Nonionizing Radiation (NIR)
Overview
Stephen Hemperly, MS, CIH, CSP, CLSO
Local Section Regional Representative
AIHA Pacific Region
Rio Grande AIHA Fall Technical Meeting
December 4, 2014
Agenda
• Introduction to nonionizing radiation (NIR)
– Optical Radiation (includes Laser Radiation)
• Ultraviolet (UV) Radiation,
• Visible Radiation,
• Infrared (IR) Radiation,
– Radio-Frequency (RF) Radiation
– Extremely Low Frequency Fields (ELF)
– Static Fields
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Characteristics & Sources
Exposure Guidelines
Biological Effects
Relevant Standards
Ancillary Hazards
Exposure Controls
Additional Information Resources
Concluding Remarks
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Electromagnetic Spectrum
NIR portion of spectrum covers 15 orders of magnitude in frequency units.
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Electromagnetic Radiation (EMR):
Definition and Physics
• The propagation of radiant energy through space and
matter by time-varying (vibrating) electric (E) and
magnetic (H) fields.
• This radiation may be characterized as particles or
waves (per wave-particle duality).
• Per quantum theory, EMR = discrete particles (photons)
• When characterized as a wave, EMR is described in
terms of wavelengths
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Electromagnetic Wave
The electric field vector (solid line) is vibrating up and down in the plane of the paper,
while the magnetic field vector (dashed line) is vibrating in and out of the plane of the
paper. The direction the radiation is moving is defined by a third vector — the
propagation vector, k. Electromagnetic fields are transverse to the direction of
propagation and contained within the envelope formed by the axis of propagation and
the sinusoidal waves.
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Electromagnetic Radiation
• May be described by three quantities:
– Photon energy (E in joules)
– Wavelength (λ) – distance between 2 points in the same
phase of consecutive wave cycles; also, one complete
cycle of a wave -- units of length: nanometers (nm, 10-9) or
micrometer (μm, 10-6)
– Frequency (ƒ) – number of complete wave cycles that
occur in one second (units of frequency: 1 hertz (Hz) = 1
cycle per second; multipliers = GHz (109 Hz), MHz (106
Hz), kHz (103 Hz)
• E = hƒ = hc/λ
Where h is Planck’s constant (6.626 x 10-34 J - seconds),
c is speed of light 3.00 x 108 m/s, is λ wavelength (m),
and ƒ is frequency in Hz
• Photons with relatively long wavelengths (and low
frequency) have relatively low energy
• Lower photon energy = lower potential hazard
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Ionizing vs. Nonionizing Radiation
Nonionizing radiation is electromagnetic radiation with
insufficient photon energy to ionize matter.
Generally, the division between nonionizing and ionizing
radiation is photon energy of 12.4 electron volts (eV)
[Photon of this energy has a wavelength of 100 nm.]
Photons with energy less than this value are nonionizing
radiation.
Unlike ionizing radiation, non-ionizing radiation cannot
dislodge electrons from atoms/molecules with which it
interacts – cannot ionize biological matter.
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Electromagnetic Fields
Field – any physical quantity that has different values at
different positions in space.
Electric fields are derived from electric charges
Magnetic fields are derived from moving electric charges
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Electric (E) Fields
• Created by any charged object whether still or moving;
lines of force or flux
• Described by the magnitude or intensity (E) of voltage
difference or gradient between two points in the field
• E is proportional to the voltage difference and inversely
proportional to the distance between the two points.
• Electric field strength is calculated by dividing the voltage
between two points by the distance between them: volts
per meter (V/m).
• Easily shielded – many common materials influence
these fields
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Electric Fields
Electric field lines – A) from positive point
charge; B) between linearly distributed positive
and negative charges
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Magnetic (B) Fields
• Created by moving electric charges – currents
• Defined by magnitude and direction of force exerted on a
moving charge (current)
• Apply force to moving ions in a biological system
• Difficult to shield effectively – many common materials
exhibit low permeability
• Permeability is a measure of how magnetizable a
material is (iron-containing materials exhibit high
permeability)
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Magnetic Fields
Current flow (I) produces
magnetic field with
magnetic flux density (B).
