Appendix B: The IARC classification scheme Group Meaning (number of agents) Basis for classification Everyday examples Evidence from studies Evidence from animal studies 1 Carcinogenic (116 agents as at 2015) Positive associations: chance, bias and confounding can be ruled out. X-rays Diesel engine exhaust Alcoholic beverages Ultra-violet (UV) radiation UV tanning devices 2A Probably carcinogenic (73 as at March 2015) Positive associations for which a causal interpretation is credible, but could also be due to chance, bias or confounding. Causal relationship established in 2 or more species, or 2 or more independent studies in a single species. PCBs Fumes from hot frying 2B Possibly carcinogenic (287 as at March 2015) Either: Coffee Pickled vegetables (traditional in Asia) Petrol engine exhaust ELF magnetic fields RF fields positive associations for which a causal interpretation is credible, but could also be due to chance, bias or confounding or has weaknesses that mean no conclusions can be drawn The data suggests a carcinogenic effect but is too limited to make a definitive evaluation. or: have weaknesses that mean no conclusions can be drawn. Causal relationship established in 2 or more species, or 2 or more independent studies in a single species. 3 Not classifiable (503 as at March 2015) Have weaknesses that mean no conclusions can be drawn. Either the data suggests a carcinogenic effect but is too limited to make a definitive evaluation, or the data has major quantitative or qualitative limitations. Chlorinated drinking water Tea Static electric and magnetic fields ELF electric fields 4 Probably not carcinogenic (1 as at March 2015) Several studies, covering the range of human exposures, which consistently show no increased risk. Bias and confounding can be ruled out, and there is an adequate follow-up time. Caprolactam (chemical used in the production of Nylon-6, which is widely used in fibres and plastics) * This summarises the minimum requirements that must be satisfied in most cases, but there may be exceptions. For a full overview of the IARC process and classification scheme, refer to
May 2014 Biological Effects Policy Advisory Group of the Institution of Engineering and Technology Updates 2012 report from the same group. Assessment based on peer-reviewed literature retrieved by monthly searches of INSPEC, MEDLINE and BIOSIS databases. Review also covers RF fields. On the balance of evidence from the last few decades, harmful health effects from environmental levels remain unsubstantiated. There is no generally accepted experimental demonstration of any biological effect from environmental levels. Pooled of epidemiological studies show an association between childhood leukaemia and high field levels, but the lack of mechanistic or experimental evidence does not support there being a causal relationship. A major epidemiological study published in 2014 suggested that the incidence of leukaemia in children living near power lines has decreased over the past 40 years and is no longer elevated. The high proportion of EMF studies that report effects, but a subsequent inability to replicate them, suggests that better quality control should be applied before publication. March 2013 SSM (Swedish Radiation Safety Authority) scientific council on electromagnetic fields Updates previous (usually annual) reports from the same group. Assessment based on articles in peer-reviewed journals. Articles assessed to determine the weight they should be given in overall assessment; evidence from different types of research (eg, epidemiology, in vivo and in vitro studies) is integrated in the final stage of evaluation. Epidemiological data is given greatest weight. Studies considered to have insufficient scientific quality are not included. Aim is to determine whether a hazard exists: the answer may not be a clear yes or no but express the likelihood that there is a hazard. If there is a hazard, the assessment should evaluate the exposure–response function. Review also covers RF fields. The question of whether ELF magnetic fields have any influence on the development of childhood leukaemia is still unresolved. A large number of other health endpoints have been studied, but mostly without finding consistent associations. Recent environmental and occupational studies on Alzheimer’s disease have reported associations but a causal relationship is not established.