Comparison of methods used to assess cell phone exposure
One of the major
challenges that researchers face when conducting epidemiological
studies of cell phones is the difficulty in accurately assessing
the exposure of an individual to the radiofrequency radiation from
the phone. The two methods most commonly employed are self-reported
use and using data on subscriptions that are supplied by a network
provider. Schüz and Johansen compared these two methods, using
data from two studies that they were able to cross-link. They found "fair"
agreement between the two methods. However, they point out the limitations
of both methods, and argue that these limitations can be minimized
in prospective studies, with exposure estimation based on traffic records
on current use of a cellular telephone.
Schüz J, Johansen C. A comparison of self-reported cellular
telephone use with subscriber data: Agreement between the two methods
and implications for risk estimation. Bioelectromagnetics 2007;28:130-136.
The International Commission for Electromagnetic Safety (ICEMS) held a conference entitled The Precautionary Approach: Rationale, Legislation, and Implementation.The City of Benevento, Italy, hosted the conference on February 22-24, 2006. The meeting was dedicated to W. Ross Adey. The scientists at the meeting drew attention to their concern that electromagnetic fields (EMFs) can have adverse effects, and made a number of recommendations to minimize exposure to EMFs.
can be found at:
Parazzini and colleagues
tested the effect of radiofrequency radiation (RFR) exposure at 900
MHz on the heart rate variability (HRV) on young adults. The found
no effect on the main outcome of R-R interval on the electrocardiogram,
and on most of the other parameters, but a weak effect on some. This
latter effect was suggestive of an effect on the sympathetic component
of the autonomic nervous
Parazzini M, Parazzini P, Tognola G, Thuroczy G, et al. Electromagnetic
fields produced by GSM cellular phones and heart rate variability.
study - this one from Norway - has been published. There was no evidence
from the study that cell phone use is associated with an increased
risk of gliomas, meningiomas,
or acoustic neuromas.
The authors discuss the common limitations of epidemiological studies,
particularly case-control studies.
These include selection and recall bias, and misclassification. They
also caution that the time interval since the introduction of cell
phone use may be too short to detect possible effects of cell phone
Klaeboe L, Blaasaas KG, Tynes T. Use of mobile phones in Norway and
risk of intracranial tumours. Eur J Cancer Prev 2007;16:158-164
An ecological analysis is the weakest type of epidemiological study. It is subject to a bias known as the ecological fallacy (Last JM, A Dictionary of Epidemiology, 1988), which may occur because an association observed between variables on an aggregate level does not necessarily represent the association that exists at an individual level. There may be a number of factors that can explain an observed correlation. For more, see "Research - Exposure Assessment".
Hallberg O. Adverse health indicators correlating with sparsely populated
areas in Sweden. Eur J Cancer Prev 2007;16:71-76.
Eltiti and colleagues
from the UK have developed an electromagnetic hypersensitivity questionnaire.
The authors consider that the scale provides an index of the type
and severity of symptoms commonly experienced by people believing
themselves to be EHS and a screening tool that researchers can use
to pre-select the most sensitive individuals to take part in their
Eltiti S, Wallace D, Zougkou K, Russo R, et al. Development and evaluation
of the electromagnetic hypersensitivity questionnaire. Bioelectromagnetics
Valberg and colleagues have published a report on a "Workshop on Base Stations and Wireless Networks" that was convened by the World Health Organization. The report details sources of radiofrequency radiation (RFR) and their exposure levels. It discusses mechanisms that would be required of RF energy to change physiological function, initiate dysfunction, or cause the onset of disease in humans or animals. It briefly summarizes research that that has been done on the health effects of RFR exposure. The report also assesses the problems in risk communication in everyday life.
Reference: Valberg PA, van Deventer TE, Repacholi MH. Workshop report: Base stations and wireless networks - radiofrequency (RF) exposures and health consequences. Environ Health Perspect 2007;115:416-424.