Americans commonly use more than 100,000 chemicals, and this doesn't take into account
mixtures or combinations of chemicals. Plus, some chemicals are altered by the atmosphere, water,
or incineration.
Scientists have been working for several decades to identify substances that cause cancer. They
have three ways to do this: through human studies, animal studies, and laboratory experiments.
![Identifying Cancer-Causing Substances](https://webarchive.library.unt.edu/eot2008/20090510225007im_/http://www.cancer.gov/images/Documents/167a5f6c-1c75-4b8a-b1bc-c7520def8d6b/slide40.jpg)
< Previous | Index | Next Slide > |