Highest radiation levels measured in 2013 government base station tests
||Antennas mounted on a water tower in Lennox Head, NSW produced the highest ever recorded levels in an ARPANSA test
Electromagnetic radiation measurements taken on a footpath near mobile phone antennas mounted on a water tower on the NSW North Coast are the highest readings recorded by the Australian radiation watchdog’s compliance testing program since it began in 2007.
The tests by the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) found exposure to mobile phone radio frequency signals in the area were just above half of one per cent of the Australian safety standard or 185 times below the limit.
“The highest level of RF EME from all nearby base stations actually measured at a location near this site was 0.540% of the ARPANSA Standard limit for public exposure,” the measurements taken at Lennox Head in May 2013 found.
The Lennox Head site was one of five base stations tested so far in 2013 as part of ARPANSA’s ongoing survey program to inform the public about actual exposures in close proximity to mobile phone base stations and to validate mobile carrier’s predictions of maximum exposure.
The ARPANSA testers calculate the expected full power exposure at a site by multiplying their highest measured value by a factor (usually by 4 to 10 times) to give the maximum possible output of all the mobile antennas on the base station.
“The resulting full power value can be thought of as the maximum level of RF EME present at the location when this base station is handling as many calls as it possibly can,” ARPANSA explained.
“The maximum level of RF EME from this [Lennox Head] base station (full power) determined from measurements at locations around this site was 3.433% of the ARPANSA Standard limit for public exposure.”
MCF Manager Ray McKenzie said the latest survey results showed the network carriers’ exposure predictions contained in the EME Reports of every mobile base station provided a worst-case estimate of the likely public exposure levels.
“Under the industry code of practice when new base stations are installed or upgraded the local community are required to be informed about the predicted maximum exposure levels through environmental reports, which are publically available at the RFNSA website, Mr McKenzie said.
“For example, the EME report for the Lennox Head base station predicted the maximum exposures to be 12.13% of the Australian standard, more than three times higher than ARPANSA’s predictions based on real life measurements.”
Mr McKenzie said the predicted levels shown in the carriers environmental reports deliberately include many conservative assumptions to ensure they clearly show a worst-case prediction of maximum exposures.
“When independent ground level tests of base stations are conducted, such as those by ARPANSA, the real life exposure levels measured are typically significantly lower than the carriers predicted levels shown in the published environmental reports.”
“This is because in normal operation base stations adapt their power output based on the number of calls they are connecting to and the distance to the connected devices.
“Mobile handsets also reduce their power output in areas of good coverage, that’s why it is important for base stations to be built close to areas where wireless services are required.”
ARPANSA also conducted tests around another water tower mounted base station in Lennox Head, which had been the centre of significant community opposition due to its location close to houses.
ARPANSA’s measurements at the Basalt Court site calculated the maximum exposure in the area to be 0.060% of the safety standard with the highest recorded level from all nearby base stations at 0.034% of the limits.
2013 ARPANSA survey results
Mr McKenzie said that although in most circumstances maximum exposure predictions in carrier EME reports were lower than ARPANSA’s maximum estimates based on measurements, there were sometimes exceptions to this rule.
For example, ARPANSA tests near a large lattice tower in Shepparton, Victoria in April 2013 calculated the highest possible exposure to be 0.434 per cent of the safety standard, while the carrier’s EME report estimated maximum exposure to be slightly lower at 0.32 per cent of the limit.
This is because carrier maximum exposure predictions are based on mathematical calculations of a base station operating with all antennas transmitting at full power, whereas ARPANSA’s testers multiply their highest measured exposure reading by four to 10 times to predict the maximum possible exposure.
ARPANSA tests since 2007 have found only six out of 28 base station surveys where their predicted maximum exposures were slightly higher than the relevant carrier EME report. The greatest difference in predicted levels was 0.54 per cent of the limit, calculated at a site in Palmerston, NT.