Monday 29 August 2011

He's not talking about magnetic fields is he?

Yes I am. But please hear me out before consigning this post to the 'what is he talking about' spam box.

I make no apology for the 'environmental' thread running through the various posts on this blog. I wouldn't say that I am particularly well-qualified to give a very detailed explanation of how our environment might modify our risk of developing lots of different things. I would like to think however that I know just about enough to be able to read about concepts such as environment and risk factors in the peer-reviewed literature so as to come to some informed opinion. As per the mantra of this blog, I am not trying to impart that opinion, merely passing a comment.

The study in question in this case is this one* by Li and colleagues: 'Maternal exposure to magnetic fields during pregnancy in relation to the risk of asthma in offspring' published in the journal Archives of Pediatrics & Adolescent Medicine.  The first thing I thought of when reading the title was '...OK, right, magnetic fields...'. I would think that many people might have a similar reaction about this area of discussion. Looking more closely at this area, there is perhaps a little more to it.

Anyone who has visited or works/worked in an analytical chemistry lab containing an NMR spectrometer will know about strong magnetic fields and what they can potentially do to that magnetic strip on your bank card or perhaps more seriously to that pacemaker you may have been fitted with. OK, the magnetic fields generated by such equipment are pretty big in comparison to what you might be exposed to on a daily basis, but the introduction of what a magnetic field can potentially do is there.

Back to the asthma study. The authors prospectively looked at the effect of low-frequency electromagnetic field (EMF) exposure on a group of pregnant women between 1996 and 1998 for a 24-hour period. Women wore monitors which recorded their magnetic field exposure during that day and were questioned about how representative their behaviour that day was to their usual routine. Participants were monitored throughout the birth and growth of their child for a further 13 years, recording the number of cases of asthma present along the way.

They found that those women with the highest level of magnetic field exposure from things like microwaves, hairdryers, etc were at greatest risk of having a child with asthma in a dose-dependent relationship. The effect was particularly pronounced when other asthma risk factors were taken into consideration; so participants having asthma themselves or their child being the first-born. It is perhaps also important to say that high-frequency EMF exposure was not looked at in this study, so no effect from mobile phones or wireless broadband technologies can be inferred.

There are a few attractive aspects to this study and its findings but be warned, a lot more study is required before any firm conclusions can be made. Asthma, like autism, like many other diagnoses, is on the rise with no clear stand-out suspects as to why. If we assume that our low- and high-frequency magnetic field exposure is going to be greater now than say 25 or 50 years ago, it is easy to point the finger (Evil Monkey-style) at that TV or microwave as a potential culprit. Several other snippets of research have hinted at the effects of magnetic fields on things like immune function, although not necessarily in a bad way. The pathway from exposure to asthma is likely to be complex and dare I say, moderated by genetic effects?

This study was not a perfect one. Basing readings carried out on one day and extrapolating that to exposure patterns over the course of pregnancy and beyond does not instill a great amount of confidence in the results. The routines of a pregnant participant might also be slightly different from the same woman when not pregnant. The added fact that higher frequencies were not looked at also leaves the study findings open to some interpretation. I will post more on this topic as and when the research unfolds.

Dr Li seems to have done a fair bit of media courting as a result of this study. I will perhaps leave you with one of the more memorable pieces of advice for pregnant women: 'Don't stand in front of the microwave when its heating food'. Wise words indeed.

To end: Christoper Walken dances a 'weapon of choice'. Take it away...Chris.

* De-Kun Li. et al. Maternal exposure to magnetic fields during pregnancy in relation to the risk of asthma in offspring. Arch Pediatr Adolesc Med. 2011


  1. I can't help but think there's something to this too, as well as pesticides, antibiotics, etc. I think of it as "the death of a thousand cuts".

  2. Thanks for the comment. I would be inclined to agree with your observations on a cumulative effect. Magnetic fields have always been perhaps a little 'out there' when it comes to human health. But very much like other non-seeing, non-sensing forces (ionising radiation for example) there is no reason to suspect that it might not have an effect on some people, some conditions.


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