In all physical respects, ultraviolet (UV) radiation is equivalent to visible light, with the exception that it does not allow us to perceive objects. Visible light, which is made up of the hues we see in a rainbow, is the kind of light that allows us to see things. Right after the violet end of the rainbow, the UV region begins. UV radiation is electromagnetic radiation in the same sense as visible light, radar signals, and radio broadcast signals are (see Figure 1). Waves are used to convey electromagnetic energy. The wavelength, frequency, and amplitude of the waves may all be calculated (the strength or intensity of the wave). One entire wave cycle is one wavelength. Wavelengths are measured in nanometers (nm) for radiation in the UV portion of the spectrum, where 1 nm is equal to one millionth of a millimeter. Different electromagnetic radiation wavelengths have various effects on people. For instance, infrared light can be utilized to keep you warm while gamma rays can be employed in cancer therapy to kill dangerous cells. In comparison to visible light, UV radiation has shorter wavelengths (higher frequencies), while X-rays have longer wavelengths (lower frequencies). There are three categories for wavelengths in UV radiation: Magnetic spectrum in Figure 1. The general characteristics of each category are outlined in Table 1. Table 1: Ultraviolet Radiation Types and Their Characteristics Type of Ultraviolet Radiation General Characteristics Ultraviolet A radiation (UVA, long-wave UV) that is not filtered out in the atmosphere, travels through glass, causes some tanning, was originally thought to be innocuous, but is now thought to be hazardous in the long run, and has rather stable levels throughout the day. Ultraviolet B radiation (UVB, sunburn radiation) causes sunburn, tanning, wrinkling, aging of the skin, and skin cancer. Some of this radiation is filtered off in the atmosphere by the ozone layer. -midday is when it is strongest The ozone layer in the atmosphere filters off ultraviolet C radiation (UVC, short-wave UV) before it reaches earth. The main artificial sources are germicidal lights (which destroy microorganisms), which burn the skin and cause skin cancer.
What are some UV radiation sources?
The main source of UV radiation is sunlight. A few different kinds of UV lamps, arc welding, and mercury vapour lamps are examples of man-made ultraviolet sources. UV radiation is frequently utilized for a variety of purposes in industrial processes as well as in medical and dental settings, including phototherapy, bacterial killing, fluorescent effects, curing inks and resins, and tanning. For various applications, different UV wavelengths and intensities are used. Examples of jobs where UV exposure could be a problem are provided in Table 2. Examples of UV radiation-using devices are shown in Table 3. Table 2: Potential Risk to Workers from UV Radiation Exposure Food and beverage sterilizers Salon employees and clients laboratory personnel lighting specialists employees of printing and lithography forensic specialists dentists and their helpers pediatricians and dermatologists general truck drivers Outdoor personnel construction personnel Surveyors and contractors Curers for paint and resin Physiotherapists operators of plasma torches Welders fisheries, forestry, and agriculture Photolithography Table 3: A Few UV Radiation-Emitting Devices bacteriostatic lights Dark-colored lights Xenon, carbon, and other arcs dental polymerization apparatus Fluorescence apparatus Deuterium and hydrogen lamps Nail-curing ultraviolet lamps halogen metal lamps Mercerized lamps Particle torches lights for phototherapy apparatus for polymerizing printing ink welding supplies fake currency detectors
What are some UV radiation exposure health effects?
