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Radiation involves the transfer of energy through space and, depending on the amount of energy the radiation carries, can be classified into ionizing radiation and non-ionizing radiation.
Ionizing radiation carries enough energy to ionize atoms and
includes high-energy ultraviolet, X-rays, and gamma rays in the electromagnetic
spectrum. If living tissue is exposed to
ionizing radiation, atoms making up DNA in cells could become ionized causing
DNA to not work correctly and potentially lead to cancer. Ionizing radiation also has many
benefits. Gamma rays are used to
sterilize medical equipment and we all know the use of X-rays in medical
imaging although the dosage in these instances are very low so the chance of
damage is also low.
Non-ionizing radiation does not have enough energy to ionize
atoms and includes low-energy ultraviolet (UV), visible light, infrared (IR), microwave (MW), radio frequency (RF) and extremely low frequency (ELF) waves. It is found in a number of occupational settings and can pose considerable health risks if not properly controlled.
UV has a high photon energy range and is particularly of concern because the symptoms of excessive exposure are delayed. Visible light is, of course, necessary for efficient and effective operations and in reducing injuries caused by poor lighting. However, excessive levels of visible radiation can damage the eyes and skin. High Intensity Optical Sources (HIOS) are broadband sources since they emit more than one wavelength of light and include explosive devices, welding, searchlights, arc lamps and UV and medical lamps. With UV and HIOS, chronic ocular effects such as cataract formation and possible photochemical retinal injuries due to visible blue-light exposures occur as well as low-level effects such as discomfort, glare, or temporary flash blindness. IR is absorbed by the cornea and lens causing cataracts although some does reach the retina and is of greatest risk in glass blowers, blacksmiths and metal foundry workers and military ranging, target designation lasers which are often IR lasers.
RF radiation applies to electromagnetic fields with frequencies between 3 kHz and 300 MHz, while MW radiation covers fields from 300 MHz to 300 GHz and includes items such as broadcast stations, cell phones, Bluetooth enabled devices, satellite communications and military radar. Since their characteristics are similar, they are usually considered together. Natural low-frequency electromagnetic fields come primarily from the sun and thunderstorms. However, recently there has been a lot of concern regarding the potential hazards from microwaves and radiofrequency radiation which, when at sufficiently high power levels, can cause thermal effects, however, none of the research to date has proven that low levels of electromagnetic radiation cause adverse health effects. Occupational exposure limits and recommended protective measures are recommended by OSHA under standard 1910.97 - Nonionizing radiation . In addition, OSHA has a Safety and Health Topics page titled "Non-Ionizing Radiation" includes an overview and training materials.
Lasers produce non-ionizing radiation and operate within
specific ranges in the electromagnetic spectrum, including ultraviolet,
visible, and infrared wavelengths. Within this range there is the Retinal Hazard
Region, which includes visible and near infrared wavelengths. Eye exposure
within this region can result in permanent retinal damage. In addition, laser light differs from ordinary light in three ways:
- Monochromatic--Laser light consists of one color or wavelength. In contrast, ordinary white light is a combination of many colors or wavelengths.
- Directional--Lasers emit light that is highly directional, that is, laser light is emitted as a relatively narrow beam in a specific direction. Ordinary light, such as from a light bulb, is emitted in many directions away from the source.
- Coherent--The wavelengths of the laser light are in phase in space and time. Ordinary light can be a mixture of many wavelengths.
It is these differences that make the laser beams useful and potentially hazardous. Laser work and similar operations create intense concentrations of heat, ultraviolet, infrared, and reflected light radiation and can result in eye injuries including retinal burns and cataracts. When exposed, all employees and visitors should use appropriate eye protection at all times.
Much of the information provided here is from the Nonionizing Radiation Division here at APHC and is also available on their sites in a less eye specific fashion. The mission of the Nonionizing Radiation Division is responsible for identifying and assessing current and emerging nonionizing radiation health threats. For addition information, go to the following sites (not all inclusive):
- Laser and Optical Radiation - Information on potential hazards associated with the operation of high intensity optical sources such as laser target designators, infrared countermeasures, industrial optical sources, nonlethal weapons, and other high technology optical sources.
- Radio Frequency Radiation and Ultrasound - Information related to the potential hazards associated with exposure to radio frequency radiation and ultrasound.
They are the ones who are responsible for the evaluation of all Army capable of generating nonionizing radiation (including radio frequency, microwave, laser, and optical radiation sources),including:
- Conducting installation and site surveys to assist commanders in developing and maintaining an effective Nonionizing Radiation Protection Program, and
- Investigating all incidents of suspected overexposure to nonionizing radiation.
For additional assistance regarding nonionizing radiation issues, contact the Nonionizing Radiation Division.
For assistance with issues regarding the eye and vision surveillance requirements and requirements for Eye Care Professionals, feel free to Contact Us.
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Eye Specific Hazards and Protection
ANSI Z136.1 hazard classification is based on ability to cause biological damage to the eyes and skin. The following chart lists the wavelengths and eye specific hazards.
