Assessment of radiofrequency exposure from cellular telephone daily use in an epidemiological study: German Validation study of the international case–control study of cancers of the brain—INTERPHONE-Study

Abstract

Objective: The objective of the study is to validate self-reported cellular phone use information by comparing it with the cumulative emitted power and duration of calls measured by software-modified cellular phones (SMP). The information was obtained using a questionnaire developed for the international case-control study on the risk of the use of mobile phones in tumours of the brain or salivary gland (INTERPHONE-study). Method: The study was conducted in Bielefeld, Germany. Volunteers were asked to use SMPs instead of their own cellular phones for a period of 1 month. The SMP recorded the power emitted by the mobile phone handset during each base station contact. Information on cellular phone use for the same time period from traffic records of the network providers and from face-to-face interviews with the participants 3 months after the SMP use was assessed. Pearson's correlation coefficients and linear regression models were used to analyse the association between information from the interview and from the SMP. Results: In total, 1757 personal mobile phone calls were recorded for 45 persons by SMP and traffic records. The correlation between the self-reported information about the number and the duration of calls with the cumulative power of calls was 0.50 (Po0.01) and 0.48 (Po0.01), respectively. Almost 23% of the variance of the cumulative power was explained by either the number or the cumulative duration of calls. After inclusion of possible confounding factors in the regression model, the variance increased to 26%. Minor confounding factors were ''network provider'', ''contract form'', and ''cellular phone model''. Discussion: The number of calls alone is a sufficient parameter to estimate the cumulative power emitted by the handset of a cellular telephone. The cumulative power emitted by these phones is only associated with number of calls but not with possible confounding factors. Using the mobile phone while driving, mainly in cities, or mainly in rural areas is not associated with the recorded cumulative power in the SMP.

Mobile phone use and risk of glioma in 5 North European countries

“…Reports of past mobile phone use are subject to random error, as recall even in the short term has been shown to be inaccurate. [26][27][28][29] Over-reporting of the amount of mobile phone use by 50-100% has been common. This is likely to attenuate any true relationship between exposure and outcome, and it might distort dose-response.…”

Call-related factors influencing output power from mobile phones

“…phone mainly in the city had no effect on estimates of the cumulative power by the number of calls (Berg et al, 2005). Similarly, an Italian study found that the difference between urban and rural areas was quite small, whereas the factors stationary-moving and outdoor-indoor were more predictive of the average power emitted by the mobile phones (Ardoino et al, 2004).…”

Recall bias in the assessment of exposure to mobile phones

“…In brain tumour studies, cases may also recall exposure with greater random error, as the tumour may affect their memory. Previous validation studies have shown substantial error in healthy volunteers' short-term recall of phone use (Parslow et al, 2003;Samkange-Zeeb et al, 2004;Berg et al, 2005;Morrissey, 2007;Vrijheid et al, 2006a;Hours et al, 2007b). However, there is as yet no direct evidence of differential recall error in studies of mobile phone use and brain tumours.…”