Carcinogenic refers to something that has the potential to cause cancer. It can be a substance, radiation or even certain viruses that can lead to the development of malignant tumors in an organism's body.
Fisher may be on to something, however: Studies have found that phytochemicals in garlic can halt the formation of carcinogenic chemicals in the body, and that women who eat more garlic have lower risk of certain colon cancers. (health.com)
Commercially prepared cured meats typically contain added nitrates, which can form potentially carcinogenic compounds when exposed to high temperatures (i.e. when cooked). (nourisheveryday.com)
The International Agency for Research on Cancer, part of the World Health Organization, classifies diesel engine exhaust as carcinogenic in humans. (globalgreenfreight.org)