180 nm – 280 nm (UV-C)
280 nm – 315 nm (UV-B)
315 nm – 400 nm (UV-A)
400 nm – 780 nm (Visible)
Photochemical and retinal injury
780 nm – 1400 nm (IR-A)
Cataract and retinal injury
1.4 μm – 3.0 μm (IR-B)
Aqueous flare, cataract, corneal injury
3.0 μm – 1 mm (IR-C)
Photokeratitis is also know as snow blindness or welder's flash and is caused by exposure of insufficiently protected eyes to the ultraviolet (UV) rays from either natural (e.g. intense sunlight) or artificial (e.g. the electric arc during welding) sources. Photokeratitis is akin to a sunburn of the cornea and conjunctiva, and is not usually noticed until several hours after exposure. Symptoms include increased tears and a feeling of pain, likened to having sand in the eyes.
Photochemical cataracts are cataracts formed due to a photochemical effect as opposed to a thermal one. A chemical reaction caused by UV absorption of the lens leads to clouding of the lens, known as a cataract.
Retinal injuries are also thermal and result in a permanent loss of vision in the affected area.
Aqueous flare is undesirable scattering of light in the aqueous humor, which is found between the iris and the cornea. This scattering, or flare, is caused by elevated protein concentration in the aqueous humor which, in this case, is from an IR laser overexposure.
Lasers are classified by their degree of potential hazard. The 8 laser classes are listed below:
|1||Emit at levels that are not hazardous under any viewing or maintenance conditions. However, as a matter of good safety practice, avoid intrabeam viewing. Examples include laser printers and, CD and DVD players and some laser rangefinders.|
Emit at levels that are not hazardous under unaided viewing conditions, but could be a hazard for intrabeam viewing through magnifying optics such as binoculars or telescopes.
New and not in Z136.1 but in Z136.3-2018. These laser products are designed explicitly for contact application to the skin or non-ocular tissue. During operation, any ocular hazards need to be prevented by engineering means.
|2||Emit in the visible portion of the electromagnetic spectrum and are a potential eye hazard only for prolonged intrabeam viewing. The aversion response, including the blink reflex, would normally prevent overexposure. Examples include bar code scanners.|
|2M||Emit visible laser wavelengths and are not a hazard for short exposure durations for unaided intrabeam viewing. A Class 2M laser is hazardous for intrabeam viewing through magnifying optics within the reported hazard distances and requires a "caution" label. The laser output cannot exceed the Class 3B AEL for optically aided viewing.|
|3R||Emit at levels that are potentially a hazard for direct intrabeam and specular reflection viewing. Diffuse reflections are not normally hazardous. Examples include laser pointers.|
|3B||Emit at levels above Class 3R lasers but less than Class 4 lasers and are a hazard for direct intrabeam and specular reflection viewing. Diffuse reflections are not normally hazardous. Class 3B lasers are also possible a skin hazard. Examples include laser light show projectors and research lasers and targeting lasers.|
Emit at levels that are hazardous for direct intrabeam exposure and some can produce a hazard from diffuse reflections. Class 4 lasers are also possible a skin hazard. They may also produce fire, material damage, laser generated air contaminants, and hazardous plasma radiation. Examples include industrial and surgical lasers and most laser weapon systems.
In addition, you should be aware of the Nominal Ocular Hazard Distance (NOHD) which is the distance from a laser source at which the intensity of a single laser beam becomes safe. However, it is important to always be safe and avoid exposure of your eyes to any laser whenever possible.
When determining requirements for eye protection, it is important to start by determining the maximum power intensity that can be produced when workers are exposed and then select lenses that protect against that maximum intensity. ANSI 136.1-2014 states that eye protection is required for Class 3B and Class 4 lasers when engineering or other admin controls are not practical and that, for routine laser operations and most alignment procedures, full protection eyewear shall be used. Alignment eyewear can only be permitted for specific authorized alignment procedures with visible laser beams but must still have the optical density necessary to provide full protection for ideal source diffuse viewing at a distance of 20cm.
For additional information on selecting appropriate eye protection go to the OSHA page "Selecting PPE for the Workplace - Optical Radiation.
Medical Surveillance Requirements
ANSI Z136.1-2014 - Safe Use of Lasers is the foundation of laser safety programs for industrial, military, medical, and educational applications nationwide. It states that medical surveillance should be considered for those who are clearly known to be at risk from particular kinds of laser radiation. Medical surveillance is not recommended for personnel using Class 1, Class 1M, Class 2, Class 2M or Class 3R lasers and is recommended for personnel using 3B and 4 lasers for those "clearly shown to be at risk."
ANSI Z136.3 (2018) - Safe Use of Lasers in Health Care provides guidance for the safe use of lasers for diagnostic, cosmetic, preventative and therapeutic applications where bodily structure or function is altered or symptoms are relieved.
