Cancer causing substances

Have you ever wondered what causes cancer? There are varying opinions, but here is a link to the list published by the U.S. Government, Department of Health and Human Services.

http://ntp.niehs.nih.gov/index.cfm?objectid=72016262-BDB7-CEBA-FA60E922B18C2540

Here's the link directly to the list:

http://ntp.niehs.nih.gov/index.cfm?objectid=32BA9724-F1F6-975E-7FCE50709CB4C932