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Source: National Institute of Environmental Health Sciences (NIEHS): EMF
Questions and Answers: Electric and Magnetic Fields Associated with Electric
Power. NIEHS, 2002. http://www.niehs.nih.gov/health/docs/emf-02.pdf
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Source: National Institute of Environmental Health Sciences (NIEHS): EMF
Questions and Answers: Electric and Magnetic Fields Associated with Electric
Power. NIEHS, 2002. http://www.niehs.nih.gov/health/docs/emf-02.pdf
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Fundamental Characteristics of NIR
Region
Wavelength
Frequency
Ultraviolet
100–400 nm
——
UVC
100–280 nm
——
UVB
280–320 nm
——
UVA
320–400 nm
——
Visible
400–770 nm
——
Infrared
770 nm–1 mm
——
IR-A
770 1 – 400 nm
——
IR-B
1.4 – 3.0 µm
——
IR-C
3.0 µm – 1mm
——
Radio-frequency (RF)
——
300 GHz–3 kHz
Extremely low frequency ——
3 kHz–3 Hz
Static fields
——
——
Note: Lower frequency RF (less than 300 MHz) and ELF
energies are referred to as fields rather than radiation.
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Spectral Bands for Optical Radiation
Region
Band
Wavelength
Ultraviolet
UV-C
UV-B
UV-A
100-280 nm
280–315 nm
315–400 nm
Visible
Infrared
400–770 nm
IR-A
IR-B
IR-C
770–1400 nm
1.4–3.0 mm
3.0 mm–1 mm
Note: Boundaries between the bands provide a framework for addressing
biological effects– but have no basis in fundamental physics.
Actinic UV refers to the UV-B and UV-C bands because of their ability to
cause chemical reactions.
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LASER (Light Amplification by
Stimulated Emission of Radiation)
• UV, visible, or infrared (IR) radiation that
propagates as a beam
• Characteristics
– Low divergence
– Monochromatic
– Coherent
– High intensity
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Nomenclature of ELF and RF
Band Designations
Frequency Range
Designation
Abbreviation
* <30 Hz
sub-Extremely Low Frequency
sub-ELF
* 30–300 Hz Extremely Low Frequency
ELF
* 300–3000 Hz
Voice Frequency
VF
3–30 kHz
Very Low Frequency
VLF
30–300 kHz
Low Frequency
LF
300–3000 kHz Medium Frequency
MF
3–30 MHz
High Frequency
HF
30–300 MHz
Very High Frequency
VHF
300–3000 MHz Ultra High Frequency
UHF
3–30 GHz
Super High Frequency
SHF
30–300 GHz Extremely High Frequency
EHF
* The IEEE definition of band designations does not include VF, and
defines ELF as 3–3000 Hz, and <3 Hz as ultralow frequency (ULF).
ACGIH identifies the region 30 kHz and below as sub-radiofrequency
(sub-RF). Microwave radiation (300 MHz to 300 GHz) is RF subset.
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Quantities & Units
• Used in nonionizing radiation exposure limits
• Many quantities because of different spectral regions
and interaction mechanisms
• Legend for following table:
W= watt; cm = centimeter; J = joule; V = volt;
A = ampere; m = meter; mA = milliampere;
μT = microtesla; mG = milligauss; T = tesla;
G = Gauss
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Quantities Used in Exposure Guidelines*
Spectral Region
Quantity
Unit
UV, IR, & Lasers*
Irradiance (E)
mW/cm2, μW/cm2
Radiant Exposure (H)
J/m2; mJ/cm2
E-field strength
V/m; V2/m2
H-field strength
A/m; A2/m2
Power density (S, W)
mW/cm2
Specific absorption rate
W/kg
Specific absorption
J/kg
Induced / contact currents
mA
Electric-field strength
V/m; kV/m
Magnetic flux density (B)
μT; mG
Current density (J)
mA/m2
Electric-field strength
V/m
Magnetic-field strength
T; G
Radiofrequency (RF)
ELF
Static fields
*For brevity, visible radiation & some laser radiation quantities are not included.
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Hierarchy of Potential Hazard Concern
•
•
•
•
Lasers
Ultraviolet (UV)
Radiofrequency (RF) / microwave
Electric and magnetic fields (frequencies 30 kHz
and below)
• Static fields (electric and magnetic)
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Ultraviolet Radiation Sources
• Sunlight* – atmosphere opaque to wavelengths < 295 nm
• Welding – gas-metal, gas-tungsten, plasma, & arc welding, and
CO2 laser welding plasma
• Low pressure mercury vapor lamps – primary emission
wavelength 254 nm for germicidal applications
• Metal halide and mercury vapor lamps – for illumination
• Tanning booths & beds* – primarily UVA with some UVB – subject
of FDA product performance standard
• Blacklights* -- broadband source of UV and visible radiation – peak
output ~ 362 nm – non-destructive testing and entertainment
applications
• Lasers – Excimer (KrF, ArF, XeCl), HeCd, frequency-tripled or
quadrupled-Nd:YAG – micro-material processing & research
*Listed as carcinogenic to humans by the IARC and known to be human
carcinogens by the NTP (13th ed.)
