Abstract
Editor's Note: The use of epidemiology studies to determine or confirm whether a substance is a human carcinogen is often quite controversial. Human beings, unlike laboratory rats, tend to be exposed to numerous chemicals at work. Which of these chemicals may be responsible for higher than expected rates of a specific cancer can be confusing. Alternatively, the confirmation that a chemical can cause cancer in humans eliminates opinions as to differences in metabolism or various genetic-repair mechanisms between animals and humans. The Journal is pleased to be able to present two distinct viewpoints that analyze the results of an investigation of excess cancers by workers who were exposed to 4,4′ -Methylene bis(2-chloroanaline) (MBOCA). These differing viewpoints serve to emphasize the difficulty of confirming human carcinogens.