Health Risks from Mobile Phone Base Stations

D Coggon

Correspondence to:
Prof. D Coggon
MRC Epidemiology Resource Centre, Southampton General Hospital, Southampton SO16 6YD, UK;

Commentary on the paper by Hutter et al (see page 307)

Keywords: base station; cognitive performance; microwaves; mobile telecommunication; sleep quality; subjective symptoms

Concerns about possible adverse health effects of mobile telephonyhave focused mainly on the risk of brain tumours in users ofmobile phones, but other types of illness have also been linkedwith the technology. In particular, several epidemiologicalsurveys have suggested associations with non-specific complaintssuch as headache, tiredness, sleep disturbance, loss of memory,and dizziness. These findings, which echo reports of illnessassociated with other types of radiofrequency (RF) radiation,¹ relate not only to use of mobile phones,^2–"⁴ but also toresidence near to mobile phone base stations.⁵

Further evidence on the latter is provided in a paper by Hutteret al in this issue.⁶ They found that symptoms such as headache,fatigue, and difficulty in concentration were more common inpeople with higher potential exposures to radiation from nearbybase stations, and that the association remained significantafter adjustment for various possible confounding factors, includingregular personal use of mobile phones.

Given these new findings, how strong is the evidence that residential proximity to mobile phone base stations causes illness, andif it does, what is the underlying mechanism?

A weakness of earlier studies was that both exposure and symptomswere ascertained by questioning participants. As a consequence,risk estimates may have been inflated through biased recall.The study by Hutter et al avoided this problem by estimatingexposures from measurements of RF fields in subjects’bedrooms. The method was still not ideal. For practical reasons,measurements could only be short term, and may not have capturedthe full range of temporal variation at the monitoring site.Moreover, participants spent only part of their time at home,and their exposures at other locations may have been quite different.In general, however, the effects of any resultant misclassificationof exposures would be to bias risk estimates towards the null,and not to give spurious associations.

A more important limitation, given the large number of healthoutcomes examined in the study, is the possibility that someassociations occurred by chance. Concerns about this are reducedinsofar as positive associations were observed with many ofthe symptoms examined. However, further confirmation is neededbefore an elevated risk of such symptoms can be regarded asestablished.

Even if there were a true association, it would not necessarilyimply a toxic effect of RF radiation. Currently there is noknown biophysical mechanism by which low level exposures couldcause toxicity in a substantial proportion of the general population(the excess prevalence of many symptoms in the Hutter et alstudy was more than 15%), when the same symptoms do not appearto be a problem in many people who regularly use mobile phonesfor prolonged periods with exposures to the head that are ordersof magnitude higher. An alternative possibility is that illnessoccurs as a psychologically mediated response to a perceivedhazardous exposure. In this respect, it is notable that similarsymptoms have also been reported in relation to a diverse rangeof chemical exposures, again without any demonstrable underlyingtoxicological mechanism.⁷

Hutter and colleagues tried to address this possibility by adjustingrisk estimates for individual beliefs about health risks frombase stations, but the fact that associations persisted afterthis adjustment does not exclude a psychological origin forthe symptoms. To give an extreme example, if everyone in thestudy had identical beliefs, the adjustment would have no impacton risk estimates whatsoever, but risk could still depend importantlyon people’s beliefs and expectations.

Another way to explore pathogenesis is by testing the effectsof exposure experimentally in blinded subjects, an approachthat will be valid provided that effects are relatively immediateand do not persist for a long time after last exposure. Onesuch study found a significant reduction in wellbeing with exposureto RF fields similar to those produced by a UMTS (universalmobile telecommunications system) base station, both in subjectswho had previously indicated symptoms that they attributed tobase stations, and also in healthy volunteers.⁸ However, therewas no parallel effect from GSM (global system for mobile telecommunication)type fields, and in an earlier experiment by Hiatenen and colleagues,⁹ the incidence of symptoms in subjects who believed that theywere sensitive to radiation from mobile phones was higher duringperiods of sham than of real exposure. Interpretation of theseinconsistencies can only be resolved by further research.

Meanwhile, decisions on the siting of base stations must bemade in a context of uncertainty. Hutter and colleagues proposethat as a precautionary measure, base stations should be positionedin a way that minimises the exposure of neighbours, and thisseems a sensible policy where other considerations are equal.However, the suspicion of a toxic effect is relatively low,and there may be disadvantages in over-precaution. Evidenceis emerging that prior beliefs about the risks from modern technologyare an important predictor of symptoms from perceived exposures.¹⁰ Thus, by distorting perceptions of risk, disproportionate precautionmight paradoxically lead to illness that would not otherwiseoccur.

FOOTNOTES

Competing interests: none declared

REFERENCES

1. National Radiological Protection Board. Health effects from radiofrequency electromagnetic fields. Chilton: National Radiological Protection Board, 2003, 107–10 (Documents of the NRPB, Vol 14, No 2).

2. Chia S-E, Chia H-P, Tan J-S. Prevalence of headache among handheld cellular telephone users in Singapore: a community study. Environ Health Perspect 2000;108:1059–62

3. Sandström M, Wilén J, Oftedal G, et al. Mobile phone use and subjective symptoms. Comparison of symptoms reported by users of analogue and digital mobile phones. Occup Med 2001;51:25–35.

4. Santini R, Seigne M, Bonhomme-Faivre L, et al. Symptômes rapportés par des utilasateurs de téléphones mobiles cellulaires. Pathol Biol (Paris) 2001;49:222–6.

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6. Hutter H-P, Moshammer H, Wallner P, et al. Subjective symptoms, sleeping problems, and cognitive performance in subjects living near mobile phone base stations. Occup Environ Med 2006;63:307–13

7. Coggon D. Occupational medicine at a turning point. Occup Environ Med 2005;62:281–3.

8. Zwamborn APM, Vossen SHJA, van Leersum BJAM, et al.Effects of global communications system radiofrequency fields on well being and cognitive functions of human subjects with and without subjective complaints. TNO report, FEL-03-C148. The Hague :2003.

9. Hietanen M, Hämäläinen A-M, Husman T. Hypersensitivity symptoms associated with exposure to cellular telephones: no causal link. Bioelectromagnetics 2002;23:264–70.

10. Petrie KJ, Broadbent EA, Kley N, et al. Worries about modernity predict symptom complaints after environmental pesticide spraying. Psychosom Med 2005;67:778–82.

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