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The Sun – Significant UV Exposure Source
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UV Lamp Spectra
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UV - Biological Effects
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•
Target organs – eyes and skin (UV does not have deep penetration)
Acute overexposure (delayed response: 2 to 12 or more hours; more
intense exposure – shorter response time)
• Erythema (redness or burning of the skin)
• Photokeratitis (inflammation of the cornea)
• Photoconjunctivitis (inflammation of the soft tissue around the eye)
Chronic overexposure
• Cataracts
• Skin aging
• Immunosuppression
• Skin cancer (melanoma, non-melanoma)
• Possible eye cancer
• UV classified as Group 1 human carcinogen by the IARC**
Natural and synthetic photosensitizers increase UV’s potency in causing
skin burns or cancer
**IARC - International Agency for Research on Cancer
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UV - Biological Effects
UV-C and UV-B wavelengths absorbed primarily by the
cornea & conjunctiva (front of the eyeball & inner
surface of eyelids)
UV-A wavelengths – potential hazard to lens & retina
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UV - Exposure Guidelines
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Cover UVR in spectral band from 180-400 nm resulting in eye and
skin exposure from the sun and all artificial UVR sources – except
lasers.
UV radiation’s effectiveness at causing skin burns or corneal
inflammation is wavelength dependent (for example, 270 nm is
wavelength most effective in producing photokeratitis).
ACGIH Threshold Limit Values (TLVs) are harmonized with
International Commission on Non-Ionizing Radiation Protection
(ICNIRP) guidelines.
Guidelines based primarily on studies of acute human / animal
exposures resulting in erythema, keratoconjunctivitis, & cataracts.
Not to be used for photosensitive individuals, those exposed to
photosensitizing agents, or ocular exposure of individuals whose
eyes lack lenses (aphakes).
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UV Radiation TLVs



For broadband sources – UV incident on the eye must be
weighted by a spectral effectiveness function to obtain the
“effective irradiance.” Integral of the effective irradiance over time
– (or, for constant irradiance, the product of the effective
irradiance and exposure time) shall not exceed 3 millijoules per
square centimeter (mJ/cm2) in one day
Eye (corneal) exposure guidelines are expected to be protective
of all skin types in the absence of photosensitizers
To protect the lens and retina from UV-A, unweighted UV-A
radiant exposure:
• Should not exceed 1 J/cm2 for daily cumulative exposure time
less than 17 minutes (1000 seconds)
• Should not exceed 1 mW/cm2 for daily cumulative exposure
time more than 17 minutes (1000 seconds)
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Flow Chart for UVR TLV
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TLVs for UV Radiation
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Actinic UV (200-315 nm) TLVs
Within an 8-hour
period, exposure of
unprotected skin or
eye to actinic UV
radiation should not
exceed the values
given in this table.
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UVR Relative Spectral Effectiveness
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UVR Exposure Duration Limits
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Basic Exposure Characterization
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Type of UVR-emitting equipment
Process or area in which the equipment is used
How operators interact with the equipment
Number of potentially exposed employees
Description of tasks involved
Amount of time spent working around the equipment
How the equipment is maintained
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Ultraviolet Radiation – Ancillary Hazards
 UV-C radiation at wavelengths less than 242 nm reacts
with oxygen to form ozone (local exhaust ventilation may
be required)
 Explosion – internal pressure of short arc lamps, even
when cold, exceed one atmosphere – when under
operation, internal pressure pf 10 to 20 atmospheres are
possible (operate such lamps in special fixtures to
contain glass shrapnel should a lamp explode; do not
touch lamp surfaces as hot spots will be produced where
there is skin oil contamination; do not operate lamps that
are scratched or chipped)
 Skin burns – from touching the surfaces of hot lamps
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UV – Exposure Controls
• Elimination / minimization of reflective surfaces from
work area
• Enclosure of work operation behind opaque or
absorptive materials
• Eyeglasses, goggles, faceshields with UV-absorbing
lenses
• Protective clothing (tightly-woven materials)
• Sunscreens (not protective against shorter wavelengths)
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Visible Radiation Sources
• Sun – all visible wavelengths transmitted by atmosphere
• Welding arcs – broadband visible emission – including blue
light with potential photochemical retinal damage
• Lamps – photoflood, metal halide, and sunlamps: intense
sources that may be rich in blue wavelengths (blue light)
• LEDs (light-emitting diodes) – indicators (e.g., vehicle tail
lights), signs, and communcations
• Lasers – Gas (Ar, Kr, HeNe), Doubled-Nd:YAG, diode (GaAs,
GaInAs, etc.)
