IARCs klassifisering av radiofrekvente elektromagnetiske felt som «muligens kreftfremkallende for mennesker» (klasse 2B), ble, som forventet, møtt med mye motstand. Mange hevder at IARCs klassifisering er uproblematisk; det er ingenting å bekymre seg for, siden kaffe, sylteagurk og snekkerarbeid har samme klassifisering. Du kan trygt si at en slik oppfatning vitner om manglende kunnskap og/eller misforståelser. Lennart Hardell forklarer følgende, i sin rapport for European Environment Agency (EEA):
IARC evaluates the hazard from potential carcinogens, i.e., ‘an agent that is capable of causing cancer under some circumstances’, while a cancer risk is an estimate of the carcinogenic effects expected from an exposure to a cancer hazard. The IARC monographs are an exercise in evaluating cancer hazards, despite the historical presence of the word ‘risks’ in the title.
IARC has categorised nearly 1000 potentially carcinogenic hazardous agents, that it has studied over the last 40 years, into 5 classifications. These are differentiated by different strengths of evidence. In descending order of strengths of evidence they are: Group 1, which are ‘established’ human carcinogens, such as asbestos, diesel engine exhaust, tobacco, and X-rays (108 agents); Group 2A, which are probable carcinogens, such as perchloroethylene (64 agents); Group 2B, which are possible carcinogens, such as other traffic fumes, lead, DDT and now radiofrequency electromagnetic fields, including mobile phones (272 agents); Group 3, where the agent is not classifiable because the evidence is inadequate and does not permit another classification (508 agents); and Group 4, where the agent is probably not carcinogenic to humans, based on fairly strong evidence against a cancer effect in both humans and animals (1 agent) (IARC, 2012).
It may be helpful to clarify the meaning of the particularly contentious groups, i.e., 2A and 2B.
IARC chooses 3 main different strengths of evidence when it is evaluating the different types of cancer evidence that may be available. The evidence evaluated comes mainly from humans; from animals; and from consideration of the biological mechanisms for cancer causation: this last can provide understanding about how carcinogens cause cancer, in contrast to whether they cause cancer.
The main strengths of evidence groups used by IARC are: ‘sufficient’, ‘limited’, and ‘inadequate’. For example, while Group 1 consists of those agents where there is ‘sufficient evidence of carcinogenicity’ in humans; Group 2A includes those agents where there is ‘limited evidence of cancer in humans’ but ‘sufficient evidence of cancer in animals’; and Group 2B, which is the radiofrequency EMF category, is those agents where there is ‘limited evidence of cancer in humans and less than sufficient evidence in animals’ and where ‘chance, bias or confounding cannot be ruled out with reasonable confidence’. ‘Evidence suggesting lack of carcinogenicity’ is used for Group 4 (IARC, 2006, p. 19–20).
Different agents in the same classification group are evaluated on the basis of very different kinds of evidence and exposure conditions that are specific for each substance. Some 2B agents will be at the lower end of the probability range, others will be close to the nearly one in two probability and the rest are somewhere in between, depending on their very specific characteristics. By loosely lumping together several randomly chosen carcinogens from the 271 in Group 2B such as dry cleaning fumes and coffee, which invites comparison to mobile phones, journalists and others help to complicate the already difficult discussion about the likelihood of cancer risks. Each agent needs to be considered on its own evidence.