Children's EMF Research Agenda
Introduction & general comments
The Working Group considered research recommendations for studies relevant to the risk of adverse health effects in children from exposure to electromagnetic fields (EMFs). The issues under consideration reflected and amplified the various suggestions and proposals made by the individual presenters at the preceding WHO Workshop on Childhood Sensitivity to EMFs held in Istanbul on 9 & 10 June 2004. The workshop proceedings are available in a special edition of Bioelectromagnetics (in press).
Particular issues included the role of extremely low frequency (ELF) magnetic fields in the development of childhood cancer and possible risks from mobile phone radiofrequency (RF) radiation, especially regarding brain cancer and cognitive function. Less emphasis was given to risks from exposure to static fields and to fields associated with security devices. However, pregnant workers are employed in retail industries with an increasing prevalence of security and identity devices, including devices for electronic article surveillance (RFID/EAS). A better understanding of the dosimetry and possible health effects for this region of the spectrum is needed, since it is not clear that extrapolation from higher and lower frequency regions is sufficient.
Separate breakout groups considered research recommendations for further epidemiological studies, laboratory studies (including those using volunteers, animals and in vitro techniques), and dosimetry work which were then discussed in a plenary session. The relevance of these different studies to health risks in people varies. Epidemiological studies of the distribution of disease in populations and the factors that influence this distribution provide direct information on the health of people exposed to an agent and are given the highest weighting. However, they may be affected by bias and confounding, and their observational nature makes it difficult to infer causal relationships, except when the evidence is strong. Experimental studies using volunteers can give valuable insight into the transient physiological effects of acute exposure, although for ethical reasons these studies are normally restricted to healthy people. Recommendations concerning laboratory studies using children are, of course, subject to appropriate ethical approval. Studies of animals, tissues and cell cultures are also important but are given less weight. Animal studies can often be expected to provide qualitative information regarding potential health outcomes, but the data may not be extrapolated to provide quantitative estimates of risk, largely because of differences between species. Studies carried out at the cellular level are normally used to investigate mechanisms of interaction, but are not generally taken alone as evidence of effects in vivo. Nevertheless, each type of study has a role to play in determining the scientific plausibility of any potential health risk.
Dosimetry provides a precise measure of the interaction of EMFs with people, and exposure assessment provides an estimate of individual and population exposure to EMFs that contributes to the assessment of the likely impact of exposure on health. Each such assessment needs to consider all sources of EMF (low and high frequencies) to which an individual or a population may be exposed.