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Infrared (IR) Sources
• Sun – near-infrared (IR-A)
• Incandescent sources – including heated elements (heated
filaments & coils) and blackbody sources (furnaces, ovens, and
coils)
• Industrial IR sources – steel mills, foundries, glass-making,
drying equipment
• Lasers – neodymium: yittrium-aluminum-garnet (Nd:YAG),
neodymium:yittrium lithium fluoride (Nd:YLF); carbon dioxide,
laser diodes (GaAs, GaAlAs, InGaAs, etc.)
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Infrared (IR) Biological Effects
•
•
•
•
•
•
•
•
•
•
Thermal burns of the cornea (IR-B and IR-C)
Thermal lesions on the iris (IR-A at or above 4.2 J/cm2)
Cataracts (IR-A and possibly IR-B)
Retinal burns (IR-A)
Retinal hemorrhaging (pulsed IR-A lasers)
Thermal skin burns
Skin vasodilation
Increased skin pigmentation
Skin pain / damage thresholds closely related (45Co or 113o F)
Thermal stress
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Laser Radiation
• Nd:Yag (neodymium:YAG) – Fundamental 1064 nm
wavelength may be frequency-doubled to 532 nm; include
Q-switched lasers with short-duration (10 to 100 nsec)
pulses. Material processing (e.g., cutting and welding) is
primary industrial application; also research applications.
• CO2 (carbon dioxide) – Output at 10.6 µm. Industrial
applications in material processing as well as human and
veterinary medicine. Carbon dioxide laser radiation
interaction with metals may produce broadband (plasma)
radiation (potential UV-C, UV-B, and blue light exposure
concerns).
• HeNe (helium neon) – primarily 633 nm output with
scanning applications for alignment (pipelines, ceiling tile
grids, other lasers) and universal product code reading
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Laser Radiation (continued)
• Ar (argon) – ion gas laser with green (514 nm) and blue
(488 nm) spectral region output for use in entertainment
(laser light shows), medicine (e.g., retinal spot welding
and lesion removal), and research labs.
• Dye lasers – tunable output in the visible and IR-A (near
infrared)
• Diode lasers – semiconductor lasers: some with output
with shorter wavelengths (visible) and some with output
with longer wavelengths (near-infared [IR-A] and midinfared [IR-B]).
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While this can not really happen, one CAN get a thermal
lesion on one's retina by staring long enough down the axis
of a laser pointer's beam. Please remember that laser
pointers are tools not toys!
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Unsafe & Illegal Laser Pointer Use (from: LaserPointerSafety.com)
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Airplane Cockpit Laser Pointer Illumination
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Laser Research Laboratory
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Lasers in Research Lab
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Laser-Containing Tool
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Lasers – Biological Effects
Laser Effects -- Wavelength dependent
(e.g., 400-1400 nm – retinal hazard region)
Eye injury
• Retinal thermal burns, acoustic damage,
photochemical injury
• Lens-related damage
• Corneal damage
• Skin damage (thermal & photochemical)
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Eye Anatomy
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Retinal Injury
December
2014 Overview
Nonionizing
Radiation
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Retinal Injury
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Optical Gain of the Eye
Lens
Cornea
Iris
Retina
Pigment Epithelium
Fovea Centralis
Macula Lutea
Optic Nerve
Aqueous
Optic Disk
Ciliary Muscle
Choroid
Sclera
For wavelengths that focus on the retina, the optical gain of the eye is ~
100,000 times: if irradiance at cornea is 1 mW / cm², then irradiance at
the retina will be 100 W /cm².
