Understanding the ARPANSA environmental EME report
The ARPANSA Environmental EME Report (abbreviated to ARPANSA EME Report on this page) is a statement of the maximum calculated levels of radiofrequency electromagnetic energy (EME) that are produced around an existing, a proposed, and a mixture of existing and proposed wireless base station or antenna before an installation of new equipment or upgrade of existing equipment. The report will generally be produced by a network operator (such as a mobile phone company) or consultants working on their behalf. In addition, NBNCo is using the ARPANSA EME Report for the NBN fixed wireless base stations being deployed as a part of the National Broadband Network.
All deployment of public mobile telecommunications service infrastructure in Australia, which includes wireless base stations and antennas, must be carried out according to an industry Code of Practice, the Communications Alliance Ltd C564:2011 Industry Code – Mobile Phone Base Station Deployment. The Code requires the supply of certain information as part of the consultative process with the local community and local government authority. The ARPANSA EME Report is part of this process and is produced according to a methodology developed by the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA). It provides objective estimates of the maximum levels of EME from the wireless base station before the installation of new or upgraded equipment.
Wireless base stations work by sending out radiofrequency (RF) EME in the form of waves carrying information. When the RF EME reaches objects, including people and animals, some of the energy carried by the waves is absorbed by the object. This can lead to heating of the object and, if levels are too high, can cause harmful effects. The ARPANSA Radiofrequency Standard provides limits of exposure with which all radio installations, including wireless base stations, must comply. The limits for EME exposure given in the ARPANSA Standard are intended to provide protection for people of all ages and medical conditions when exposed 24 hours per day, 7 days per week. The ARPANSA EME Report shows the maximum calculated levels from a proposed installation.
The report gives the address of the installation, together with a list of the companies using the site and the types of mobile network currently installed and being proposed. It also includes details of calculated levels of RF EME. If the site already has antennas in place, the report includes separate information on the existing and for the combined existing and proposed installations. The report estimates RF EME from all of the identified wireless transmitters at this site. The calculated levels do not include RF EME from other types of radio transmitters (that are not subject to the industry Code) which may be installed on the same structure.
The tables of calculated EME levels on the report provide maximum levels of EME found at various distances from the base of the tower or supporting structure. Within each range of distances, the highest value is given regardless of direction. The values of EME are given in physical units of volts per metre (V/m), milliwatts per metre squared (mW/m²) and as percentages of the permitted limit in the ARPANSA Standard. When expressed as a percentage, a value of 100% corresponds to the general public exposure limit. A typical highest value of 1% means that the total EME level from all wireless network transmitters on the site, all operating at their maximum power, will be no more than one hundredth (1/100) of the limit set by the ARPANSA Standard for members of the public.
The tables of calculated EME levels provide values at 1.5 m above a flat landscape. Commonly, wireless base stations are located on a high point and the assumption of flat ground provides a worst-case estimate for these situations. Sometimes, however, the ground may slope upwards away from the base station and this can cause concern that levels may be higher than calculated. In these cases the 'Other Areas of Interest' table will include the levels of EME at a selection of heights where maximum levels are expected.
The industry Code requires the companies to take account of community concern about locations of particular interest, such as places where children spend a lot of time, or multistorey residential buildings facing the antennas. The table 'Other Areas of Interest' on the report provides additional estimates of EME levels at a small number of such locations. These locations may be identified as being of particular concern to the community during the consultation process required by the Code. Typically, levels may be given for the closest point of a children’s facility, or for a small number of other locations.
The calculations of the maximum levels are based on well understood principles of physics that deal with how electromagnetic waves travel and spread out. The total amount of energy emitted from the antenna is limited by the power of the amplifier used and cannot exceed a certain specified amount. As the energy leaves the antenna, it spreads out to cover bigger and bigger areas and so gets less intense the further away it gets.
The antenna is usually designed to direct most of the energy out towards the horizon, or a few degrees below, so that most of the energy goes where it is needed to communicate with the mobile phone handsets or other user equipment. As one moves along the ground, the levels first increase as you move away from the base station up to a maximum and then get less as you move still further away. Typically, the maximum EME level at ground level will occur between 75 m and 200 m from the base of the antenna.
The companies sometimes need to adjust the angle of the antennas to obtain the best coverage and this can alter slightly the distance at which the maximum occurs and exactly what EME level is found there. Often, the ARPANSA EME Report will take likely alterations into account and include the highest levels that might occur if the antenna is moved in the future.
