ABSTRACT
I. INTRODUCTION
The need for screening of substances for carcinogenicity was discussed in Chapter 8. In this chapter we will review statistical methods and issues related to animal experiments which are designed to screen substances for carcinogenic potential. The need to evaluate new substances before large numbers of people are exposed to them is a major justification for the use of animal experiments for such screening purposes. Animal studies are also useful for studying the carcinogenic effects of substances that are already in the environment. Epidemiologic studies of such substances are sometimes impractical because they would be prohibitively expensive or complex. In addition, in human studies, there is generally no experimental control over exposure levels and the precise measurement of exposure levels is often difficult. Animal studies, in contrast, are relatively inexpensive and allow for precise control of levels of exposure to the tested substance.
