Saturday May 13, 2006
“Electromagnetic fields stemming from gadgets such as kettles, computers and microwaves, contribute towards a cloud of unseen emissions – even when they are switched off.” It’s a sinister idea, and “Electromagnetic Hypersensitivity” is sweeping the nation, or at least the Independent and the Daily Mail last week. Symptoms include fatigue, tiredness, headaches, concentration difficulties, dizziness, nausea, heart palpitations, and digestive disturbances: and since these are real symptoms, causing genuine distress, the problem deserves to be considered seriously, and carefully.
There are two things the newspapers left out of their stories: the first is the scientific evidence, and the second is a very crucial nuance. We’ll deal with the evidence first, because science is “hard”. There have been 31 studies looking at whether people who report being hypersensitive to electromagnetic fields can detect their presence, or if their symptoms are worsened by them. A typical experiment would involve a mobile phone that was hidden in a bag, for example, with each subject reporting their symptoms without knowing if the phone was on or off.
31 is a good number of studies, and 24 found that electromagnetic fields have no effect. But 7 did find some measurable effect, and because I have a reputation for pedantry to uphold: in 2 of those studies with positive findings, even the original authors have been unable to replicate the results; for the next 3, the results seem to be statistical artefacts (details below); and for the final 2, the positive results are mutually inconsistent (one shows improved mood with provocation, and the other shows worsened mood). It’s a slightly obsessive form of value for money you get here, but it’s value nonetheless.
Meanwhile the “nuance” here is in whether recognising distress is the same as acknowledging causality. It’s easiest to see with examples. According to the Daily Mail, Health Protection Agency spokesman Dr Jill Meara â€œsaid household appliances could be health hazards to some. She advised those with a condition called electrical sensitivity to stay away from such devices such as kettles and microwaves.â€ As far as I can see, what she actually said was: “There is no proof that the symptoms are caused by exposure to electromagnetic fields, but people still have real symptoms. There is sufficient uncertainty that it is worth telling members of the public practical things they can do to reduce exposure in case they feel they are suffering from these fields.â€
The Mail go on. â€œThe WHO, meanwhile, has described electrical sensitivity as ‘one of the most common and fastest growing environmental influences’. It ‘takes seriously’ concerns about the health effects, adding that ‘everyone in the world’ is exposed to the emissions, while ‘levels will continue to increase as technology advances’.â€ And yet, in the very same report from which they are quoting, WHO make it clear that there is no scientific evidence to link the symptoms to electrical fields. In fact they say this: “EHS has no clear diagnostic criteria and there is no scientific basis to link EHS symptoms to EMF exposure. Whatever its cause, EHS can be a disabling problem for the affected individual.”
This is a frightening area for any compassionate person to write in. Of those who play to the evidence, the the Today program on Radio 4 says this: “sceptics fear they are preying on the fears of people who are ill and desperate, another manifestation, they say, of the hypochondriac society.”
That’s harsh. I don’t think people who report being hypersensitive to electrical fields are hypochondriacs: I think they have real and distressing symptoms, but I also think, in the light of the evidence above, that electromagnetic fields probably aren’t causing those symptoms, and they may remain unexplained for the moment.
But explanations are what everyone wants, and not just for reassurance and meaning: in the age of science, it’s as if our culture demands that we have a biomedical explanation to justify the very existence our symptoms and distress, otherwise they’re simply not valid. If there is no real explanation, then perhaps a “placebo” explanation – like “electromagnetic hypersensitivity” – can have almost all the same properties as a real one.
The 31 studies looking at whether electromagnetic fields can have effects on sensitive individuals are examined in this excellent review paper from 2005:
Before we look at the apparent positive results in 3 of the 31 papers, it’s important to remember that none of this is to “trash” those papers, or ridicule their authors: they are not in the same category as a Gillian McKeith article, and these are technical criticisms of the kind you’d hear at any academic journal club taking a critical look at their work. These points are all also covered in the discussion section of the review paper above.
In one case there is the question of whether it was appropriate to use a one-tailed significance test. Using a one-tailed significance test makes the assumption that electromagnetic fields can only have an effect in one direction (for example, if you were measuring “mood”, then it would assume that EM fields could only possibly worsen your mood, and not improve it). This, I would argue, is not a valid assumption, with such an illusive and inconsistently measured effect as sensitivity to electromagnetic fields. A two-tailed significance test allows for the fact that the exposure (electromagnetic fields) could have an effect in either direction, and is more appropriate. One-tailed tests are
often more likely to give a positive result, which is why it is wise to be cautious and only use them when you are sure the effect you are measuring could only go in one direction, to avoid false positives.
In the other case there is the issue of multiple significance tests being performed. This is a similar problem to the one we considered a few weeks ago here in the discussion on cocaine use doubling (according to the front page of The Times): essentially, the more significance tests you do, the more likely you are to turn up a positive one merely by chance.
And lastly, a personal note: the symptoms that people are currently attributing to electromagnetic hypersensitivity are unpleasant and often disabling, even if the electromagnetic fields are not the cause of them. Calling people who believe they experience symptoms because of electromagnetic fields “hypochondriacs”, weak-minded, or oversensitive: is offensive, unhelpful, and most damnably of all, untrue. Denying the reality of people’s symptoms is similarly offensive and unhelpful. I will give no quarter on this.
EDIT March 2007:
Another 5 studies have come out since that review was published, all negative. They are:
Rubin GJ, Hahn G, Everitt B, Cleare AJ, Wessely S. Are some people sensitive to mobile phone signals? A within-participants, double-blind, randomised provocation study. BMJ 2006; 332:886-889.
Frick U, Kharraz A, Hauser S, Wiegand R, Rehm J, von Kovatsits U et al. Comparison perception of singular transcranial magnetic stimuli by subjectively electrosensitive subjects and general population controls. Bioelectromagnetics 2005; 26:287-298.
Wilen J, Johansson A, Kalezic N, Lyskov E, Sandstrom M. Psychophysiological tests and provocation of subjects with mobile phone related symptoms. Bioelectromagnetics 2006; 23:204-214.
Regel SJ, Negovetic S, Roosli M, Berdinas V, Schuderer J, Huss A et al. UMTS base station-like exposure, well being and cognitive performance. Environ Health Perspect 2006; 114(8):1270-1275.
Wenzel F, Reibenweber J, David E. Cutaneous microcirculation is not altered by a weak 50Hz magnetic field. Biomed Tech (Berl) 2005; 50:14-18.
EDIT July 2007:
A 37th provocation study came out last month:
Oftedal G, Straume A, Johnsson A, Stovner LJ. Mobile phone headache: a double-blind, sham-controlled provocation study. Cephalalgia 2007; 27:447-455.
Negative. Same results as all the others.