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Viewing Conditions
LASER
Intrabeam Direct (primary)
Beam
LASER
Curved
mirror
Intrabeam - Curved
Surface Specular
Reflection
LASER
Intrabeam - Flat
Surface Specular
Reflection
LASER
visual angle
Point Source Diffusion Reflection (Extended
Source Viewing When Apparent Visual Angle
Exceeds Some Minimum)
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Laser Radiation Skin Penetration
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Laser Safety-Related Parameters
• Wavelength (Several thousand laser lines but only about 20
developed for routine applications)
• Exposure duration
• Radiant power (in watts or Φ) for continuous wave (CW) lasers
• Beam divergence (in milliradians)
• Exit beam diameter (in millimeters)
• Pulse energy (joules J or Q), pulse repetition frequency (PRF or
F), & pulse width (in milli-, micro-, nano-, pico-seconds) for
pulsed lasers
• Focal length, mode field diameter (single-mode fiber), &
numerical aperture (multi-mode fiber) for fiber optic output
• Focal length & size of beam on lens for “laser on lens” output
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Laser Safety Exposure Guidelines
 American National Standards Institute (ANSI) – maximum
permissible exposure (MPE) values per ANSI Z136.1 and
other standards in Z136 series: MPEs depend on laser
emission characteristics and viewing conditions
 Federal Occupational Safety and Health Administration
(OSHA) – General Duty Clause of OSH Act
 U.S. Food and Drug Administration's Center for Devices
and Radiological Health (CDRH)
 International Electrotechnical Commission (IEC) [European]
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Laser Safety Standards
• Federal OSHA (and Cal/OSHA) have some standards that
address laser use in construction and laser eye protection
• The CDRH has the Laser Product Performance Standard in Title
21 Code of Federal Regulations (CFR) Subchapter J, Part 1040
– these regulations are mandatory for all laser products sold to
end users in the United States.
• The IEC has a series of Laser Product Standards applicable to
both manufacturers and users of lasers
• Efforts continue to harmonize the various sets of laser safety
standards. For example, the most recent (2014) version of the
primary ANSI laser safety standard (Z136.1) adopts the laser
classification scheme found in its IEC laser safety standard
counterpart.
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Laser Safety Standards
 ANSI—most important series of voluntary U.S. national
consensus laser safety standards (periodically revised)
– ANSI Z136.1-2014 Safe Use of Lasers
– ANSI Z136.2-2012 Safe Use of Optical Fiber Communication
Systems Utilizing Laser Diode and LED Sources
– ANSI Z136.3-2011 Health Care Facilities
– ANSI Z136.4-2010 Measurements for Hazard Evaluation
– ANSI Z136.5-2009 Educational Institutions
– ANSI Z136.6-2005 Lasers Outdoors
– ANSI Z136.7-2008 Testing & Labeling of Laser Protective
Equipment
– ANSI Z136.8-2012 Research, Development or Testing
– ANSI Z136.9-2013 Manufacturing Environments
 ANSI laser safety standards under development:
– ANSI Z136.10 Entertainment, Displays, & Exhibitions
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Laser Hazard Classes
Class
Exposure Condition
Control Actions Required
1
Eye safe, even with
optical aids
None – except for
enclosed Class 3B or 4
1M
Class 1, except with
optical aids
No optical aids; or aids
adequately attenuated
2
(visible)
Safe for momentary
viewing
0.25 sec. aversion
response protective
2M
(visible)
Class 2, except with
optical aids
No optical aids; or aids
adequately attenuated
3R
Marginally unsafe for Limited controls (e.g.
intrabeam viewing
labels and training)
3B
Unsafe for intrabeam LSO; harmful access
viewing
preventing controls
4
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Eye and skin hazard
Restrict source output or
prevent personnel access
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Lasers - Ancillary Hazards
– Electrical
– Laser-generated air
contaminants
– Collateral radiation
(X-ray, UV, visible, RF,
plasma radiation)
– Fire
– Explosion
– Compressed gases
– Laser dyes and
solvents
– Robotic mechanical
– Noise
– Waste disposal
– Limited work space
– Ergonomics
Per ANSI Z136.1-2007, Section 7
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Lasers – Control Measures
• Prevent access to class 3B / 4 laser output (interlocks
on lab doors or tools with these higher hazard lasers
inside)
• Confinement of beam paths to optical tables and
minimization of stray beams
• Personal protective equipment
– Laser eye protection with adequate attenuation (optical density)
at the wavelengths or wavelength ranges in use (must provide
adequate visible luminous transmission) – particularly during
beam path alignment
– Skin protection if UVR emissions are present
• Other controls that address ancillary hazards present
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Optical Density
Diffuse reflection OD—minimum needed for
alignment eye protection (generally based on
600-second exposure duration)
Intrabeam OD—required for "full" protection (for
visible wavelengths can be based on short
aversion response exposure durations)
OD = Log10(Hp/MPE)
• Hp = Potential eye exposure expressed in same
units as MPE
• MPE = maximum potential exposure
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Radio-Frequency Radiation (RF)*
• Dielectric heaters – operate at 10 – 100 MHz (many at 27 MHz) to
heat dielectric materials (e.g., plastics) to cure, bake, mold seal, or
emboss; unshielded units may produce overexposures.
