Elektromagnetische Felder

9. What is known about environmental effects of electromagnetic fields?

• 9.1 What species might be sensitive to electromagnetic fields?
• 9.2 What possible environmental effects have been studied?
• 9.3 Conclusion on Environmental effects?

The source document for this Digest states:

3.7.Environmental Effects

What was already known on this subject?

The CSTEE opinion did not consider possible environmental impacts of EMF. It is noted that the majority of the relatively few published studies on environmental effects at the time of the CSTEE opinion were laboratory based using short exposure periods, in a single species. In addition some field investigations were reported around intense point sources of EMF, in particular overhead power cables.

Source & ©: ,  Possible Effects of Electromagnetic Fields (EMF) on Human Health (2007)
Section 3.7 Environmental Effects, p.38

9.1 What species might be sensitive to electromagnetic fields?

The source document for this Digest states:

Certain species have been recognised as likely to be particularly sensitive to EMF namely:

• species that are strongly dependent on magnetic fields for orientation/migration (migratory birds, certain fish and insects, bats etc) and/or possess electric sense organs (e.g. sharks and rays).
• species with a high vulnerability to stress due to poorly developed or impaired defence mechanisms. For example animals with poor thermoregulation may be more vulnerable to the effects of high frequency EMF.

Nonetheless data to characterise this vulnerability and its implications have been very limited. Foster and Repacholi (2000) in their important review of the published data concluded that: ‘attempts at environmental analysis of the effects of environmental EMF, with few exceptions have been scattered in focus, sporadic in publication and uneven in quality’.

The available data thus provided a seriously inadequate basis to assess the risk of EMF to environmental species. However, apart from some local minor effects no significant effects of EMF on environmental species were identified.

Source & ©: ,  Possible Effects of Electromagnetic Fields (EMF) on Human Health (2007)
Section 3.7 Environmental Effects, p.38-39

9.2 What possible environmental effects have been studied?

The source document for this Digest states:

What has been achieved since then?

Despite the obvious need for some definitive studies there has been no significant increase in the volume or general quality of research activity in this area since. The majority of these studies have focussed on ELF fields.

There has however been a substantial shift in the form of the studies, in particular in the nature of the endpoints examined. Thus the majority of studies published before 2000 used visible endpoints that are obviously associated with an adverse effect. These had the advantage that their interpretation is quite straightforward. However such endpoints in many cases lack sensitivity. In the last few years an increasing number of studies on the effects of EMF have concentrated on the measurement of more sensitive biomarkers.

These have included:

• antioxidant status/ antioxidant enzyme measurements
• stress markers e.g. alanine (plants) and heat shock proteins (animals)
• changes in cell growth (e.g. meristems in plants)
• DNA changes (e.g. using the comet assay).

The majority of the few publications on the impact of EMF on environmental species have been in plants. The paper by Monselise et al. (2003) illustrates the use of new markers of cell/tissue change. These authors found that in duck weed, exposed in the laboratory to low intensity sinusoidally varying magnetic fields at 60 and 100Hz, an accumulation of alanine occurred. Alanine accumulation is found as a stress signal following many other kinds of stress. (NB This effect may have parallels with the formation of heat shock proteins in the mammalian kidney in response to various stressors). The authors postulate that this effect arose from free radical generation by the EMF.

Regoli et al. (2005) have reported the effect in snails of low frequency 50Hz EMF fields both in the laboratory and under overhead power cables. A range of biological markers was employed. They demonstrated that the EMF had particular effects on markers of oxidative stress such as catalase and glutathione reductase both in the laboratory and in the field situations. The time to an effect was shown to be dose dependant with effects in the field occurring even at low levels (after 40 days at 0.75°T). The authors attribute the effects to the generation of free radicals by the low frequency electromagnetic fields. The authors also observed a reduction in lysosomal stability and of DNA integrity (at 2.88°T under field conditions). However, no physical damage to the snails was reported.

These biomarkers do appear to be detecting changes at low, much more environmentally relevant field strengths. However, their interpretation in terms of species and ecosystem health is more challenging. Unfortunately these techniques have not focussed particularly on species that would be expected to be among the most sensitive to EMF.

Using more classical endpoints Zaidi and Khatoon (2003) have studied the impact on pollen production of plants growing under overhead power cables using plants grown nearby as a control group. They found that plants growing under the high tension lines at higher voltages (132000 and 220000 volts) had some decrease in pollen fertility and that the pollen had a higher percentage of diads and diploid pollen grains which is an indicator of genetic change. This finding needs to be examined further.

Several studies have examined the impact of co-exposure to EMF and other stressors in plants. Thus Tafforeau et al. (2004) describe the impact of exposure to EMF combined with calcium deprivation, from either a GSM telephone or a single 2h exposure to 105GHz (from a Gunn oscillator) on meristem production in flax seedlings (i.e. increase in actively dividing cells in the hypocotyls of the growing seedling). An increase in meristem production was observed from each of these EMF sources. It should be noted however that no visible damage to the seedlings was observed in these studies and that other environmental stressors can also produce an increase in meristem production.

Yao et al. (2005) have examined the impact of EMF (0.2 and 0.45T) together with UV-B radiation on cucumber seedling growth. EMF alone produced an increase in seedling germination, seedling growth in parallel with an increase in lipid peroxidation. However in combination with UV-B seedling growth and development were significantly decreased.

These studies raise the question as to whether the impact of EMF may be additive with other significant environmental stressors in the field situation and if so, what are the practical consequences of this for individual plants and ecosystems. The data presently available are inadequate to assess this.

Source & ©: ,  Possible Effects of Electromagnetic Fields (EMF) on Human Health (2007)
Section 3.7 Environmental Effects, p.39-40

9.3 Conclusion on Environmental effects?

The source document for this Digest states:

Discussion

The continued lack of good quality data in relevant species means that there are insufficient data to identify whether a single exposure standard is appropriate to protect all environmental species from EMF. Similarly the data are totally inadequate to judge whether the environmental standard(s) should be the same or significantly different from those appropriate to protect human health.

The demonstration that the impact ofEMF maybe additive with some other environmental stressors at least in plants needs further examination to gauge its practical significance.

At present it is not possible to draw any conclusions regarding human health from this data base. Nonetheless, long-term monitoring of the viability of carefully selected species and/or ecosystems may be valuable to gauge the potential of EMF to influence human health.

Source & ©: ,  Possible Effects of Electromagnetic Fields (EMF) on Human Health (2007)
Section 3.7 Environmental Effects, p 40