1. Senior Program Director
Radiofrequency (RF) Safety Overview Massachusetts Environmental Health Association
This is designed as a “self-study” training program to provide an introduction and general awareness of the safety procedures to be used to work safely around active antennas on rooftop and other installations.
After reviewing these slides you will be asked to complete a short quiz that will reinforce the key safety related concepts provided in this training.
It is most important that you exercise caution around all antenna installations and assume that they are actively transmitting and observe all signage and barrier restrictions that may be installed at a particular site.
Note: this is not to be considered a complete OSHA approved course as it summarizes information that is typically delivered in a ½ day or full day seminar; please review the limitations provided at the conclusion of this course and indicate your understanding of these conditions.
May 16, 2018
Kevin McManus
Senior Program Director
(cell)

2. Agenda RF-EME 101 FCC Regulatory Limits RF Health Impacts
What is RF energy?
Antenna Basics
Documented Health Impacts
FCC Regulatory Limits
RF Health Impacts
This agenda covers the health and regulatory aspects of radiofrequency radiation, as administered by both the Federal Communications Commission (FCC) and Occupational Safety and Health Administration (OSHA). Please note that there are other regulatory drivers such as local and county regulations that may also affect the status of a particular site, but the key regulatory programs are federal, and local jurisdictions must utilize FCC compliance requirements to assess RF emissions impacts for all sites they review.

3. Electromagnetic Spectrum

4. Cell Phone In Call, poor signal
This chart tracks exposure to RF emissions present in everyday life. As you can see, people are more likely to be exposed to RF emissions from WiFi routers and baby monitors than Cell towers. Devices held against the body – like smartphones provide a much higher concentration than any other source.
Cell Phone In Call, poor signal
10.0

5. Typical Microcell Tower Installation
Utility Pole

6. Effect of Distance on RF Energy Levels
Main Antenna Beam/Pattern

7. Directional (Panel) vs. Omni Antennas
Antennas shape and project RF energy waves in a specific direction
Panel antennas produce more focused signal (higher gain) than an omnidirectional antenna
Analogy: A flashlight (vs. a light bulb)
Directional antennas shape a project a EM waves in a specific direction by using reflectors. These antennas also only receive information from a specific direction. These are omni antennas that take advantage of the reflecting properties of waves to focus the EME in a particular direction to increase the gain of the antenna. These antennas are good at sending EME to particular locations and keeping it out of other areas. They help limit possible interfering affects by focus the radio waves.

8. Some Facts About RF Energy To Keep In Mind
RF energy levels decline significantly as one moves away from an RF source (in much the same way that visible light sources decrease in intensity with distance)
Wireless antennas are designed and installed to send RF signals towards the horizon, away from the building or tower; antennas are designed to direct very little power downward (toward the ground or roof surfaces)

9. Some Facts About RF Energy To Keep In Mind (cont.)
Within buildings, the weak RF emissions at the roof surface level are further reduced by the intervening roof materials. In many cases, roof surfaces reduce RF signals by 90% or more.
All cell carriers operating antennas are required by state and Federal regulations to meet specified emission limits and provide safety measures to prevent harmful RF exposures.

10. FCC’s Maximum Permissible Exposure Limits for Licensed RF Transmitters
The occupational or controlled MPE limit applies to individuals who may come into contact with RF EME as a consequence of employment, but have been made fully aware of the potential for exposure and have the ability to exercise control over the exposure.
The general population or uncontrolled MPE limit applies to the exposure the general public may experience, and they are generally unaware of the potential for exposure.
Worker does not need to be a wireless carrier employee to fit into the occupational exposure category.

11. Maximum Permissible Exposure Limits
Typical PCS Frequencies MHz
In the Typical Wireless Carrier Range (>1800 MHz)
Controlled Exposure: 5 mW/cm2 (6-minute avg)
Typical Cellular Frequencies MHz
Uncontrolled Exposure: 1 mW/cm2 (30-minute avg)
MPEs are measured in terms of the power of power density over an exposed surface area. These MPEs vary with the frequency of the of the RF energy being emitted. 12

12. Commonly-used Frequencies
Low
AM Radio: 520 KHz-1610 KHz (commercial)
FM Radio: 87.5 MHz-108 MHz (commercial)
Cellular Phones: 850 MHz-2300 MHz
Television:
VHF: 51 MHz-201 MHz
UHF: 471 MHz-801 MHz
Microwave Oven: 2450 MHz
High

