Exposure limits and policy

Limits during pregnancy

The exposure limits for EMFs are designed to protect against established effects on the body, whereby EMFs can induce currents and voltages in the body that can interfere with nerves. 

Read about exposure limits

There is no established mechanism whereby either a pregnant person or the baby they are carrying would be any more sensitive to these effects than any other adult. The evidence on exposure to EMFs and pregnancy outcomes is reassuring.

Current evidence on health

Despite the lack of evidence, there may be an entirely understandable wish to take an extra level of precaution when it comes to pregnancy, for peace of mind.

What do the exposure limits say?

Many of the EMF exposure guidelines that have been published make no specific reference to pregnant people. The issue is not mentioned explicitly in ICNIRP 1998, EU 1999, or ICES 2002.

Exposure limits from organisations

NRPB 2004, the NRPB's most recent recommendations on exposure limits, does mention pregnant people but mainly in the context of radiofrequency (RF) EMFs. For RF EMFs they suggest that the foetus may be more susceptible to heating effects than the adult is, so the public exposure limits (which are lower than the occupational limits) should apply to all pregnant people, to ensure excess heating does not occur. Power-frequency EMFs do not cause heating, so this argument does not directly apply to power-frequency EMFs.

For power-frequency fields, they state:

“The ad hoc expert group (NRPB, 2004) considered that such sensitive people [discussed in the previous sentences] should be adequately protected at lower induced electric field strengths, possibly about a factor of five lower than for normal adults. In addition, the group considered that this reduction factor would be adequate to protect the developing nervous system in utero, and in neonates and young children. It is concluded that a restriction of the induced electric field in the tissue of the CNS to less than 20 mV/m is adequate to protect these members of the population.”

What does this mean in practice? The exposure limits that protect against biological effects are the occupational limits. For members of the public, which may include people more sensitive to EMFs where exposure cannot be controlled, an additional safety factor is applied. These are the public exposure limits in the UK and include safety factors to protect pregnant people. 

ICNIRP 2010 does not specifically say anything about pregnant people in its actual recommended guidelines. But in the "definitions" it does say:

"General public

The term General public refers to the entire population. It includes individuals of all ages, and of varying health status, and this will include particularly vulnerable groups or individuals such as the frail, elderly, pregnant workers, babies and young children."

This implies that pregnant people may be regarded as "particularly vulnerable". But it doesn't specifically say how to treat pregnant people who are at work.

The UK Regulations that implement the EU Directive for occupational exposure define pregnant people as one of the groups of "workers at particular risk". Employers are required to take specific account of these workers in their Risk Assessment (Regulation 8(2)(j)). In their Guide to the Regulations, the HSE state (Section F):

“Expectant mothers

As working with certain levels of EMFs could result in a greater risk to an expectant mother, you should encourage your workers to advise you in writing if they become pregnant. You may wish to take a practical approach and limit the exposure of expectant mothers to the public exposure limits. These are stated in Council Recommendation1999/519/EC, see Useful links ref2

If risks from EMFs are identified during pregnancy, you must take appropriate action to eliminate, reduce or control the risks; they must be included and managed as part of the general workplace risk assessment. You can find more general information on ‘Workers at particular risk – expectant mothers’ on the HSE website; see References and Further reading, New and expectant mothers; ref6.

Table 5 contains a non-exhaustive list of sources of EMF which may pose specific risks. You will need to consider these in addition to the information contained in Table 3; Sources of EMF which may pose a risk to workers.”

What would be a sensible approach?

The various exposure guidelines all agree that there is no need for exposure limits for pregnant people any more restrictive than the limits that apply to all members of the public. The public exposure limits are valid for pregnant people and their unborn babies.

When a pregnant person is at work, the wording of the various existing exposure guidelines implies it is acceptable to continue to use the occupational guidelines, which are higher than the public guidelines. But as a precautionary measure, it may be sensible to apply the public guidelines to pregnant people at work.