Determinants of mobile phone output power in a multinational study: implications for exposure assessment.

OBJECTIVES: The output power of a mobile phone is directly related to its radiofrequency (RF) electromagnetic field strength, and may theoretically vary substantially in different networks and phone use circumstances due to power control technologies. To improve indices of RF exposure for epidemiological studies, we assessed determinants of mobile phone output power in a multinational study. METHODS: More than 500 volunteers in 12 countries used Global System for Mobile communications software-modified phones (GSM SMPs) for approximately 1 month each. The SMPs recorded date, time, and duration of each call, and the frequency band and output power at fixed sampling intervals throughout each call. Questionnaires provided information on the typical circumstances of an individual's phone use. Linear regression models were used to analyse the influence of possible explanatory variables on the average output power and the percentage call time at maximum power for each call. RESULTS: Measurements of over 60,000 phone calls showed that the average output power was approximately 50% of the maximum, and that output power varied by a factor of up to 2 to 3 between study centres and network operators. Maximum power was used during a considerable proportion of call time (39% on average). Output power decreased with increasing call duration, but showed little variation in relation to reported frequency of use while in a moving vehicle or inside buildings. Higher output powers for rural compared with urban use of the SMP were observed principally in Sweden where the study covered very sparsely populated areas. CONCLUSIONS: Average power levels are substantially higher than the minimum levels theoretically achievable in GSM networks. Exposure indices could be improved by accounting for average power levels of different telecommunications systems. There appears to be little value in gathering information on circumstances of phone use other than use in very sparsely populated regions.

Can loud noise cause acoustic neuroma? Analysis of the INTERPHONE study in France.

OBJECTIVES: To investigate possible associations between risk of acoustic neuroma and exposure to loud noise in leisure and occupational settings. METHODS: A case-control study was conducted in France within the international INTERPHONE study. The cases were the 108 subjects diagnosed with acoustic neuroma between 1 June 2000 and 31 August 2003. Two controls per case were selected from the electoral rolls and individually matched for gender, age (5 years) and area (local authority district) of residence at the time of the case diagnosis. Multivariate analyses were conducted using conditional logistic regression. Adjustment was made for socioeconomic status. RESULTS: Acoustic neuroma was found to be associated with loud noise exposure (odds ratio (OR) = 2.55; 95% CI 1.35 to 4.82), both in leisure settings, particularly when listening to loud music (OR = 3.88; 95% CI 1.48 to 10.17) and at work (OR = 2.26; 95% CI 1.08 to 4.72). This risk increased with exposure duration (>6 years' leisure exposure: OR = 3.15; 95% CI 1.07 to 9.24). Risk varied according to the type of noise (continuous or explosive vs intermittent). CONCLUSION: The present results agree with other recent reports implicating loud noise in the risk of acoustic neuroma.

[Cell Phones and Risk of brain and acoustic nerve tumours: the French INTERPHONE case-control study]. / Téléphone mobile, risque de tumeurs cérébrales et du nerf vestibuloacoustique: l'étude cas-témoins INTERPHONE en France.

BACKGROUND: Use of cell phones has increased dramatically since 1992 when they were first introduced in France. Certain electromagnetic fields (at extremely low frequency) have been recognized as possibly carcinogenic by the International Agency for Research on Cancer. Given the use of radiofrequency technology in cell phones, the rapid increase in the number of cell phones has generated concerns about the existence of a potential health hazard. To evaluate the relationship between the use of cell phones and the development of tumors of the head, a multicentric international study (INTERPHONE), coordinated by the International Agency for Research on Cancer, was carried out in 13 countries. This publication reports the results of the French part of the INTERPHONE study. METHODS: INTERPHONE is a case-control study focused on tumors of the brain and central nervous system: gliomas, meningiomas and neuromas of cranial nerves. Eligible cases were men and women, residents of Paris or Lyon, aged 30-59, newly diagnosed with a first primary tumor between February 2001 and August 2003. The diagnoses were all either histologically confirmed or based upon unequivocal radiological images. Controls were matched for gender, age (+/-5 years) and place of residence. They were randomly drawn from electoral rolls. Detailed information was collected for all subjects during a computer-assisted face-to-face interview. Conditional logistic regression was used to estimate the odds ratio (OR) for an association between the use of cell phones and risk of each type of cancer. RESULTS: Regular cell phone use was not associated with an increased risk of neuroma (OR=0,92; 95% confidence interval=[0.53-1.59]), meningioma (OR=0,74; 95% confidence interval=[0.43-1.28]) or glioma (OR=1.15; 95% confidence interval=[0.65-2.05]). Although these results are not statistically significant, a general tendency was observed for an increased risk of glioma among the heaviest users: long-term users, heavy users, users with the largest numbers of telephones. CONCLUSION: No significant increased risk for glioma, meningioma or neuroma was observed among cell phone users participating in Interphone. The statistical power of the study is limited, however. Our results, suggesting the possibility of an increased risk among the heaviest users, therefore need to be verified in the international INTERPHONE analyses.

Validation of short term recall of mobile phone use for the Interphone study.

AIM: To validate short term recall of mobile phone use within Interphone, an international collaborative case control study of tumours of the brain, acoustic nerve, and salivary glands related to mobile telephone use. METHODS: Mobile phone use of 672 volunteers in 11 countries was recorded by operators or through the use of software modified phones, and compared to use recalled six months later using the Interphone study questionnaire. Agreement between recalled and actual phone use was analysed using both categorical and continuous measures of number and duration of phone calls. RESULTS: Correlations between recalled and actual phone use were moderate to high (ranging from 0.5 to 0.8 across countries) and of the same order for number and duration of calls. The kappa statistic demonstrated fair to moderate agreement for both number and duration of calls (weighted kappa ranging from 0.20 to 0.60 across countries). On average, subjects underestimated the number of calls per month (geometric mean ratio of recalled to actual = 0.92, 95% CI 0.85 to 0.99), whereas duration of calls was overestimated (geometric mean ratio = 1.42, 95% CI 1.29 to 1.56). The ratio of recalled to actual use increased with level of use, showing underestimation in light users and overestimation in heavy users. There was substantial heterogeneity in this ratio between countries. Inter-individual variation was also large, and increased with level of use. CONCLUSIONS: Volunteer subjects recalled their recent phone use with moderate systematic error and substantial random error. This large random error can be expected to reduce the power of the Interphone study to detect an increase in risk of brain, acoustic nerve, and parotid gland tumours with increasing mobile phone use, if one exists.