Indoor transformer stations as predictors of residential ELF magnetic field exposure

Abstract

Transformer stations in apartment buildings may offer a possibility to conduct epidemiological studies that involve high exposure to extremely low frequency magnetic fields (MF), avoid selection bias and minimize confounding factors. To validate exposure assessment based on transformer stations, measurements were performed in thirty buildings in three Finnish cities. In each building, spot measurements in all rooms and a 24-h recording in a bedroom were performed in one apartment above a transformer station (AAT), in one first floor (FF) reference apartment, and one reference apartment on upper floors (UF). The apartment mean of spot measurements was 0.62 microT in the AATs, 0.21 microT in the FF and 0.11 microT in the UF reference apartments The 24-h apartment mean (estimated from the spot measurements and the bedroom 24-h recording) was 0.2 microT or higher in 29 (97%) AATs, in 7 (25%) FF and in 3 (10 %) UF reference apartments. The corresponding numbers for the 0.4 microT cut-off point were 19 (63%), 4 (14%), and 1 (3.3%). The higher MF level in the FF reference apartments indicates that they should not be considered "unexposed" in epidemiological studies. If such apartments are excluded, a transformer station under the floor predicts 24-h apartment mean MF with a sensitivity of 0.41 (or 0.58) and a specificity of 0.997 (or 0.97), depending on the MF cut-off point (0.2 or 0.4 microT). The results indicate that apartments can be reliably classified as high and low MF field categories based on the known location of transformer stations.

Exposure to 50 Hz magnetic fields in apartment buildings with indoor transformer stations in Israel

“…Because the location of an apartment relative to the ITS can easily be identified, this approach can reliably be used for exposure assessment in an epidemiologic study without obtaining access to the residences. Overall, the results of our study are in good agreement with those reported by Ilonen et al (2008) and Thuro´czy et al (2008). Dissimilarities in the MF exposure among different countries should be considered in any future research and emphasis should be given to the necessity of a comprehensive technical characterization of the ITSs before conducting any exposure assessment study.…”

“…Thus, they can be used as a control group due to similar socioeconomic status (SES) of the population of those floors (the SES in Israel is generally related to the floor level of the apartment). These results are similar to those reported by Thuro´czy et al (2008), but differ from those of Ilonen et al (2008), where MFs of FF are higher than those of the HF.…”

“…To verify this assumption, a pilot study is being performed in each participating country, to understand whether and how the levels of exposure in the different apartments in these buildings could be classified according to their location relative to the ITS and perhaps according to its technical characteristics, and to determine the extent of this classification's specificity and sensitivity. Results of such pilot studies have been reported by Ilonen et al (2008) and Thuro´czy et al (2008). A previous survey conducted by Szabo et al (2007) was the first to characterize the MFs within such buildings.…”

Exposure Assessment of Magnetic Field in Dwellings with Built-in Transformers in Bulgaria

“…Conducted measurements for the pilot TRANSEXPO study, show a clear distinction between the magnetic field values in the "exposed" apartments and all other apartments located on same buildings [6,7,8]. The apartments located on the same floor as the "exposed" ones can not be considered as an"unexposed", taking into account the measured values of the magnetic field.…”

Development of a New Personal Magnetic Field Exposure Estimation Method for Use in Epidemiological EMF Surveys among Children under 17 Years of Age

“…The concerns over the possible biological effects of power lines and other power sources began in 1979, when Wertheimer and Leeper reported that children living in the vicinity of high-voltage transmission lines have a higher risk of developing leukemia. Although a number of researches have been conducted on this subject, the biological effects of EMF remain a heated technological and medical controversy [2][3][4][5][6][7][8][9][10][11][12]. An indirect method to estimate the MF exposure level of the children, who were less than 17 years of age, was developed in this study.…”