Enhanced Deposition of Radon Daughter Nuclei in the Vicinity of Power Frequency Electromagnetic Fields
International Journal of Radiation Biology (Vol. 69 No. 1, pages 25-38) Published Wednesday 14th February 1996.
The above research findings went through the normal academic assessment procedure before they were accepted for publication by the International Journal of Radiation Biology. We were asked to respond to a number of specific points which, in view of the wider public interest, we are reproducing below :
Question: Is it not true that electric fields reduce the radon decay product concentration in a room, so leading to a reduction not an increase in dose ?
Reply: The short reply is that AC fields provide no real reduction. A large source of AC fields in a room is like introducing a pot of honey to a room of bees. The bees hover around the honey pot and if you sit next to the pot the bees may sting you - the total number of bees in the room is not the issue.
Technical reply: This question deserves a more detailed technical reply. High intensity DC fields have been used for reducing radon decay product concentration in a room. These work like an extractor fan, which if placed in the far corner of a room extract radon decay products. However, if the DC source was strapped behind your head, then this would be rather like sitting in the mouth of a vacuum cleaner or an extractor fan - you would be in the line of fire of all of the dust!
The situation with AC is different cf count at 100V in fig 7 with fig 9 of our paper). For AC fields we can find no information that anyone has ever used AC for reducing radon decay product concentration in a room, and indeed our experimental data show an increase near the source. In the presence of AC fields charged radon decay product aerosols will oscillate, but this is with a tiny amplitude, much smaller than normal thermal motion. This leads to a theoretical possibility of a small loss of aerosols at the walls of a room but this is more than compensated by the increased availability for inhalation by a person sat near to the EM-field source. The main effect in practice is diffusive drift towards the source of EM-fields.
These considerations are, however, merely esoteric theory. In our paper we have experimental measurements of a real increase in airborne activity in a room in the vicinity of an EM-field source. In short it is not the concentration of decay products that matters but their distribution near sources of EM-fields. We postulate an increase in dose because the experimental results in fig 9, supported by modern theoretical understanding in aerosol science show increased radon decay product alpha-activity in the vicinity of an 50 Hz EM-field.
Question: Surely there is no sound epidemiological evidence that domestic radon exposure is a cause of leukaemia?
Reply: Radon and its decay products emit alpha-radiation (alpha-particles) and it is this type of radiation that is implicated in leukaemia induction. The following evidence has emerged in recent years:-
(i) Geographical links between domestic radon exposure and leukaemia incidence, especially in children. The observation has been made in many independent data sets and these statistical data are robust. (Ref 1).
(ii) Alpha-radioactivity from the alpha-radionuclide polonium-210 (210Po) has been shown to be elevated in the teeth of children living near motorways. On average the activity is doubled close to motorways. These findings were published in The Lancet in February 1995 (Ref 2) and received wide publicity worldwide. Separate research by Savitz and Feingold in the USA (Ref 3) has shown, in a case-control study, that the incidence of childhood cancer is elevated near sources of heavy traffic. Obviously motor vehicle exhausts emit many potential carcinogens apart from 210Po.
(iii) In related but so far unpublished work, alpha-radioactivity from the radionuclide 210Po has also been shown to be elevated in children's teeth near the Severn Estuary in Avon. The Estuary is known to contain high levels of 210Po. In an analysis of UK estuaries, which included the Severn Estuary, Leukaemia Research Fund scientists at the University of Leeds have published evidence of elevated incidence of childhood cancer.
(iv) Research at the Medical Research Council Radiation and Genome Stability Unit at Harwell has shown that alpha-particles can engender genetic instability in human bone marrow stem cells, the target cells for leukaemia induction. Such cellular damage, which can be caused by just one alpha-particle, causes the sort of disruption that could constitute the early damage to cells that may lead to leukaemia induction. (Ref 4)
Taken together we would say that the above evidence ranges between being very suggestive and extremely suggestive that alpha-particles do cause some leukaemia in the population. This includes that from radon exposure.
Question: Is not exposure to radon decay products outdoors too low to be of concern ?
Reply: Exposure to alpha-radioactivity outdoors has been considered above in relation to traffic fumes and airborne pollution generally. Radon daughters from the ground are but a minor constituent of outdoor airborne alpha-activity. Airborne 210Po is important and has been measured in children's teeth. 210Po is present attached to aerosols emitted from car exhausts. Non-radioactive aerosols will behave in a similar way to radon daughter aerosols, leading to enhanced exposure to trace chemicals in air.
It should be emphasised that our findings relate to aerosols in general and not just radon daughter aerosols. Nevertheless we have been surprised how much alpha-activity is detected outdoors when all alpha-radionuclides present are taken into account.
Question: A person in a room distorts the electric field, do they not ?
Reply: Yes, they concentrate the field lines around themselves leading to higher field gradient around the body and potentially a greater attraction of Rn daughters.
Question: Referring to the results in the paper, when the electric field is applied surely the smaller aerosols vibrate more and can therefore attach themselves to larger aerosols so reducing their chance of being inhaled or retained in the lung ?
Reply: There is no evidence of any such effects in the experimental findings in our paper.
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Contact telephone numbers: 0117 9260353 (direct) or 0117 9289000, Extn 8705/8763/8765; Fax 0117 9251723
1. Henshaw, D. L., Eatough, J. P. and Richardson, R. B., Radon: A causative factor in the induction of myeloid leukaemia and other cancers in adults and children? The Lancet, 335, 1008-1012, (1990).
2. Henshaw, D. L., Keitch , P. A. and James P. R., Lead-210, polonium-210 and vehicle exhaust pollution. The Lancet, 345, 324-325, (1995).
3. Savitz, D. A. and Feingold, L., Association of childhood cancer with residential traffic density. Scandinavian Journal of Work and Environmental Health, 15, 360-363 (1989).
4. Kadhim, M. A., Lorimore, S. A, M., Townsend, K. M. S., Goodhead, D. T., Buckie, V. J. and Wright, E. G., Radiation-induced genomic instability: delayed cytogenetic aberrations and apoptosis in primary human bone marrow cells. International Journal of Radiation Biology Vol. 67, no. 3, p287-293 (1995).
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