By David Coggon

(Image: WestEnd61/Rex)

A group of doctors, scientists and non-profit organisations have launched an unofficial campaign encouraging pregnant women to limit their exposure to radiation from phones, Wi-Fi routers, computers and wireless telecommunications equipment in general “to protect themselves and their unborn children”.

How seriously should we take this warning, and is the campaigners’ advice on steps to limit exposure sensible?

Public concern about mobile telephony has centred largely on the question of cancer risk, but this new initiative – called the BabySafe Project – focuses on potential exposure of the fetus in the womb and suggests this could result in neurological and behavioural problems.

There are good reasons to cast a critical eye over its claims. The non-ionising radio frequency radiation through which devices such as mobile phones communicate is of low energy, and as yet no plausible biophysical mechanism has been established by which exposures below internationally recommended limits could cause adverse effects in humans.

Furthermore, this radiation generally penetrates tissues poorly, giving up its energy as heat in the first few centimetres. Thus, the fetal brain should be well shielded.

Nevertheless, if adverse effects were possible, the developing brain might be particularly vulnerable, as it is to toxic substances in the environment, such as lead. Partly for this reason, the Stewart Committee – set up in the UK to examine the potential health implications of cellphone use – in 2000 recommended that, as a precaution, children should avoid unnecessary use of such phones.

Since then, a few studies have looked for effects on cognitive function and behaviour, either experimentally in lab animals or through epidemiological observation of human populations. Most were included in an authoritative review by the Advisory Group on Non-Ionising Radiation (which provides independent advice to the UK government) published in 2012. The review concluded that evidence for such effects in animals was “not strong”, but noted that relatively few experimental models had been investigated.

The US campaign cites a more recent study which found evidence of symptoms similar to those of attention-deficit hyperactivity disorder in the offspring of mice exposed to cellphone radiation. But that paper clearly states “the exposures used… are not identical to those experienced by the human fetus” and that “the extrapolation of this animal model to humans is limited”. Furthermore, the exposure system used – a phone suspended in the animals’ cage – did not meet currently recommended standards to allow an accurate assessment of exposure.

Four epidemiological studies, three considered by the UK advisory group in 2012 and a later one, have suggested small effects on neurological development from prenatal maternal use of mobile phones, but the three the review considered had important methodological limitations, and the advisory group considered that stronger prospective studies – those in which exposures are assessed before any negative effects are observed and not estimated post-hoc, from memory – were needed before conclusions could be drawn.

Research in this area has been fraught with suggestive positive findings that could not be replicated in later, more rigorous studies.

Even though suspicions of a hazard are not strong, more information is needed about possible effects on cognitive development, and it has been identified as a research priority by the World Health Organization.

Meanwhile, some pregnant women may be sufficiently concerned that they wish to reduce their exposure as a precaution. In choosing what action to take, they should bear in mind that devices only emit radiation when they are transmitting and not when receiving signals. Also, exposures fall off rapidly with distance from the source antenna (in an inverse square relationship).

Of the steps recommended by the new campaign, not holding wireless devices against the body when in use, and avoiding prolonged exposure to nearby Wi-Fi routers when they are transmitting might materially reduce exposure to the womb. However, others, such as unplugging home routers at bedtime, are unlikely to have much impact.