Exposure levels of ELF magnetic fields in the residential areas of Mangaung Metropolitan Municipality

摘要

The aim of this study was to evaluate the exposure levels of ELF magnetic fields in the residential areas of Mangaung metropolitan municipality. Fifteen residential sites were randomly selected in Bloemfontein, nine in Botshabelo and six in Thaba Nchu areas of Mangaung. Measurements were collected at the distances of 3 m, 6 m and 9 m outside electrical substations, near every corner, using a Trifield meter model XE 100. Measurements were also collected from four different corners inside substations, near barrier screening and were referred to as a distance of 0 m (reference point). The results indicated a non-significant difference among 15 residential areas; BRE1 to BRE15 and six areas; TNRE1 to TRNE6. The exposure levels were significantly high in one residential area BORE1 (0.55 mu T) as compared to other residential sites in Botshabelo (p 0.001). The results obtained from the measurements also show a significant difference between the residential areas BORE4 and BORE8 (p 0.01) as well as BORE4 and BORE9 (p 0.006). The four distance interims also demonstrated a highly significant difference (p 0.0001) when compared to one another. The t test showed a statistically significant difference for exposure levels recorded at 3 m, 6 m and 9 m in comparison to 0 m (p 0.01). The exposure levels recorded at 3 m were also significantly different to those recorded at 6 m (p 0.05) and 9 m (p 0.01). The exposure levels measured at all distances are below the ICNIRP guidelines and the fields decrease rapidly with an increased distance from the source.