13. Why Do We Care About RF-EME Hazards?
Moving charge causes stationary charge to move
Water molecules are polarized
Water molecules move when an E-M wave passes
Increased motion leads to increased body temperature (humans are made up of ~60% water)
RF heating effects are temporary and are reduced with distance
Because electromagnetic waves are made up of moving electric charges these moving electric charges can cause stationary charges to move (much like moving a magnet near a stationary magnet.) A water molecule is made up of two hydrogen atoms covalently bonded to one oxygen atom. Each hydrogen atom is able to lose 1 electron and the oxygen atom is able to gain two electrons. By sharing the 2 available electrons from the hydrogen atom, the hydrogen atoms are able to bond with the oxygen atom. The structure of the molecule is such that one side of the molecule ends up positively charge (where the two hydrogen atoms are located [they lost electrons and became positively charged]) and the other side ends up being negatively charged (where the oxygen atom is located [it gained electrons and became negatively charge]). This is a polarized structure and each side will respond to the moving charge by either being repelled or attracted. Essentially, the water molecule experiences a torque. Increased motion in the water molecules will increase its energy and this will manifest as an increase in the water molecules temperature. (This is how a microwave heats food. The watery parts heat up first, but the ice part takes longer. Stirring is a strategy to help even out the heating.) Since humans are made up of ~60% water, we have an abundance of molecules that can experience this heating. 14

14. Injuries resulting from RF exposure incidents
Thermal effects caused by excessive RF energy include:
Cataract formation
Keratitis (eye cornea infection/inflammation)
Testicular degeneration
Decreased sperm count
“Microwave Hearing”
Auditory Response to Pulsed
Radiofrequency Energy
J.A. Elder* and C.K. Chou
Motorola Florida Research Laboratories, Ft. Lauderdale, FL, USA
The human auditory response to pulses of radiofrequency (RF) energy, commonly called RF hearing,
is a well established phenomenon. RF induced sounds can be characterized as low intensity sounds
because, in general, a quiet environment is required for the auditory response. The sound is similar to
other common sounds such as a click, buzz, hiss, knock, or chirp. Effective radiofrequencies range
from 2.4 to MHz, but an individual’s ability to hear RF induced sounds is dependent upon high
frequency acoustic hearing in the kHz range above about 5 kHz. The site of conversion of RF energy to
acoustic energy is within or peripheral to the cochlea, and once the cochlea is stimulated, the detection
of RF induced sounds in humans and RF induced auditory responses in animals is similar to acoustic
sound detection. The fundamental frequency of RF induced sounds is independent of the frequency of
the radiowaves but dependent upon head dimensions. The auditory response has been shown to be
dependent upon the energy in a single pulse and not on average power density. The weight of evidence
of the results of human, animal, and modeling studies supports the thermoelastic expansion theory as
the explanation for the RF hearing phenomenon. RF induced sounds involve the perception via bone
conduction of thermally generated sound transients, that is, audible sounds are produced by rapid
thermal expansion resulting from a calculated temperature rise of only C in tissue at the
threshold level due to absorption of the energy in the RF pulse. The hearing of RF induced sounds at
exposure levels many orders of magnitude greater than the hearing threshold is considered to be a
biological effect without an accompanying health effect. This conclusion is supported by a comparison
of pressure induced in the body by RF pulses to pressure associated with hazardous acoustic energy
and clinical ultrasound procedures. Bioelectromagnetics Supplement 6:S162–S173, 2003. 15

15. Health Impacts from RF & microwave fields
RF fields at frequencies between 1 MHz and 10 GHz penetrate bodily tissue and heat it due to the absorbed energy.
The depth of penetration decreases at higher frequencies.
Heating occurs from the inside; it is not perceived (or it is perceived too late) because our receptors are situated near the skin surface.
The body handles heating as a result of small amounts of RF energy through its normal thermoregulation processes.

16. RF and Health Impacts
World Health Organization: “Studies… have not provided evidence that RF exposure from the transmitters increases the risk of cancer. Likewise, long-term animal studies have not established an increased risk of cancer from exposure to RF fields, even at levels that are much higher than produced by base stations and wireless networks.”
BCCDC (2016); “Ongoing research regarding the potential health effects of RF has not demonstrated clear evidence of impacts on cancer, reproduction, and development...”

17. RF and Health Impacts
FCC: “Radiofrequency emissions from antennas used for cellular and PCS transmissions result in exposure levels on the ground that are typically thousands of times below safety limits. There is no reason to believe that such towers could constitute a potential health hazard to nearby residents or students.”
To date, no U.S. public health agencies have identified any RF health impacts beyond thermal effects (e.g. body heating)

18. Some Recent Summary Documents on RF Health

19. Environmental Noise Sources?
Typical Microcell Equipment list:
Some RRU units may be fan-cooled; need to check specification sheets