IDK Communications Study, Maximum

MAXIMUM PERMISSIBLE
EXPOSURE STUDY
Town of Wayland
Rivers Edge Site
484-490 Boston Post Road, Wayland,MA
Based upon
Sudbury Wireless Tower
20 Boston Post Road, Sudbury,MA
(Sudbury Transfer Station)
IDK
Communications
March 13, 2014
INTRODUCTION
IDK Communications has conducted this theoretical analysis for the Town of Wayland as it
relates to Federal communications Commission (FCC) regulations. The analysis examines the
amount of radiation exposure from an existing wireless facility located at the Sudbury Transfer
Station which borders Parcel 22-3 in Wayland at 484-490 Boston Post Road. This Parcel is
proposed for a residential development in the future. See site details below.
In 1985, the FCC first adopted guidelines to be used for evaluating human exposure to RF
emissions. The FCC revised and updated these guidelines on August 1, 1996, as a result of a rulemaking proceeding initiated in 1993. The new guidelines incorporate limits for Maximum
Permissible Exposure (MPE) in terms of electric and magnetic field strength and power density
for transmitters operating at frequencies between 300 kHz and 100 GHz.
In 1996, the FCC adopted new guidelines and procedures for evaluating environmental effects of
RF emissions. The new guidelines incorporate two tiers of exposure limits based on whether
exposure occurs in an occupational or "controlled" situation or whether the general population is
exposed or exposure is in an "uncontrolled" situation.
The FCC guidelines incorporate two separate tiers of exposure limits that are dependent on the
situation in which the exposure takes place and/or the status of the individuals who are subject to
exposure. The decision as to which tier applies in a given situation should be based on the application
of the following definitions.
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Occupational/controlled exposure limits apply to situations in which persons are exposed as a
consequence of their employment and in which those persons who are exposed have been made fully
aware of the potential for exposure and can exercise control over their exposure.
Occupational/controlled exposure limits also apply where exposure is of a transient nature as a result
of incidental passage through a location where exposure levels may be above general
population/uncontrolled limits, as long as the exposed person has been made fully aware of the
potential for exposure and can exercise control over his or her exposure by leaving the area or by
some other appropriate means.
General population/uncontrolled exposure limits apply to situations in which the general
public may be exposed or in which persons who are exposed as a consequence of their employment
may not be made fully aware of the potential for exposure or cannot exercise control over their
exposure. Therefore, members of the general public would always be considered under this category
when exposure is not employment-related, for example, in the case of a telecommunications tower
that exposes persons in a nearby residential area.
FCC Guidelines
FCC OET Bulletin 65 provides assistance in determining whether proposed or existing
transmitting facilities, operations or devices comply with limits for human exposure to
radiofrequency (RF) fields adopted by the FCC. The following tables identify by frequency range
what the MPE limits are for uncontrolled and controlled environments.
TABLE 1 – MPE Limits for Uncontrolled Environments
Frequency Range
(MHz)
Power Density (mW/cm²)
Averaging Time Limit in Minutes
0.3 – 1.34
100
30
1.34 – 30
30 – 300
180/f²
0.2
30
30
300 – 1500
1500 – 100,000
f/1500
1.0
30
30
F = frequency in MHz
-
Frequency range for this analysis
TABLE 2 – MPE Limits for Controlled Environments
Frequency Range
(MHz)
Power Density(mW/cm²)
Averaging Time Limit in Minutes
100
6
0.3 – 1.34
1.34 – 30
30 – 300
300 – 1500
1500 – 100,000
900/f²
1.0
f/300
5.0
F = frequency in MHz
6
6
6
6
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Commonwealth of Massachusetts – Department of Public Health
The Commonwealth of Massachusetts Department of Public Health has regulations that identify
the maximum limitations of radiation exposure. They are found in CMR 105 Section 122. The
limitations for both the controlled and uncontrolled environments are the same as the FCC MPE
limits found in Tables 1 and 2.
RF EXPOSURE CALCULATION
To determine what the power density is for a given installation a calculation in accordance with
the FCC OET Bulletin 65 formula # 7 is used.
S = (2.56*1.64*ERP) / (4*π*R²)
S = Power Density
ERP = Effective Radiated Power
R= Radial Distance From Antenna
For the purposes of this analysis the following parameters were used:
1.) The Sudbury Wireless Facility is built out to contain all current PCS/Cellular/LTE carriers in
this region. PCS stands for Personal Communication Service which has systems in the 2 GHz
frequency range. Cellular has systems in the 800 MHz frequency range. LTE stands for Long
Term Evolution and has systems in the 700 MHz and 2 GHz frequency ranges. Currently the
Sudbury Wireless Facility does not have all carriers and systems installed, but for the purposes
of this analysis a worst case was used.
2.) All antennas are assumed to be pointed at the general population located on Parcel 22-3. A
vertical height differential between a residential structure and antennas on the Sudbury
wireless structure equals 50 feet. A vertical height differential between a resident standing at
the Town border and antennas on the Sudbury wireless structure equals 84 feet. Using these
vertical heights the distance from the antennas to the residential structure would be 144 feet
and to a person on the Town border it would be 120 feet. (See Appendix A for Visual
Summary)
3.) The ERP (Effective Radiated Power emitted from antennas) from each carrier are values
determined from analysis of existing wireless facilities currently in operation. A derating of 6
dB is used to account for minor antenna lobe reduction from the main beamwidth emitting
from the antenna.