• Semiconductor manufacturing tools – sputterers, plasma etchers
• Induction heaters – operate at < 500 MHz to harden, weld, forge,
found, solder, anneal, or temper conductive materials.
• Broadcasting – AM radio (535-1605 kHz), FM radio (88 – 108 MHz),
VHF TV (54-72 MHz, 76-88 MHz, 174-216 MHz) and UHF TV (470890 MHz)
• Communications – Fixed systems (satellite, microwave relay),
mobile devices (cellular, wireless, walk-talkie, CB)
• Radar – pulsed microwave emissions; commercial, military, marine &
traffic control radars. Most in SHF spectral region.
• Diathermy – Shortwave (13 & 27 MHz) & microwave (915 & 2450
MHz) used to heat tissues: both pulsed and CW mode.
* 30 kHz – 300 GHz listed as possibly carcinogenic to humans (IARC Group 2B)
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Sputtering Device
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Typical Emissions – Various RF Sources
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RF – Biological Effects
Frequency (thus, wavelength) dependent
Thermal effects
• Behavioral/other nervous
system effect (reversible)
• Reproductive &
developmental effects
(animal data only)
• Cancer (animal data only –
inconclusive)
•Ocular effects (restrained
animals only)
• Skin burns (delayed &
similar to sunburn)
• MW clicking – cochlear
thermal elastic expansion &
contraction
Note: Specific non-thermal effect mechanism not
identified – no effects clearly linked to non-thermal
exposures
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Exposure Guidelines – RF & Lasers
Radio-frequency (RF)
Radiation
Maximum Permissible
Exposure (MPE) values for
controlled environments
Per IEEE Std. C95.1-2005
Laser Radiation
MPE values
Per ANSI
Z136.1depending on
emission characteristics
and viewing conditions
Action Levels
• C95.1 Lower tier limits
• Gen. public guidelines
(FCC & ICNIRP)
• One-fifth of ACGIH TLVs
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RF – Exposure Guidelines
Maximum Permissible Exposures for RF in Controlled Environments
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RF – Exposure Guidelines
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RF Sources - Ancillary Hazards
– Electric shock
– Ionizing radiation
– Mechanical
– Eye hazards
– Heat exchange
systems
– Fall from heights
and/or through
openings
– Confined space
entry
– Trip hazards
– Welding/cutting
operations
– Heat stress
– Toxic chemicals/gases
– Cooling refrigerants
– Optical radiation
sources, coherent
(lasers) and noncoherent sources
Per IEEE C95.7, Section 4.7
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RF Exposure Control Categories
RFSP
Category
Exposure Condition
Control Actions
Required
1
Action level not
exceeded
None; except when
action level exceeded
2
Possible action level,
but not exposure
limit, exceedance
Exposure limit
exceedance w/o
mitigating controls
Exposure limit
exceeded in
accessible areas
Some program
elements, signage,
time averaging
More program
elements, RFSO,
more training,
Restrict source
output or prevent
personnel access
3
4
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Radio Frequency Safety Program
(RFSP) Elements per IEEE C95.7
• Administrative (includes designation of
Radio Frequency Safety Officer [RFSO])
• Identification of Potential RF Hazards
• Controls
• Personal Protective Equipment (PPE)
• Training
• RFSP Audit
• Ancillary Hazards
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Extremely Low Frequency (ELF)
• Power-frequency fields – electric and magnetic fields*
associated with the generation, transmission, distribution and
use of electricity: 60 Hz in U.S. & small part of Japan; 50 Hz
elsewhere.
• Degaussing – ELF magnetic fields may be used to
demagnetize material: used for magnetizable media (e.g.
storage tapes), computer screens, airplanes, and naval
vessels.
• Welding – Electric arc and resistance welding.
• Furnaces – Electric furnaces (ladle, arc, induction, and
channel) used for hardening, smelting, and heat-treating
conductive materials.
