repeated daily exposure, 2 h/day, 5 days/week, for 24 months
Reference article: L. Puranen, A. Turunen, T. Toivo, A-P. Sihvonen, S. Rautio, T. Toivonen, K. Jokela, R. Pitkäho, K. Laukkanen and J. Juutilainen, Space efficient system for whole-body exposure of unrestrained rats to 900 MHzelectromagnetic fields. Bioelectromagnetics, in press.
Nine radial transmission line (RTL) exposure chambers were used, three for each exposure condition [Puranen et al.]. Each chamber consisted of two horizontal circular aluminium plates with 150 cm diameter and 15 cm separation.
24 truncated wedge-shaped polycarbonate cages, each containing an unrestrained rat, were placed in the chamber with their wider end near the absorbing material. A monopole antenna at the center of the lower plate generated a radial plane wave. The EF was vertical (perpendicular to the plates) and the MF was circumferential, parallel to the plates.
The forward and reflected powers at the input of the exposure chambers were monitored with RFpower meters. The whole-body average SARs for rats in the center of the cage with their noses pointing at the center of the chamber were determined based on analytical calculations modelling rats as homogeneous prolate spheroids and on calorimetric measurements using cylindrical ratphantoms, and were confirmed by FDTD calculations. The resulting SARs decreased linearly with increasing rat mass from 100 g to 320 g and varied with different horizontal positions. For small rats (<110 g), the highest SAR may have been 1.2 W/kg for the low-level exposure and 3.6 W/kg for the high-level exposure if the rat was standing in an upright position.