The WHO has come to the conclusion on the advice of its International Agency for Research on Cancer, which assesses the best available scientific evidence.
It has now placed processed meat in the same category as plutonium, but also alcohol as they definitely do cause cancer.
However, this does not mean they are equally dangerous. A bacon sandwich is not as bad as smoking.
"For an individual, the risk of developing colorectal (bowel) cancer because of their consumption of processed meat remains small, but this risk increases with the amount of meat consumed," Dr Kurt Straif from the WHO said.