*30 kHz – 300 GHz listed as possibly carcinogenic to humans (IARC Group 2B)
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TLVs – Sub-RF Magnetic Fields
1 to 300 Hz
TLV – ceiling values in mT;
(current limits in mA)
Whole-body exposure: 60 / f
1 to 300 Hz
Arms and legs:
300 / f
1 to 300 Hz
Hands and feet:
600 / f
300 Hz to 30 kHz
Whole & partial body:
1 Hz to 2.5 kHz
Point contact current limit: 1.0
2.5 kHz to 30 kHz
Point contact current limit: 0.4f
Frequency Range
0.2
Pacemaker and medical electronic device wearer exposure should be
maintained at or below 0.1 mT at power frequencies.
Source: ACGIH 2010 TLVs for Sub-Radiofrequency [30 kHz and below
mT = millitesla; mA = milliamperes; f = frequency in Hz (kHz for current
limit)
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EMF in the Electromagnetic Spectrum
Source: National Institute of Environmental Health Sciences (NIEHS): EMF
Questions and Answers: Electric and Magnetic Fields Associated with Electric
Power. NIEHS, 2002.
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Exposure Limits – Power Frequency Fields
Sources: IEEE C95.6-2002 Standard for Safety Levels with
Respect to Human Exposure to Electromagnetic Fields, 0 – 3
kHz and ACGIH 2014 TLVs for Sub-Radiofrequency (30 kHz and
below) and Static Electric Fields
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Static Fields Sources
• Current-intensive processes – aluminum extraction and
chlor-akalai plants. Static magnetic fields
• MRI and NMR – magnetic resonance imaging (MRI) in
healthcare environment and nuclear magnetic resonance
(NMR) as analytical method; can also produce pulsed
magnetic fields and radio-frequency (RF) fields
• Superconducting magnets – static magnetic fields in
analytical labs.
• Televisions and computer monitors – operation of
devices that incorporate cathode ray tubes (CRTs) that
produce a static electric fields at the screen.
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Magnetic Fields
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Static Field Sources
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TLVs – Static Magnetic Fields
Exposure
Ceiling Value
Whole body (general
workplace)
Whole body (special
worker training and
controlled work
environment)
Limbs
Medical device wearers
2T
8T
20 T
0.5 mT
Source: ACGIH 2014 TLVs for Static Magnetic Fields
T = tesla mT = millitesla
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CAUTION
December 2014
Strong Magnetic Field
People with ferromagnetic or
electronic medical implants
must stay away [at least __ feet ]
from the sides of this tool.
Damage to watches, instruments
and magnetic media possible.
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CAUTION
December 2014
Strong Magnetic Field
People with ferromagnetic or
electronic medical implants
should not enter this lab area as
magnetic field strengths inside it
can exceed 5 Gauss.
Damage to watches, instruments
Nonionizing
Radiation Overview
and
magnetic
media possible. 83
MRI Precautions
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Magnetic Field Controls
• Establishing controlled areas and restricting
access into those areas
• Field cancellation using closely spaced
conductors, have grounding exit a building
where electrical service enters it, eddy current
production with nonpermeable metals.
• Shielding enclosure with relatively high
permeability metals (special ferrous alloys)
• Administrative controls: distance restrictions,
warning signs, and information & training
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Electric Field Controls
• Establishing controlled areas and restricting
access into those areas
• Proper grounding to counter indirect coupling
• Shielding with grounded conductive solid or
perforated sheeting; perforation sizes < 0.25
wavelength of frequencies being shielded
• Administrative controls: approach distance
restrictions, warning signs, and information &
training
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Electromagnetic Spectrum
NIR portion of spectrum covers 15 orders of magnitude in frequency units.
