A method for quantitative assessment of reproductive risks to the human male

There is a need for quantitative assessment of reproductive risks following human exposure to toxic agents. Current methods only estimate exposure levels that are unlikely to produce appreciable risk; they do not address the magnitude of risk. The quantitative reproductive risk estimation (QRRE) approach presented here enables calculation of the increased incidence of infertility in a human population resulting from exposure of males to a toxic agent. The four steps involve (A) obtaining a dose-response curve in experimental animals for the effect of a toxicant on a measure of reproductive function; (B) applying an interspecies extrapolation factor (IEF) derived for a similar toxicant to relate doses in animals and humans that produce equivalent reproductive toxicity; (C) using human exposure and uptake levels, along with the IEF and the dose-response curve, to calculate impairment of the measure in humans; and (D) computing the increase in human infertility caused by that impairment. The QRRE method is used to compute reproductive risks from dibromochloropropane exposure.