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What do classifications in Groups 2A and 2B mean

Posted Date:2025/6/3 1

What do classifications in Groups 2A and 2B mean?

Group 2A means that the agent is probably carcinogenic to humans. For agents in this category, there is usually convincing evidence that the agent causes cancer in laboratory animals and some evidence that it could cause cancer in humans, but the evidence in humans is not conclusive. There could also be consistent mechanistic evidence, showing that the agent exhibits one or more of the recognized key characteristics of human carcinogens, or that it belongs (based on mechanistic considerations) to a class of agents for which one or more members have been classified as carcinogenic to humans or probably carcinogenic to humans.

Group 2B means that the agent is possibly carcinogenic to humans. Agents can be classified in Group 2B in several different ways. Usually a classification of Group 2B means that there is convincing evidence that the agent causes cancer in experimental animals but little or no information about whether it causes cancer in humans. This category can also be used when there is some evidence that the agent could cause cancer in humans and in experimental animals but neither the evidence in humans nor the evidence in experimental animals is convincing enough to permit a definite conclusion to be drawn. There may also be consistent mechanistic evidence, showing that the agent exhibits one or more of the recognized key characteristics of human carcinogens.

For example, radiofrequency electromagnetic fields are classified in Group 2B because there is evidence that falls short of being conclusive that exposure may cause cancer in humans and in experimental animals. Whole leaf extract of aloe vera is also classified in Group 2B, on the basis of studies showing that it causes cancer in rats, but it has not been studied in humans.