The values of EME provided in the report are intended to be maximum levels that can almost never be exceeded when the base station is operating. The values assume, for example, that all the planned transmitters are installed and are all operating at maximum power. Some of the transmitters at a base station are only used when there are a certain number of telephone calls or data transmissions actually in progress; otherwise they are turned off. Even when a call is in progress, the power transmitted is adjusted to be only as high as necessary to communicate with the handset. If the handset is close, or in a good signal area, the base station transmitter will reduce its power automatically.
The calculations do not take into account trees, vegetation or buildings which may alter the EME levels, generally decreasing them. Some of the EME is reflected from buildings and the ground and often this signal is used by a handset when the direct signal is blocked by a building. When the reflected signal and direct signal combine the overall level can be lower or higher than the direct signal alone depending on the exact location.
Measurements around base stations have shown actual values of EME are usually less than calculation by factors of 10 to 1000 or even more. Values of EME indoors will typically be even lower as walls, windows and roofs absorb or reflect the energy.
The example table below provides the following information:
- The highest calculated level of RF EME coming from the existing equipment at this base station is found at a distance of approximately 82 m and is 0.5% or approximately 1/200 of the ARPANSA Standard exposure limit. In physical units this is a power density of 22.53 milliwatts per metre squared (mW/m²), equivalent to an electric field strength of 2.92 volts per metre (V/m).
- Subsequent to the proposed alterations to the equipment at this site, the highest calculated level of RF EME rises to a power density of 89.15 mW/m² or an electric field strength of 5.79 V/m which is equivalent to 1.33% of the ARPANSA Standard exposure limit (or approximately 1/75 of the limit). This maximum is found at a distance of approximately 122 m from the base of the tower.
- The values reported here are only expected to occur when the transmitters are all operating at full power and where there is clear line-of-sight to all antennas. Levels indoors will be lower.
- At any location on level ground within 50 m of the base of the tower, the EME levels should be lower than 0.18% or 1/555 of the ARPANSA Standard exposure limit for the existing equipment and 0.3% or 1/333 of the ARPANSA Standard exposure limit for the existing and proposed equipment.
- At any distance within 500 m of the tower the table can be used to determine the maximum level. For example at a location 330 m from the tower, that is between 300 m and 400 m, the calculated level will be less than 0.059%, or 1/1695 of the ARPANSA Standard exposure limit for the existing equipment and 0.28% or 1/357 of the ARPANSA Standard exposure limit for the existing and proposed equipment. In many directions, and at most times, the actual level will be much lower than this calculated level.
Calculated EME levels
|Distance from the antennas at 123 High St in 360° circular bands||Maximum cumulative EME level – all carriers at this site|
|Existing equipment||Existing and proposed equipment|
|% ARPANSA exposure limits||Electric field
|% ARPANSA exposure limits|
|0m to 50m
50m to 100m
100m to 200m
200m to 300m
300m to 400m
400m to 500m
|Maximum EME level||2.92||22.53||0.5%||5.79||89.15||1.33%|
|81.72 m, from the antennas at
123 High St
|122.35 m, from the antennas at
123 High St
For a new wireless base station where there are no antennas already installed, the above table will only contain data under the 'Existing and Proposed Equipment' columns. Similarly, for a wireless base station that is not being upgraded, the table will only contain data under the 'Existing Equipment' columns.
Calculated EME levels at other areas of interest
|Additional locations||Height/scan relative to location ground level||Maximum cumulative EME Level
All carriers at this site
Existing and proposed equipment
|% of ARPANSA exposure limits|
|1||corner of High Street
and Main Street
|0m to 12m||4.88||63.16||1.09%|
on Station Street
|0m to 6m||3.81||38.55||0.51%|
|1m to 3m||1.03||2.83||0.04%|
The 'Other Areas of Interest' table provides calculated levels of RF EME at locations considered to be of special community interest or at elevated locations where there may be concern about higher levels of EME.The calculations are performed over the indicated height range and include all existing and any proposed radio systems for this site.
Communications Alliance Ltd Code of Practice
ARPANSA Radiation Protection Standard No.3 (RPS 3) - Maximum Exposure Levels to Radiofrequency Fields - 3 kHz to 300 GHz
Australian Communications and Media Authority