4.) When an analysis achieves 100% of the MPE then the limit of exposure has been reached.
CALCULATION RESULTS
The following Table 3 identifies the predicted power density in an uncontrolled environment
(general population) to a residential structure from the wireless facility at the Sudbury Transfer
Station.
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TABLE 3 (Power Density at Closest Rivers Edge Structure, 144 feet of distance)
PCS/LTE
Distance from antenna (ft)
144
144
144
144
144
144
144
Carrier
AT&T
Sprint
T‐Mobile
AT&T/LTE
Verizon/LTE
Sprint/LTE
T‐Mobile/LTE
ERP (dbm)
53.97
53.97
53.97
53.97
53.97
53.97
53.97
ERP (Watts)
250
250
250
250
250
250
250
Building Losses
0
0
0
0
0
0
0
Power Density (S)
0.004028242
0.004028242
0.004028242
0.004028242
0.004028242
0.004028242
0.004028242
Total PCS Power Density
MPE Limit
1.00
1.00
1.00
1.00
1.00
1.00
1.00
0.028197697
Total PCS/LTE MPE %
Cellular/LTE
%MPE
0.40%
0.40%
0.40%
0.40%
0.40%
0.40%
0.40%
2.82%
Distance from antenna (ft)
144
144
144
144
Carrier
Verizon
AT&T
Verizon/LTE
AT&T/LTE
ERP (dbm)
50.96
50.96
53.97
53.97
ERP (Watts)
125
125
250
250
Building Losses
0
0
0
0
Power Density (S)
0.002014121
0.002014121
0.004028242
0.004028242
Total Cellular Power Density
MPE Limit
0.59
0.59
0.497
0.497
0.012084727
Total Cellular/LTE MPE %
2.30%
TOTAL POWER DENSITY (PCS/LTE/CELLULAR) = 0.04028
TOTAL MPE% = 5.12%
Table 4 on the next page identifies the predicted power density in an uncontrolled environment
(general population) to a person at the Town border from the wireless facility at the Sudbury
Transfer Station.
%MPE
0.34%
0.34%
0.81%
0.81%
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TABLE 4 (Power Density at Property Line/Town Border, 120 feet of distance)
PCS/LTE
Distance from antenna (ft)
120
120
120
120
120
120
120
Carrier
AT&T
Sprint
T‐Mobile
AT&T/LTE
Verizon/LTE
Sprint/LTE
T‐Mobile/LTE
ERP (dbm)
53.97
53.97
53.97
53.97
53.97
53.97
53.97
ERP (Watts)
250
250
250
250
250
250
250
Building Losses
0
0
0
0
0
0
0
Power Density (S)
0.005800669
0.005800669
0.005800669
0.005800669
0.005800669
0.005800669
0.005800669
Total PCS Power Density
MPE Limit
1.00
1.00
1.00
1.00
1.00
1.00
1.00
%MPE
0.58%
0.58%
0.58%
0.58%
0.58%
0.58%
0.58%
0.040604684
Total PCS/LTE MPE %
Cellular/LTE
4.06%
Distance from antenna (ft)
120
120
120
120
Carrier
Verizon
AT&T
Verizon/LTE
AT&T/LTE
ERP (dbm)
50.96
50.96
53.97
53.97
ERP (Watts)
125
125
250
250
Building Losses
0
0
0
0
Power Density (S)
0.002900335
0.002900335
0.005800669
0.005800669
Total Cellular Power Density
MPE Limit
0.59
0.59
0.497
0.497
%MPE
0.49%
0.49%
1.17%
1.17%
0.017402008
Total Cellular/LTE MPE %
3.32%
TOTAL POWER DENSITY (PCS/LTE/CELLULAR) = 0.0580
TOTAL MPE% = 7.38%
NOTE *
The distance where levels will approach the 100% MPE values is around 30 feet from
the antennas.
WIFI Example
In order to understand what level a 5% MPE would roughly equate to at a residential building,
Table 5 on the following page shows a similar level from a wireless router typically used in a
household for WIFI. At a distance of 3 feet from the router the level of exposure is pretty close to
what would be seen from the Sudbury wireless facility, with the worst case parameters identified
above.
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TABLE 5
WIFI
Distance from antenna (ft)
3
Service
WIFI
ERP (dbm)
ERP (Watts)
31.76
1.5
Building Losses
Power Density (S)
0
0.055686424
Total WIFI Power Density
MPE Limit
1.00
%MPE
5.57%
0.055686424
Total WIFI MPE %
5.57%
CONCLUSION
Both scenarios, at a residential building and at the Town border, predict Power Density levels well
within the FCC guidelines for exposure with the percentage of the MPE being substantially below
100 percent. This is a worst case analysis as the actual values will be less seeing that not all
carriers will have antennas pointed directly at the general population at 484-490 Boston Post Road.
Additionally, being inside a building will also reduce the exposure levels due to the exterior
construction. Predicted levels with the worst case analysis are similar to a household wireless
router used for WIFI.
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APPENDIX A
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