What You Need to Know. What You Can Do.
How do scientists decide which substances to test in animals, human laboratory cells, or human population studies?
Upon completion of this section, you will be able to
Strategies for Testing in Animals or Human Laboratory Cells
Because resources are limited, scientists must decide out of thousands of candidates which substances to select for testing in animals or in human cells. The tests are costly and time-consuming: determining whether a chemical causes cancer in rats or mice can cost several million dollars and take several years to complete. Three factors generally guide the decision to test a substance.
The Number of People Exposed
We want to test those chemicals that affect a large number of people or those for which the exposure levels have been unusually high. Pesticides, for example, fit both categories. They potentially affect a large number of people because of trace amounts on foods and their use in or around the home, and in farming-related occupations, exposure levels are high.
This could be a report that in laboratory cells, a chemical causes alterations in human DNA. Or it could be a report that people exposed to a particular chemical in the workplace or at a specific geographical location have developed specific cancers at higher rates than expected. This kind of information provides important clues for decisions about animal testing. Even before any animal testing was done, studies on human and animal cells indicated dioxins and polycyclic aromatic hydrocarbons were suspected carcinogens.
Chromium and some pesticides are examples of a group of concerned citizens first bringing to the attention of public health officials concerns about chemicals. The National Toxicology Program has a Web site available to the public to suggest agents suspected of causing cancer: ntp-server.niehs.nih.gov; click on “ Nominations to the Testing Program.”
|Strategies for Carrying out Large Population Studies||
Similar considerations guide epidemiologists as to whether to begin large population studies. Some of these factors include
Choose the best answer.
|Previous Section||Next Section|