Virtually all of the U.S. domestic as well as all international standards divide lasers into four major hazard categories called the laser hazard classifications. The classes are based upon a scheme of graded risk and are based upon the ability of a beam to cause biological damage to the eye or skin. Service specific requirements follow.
|References||DoD 6055.05M ||AFI 48-139 ||DA PAM 40-506 TB MED 524 ||BUMEDINST 6470.23 |
|Requirements||Medical surveillance is required for personnel working with Class 3b and Class 4 lasers and laser systems. It is not a requirement for personnel working with Class 1, Class 2, or Class 3a lasers or laser systems.||Same||Same||Same but states that actual enrollment is determined by the Laser Surveillance Officer.|
|Periodicity||Preplacement and termination||Same||Same||Same|
|Tests Required - Laser Workers||Ocular and visual history, visual acuity, color vision test, and a central visual fields test (via Amsler Grid or similar macular integrity test) at preplacement and termination - performed on each eye separately. Any deviation from the acceptable normals shall be evaluated to determine the reason. This may be done by ocular funduscopic examination or other tests as deemed appropriate by the eye care professional. Baseline funduscopic photography may be useful for documenting the retinal status.||Same. An Installation Occupational and Environmental Medicine Consultant in consultation with an optometrist shall determine medical examination requirements and frequency for users of optical radiation sources and shall reflect requirements in local regulations. ||Same||Ocular history with special emphasis on photo-sensitizing medications, lens surgery, unusual sensitivity to sunlight, and skin diseases. Visual acuity - distance and near. External ocular and fundus examination. As deemed necessary by the medical examiner: Amsler Grid or other test of macular function; and dilated direct view ophthalmoscopic examination and slit lamp examination to describe and pathology or deviations from normal.|
|Tests Required - Incidental Workers||Each eye screened for visual acuity as part of the preemployment physical.||Same||Same||Not required.|
Laser Induced Injury Evaluation
Following a suspected or actual laser-induced injury, ANSI requires that an evaluation be performed as soon as practical - usually within 48 hours.
6.1 Examinations Following a Suspected or Actual Laser-Induced Injury.
Medical examinations need to be performed as soon as practical (usually within 48 hours) when a suspected injury or adverse effect from a laser exposure occurs. In addition to the acute symptoms, consideration shall be given to the exposure wavelength, emission characteristics and exposure situation to ensure appropriate medical referral. Service specific requirements follow.
|References||AFI 48-139 USAFSAMS Laser Injury Guidebook|
DA PAM 40-506 TB MED 524
|BUMEDINST 6470.23 |
|Requirements||Any accident/incident involving a suspected laser, broadband or other optical radiation overexposure, visible laser illumination that negatively impacts mission operations or a laser exposure causing personal injury to personnel and material damage to AF equipment, systems or sensors shall be investigated and documented and evaluated by an eye specialist if one is available, otherwise by a flight surgeon.||Any soldier or DOD employee with a confirmed or suspected, unprotected exposure to a Class 3b or more powerful laser will have a diagnostic vision examination by an optometrist or ophthalmologist at the nearest military treatment facility (MTF). ||All mishaps involving suspected overexposure to class 3, 4, or military exempt lasers require an investigation and report through the appropriate chain of command. Those incidents involving suspected or observed laser eye injury require a complete medical examination.|
|Timeline||As soon as possible, and again at 24 hours.||As soon as possible - no later than 24 hours.||Immediately|
|Tests Required||Minimum requirements: Detailed history of the event. External ocular exam. Best corrected visual acuities - distance and near. Confrontational visual fields. If available, stereopsis and color vision. ||Minimum requirements include a history of the event and a thorough vision and ocular examination including ocular history, distance VA, Amsler grid (or similar central visual field) test, slit lamp examination, ocular fundus evaluation through dilated pupil, ocular fundus photographs that depict the extent of injury or lack of injury, and photographs of any external or anterior segment injury. If ophthalmic photographic capabilities are not available, then a detailed representation of the finding may be hand-drawn or the patient will be referred to the nearest MTF (or authorized local civilian provider) having such capabilities.||Requires color retinal photos. If unavailable, a diagram of the eye documenting the injury and pathology will suffice until a photo can be obtained. Various visual examinations are helpful including Snellen acuity, confrontation visual fields and Amsler grid are essential. External examination and Opthalmoscopy also provide valuable information.|
|Reporting Requirements||Contact tri-service laser safety hotline ASAP - 1-800-473-3549||Once an acute laser overexposure has been confirmed, notify: The division/installation LDO, the division/installation RSO, the Tri-Service Laser Incidence Hotline - 1-800-473-3549, and TSVCRD at 410-436-2464||Report is required for all incidents involving personnel with suspected or observed exposure to class 3B or class 4 lasers 1. Notify BUMED (M3B4) ASAP at 703-681-9276 2. Notify BUMED (M3B4) ASAP” 703-681-9276|
3. Contact tri-service laser safety hotline ASAP” at 800-473-3549 4. Submit a incident report via LSSO to BUMED within 30 days - Tech Lead Agent - Dahlgren at 540-653-2442
The following video, titled "Green Laser Safety," was developed for the U.S. Army Combat Readiness Center and serves as good general information regarding all laser eye safety in the military.. Released in 2014, the resources are dated however the content provides a good introduction to all laser safety as it pertains to the eyes. To view the source, go to Green Laser Safety video .
Other videos on Laser Safety that were produced by the Nonionizing Radiation Division of APHC on the APHC YouTube site and are available for you to utilize as training videos.
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