The need for some UV exposure is fundamental for health. It increases the body's production of vitamin D. One instance of this in use in medicine is the use of UV lamps to treat psoriasis (a condition causing itchy, scaly red patches on the skin). Excessive UV light exposure has been linked to several forms of skin cancer, sunburn, rapid skin aging, cataracts, and other eye conditions. The wavelength, intensity, and length of exposure all affect how severe the effect is (see Figure 2). Skin-related effects The greatest risk is from UV-C shortwave light. UV-C radiation from the sun is emitted, but it is stopped before it reaches the planet by the ozone layer in the atmosphere. Consequently, UV-C from the sun has no effect on humans. Some artificial UV sources also produce UV-C. However, the laws governing these sources limit the UV-C intensity to a very low level and may call for the installation of particular guards, shields, and interlocks to stop UV exposure. Skin burns, erythema (reddening of the skin), and skin darkening are all effects of medium wave UV (UV-B). Skin cancer risk is increased by extended exposure. Figure 2 shows how sensitive the skin and eyes are to various wavelengths of UV radiation. Up to 95% of the UV light that reaches the surface of the earth is longwave UV radiation (UV-A). Although UV-A is less intense than UV-B, it is more prevalent and can penetrate deeper into the skin layers, affecting the connective tissue and blood vessels, which results in premature aging. As photosensitizing agents, certain substances and drugs increase the impact of UV radiation from the sun or other sources. Such agents include thiazide diuretics (drugs which cause excessive urine production), drugs used in the treatment of high blood pressure, certain antibiotics (tetracyclines, sulfonamides), cosmetics, and thiazine tranquilizers. These are but a few instances; this is not meant to be an exhaustive list. However, it is important to know that these photosensitizing effects can occur in case people are exposed to UV radiation at work. For example, an inexperienced welder, who was taking a phenothiazine anti-depressant drug, suffered damage in both eyes in the part of the retina that absorbs short wavelength light (bilateral maculopathy). He began complaining of eye problems a day after he was arc welding for two minutes without wearing any eye protection. This damage, that fortunately was reversible after several months, occurred because the drug he was taking sensitized him to the UV radiation to which he was exposed. Various plants such as carrot, celery, dill, fig, lemon and some types of weeds are known to cause photosensitivity. Exposure to fluids from these plants, especially if crushed, followed by exposure to sunlight can cause dermatitis. Citrus fruit handlers and vegetable harvesters, gardeners, florists and bartenders are at risk for experiencing dermatitis following exposure to certain plants and then to sunlight (phytophotodermatitis). Coal tar and creosote are examples of photosensitizing agents in the workplace. Effects of repeated exposures (chronic effects) include skin aging and skin cancer. There is a strong causal link between skin cancer and prolonged exposure to solar UV and from artificial sources. Effect on the eyes The eyes are particularly sensitive to UV radiation. Even a short exposure of a few seconds can result in a painful, but temporary condition known as photokeratitis and conjunctivitis. Photokeratitis is a painful condition caused by the inflammation of the cornea of the eye. The eye waters and vision is blurred. Conjunctivitis is the inflammation of the conjunctiva (the membrane that covers the inside of the eyelids and the sclera, the white part of the eyeball); (see Figure 3) which becomes swollen and produces a watery discharge. It causes discomfort rather than pain and does not usually affect vision. Figure 3 - The eye Examples of eye disorders resulting from UV exposure include """"flash burn"""", """"ground-glass eye ball"""", """"welder's flash"""" and """"snow blindness"""" - depending on the source of the UV light causing the injury. The symptoms are pain, discomfort similar to the feeling of sand in the eye and an aversion to bright light. The eyes are most sensitive to UV radiation from 210 nm to 320 nm (UV-C and UV-B). Maximum absorption by the cornea occurs around 280 nm. Absorption of UV-A in the lens may be a factor in producing cataract (a clouding of the lens in the eye).
How can you measure exposure?
The intensity of UV radiation is measured in the units of milliwatts per square centimetre (mW/cm2) which is energy per square centimetre received per second. Also, it is measured in the units of millijoules per square centimetre (mJ/cm2), which is energy received per unit area in a given time. A variety of instruments are commercially available for measuring UV radiation in the laboratory and in the workplace. Specifications and purchasing information can be obtained from suppliers of workplace monitoring equipment.
Are there occupational exposure limits?
Many jurisdictions follow the limits recommended by the American Conference of Governmental Industrial Hygienists (ACGIH, 2022). For the UV-A (315 to 400 nm), exposure to the eye should not exceed 1 milliwatt per square centimetre (1.0 mW/cm2) for periods greater than 1000 seconds (approximately 17 minutes). Additional exposure limits apply to the amount of UV light exposure to the skin and the eyes. The amount of UV exposure a person can receive on their skin or eyes during an 8-hour period varies with the wavelength of the UV radiation. For specifics or other limits, please consult the Ultraviolet Radiation section of the current edition of the ACGIH publication Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices®.
How do you protect yourself from UV radiation?
UV radiation is invisible and therefore does not stimulate the natural defences of the eyes. Workers must use eye and skin protection while working with UV radiation sources which present the potential for eye harmful exposure. The selection of eye protection depends on the type and intensity of the UV source. For more information consult CSA Standard (CAN/CSA-Z94.3 2020) Eye and Face Protectors. UV radiation is easily absorbed in a variety of materials. Shielding is usually easy to design. Mercury lamps and metal halide lamps have an outer glass cover to stop UV radiation, and are designed such that if the outer glass is broken, the lamp ceases to function. For information on how to protect yourself from ultraviolet radiation in sunlight, please see the OSH Answers Skin Cancer and Sunlight."""