of the Teratology Society, held June 23-28, 2001, in Montreal, Canada. The event was attended by IITRI's lead teratologist, Dr. Ali Faqi, who summarizes the key points of the symposium here.

Of the many chemical agents and mixtures that have been evaluated in men by semen analysis, about half (mostly drugs and a few occupational exposures) reduced sperm quantity and quality. Several of these agents also affected the fertility of exposed men.

It is becoming apparent that the father's role in reproduction goes beyond fertilization. Abnormalities in paternal chromosomes (structural and numeric) have been found in various abnormal reproductive outcomes, including chromosomal abnormality syndromes among newborns.

Data in animal studies have shown that exposure of male animals to mutagens before mating induces transmissible cytogenetic and genetic abnormalities, as well as morphologic defects and cancer among offspring.

Consistent with animal findings, there is growing epidemiologic evidence of associations between male exposures to exogenous agents and abnormal reproductive outcomes, such as fetal loss, birth defects and childhood cancer. However, efficient measurements (including biomarkers) of relevant exposure, early biologic effects and susceptibility in human males are still under development.

A major concern, therefore, is the risk assessment of male-mediated developmental and genetic toxicity. Future areas of emphasis should include: (1) risk characterization in sensitive laboratory species, (2) epidemiologic studies of exposed human populations, and (3) studies of the molecular mechanisms of action of toxicants.