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Exposure Defining Information
• Ultraviolet (UV) – source type; spectral distribution; reflection
potential; photosensitization potential
• Laser – wavelength; continuous wave (CW); radiant power;
pulsed operation; energy / pulse; pulse repetition frequency;
pulse width (duration); direct beam NHZ (nominal hazard
zone); beam divergence; emergent beam diameter; focused
beam NHZ; focal length; beam diameter incident on lens;
reflection potential; photosensitization potential
• RF – frequency; near-field aperture antenna; power; antenna
area; gain, distance from emitter; pulsed emitters; duty cycle;
potential for reflection; potential for hot-spot formation;
conductive surfaces that pose contact current hazard
• ELF – frequency; users of medical devices; whole-body
and/or partial-body exposure
From: Hitchcock, R.T.: Chapter 15 in A Strategy for Assessing and Managing
Occupational Exposures, 3rd Ed. (AIHA, 2006)
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ACGIH Threshold Limit Values (TLVs)
• Optical Radiation
– Light (including Blue Light) and Near-IR
– Ultraviolet Light
– Lasers (see ANSI Z136 standard series)
• Radiofrequency / Microwave Radiation
• Subradiofrequency (30 kHz and below) Electric
Fields & Static Electric Fields
• Subradiofreqency (30 kHz and below) Magnetic
Fields
• Static Magnetic Fields
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Additional Information Sources
• AIHA Nonionizing Radiation Committee Website https://www.aiha.org/get-involved/VolunteerGroups/
(click on Nonionizing Radiation in list of AIHA Volunteer Groups
– Quick Reference Sheets (Ultraviolet Radiation, Lasers, Radiofrequency and
Microwave Radiation, Blue Light Hazard, Static Magnetic Fields
• Health Physics Society - http://www.hps.org/
• ACGIH Documentation of the Threshold Limit Values for
Physical Agents - http://www.acgih.org/TLV/
• Radiofrequency Toolkit for Environmental Health
Practitioners
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Additional Information Sources
• International Commission on Non-Ionizing Radiation
Protection (ICNIRP) - http://www.icnirp.org/
– Guidelines on different NIR frequency and wavelength segments
• IEEE Standards Association - http://standards.ieee.org/
– IEEE C95.1 – 2005 Safety Levels with Respect to Human
Exposure to Radio Frequency Electromagnetic Fields, 3 kHz to
300 GHz
– IEEE C95.7 – 2014 IEEE Recommended Practice for Radio
Frequency Safety Programs, 3 kHz to 300 GHz
• International Agency for Research on Cancer (IARC) http://www.iarc.fr/
– Monographs containing evaluations of carcinogenic risk to
humans posed by occupational and environmental exposure to
NIR and other agents
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References
• Peter H. Wald and Greg M. Stave (eds.): Physical and
Biological Agents of the Workplace, 2nd Edition. New
York: John Wiley & Sons, 2002.
• T.P. Fuller and R.T. Hitchcock: Chapter 25, Nonionizing
Radiation in The Occupational Environment: Its
Evaluation, Control, and Management, 3rd Edition.
Fairfax, VA: AIHA, 2011.
• National Institute of Environmental Health Sciences
(NIEHS): EMF Questions and Answers: Electric and
Magnetic Fields Associated with Electric Power. NIEHS,
2002. http://www.niehs.nih.gov/health/docs/emf-02.pdf
• Miller, G.C. with revision by M. Yost: Chapter 11,
Nonionizing Radiation in Fundamentals of Industrial
Hygiene, 5th Edition. National Safety Council, 2002.
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References
• American Conference of Governmental Industrial
Hygienists (ACGIH): Threshold Limit Values® for
Physical Agents. Cincinnati, OH: ACGIH, 2014.
• American Industrial Hygiene Association (AIHA): General
Concepts for Nonionizing Radiation Protection. Fairfax,
VA: AIHA, 1998.
• Patterson, R.M., and R.T. Hitchcock: Radio-Frequency
and ELF Electromagnetic Energies. New York: VanNostrand Reinhold, 1995.
• Radiofrequency Toolkit for Environmental Health
Practitioners (BC Centre for Disease Control & National
Collaborating Centre for Environmental Health, 2013)
http://www.bccdc.ca/healthenv/ElectromagFields/RadioF
requency/default.htm
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Concluding Remarks
• The nonionizing radiation (NIR) portion of the electromagnetic
spectrum is very broad.
• The NIR spectral region includes ultraviolet, visible, infrared,
radio-frequency (RF), and extremely low frequency (ELF)
radiation as well as laser radiation.
• The use of NIR in our society provides not only benefits but
also potentially significant hazards.
• Some NIR sources pose significant ancillary hazards –
hazards unrelated to direct NIR exposure.
• NIR control measures include exposure avoidance, exposure
duration reduction, source isolation (e.g., source approach
distance restrictions), containment, and attenuation as well as
provision of information (e.g., signage) & training.
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Thank you for your kind attention!!!
Should you have an interest in joining the
AIHA Nonionizing Radiation Committee –
or if you have questions after this meeting,
I may be contacted at:
steve.hemperly@hgst.com
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