Optimize optical radiation safety
Most safety managers are well aware of the important role safety eyewear plays in protecting workers’ eyes from impact, heat, chemical and dust hazards. In general, the better the fit and the greater the coverage, the greater the protection safety eyewear delivers from those hazards. However, a less obvious — but equally important — safety benefit delivered by such eyewear is protection from optical radiation.
Optical hazards range from visible light to invisible rays including ultraviolet (UV) and infrared (IR) radiation. Whether the source is natural or artificial, repeated or extended exposure to optical radiation can cause serious damage to the eyes. Over time, exposure to ultraviolet rays alone can lead to macular degeneration — a leading cause of vision loss for older Americans — as well as cataracts, skin cancer around the eyelids, corneal sunburn and other temporary and permanent vision problems.
In an effort to better support eye safety attributed to harmful rays in the workplace, the American National Standards Institute modified its Z87.1 standard for eye and face protection in 2010. The changes help clarify the types of lens filters required for particular applications, while enabling proper lens selection and identification through the use of informative lens markings. This article examines the types of optical radiation found in the workplace and the corresponding lens tints appropriate for protecting workers’ eyes and faces.
ANSI changes facilitate eyewear selection
The revisions in ANSI Z87.1-2010 update the 2003 version. The foremost change for end-users is that now, rather than being organized by protector type, the standard is organized by hazard category. New classifications and marking requirements have been added to indicate lenses’ radiation filtration properties and the hazards for which they are suitable. This change was intended to help ease the process of selecting the proper lens tint or filter shade for the job.
Lenses that protect from optical radiation are now marked with a letter and number combination to denote their protective properties. Ultraviolet filters are marked with a “U,” while visible light (glare) filters are marked with an “L,” and infrared (heat) filters are marked with an “R,” all followed by a scale number. Welding filters are marked with a “W” followed by the shade number. Lenses marked with a “V” denote a variable tint while those with an “S” signify special purpose lenses.
Protecting from sunlight & glare
Ultraviolet is a type of invisible radiation produced by the sun and a range of industrial processes, such as welding. Any intense exposure to UV light can lead to photokeratitis, an extremely uncomfortable corneal injury resulting in redness, swelling and a dry, scratchy feeling in the eyes. Furthermore, long-term exposure to UV can lead to permanent blindness or cataracts, so employees who spend any time outside should be outfitted with eyewear that blocks UV and whose lenses are marked with a corresponding “U.” Safety managers may be surprised to learn that most safety lenses today — whether clear or tinted — provide 99-percent protection from the UVA and UVB spectrums.
When working outdoors, workers are also exposed to visibly bright sunlight and glare, an additional form of optical radiation commonly overlooked in safety audits. Effects of overexposure to direct or reflected light include headaches and eye fatigue, redness, dryness and irritation. To combat natural light hazards, eyewear with standard gray, brown or mirrored lens tints offer suitable protection and may be selected based on user preference.
Glare is intense reflected or scattered light that causes the pupils to constrict, limiting the amount of natural light transmitted to the retina and impairing vision. Glare occurs when light is reflected off of water, sand, snow, glass, sheet metal, concrete or any reflective surface. To combat glare, eyewear should be mirrored, polarized or darkly tinted, preferably in wraparound-style frames to cover all angles. Appropriate lenses should be marked with an “L.” Indoor glare is also common and can cause headaches and vision problems. Indoor lighting can be counteracted with specialized tints such as light blue lens filters for individuals working in yellow or sodium vapor light or pink lenses for those working in fluorescent or halogen lighting. Such lenses should be marked with an “S” to denote their specialized application.
Lenses for frequent lighting transitions
For workers frequently transitioning between indoor and outdoor settings, switching out safety eyewear from dark to clear lenses is a common solution. However, this approach not only doubles an individual’s PPE, but during the time it takes the eyes to adjust to extreme changes in light — up to several minutes — the workers’ vision is compromised, heightening their risk of injury. Furthermore, the darkly-tinted lenses worn outdoors are typically inappropriate for use in dimmer indoor light. Variable, or photochromic, lenses are an ideal solution. Through an advanced chemical reaction, they respond to UV and automatically transition from clear during indoor use to tinted when outdoors. Under the 2010 ANSI revision, such lenses intended for variable light applications should be marked with a “V.”
Protecting eyes during welding operations
Photokeratitis, also known as welder’s flash, is common among welders exposed to the intense ultraviolet radiation created by the arc. Results can range from temporary blindness and extreme discomfort to permanent blindness.
A welding helmet’s filter lens provides shade to the eyes at a level corresponding to that of the arc radiation generated by the application. For electric arc welding applications, typical filter lens shades range between 10 and 14. For gas welding or viewing gas-fired furnaces and boilers, shades between four and eight may be ample. Because welding helmets are a secondary form of protection, ANSI requires that primary safety eyewear (spectacles or goggles) always be worn under them.
In workplaces with heavy concentrations of welding activity, consider primary eyewear with specialized lens filters that employ IR-absorbing or reflecting materials to minimize the heat load to the eyes and face. Also, keep in mind that individuals working within 20 feet of the welding application, as well as those passing by it, face indirect exposure to radiant energy and spatter and should be outfitted with the corresponding level of safety eyewear as well. When selecting safety eyewear for welding applications, confirm that all required components are permanently marked “Z87” to ensure conformance with the standard.