Factbox-Agents and substances categorized as carcinogenic to humans
According to the IARC, there are four different levels of classifications - carcinogenic, probably carcinogenic, possibly carcinogenic and not classifiable. The levels are based on the strength of the evidence, rather than how dangerous a substance is. Here is a look at some of the top agents that are carcinogenic to humans based on their classifications: CATEGORY-1: WHEN AN AGENT IS CONSIDERED 'CARCINOGENIC TO HUMANS' As per IARC, this classification is used when there is enough proof that the agent causes cancer in people.