Slow cookers are safe. This appliance, cooks foods slowly at a low temperature—generally between 170° and 280° F. The low heat helps less expensive, leaner cuts of meat become tender and shrink less.

The combination of direct heat from the pot, lengthy cooking and steam created within the tightly-covered container destroy bacteria and make the slow cooker a safe process for cooking foods.

Additional Resources:
http://www.fsis.usda.gov/Fact_Sheets/Focus_On_Slow_Cooker_Safety/index.asp
http://www.fsis.usda.gov/Fact_Sheets/Focus_On_Slow_Cooker_Safety/index.asp