Public Exposure to Extremely Low Frequency Magnetic and Electric fields in Ramallah City-Palestine
Date
2017-03-28
Authors
Abuasbi, Falastine Awadallah Ahmad
Journal Title
Journal ISSN
Volume Title
Publisher
An-Najah National University
Abstract
In this study, the public exposure to extremely low frequency magnetic and electric fields originated from power frequency (50 Hz) was investigated both indoor and outdoor in the city of Ramallah-Palestine. Spot measurements were used to record fields’ intensities over six-minute period. Outdoor measurements were performed at one meter above ground level and directly underneath 40 randomly selected power lines distributed fairly within the city. Outdoor electric fields varied depending on the line’s category (Power line, transformer or distributor), a minimum mean electric field of 3.89 V/m was found under a distributor line, and a maximum of 769.4 V/m under a high voltage power line. However, results of outdoor electric fields showed a log-normal distribution with geometric mean and geometric standard deviation of 35.88 V/m and 2.81 V/m respectively. Outdoor magnetic fields measured at power lines, on contrast, were not log-normally distributed; the minimum and maximum mean magnetic fields under power lines were 0.894 µT and 3.5 µT respectively.
For indoor measurements, a group of 32 semi-randomly selected residences distributed amongst the city were under investigations of 50-Hz electric and magnetic fields. Measurements were also carried at one meter above ground level in the residence’s bedroom or living room under both zero and normal-power conditions. Fields’ variations were recorded over six-minutes and some times over few hours. Indoor electric fields under normal-power use were relatively low; about 59% of residences experienced mean electric fields less than 10 V/m. The highest mean electric field of 66.9 V/m was found at residence R27. However, indoor electric fields were log-normally distributed with geometric mean and geometric standard deviation of 9.6 V/m and 3.49 V/m respectively. Indoor background electric fields measured under zero-power use, were very low; about 80% of residences experienced background electric fields less than 1 V/m. Under normal-power use, the highest indoor mean magnetic field (0.448 µT) was found at residence R26 where an indoor power substation exists. However, about 81% of residences experienced mean magnetic fields less than 0.1 µT. Magnetic fields measured inside the 32 residences showed also a log-normal distribution with geometric mean and geometric standard deviation of 0.044 µT and 3.14 µT respectively. Under zero-power conditions, about 7% of residences experienced average background magnetic field greater than 0.1 µT. Fields from appliances showed a maximum mean electric field of 67.35 V/m from hair dryer, and maximum mean magnetic field of 13.67 µT from microwave oven. However, no single result (of both indoor and outdoor measurements) surpassed the ICNIRP limits for general public exposures to ELF fields.
A strong negative correlation was found between indoor electric fields and distance from closest operating appliance with correlation coefficient and p-value of – 0.8 and 0.000 respectively. On the other hand, a moderate negative correlation was found between indoor magnetic fields and distance from closest operating appliance with correlation coefficient and p-value of – 0.41 and 0.020 respectively.