animals and other relevant data. The classification is based only on the strength of evidence for carcinogenicity, not on the relative increase of cancer risk due to exposure, or on the amount of agent exposure necessary to cause cancer. Group 1: The agent is carcinogenic to humans. There is sufficient evidence of carcinogenicity in humans. Exceptionally, an agent (or mixture) may be placed in this category if there is less than sufficient evidence in humans, but sufficient evidence in experimental animals and strong evidence in exposed humans that the agent acts through a relevant mechanism of carcinogenicity. Examples of agents classified as Group 1 include tobacco smoke, alcoholic beverages, Chinese-style salted fish and consumption of processed meat. Group 2A: The agent is probably carcinogenic to humans. There is limited evidence of carcinogenicity in humans and sufficient evidence in experimental animals. Occasionally, an agent (or mixture) may be classified here when there is inadequate evidence in humans but sufficient evidence in experimental animals and strong evidence that the carcinogenesis is mediated by a mechanism that also operates in humans. Exceptionally, an agent (or mixture) may solely be classified under this category if there is limited evidence of carcinogenicity in humans, but if it clearly belongs to this category based on mechanistic considerations. Examples of agents classified as Group 2A include emissions from high-temperature frying of food, the occupational exposures as a hairdresser or barber, consumption of red meat and night shift work . Group 2B: The agent is possibly carcinogenic to humans. There is limited evidence of carcinogenicity in humans and less than sufficient evidence in experimental animals. It may also be used if there is inadequate evidence in humans but sufficient evidence in experimental animals. Occasionally, an agent (or mixture) may be placed in group 2B if there is inadequate evidence in humans and less than sufficient evidence in experimental animals but there is supporting evidence of carcinogenicity from mechanistic and other relevant data. An agent or a mixture may also be classified in this category solely on the basis of strong evidence of carcinogenicity from mechanistic and other relevant data. Examples of agents classified as Group 2B include occupational exposures in working in the textile manufacturing industry, printing processes, traditional Asian pickled vegetables, and radiofrequency electromagnetic fields. Group 3: The agent is not classifiable as to its carcinogenicity to humans. The evidence is inadequate in humans and inadequate or