Is electromagnetic radiation safe or does this risk factor change based on length of cumulative time of exposure?
Let's Talk about Dose-response and non-linearity
The orthodox response to whether any electromagnetic environment is ‘safe’ is to measure it. And since there are many ways to measure (averaging, peak, spectrum analysis, structure, pattern etc.) one goal is to produce a personal dosimeter to map exposures over time more comprehensively.
All this can achieve, however, is a specific illustration under certain parameters. It cannot be concluded from any such measurement that if an FM radio station signal has a higher average signal strength at a particular location than a UMTS signal, the latter is less harmful, or that by comparison with ICNIRP reference levels for ‘safe’ exposure over six minutes, complaints of sleep disturbance attributed to the arrival of such a source must be psychosomatic. Hypotheses of ‘safe dose’ are notoriously full of broad and unwarranted assumptions.
Why is this important?
- With regards to heating damage from microwave radiation, a raw energy absorption effect is fairly linear. Protective guidelines (eg ICNIRP) are therefore straightforward to devise, and specific absorption rates (SAR) can be quoted for individual mobile phones.
- For long-term low-level chronic exposure to EM Fields, however, the effects are in all likelihood dependent on multiple factors such as power, frequency (for penetration, but also coincidence with functional bio-frequencies), co-factors, and susceptibility in any one of several biological functions. It really isn’t easy!
- Clearly it is not enough to use energy absorption guidelines for frequency effects, but it would seem important to see if there is a level of environmental microwave radiation (for example) that can be considered safe for everyone. But is there a straightforward dose-response ratio?
- Read more about electro-hypersensitivity (EHS)
Force equals mass times acceleration. F = M × A. Newton’s second law of motion.
In so many situations it appears that the more you put in the more you get out; there is proportionality. Such relationships are so common that it is easy to presume everything is like this. Sometimes the relationship is inverse; sometimes it is in a straight ratio (linear). Sometimes the relationship is (as in population expansion) exponential, whilst at others there is a curved distribution or ‘window’ – a range within which the greatest effects occur.
Is a linear dose-response true of toxins and pharmaceutical drugs?
No, it isn’t. Some toxins are most potent at very low levels and not proportionately worse at higher levels. Many medicines will kill you at high doses. One reason for this is that their effects are not singular: they interact on many systems simultaneously. One effect may limit an imbalance while another creates an imbalance, and providing the dose causes one much more than the other, what might be a toxin is instead a medicine.
Dose-response may also be bi-phasic or even multi-phasic: in other words a low dose is insufficient to trigger a protective response to a cumulative effect, a medium dose may induce an over-reaction, and a high dose may match (and counteract) the harmful agent, until a point of being overwhelmed by it is reached.
Finally, there is the threshold effect (where a cause has no effect below a certain value), and the ‘rain-barrel’ effect (where an accumulation of effects eventually becomes too much and overflows).
Analogy: The accident and the vandals
Every now and then a vehicle leaves the road and ploughs through a garden wall. For a month, while insurance claims are cleared, there is a pile of stones and a hole in the wall. But before very long, the boundary is restored, the plants recover, and if you didn’t pass by around the time, you might never know what had happened.
In another neighborhood, local lay-abouts seem to have nothing better to do than to pull stones off walls. Some owners repair each spate of damage straight away, because loose stones are easier to damage further. Some owners grow weary of the constant repair battle, or can’t keep up with the bills and effort, and soon a few bricks are followed by a few bricks, and a few more, and repair becomes a really big undertaking. Rubbish accumulates in the garden, dogs enter it and foul it, and even maintaining the garden becomes too much.
Which leaves the greater long-term damage? The vehicle? Or the few-stones-at-a-time yobs and the overwhelmed house owner?
- This analogy is given as a valid comparison between a large but short-term dose of electromagnetic radiation, from which the body may easily recover, and chronic exposure leading to constant free radical formation. Remember, among the effects of low dose EM fields are not just increased free-radical formation, but an impaired immune system.
[More under health.]
- Resonance effects: calcium and potassium at cell membranes are sensitive to EM frequencies in non-thermal ways. Persistent exposure matters but is not a feature of any protective or precautionary guidelines.
Dose-response and electromagnetic fields
- The concern therefore is to determine if, with all our pervasive wireless technology and power lines, appliances and machines, there is a safe level of electric, magnetic and electromagnetic fields (or indeed safe frequencies) with which to work. If so, how can we adopt and ensure safe levels? If not, what are the alternatives or consequences?
- Neither EM fields nor living organisms are easy to assess, let alone their complex interaction.
- Determining what frequencies, power levels and durations might lie behind consequences such as electro-hypersensitivity is very complex indeed with living organisms dependent on extremely subtle electromagnetic messaging to maintain homeostasis.
- But what it is not, is a direct linear response to energy absorption, and in all likelihood it is not due to a single interaction mechanism.
Measurement and dose
Environmental EM fields can be measured in many ways, but to create a research base for any situation, every aspect must be recorded.
- What fields do people who claim adverse effects encounter in their average day?
- A personal dosimeter must record what frequencies and power levels are present on a time-sliced basis, but also it must record signal structures. For example, there is a difference between a 900MHz carrier wave and its 217Hz time-sliced pulse, or the 50Hz electricity supply and radiofrequencies riding on it.
- Fast, high but recurring transients must not be missed.
- Ideally, such a dosimeter should be used with other devices that record physiological responses rather than a diary record of well-being, thus avoiding ‘over-awareness’.
Several factors make this kind of meaningful record difficult.
- systems such as UMTS (3G mobile phones) use frequency-hopping, and recording these may be difficult
- a dosimeter worn on one part of the body (eg waist) will not record peak doses (eg a mobile phone at the head)
- the record is what the EM environment was like, not the person’s health, or which element was having a given effect (if any).