1. Kjell Hansson Mild There has been much debate in the media if young persons might be more sensitive to microwave emissions from cellular phones than older ones. As to carcinogenesis this has support from reports on atomic bomb survivors indicating that the risk was highest in children and teenagers for leukemia (1,2), breast cancer (3) and thyroid cancer (4). To elucidate this matter we have made further analysis of our recent study (5-8) and analysed the association of brain tumours and the use of cellular or cordless phones in different age groups. We included in a case-control study on brain tumours and mobile and cordless telephones 1 617 patients aged 20-80 years of both sexes diagnosed during Jan 1, 1997 – June 30, 2000. They were alive at the study time and had histopathology verified brain tumour. One matched control to each case was selected from the Swedish Population Register.

2. Kjell Hansson Mild Assessment of Exposure Exposures to cellular and cordless phones were assessed by a questionnaire - answered by 1429 (88%) cases and 1470 (91%) controls - including also exposure to certain agents and lifetime work history. The answers were supplemented over the phone using a written protocol. Mean number of daily calls and minutes were asked for to calculate the cumulative use in hours for all years. The ear most frequently used during cellular phone calls was asked for, or if both sides were equally used. Statistical Methods Unconditional logistic regression analysis was used to calculate odds ratios (OR) and 95 % confidence intervals (CI), (SAS Institute, Cary, NC). The material was divided into two groups, exposed and unexposed. The exposed cases and controls were further divided according to phone type, analogue, digital and cordless. Note that a person may have been using more than one type of telephone. The unexposed group consisted of cases and controls without exposure to cellular or cordless telephones. Adjustment was made for sex, age and SEI-code. In the calculations of laterality of exposure the corresponding control was assigned the same anatomical localization as for the respective case.

3. Kjell Hansson Mild Results Tables 1-3 displays the overall results and for different age groups and latency periods. Analogue cellular phones yielded significantly increased risk with OR=1.31, 95% CI=1.04-1.64, increasing further to OR=1.65, 95% CI = 1.19- 2.30 for ipsilateral use. The risk was highest in the age group of 20-29 years with OR=1.68, 95% CI=0.60-4.74 and for ipsilateral use OR=5.91, 95% CI=0.63-55. Also digital cellular phones increased the risk for ipsilateral use with OR=1.34, 95% CI=1.02-1.75. The risk was somewhat higher in the age group 20-29 year and 70-80 years. Cordless phones did not increase the risk overall. The highest risk was found for ipsilateral use in the age group 20-29 years; OR=2.84, 95% CI=0.94-8.52. For analogue phones the highest risk was found with >10-year latency yielding OR=1.63, 95% CI=1.07-2.47. Regarding different age groups a high risk was found for the age group 20-29 with > 5 year latency with OR=8.17, 95% CI=0-94-71. With >10-year latency time only 2 cases and no control were exposed in that age group.

4. Kjell Hansson Mild For cordless phones a significantly increased risk was found in the whole material with > 5 year latency period yielding OR=1.40, 95% CI=1.07-1.82. When analysed according to different age groups the highest risk was found for 20-29 years with >5-year latency period with OR=4.30, 95% CI=1.22-15. The results in the group with >10-year latency period were based on low numbers and did not permit any conclusions. Figure 1 displays the results for ipsilateral use. The highest risk was found in the age group 20-29 years with OR=5.91, 95% CI=0.63-55 for ipsilateral use of analogue phones. With >5-year latency period the highest risks were found in the age group 20-29 years for analogue phones; OR=8.17, 95% CI=0.94-71, and cordless phones; OR=4.30, 95% CI=1.22-15, whereas no consistent pattern was found for digital phones. In our study the median time of use (tumour induction period) was 7 years for analogue phones, 3 years for digital phones and 5 years for cordless phones. Figure 2 displays the median latency times found for ipsi- and contralateral use of the phones.

5. Kjell Hansson Mild Discussion A higher risk was found in the temporal area as would be expected since this part of the brain is most exposed to microwaves during cellular and cordless telephone calls. The risk increased further with tumour induction period. Considering ipsilateral use of a phone the risk was higher than overall for all studied phone types, significantly so for analogue and digital phones. This seems to be of biological relevance since contralateral use did not significantly increase the risk. Analysis according to age groups yielded fairly consistently highest odds ratio in the age group 20-29 years. The risk was highest in that age group with > 5-year latency period. The results seem to indicate that the association between cellular and cordless phones was most pronounced in the age group 20-29 years, although also the age group 70-80 years in some of the calculations yielded a higher risk than in other age groups. A clear relation of age with higher risk among young person for malignant disease among A-bomb survivors has been shown (1-3). In our study teenagers were not included but certainly with a reasonable latency period at least some of these subjects were exposed as teenagers.

6. Median latency periods (years) for ipsilateral and contralateral use of cellular and cordless phones.

7. Kjell Hansson Mild

8. Analogue phones Odds ratio (OR) and 95% confidence interval (CI) for the use of cellular and cordless phones in different age groups. Numbers of exposed cases (Ca) and controls (Co) are given.

9. Kjell Hansson Mild Digital phones Odds ratio (OR) and 95% confidence interval (CI) for the use of cellular and cordless phones in different age groups. Numbers of exposed cases (Ca) and controls (Co) are given.

10. Kjell Hansson Mild Cordless phones Odds ratio (OR) and 95% confidence interval (CI) for the use of cellular and cordless phones in different age groups. Numbers of exposed cases (Ca) and controls (Co) are given.

11. Kjell Hansson Mild The present study showed an increased risk for brain tumors among users of analogue cellular telephones. For digital cellular phones no significantly increased risk was found overall, but ipsilateral exposure increased the risk significantly. Cordless phones yielded significantly increased risk overall with a >5-year latency period. The risk seemed to be highest in the age group 20-29 years indicating that young subjects should adopt the precautionary principle for emissions from cellular and cordless phones. Certainly childhood exposure should be more studied in the future.

12. Kjell Hansson Mild References: 1. Beebe GW, Kato H, Land CE. Radiat Res 1978; 75: 138-201. 2. Biological Effects of Ionizing Radiations. The effects on populations of exposure to low levels of ionizing radiation: 1980. Washington, DC: National Academy Press 1980. 3. Shore RE. In: Radiation Carcinogenesis. Upton AS, Albert RE, Burns FJ, Shore RE (eds). Elsevier New York, Amsterdam, London 1986, pp 279-291. 4. Prentice R, et al. Monog Natl Cancer Inst 1982; 62: 207-212. 5. Hardell L, Hallquist A, Hansson Mild K, et al. Eur J Cancer Prev 11: 377-386, 2002. 6. Hardell L, Hansson Mild K, Carlberg M. Int J Radiat Biol 2002; 78 (10): 931-936. 7. Hardell L, Hansson Mild K, Carlberg M. Int J Oncol 2003; 22: 399-407. 8. Hardell L, Hansson Mild K, Sandström M, et al. Neuroepidemiology 2003; 22: 124- 129.