When scientists are testing whether agents cause cancer or not, one important test is whether they produce cancer in rodents (mice and rats). There are standardised protocols for these tests, e.g. as conducted under the auspices of the National Toxicology Program in the USA, exposing hundreds or often a thousand animals for the whole of their lifetime, and the results, in either direction, are widely regarded as strong evidence.
There have been 5 experiments using "normal" or "wild type" rodents, and another 5 on mice genetically modified specifically to show effects on leukaemia or lymphoma. These experiments were reviewed by the World Health Organization in their Environmental Health Criteria. The following summary is a simplified form of Table 78 from the EHC. The links are to a separate page where we list the abstracts of these studies.
The overall conclusion from these studies is that 50 or 60 Hz fields have not been shown to produce cancer in rodents. The WHO EHC concludes:
"Overall there is no evidence that ELF exposure alone causes tumours."
They also review other experiments on rodents in which EMF exposure has been combined with other carcinogens, and conclude:
"The evidence that ELF field exposure can enhance tumour development in combination with carcinogens is inadequate."
Animal model | Field | Exposure | Result | Reference |
---|---|---|---|---|
Large-scale lifetime studies | ||||
Male and female mice | 60 Hz | 2 years | No effect on incidence of most tumours | McCormick et al 1999 |
Male and female rats | 50 Hz | 2 years | No effect on incidence of most tumours | Yasui et al 1997 |
Female rats | 60 Hz | 2 years | No effect on tumour incidence | Mandeville et al 1997 |
Male and female rats | 60 Hz | 2 years | No effect on incidence of most tumours. Increase in thyroid tumours in males. | Boorman et al 1999 |
Male and female mice | 50 Hz | Exposure prior to mating and during pregnancy. Follow-up 78 weeks | No effect on incidence of tumours in offspring. | Otaka et al 2002 |
Leukaemia/lymphoma | ||||
Leukaemia-prone female mice | 12 Hz or 460 Hz | 1 hr/week until death, 5 generations | No effects on survival | Bellossi 1991 |
Male and female mice | 60 Hz | 3 generations | Increase in lymphoma incidence in 3rd generation, but could be age effect | Fam and Mikhail 1993, 1996 |
Transgenic mice prone to lymphoma | 50 Hz | 18 months | No effect on lymphoma | Harris et al 1998 |
Knock-out mice prone to low incidence of lymphoma | 60 Hz | 18.5 hours/day 23 weeks | No significant effect on lymphoma incidence | McCormick et al 1998 |
Mice with virus predisposed to lymphoma | 50 Hz | 38 weeks from 4-5 weeks of age | No significant effect on lymphoma incidence | Sommer and Lerchl 2004 |
See also:
- how evidence from the laboratory fits into the overall evidence
- why these negative animal results, although strong, are not conclusive.