In the April 15, 1996 edition of the American Journal of Epidemiology, Erren (1) pointed to five studies, three occupational and two residential, where exposure to electromagnetic fields of various types showed an association with lung cancer. Although there has been no hypothesis regarding a specific carcinogenic effect of electromagnetic field exposure on the lung, Erren pointed out that since lung cancer in the US is epidemic, a link between electromagnetic field exposure and lung cancer would have considerable public health relevance. Research at Bristol University has recently demonstrated the ability of the electric field component of power frequency electromagnetic fields to attract and concentrate airborne radon progeny in their vicinity (2). Radioactive radon progeny atoms when formed rapidly attract water molecules in air growing into a so-called ultrafine aerosol around 10 nm in size. Depending on availability such aerosols may then attach to larger aerosol particles up to 1 µm in size. The Bristol observations are therefore indicative of the behaviour of aerosols in general and demonstrate that airborne chemical pollutant aerosols, bacteria and viruses would be expected to be similarly concentrated by electric fields. Two main physical processes govern these observations: the oscillation of electrically charged aerosols affecting mainly the ultrafine aerosols and the movement up field gradients by the polarisation force affecting mainly larger aerosols. These processes lead naturally to possible mechanisms of increased skin deposition, inhalation and lung retention of aerosols as well as transport to all body organs. In the case of radon progeny aerosols the dose to red bone marrow following inhalation has been specifically modelled (3). The possibility of increased lung cancer in relation to electromagnetic field exposure constitutes one prediction from the Bristol observations. Therefore the finding of lung cancer in several studies suggests the possibility of a causal relationship. Most epidemiological studies of electromagnetic field exposure have concentrated on magnetic field exposure because unlike electric fields these readily penetrate the human body. The Bristol findings, however, suggest an importance of electric fields. In the July, 1996 edition of the American Journal of Epidemiology, Miller et al (4) reported a non-significant odds ratios for leukaemia incidence of 1.6 in Ontario electric utility workers exposed to magnetic fields, but this increased to 11.2 (95 percent CL 1.3 - 97.2) when combined exposure to electric and magnetic fields was considered. Furthermore there was a suggestion of a dose response curve in relation to electric field exposure as well as a suggestion of increased risk of melanoma. As has been pointed out elsewhere (5) the leukaemia risks are some of the highest ever reported in a major epidemiological study. Miller et al conclude that their analysis shows associations for all leukaemia and its subtypes with increasing electric field exposure, with a dominant effect of electric field exposure on leukaemia when both electric and magnetic field exposures are considered together. The findings of Miller et al therefore represent a further epidemiological test of an electric field/aerosol interaction and further raises the possibility that the findings are causal. The above consideration suggest an urgent assessment of electric field exposure in both previous and future epidemiological studies of the possible health effects of electromagnetic field exposure is warranted. ---------------------------------------------------------------------------- References 1. Erren TC, Re: ŇAssociation between exposure to pulsed electromagnetic fields and cancer in electric utility workers in Quebec, Canada, and FranceÓ Am J Epidemiol 1996: 143: 841 (Letter). 2. Henshaw DL, Ross AN, Fews AP and Preece AW, Enhanched deposition of radon daughter nuclei in the vicinity of power frequency electromagnetic fields International Journal of Radiation Biology 1996; 69(1): 25-38. 3. Richardson RB, Eatough JP and Henshaw DL; Dose to red bone marrow from natural radon and thoron exposure. British Journal of Radiology 1991; 64: 608-624. 4. Miller AB, To T, Agnew DA, Wall C and Green LM, Leukaemia following occupational exposure to 60 Hz electric and magnetic fields among Ontario electric utility workers Am J Epidemiol 1996; 144: 150 - 160. 5. Anonymous. Both electric and magnetic fields seen as critical to cancer risk. Microwave News 1996; 16(4): 1,5,6. ---------------------------------------------------------------------------- Denis L. Henshaw H H Wills Physics Laboratory University of Bristol Tyndall Avenue Bristol BS8 1TL, UK Return to: The electromagnetic fields and radon base page The Track Analysis group home page The Physic dept or The University home page ---------------------------------------------------------------------------- Comments and corrections for this page to Paul Keitch. Scientific comments to Professor Denis Henshaw