Accuracy of short-term residential measurement in the prediction of 72-h exposure to power frequency magnetic field in households very close to high-tension transmission lines

Abstract

, a total of 80 single-dwelling households close (o70 m) to high-tension (161 or 345 kV) power lines in a northern community of Taiwan received measurements of indoor extremely low-frequency (ELF) magnetic field for 72 h. Measurements were performed with EMDEX IIt meter at a sampling rate of every 300 s, yielding some 860 readings of ELF magnetic field for each household. In addition to the 72-h mean ELF magnetic field, we also calculated arithmetic means of the first 2, 6, 12, and 288 readings taken in each household to represent the information on spot, 30-min, 60-min, and 24-h exposures, respectively. The mean 72-h exposure to ELF magnetic field for the 80 study households was estimated at 0.80 micro-Tesla (mT) with a standard deviation (SD) of 1.13 mT. The mean for pot, 30-min, 60-min, and 24-h exposure was 0.88 (SD 1.38), 0.90 (SD 1.40), 0.9 (SD 1.17), and 0.83 (SD 1.17) mT, respectively. There were high agreements, indicated by a nearly perfect intra-class correlation coefficient, between 72-h mean exposure and those short-term exposure measures. Additionally, the sensitivity and specificity of various short-term exposures in the prediction of 72-h exposure greater than 0.4 mT were similar at values of 0.82-0.87 and 0.93-0.95, respectively. This study indicates that short-term measurements of indoor ELF magnetic field seem adequate to represent the mean 72-h exposure, but tended to overpredict 72-h exposure greater than 0.4 mT. Further investigation is needed to assess whether these findings can be replicated in households far away from high-tension power lines.

Assessment of non‐response bias in a survey of residential magnetic field exposure in Taiwan

“…Second, our data showed that 87% of urban residences were located in apartment buildings while only 18% of residences were apartments in the rural sample. Two previous studies reported an association between residential characteristics and indoor ELF-MF where residences of apartment buildings were likely to have higher ELF-MF exposure than single-dwelling houses [Clinard et al, 1999;Ger et al, 2006]. This study presented no significant urban rural differences in residential measures of ELF-MF, which may be largely due to the household appliances and utilities not having much variation among general population in Taiwan.…”

“…Although we noted that the proportion of residences with ELF-MF higher than 0.3 or 0.4 mT was also higher in urban residences, such differences reached no statistical significance mainly due to a small number of residences with high exposure in our sample. Findings from previous studies showed an apparent geographic variation in residential ELF-MF in which urban residences tended to have higher levels of indoor ELF-MF [Li et al, 1997;Clinard et al, 1999;Ger et al, 2006]. A number of factors could contribute to such urban rural differences in ELF-MF exposure level.…”

“…A number of factors could contribute to such urban rural differences in ELF-MF exposure level. First, distance to the nearby power facilities was generally shorter for urban homes than for rural homes [Ger et al, 2006]. Second, our data showed that 87% of urban residences were located in apartment buildings while only 18% of residences were apartments in the rural sample.…”

Analysis of individual‐ and school‐level clustering of power frequency magnetic fields

“…We are not surprised to note higher ELF-MF exposure (including mean and 25th, 50th and 75th percentiles) in those campuses in such close proximity to high-voltage power lines, since other studies have reported similar findings; indeed the increase has been found to be as high as 6.0 mT [Ger et al, 2007].…”

Everyday exposure to power frequency magnetic fields and associations with non-specific physical symptoms

“…However, distance from the dwelling to a powerline is neither a sufficient proxy for residential exposure to ELF MF (Ger et al, 2007;Maslanyj et al, 2009), nor for 24 h' exposure. Therefore, in this study we further explored the association between NSPS and exposure to ELF MF as determined by a 24 h' personal measurement using exposimeters.…”