The Most Common Method of Determining Whether a Chemical Causes

Multiple Choice

The most common method of determining whether a chemical causes cancer is to expose groups of laboratory animals, such as rats, to various large doses and count how many animals develop cancer at the different levels. All of the following are problems with this approach in terms of understanding the health risks to humans EXCEPT:

A) This method is indirect and uncertain as human and rats are different organisms and may respond differently to exposure to the same chemical.
B) For expediting the research process, in lab settings rats are exposed to massive doses of suspected carcinogens relative to body size whereas humans are usually exposed to much lower amounts.
C) For ethical reasons, rats in lab settings are given very small doses of suspected carcinogens relative to body size whereas humans are usually exposed to much higher amounts
D) Risk assessment assumes that we can extrapolate from studies in rats to determine the expected rates of cancer in humans but extrapolating from one species to another and from one dose level to another is uncertain and may overestimate or underestimate a toxicant's danger.