Auteurs
Tomitsch J, Dechant E, Frank M. Survey of electromagnetic field exposure in bedrooms of residences in lower Austria. Bioelectromagnetics. Ahead of print. Sep 24, 2009.

Objective
This study was conducted to examine the effects of extremely low-frequency electric fields (ELF-EF), extremely low-frequency magnetic fields (ELFMF), or radio frequency electromagnetic fields (RF-EMF) in residences.

Methods
Exposure was monitored in bedrooms to study the effect of long-term exposure. Participants were selected from throughout the county of Lower Austria, which consists of 573 municipalities. Measurements were conducted at bedside, both under normal conditions and after simple field reduction measures had been applied. The measurements were done in two phases. First, the measurements of the electrostatic fields, ELF-EFs, ELF-MFs, and RF-EMFs were done in the typical night’s situation. In the second phase, the status or arrangement of these devices was changed to achieve as much reduction of field strengths as possible by simple measures. Arithmetic mean and standard deviation, geometric mean and scatter factor (antilog of the standard deviation of the geometric mean), 5% trimmed mean, median, and quartiles of the measurements were calculated.

Results
The results of the short-term measurements of ELF-MFs of electricity supply revealed 100 nT or more in 18.2% of the households. These values were due to transformers of devices (in 10.2% of all beds) and high current flow of power lines both inside the buildings and outside the residences (in 8%). Three hundred nanotesla or more were measured in 3.1% of the cases, where 2.2% were due to transformers and 0.9% to high current. Generally, the highest RF-EMF values were measured for mobile phone and DECT downlink signals and in homes with devices working in the 2400MHz band. The highest value of all RF-EMFs measured occurred in a household with a DECT telephone located in the bedroom. Of 16 households with overall RF-EMF exposure above 1000 mW/m2, 7 values occurred due to DECT telephone base stations, 4 to mobile phone base stations, 2 to USW stations, and 3 to a mixture of the ranges.  After reduction measures (removing or rearranging clock radios and transformers of devices for ELF electric and magnetic fields. measures to reduce ELF-EFs consisted of removing or rearranging bedside lamps, rearranging extension cables and multiple outlets, removing fuses or changing phase and neutral line), the arithmetic mean of ELF-EFs could be reduced from 37.4 to 14.4 V/m. The arithmetic mean of ELF-MFs could be reduced from 56.4 to 33.8 nT, and very high values caused by transformers were also diminished.

Interpretation and Conclusions
It can be concluded that highest ELF-EFs were primarily due to lamps beside the bed (max¼166 V/m), and highest ELF-MFs because of transformers of devices. Differences between urban and rural areas were apparent for RF-EMFs, with higher values in urban areas. This is consistent with earlier reports indicating lower base station signal intensity in rural areas. For ELF fields from electricity supply, bedside lamps, electric alarm clocks, extension cables, and transformers of devices were sources of high exposure that could easily be avoided.


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