Two primary schools in a suburb of Guangzhou were selected which were similar in respect to good air quality, noise and green area around each school. School A had no power lines in close proximity within 4 km whereas school B was located in a distance of 94 m away from 500 kV power lines. There were no other electromagnetic field sources, such as TV tower or mobile phone base stations around both schools.
Neurobehavioral function in children was evaluated using four established computerized neurobehavioral tests including Visual Retention Test (visual perception and visual memory), Visual Simple Reaction Time, Digit Symbol, and Pursuit Aiming Test.
|Reference group 1||pupils of school A|
|Group 2||pupils of school B|
All measured values were lower than the reference limits for public electric fields (4000 V/m) and magnetic fields (0.4 µT) in China. Median electric field strength at school A and school B was 0.417 V/m (ranging from 0.016 V/m to 2.919 V/m) and 1.34 V/m (ranging from 0.522 V/m to 3.93 V/ m), respectively. Median magnetic flux density at school A and school B was 0.028 µT and 0.20 µT, respectively. The highest measurement values obtained at school A and B were 0.072 µT and 0.36 µT, respectively. The differences of electric field strength and magnetic flux density between the two schools were statistically significant.
After adjusting for potential confounding factors, the results showed that children attending a school near 500 kV power lines had statistically significant poorer performance in two of four computerized neurobehavioral tests (Visual Retention and Pursuit Aiming) compared to children attending a school not located in close proximity to power lines.
The authors concluded that long-term low-level exposure to electromagnetic fields from power lines might have a negative impact on neurobehavioral function in children. However, more studies are needed because the results of only two of four tests achieved statistical significance and the study has potential limitations.