nonionizing radiation (nir) overview stephen hemperly, ms, cih, csp, clso, aiha fellow

Nonionizing Radiation (NIR)Overview

Stephen Hemperly, MS, CIH, CSP, CLSO, AIHA Fellow

December 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

• Characteristics & Sources• Exposure Guidelines• Biological Effects• Relevant Standards• Ancillary Hazards• Exposure Controls • Additional Information Resources• Concluding Remarks

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December 2014

Electromagnetic Spectrum

NIR portion of spectrum covers 15 orders of magnitude in frequency units.


December 2014

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


December 2014

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.


December 2014

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 hazard6Nonionizing Radiation Overview

December 2014

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.


December 2014

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


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

December 2014 9Nonionizing Radiation Overview

Electric Fields

Electric field lines – A) from positive point charge; B) between linearly distributed positive and negative charges


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)


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.pdfDecember 2014 Nonionizing Radiation Overview

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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

December 2014 Nonionizing Radiation Overview

December 2014

Fundamental Characteristics of NIRRegion Wavelength FrequencyUltraviolet 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 kHzExtremely low frequency —— 3 kHz–3 HzStatic fields —— ——

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Note: Lower frequency RF (less than 300 MHz) and ELF energies are referred to as fields rather than radiation.

Nonionizing Radiation Overview

December 2014

Spectral Bands for Optical RadiationRegion Band Wavelength

Ultraviolet UV-C 100-280 nm UV-B 280–315 nm

UV-A 315–400 nm

Visible 400–770 nm

Infrared IR-A 770–1400 nmIR-B 1.4–3.0 mIR-C 3.0 m–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.


December 2014

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


December 2014

Nomenclature of ELF and RF Band Designations

Frequency Range Designation Abbreviation* <30 Hz sub-Extremely Low Frequency sub-ELF* 30–300 HzExtremely Low Frequency ELF* 300–3000 Hz Voice Frequency VF 3–30 kHz Very Low Frequency VLF 30–300 kHz Low Frequency LF 300–3000 kHzMedium Frequency MF 3–30 MHz High Frequency HF 30–300 MHz Very High Frequency VHF 300–3000 MHzUltra High Frequency UHF 3–30 GHz Super High Frequency SHF 30–300 GHzExtremely 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. 18Nonionizing Radiation Overview

December 2014

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


December 2014

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

Radiofrequency (RF) 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

ELF Electric-field strength V/m; kV/m

Magnetic flux density (B) μT; mG

Current density (J) mA/m2

Static fields Electric-field strength V/m

Magnetic-field strength T; G*For brevity, visible radiation & some laser radiation quantities are not included.


December 2014

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)


December 2014

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.)


December 2014

The Sun – Significant UV Exposure Source


December 2014 Nonionizing Radiation Overview 24

UV Lamp Spectra


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

UV - Biological Effects


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


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).

UV - Exposure Guidelines


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)

UV Radiation TLVs


Flow Chart for UVR TLV


TLVs for UV Radiation


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.


UVR Relative Spectral Effectiveness


UVR Exposure Duration Limits


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

Basic Exposure Characterization

December 2014

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


December 2014

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)


December 2014

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.)


December 2014

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.)


December 2014

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


December 2014

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


December 2014

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 mid-infared [IR-B]).


December 2014

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!


December 2014

Unsafe & Illegal Laser Pointer Use (from: LaserPointerSafety.com)


December 2014

Airplane Cockpit Laser Pointer Illumination


December 2014

Laser Research Laboratory


December 2014

Lasers in Research Lab


December 2014

Laser-Containing Tool


December 2014

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)


nonionizing radiation (nir) overview stephen hemperly, ms, cih, csp, clso, aiha fellow

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