Non-Ionizing Radiation

Nonionizing radiation

generally means electromagnetic radiation whose quantum energy is less than 12 eV

Although “nonionizing” radiation, photons whose energy is as low as _____ may ionize certain molecules

4 eV

By the end of WWII, there was evidence for damage to the eyes from

• viewing solar eclipses

• exposure to UV light among welders

• exposure to infrared energy among glass blowers and steel workers

What caused more people to pay attention to NIR effects with respect to public health?

boom in electronics and communications, increasing use of lasers

In 1977, the IRPA expanded their scope to include NIR, which led to the creation of

International Non-ionizing Radiation committee (INIRC) → International Commission on Non-ionizing Radiation Protection (ICNIRP)

Unlike ionizing radiation, where quantum energy is usually expressed in eV, the energy of NIR Is expressed as

frequency or wavelength

UV wavelengths

100-400 nm

UVA wavelengths

400-315 nm

UVB wavelengths

315-280 nm

UVC wavelengths

280-100 nm

Sources of UV radiation

• sun (largest, mainly UVA, some UVB, UVC filtered by ozone)

• black lights

• carbon arcs

• dental polymerizing instruments

• fluorescence equipment

• germicidal lamps

• hydrogen lamps

• metal halide lamps

• mercury lamps

• plasma torches

• printing ink polymerization

• welding arcs

• tanning equipment

For killing bacteria and bacterial spores, UV light in the wavelength range of _____ has been found to be most effective

250-270 nm

UV rays become increasingly penetrating to the eye as wavelength

increases

UVC can damage the ____ of the eye

cornea (causes photokeratitis)

UVB can damage the _____ of the eye

lens and cornea (and can cause cataracts)

UVA can be absorbed by the ______ of the eye and is associated with cataracts

lens

Blue light can produce scarring on the _____ which can lead to vision loss

retina

All wavelengths of UV damage collagen fibers in the skin and accelerate

changes due to aging

UVA plays a major role in the production of

wrinkles

UVB is responsible for delayed photochemical effects like

tanning and erythema

What type of skin is most at risk with UVB?

less pigmented

What 3 types of skin cancer are UVA and UVB associated with?

• basal-cell carcinoma

• squamous-cell carcinoma

• melanoma

What is the most common diagnosed cancer in the US?

skin

The chief environmental cause of skin cancer is

ultraviolet radiation

In recent years, there have been bans on _____ due to its association with skin cancer

tanning beds

Are UV lights for nail polish damaging to skin?

evidence is inconclusive but honestly probably

How do you protect from UV?

• Shade

• UPF

• Sunglasses, goggles, face shield

• Sunscreen/sunblock

What does LASERS stand for?

Light Amplification by Stimulated Emission of Radiation

Lasing medium

substance (of any state) that can be excited to a metastable state; light of specific wavelength is amplified

Optical cavity

pair of mirrors to increase amplification

Energy pumpt

source of energy needed to excite atoms of the lasing medium

Characteristics of laser light

• monochromatic

• coherent

• collimated

Monochromatic

single wavelength and frequency originating from stimulated emission. Can be in UV, visible, or infrared regions of EM spectrum

Coherent

all waves in phase

Collimated

bc of bouncing back between mirrored ends of a laser cavity, those paths which sustain amplification must pass between the mirrors many times and be very nearly perpendicular to the mirrors. as a result, laser beams are very narrow with little divergence

How many laser classes are there?

4

Class I laser

laser can’t cause injury either bc it’s too low powered or bc of engineered safety controls

Class II laser

may be viewed for less than 0.25 seconds. the aversion response (blink) is sufficient to prevent injury to eye. Max power is 1 mW

Class IIIA laser

can injure eye in intrabeam viewing for <0.25 second, or viewing A specular reflection for <0.25 second. max power is 5 mW

Class IIIB laser

same as IIA, except max power is 500 mW. max radiant exposure is 10 J/cm² per pulse

Class IV laser

hazardous to eyes and the skin during intrabeam and diffuse exposure. potential fire hazard. power level > 500 mW

Mechanisms of biological damage include

heating effects due to absorbed energy and photochemical reactions

The chief mode of damage depends on the

wavelength of radiation, rate at which tissue is irradiated, and the duration of exposure

The eye does have a self-defense mechanism; the aversion response is commonly assumed to occur within _____ seconds and is only applicable to visible laser wavelengths

0.25

Can the eye aversion response help with high powered lasers?

no

Photobiomodulation

cold laser therapy and low-intensity laser therapy; a form of light treatment that uses nonionizing forms of light sources, including lasers, light emitting diodes and broad-band light, in the visible and infrared spectrum, involving a non-thermal process with endogenous chromophores eliciting photophysical and photochemical events at various biological scales

Major biologic responses to PBM therapy

• alleviation of pain and inflammation

• modulated immune response

• tissue healing and regeneration

Proposed molecular mechanisms for PBM therapy involve absorption of specific wavelengths by _____ components

cellular

Electromagnetic radiation assumes many forms and can be generated in different waves

• a changing electric field produces a magnetic field

• a changing magnetic field produces an electric field

• interaction of the changing fields results in a wave of electric and magnetic fields that can propagate through space

Technically, any electricity-using device can create electric and magnetic fields by virtue of

the current flowing through the device

Radiofrequency radiation is defined arbitrarily as

electromagnetic radiation in the frequency range of 3 kHz to 300 MHz, while the arbitrary definition of microwaves includes electromagnetic radiation whose frequencies range from 300 MHz to 3000 GHz

Generally, power densities that members of the public are exposed to from common sources are low - on the order of

microwatts/cm²

Electrostimulatory effects

3 kHz-5 MHz, at high enough levels an electric field can generate painful nerve impulses

Thermal effects

100 kHz-3 GHz temperature rise, either whole body or localized, when the body absorbs energy faster than its thermoregulatory system

Skin heating effects

3-300 GHz at frequencies greater than 3 GHz, energy absorbed mainly in the skin and microwave radiation behaves similar to infrared radiation; increase in skin temp to 45 C causes sufficient pain, also associated with exposure to open waveguide from high powered source

Thermal biological effects

• mainly due to heating

• basis of diathermy

• heat must be dissipated in environment

Non-thermal biological effects

effect that can’t be contributed to heating (< 10 mW/cm²)

What do people worry about?

• cancer

• birth defects

• genetic effects

• behavior effects