I do not wear sunscreen every day. I apply it only when I plan to be out of doors for a significant amount of time, without other means of shading my skin, such as an umbrella or long sleeves. I use Hamilton's “Quadblock”, on days when I apply sunscreen. I like it for holidays, when I am hiking and sightseeing, but it is tedious to apply sunscreen properly on all skin, and leaves me feeling “greasy”, so it is not a daily routine for me. I also worry a little about the safety aspect of applying such chemical agents to skin; I wonder how safe the substances are. I will use them, when necessary, but not every day if there is little UV risk.
When I am indoors, I expect to encounter no UV sources, but we may have such indoors exposure, without realising it. Did you know that some lamps can emit significant levels of UV, and should not be used indoors near people with Gorlin Syndrome? Any light source that emits a bright – white light may emit UV; you need to be careful when buying lamps, and investigate the properties of the radiation emitted by the apparatus.
This is why you need to be careful about choosing light sources for the home:
Modern lighting is generally designed to deliver light of a type similar to sunlight. Candles, and other fires, deliver red to yellow light, but modern people desire brighter and “whiter” light than that; even old incandescent globes delivered a yellowish light, that is seldom desired for work and study, now. This brings the risk of UV exposure, indoors.
Visible light is part of the “electromagnetic spectrum”. Red light has the longest wavelength, and blue / violet light has the shortest. The range of energy is the reverse: blue / violet light has photons of higher energy than red light. Just outside the ranges of wavelength and energy are infra – red radiation (heat energy, that is longer wavelength and lower energy than red light) and, at the other end of the spectrum of visible light, is ultra - violet light (shorter wavelength and higher energy than violet light).
You can view diagrams of these relationships here:
Much background information on the nature of light, and other electromagnetic radiation, can be read in the source pages at Wikipedia (it might be too much information!):
has a table of wavelength, frequency and energy of photons of the different types of EM radiation.
Why do sources of visible light emit UV? It depends on details of the physics involved. I am not a physicist, but I will attempt to explain some of the principles involved.
Heat an object (that does not burn or evaporate) and it will glow dull red. Heat it more, and it glows yellow. Hotter still, it will emit light that is more white. Heat it more, and it will emit some UV as well. To generate very high energy radiation, such as X rays, the temperature must be very high, and special apparatus is required.
The change in colour results from more high energy photons being emitted, as well as the lower energy photons; as the temperature rises, first yellow and then blue parts of the spectrum are being emitted, and as they mix with the red, the overall colour is white light …. eventually …. if you achieve a high enough temperature. This is the principle of an “incandescent” light globe. See Wikipedia, if you want more info on the physical principles:
I note the experts are warning that some people need to be careful near these globes, but the warnings are possibly being inadequately - disseminated to those who most need to know, such as people with Gorlin syndrome. See this section:
" Health issues
Although some sources claim fluorescent lighting causes more health problems than incandescent lighting (see Light sensitivity and Over-illumination for discussion), more research needs to be done in this field. According to the European Commission Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR) in 2008, the only property of compact fluorescent lamps that could pose an added health risk is the ultraviolet and blue light emitted by such devices. The worst that can happen is that this radiation could aggravate symptoms in people who already suffer rare skin conditions that make them exceptionally sensitive to light. They also stated that more research is needed to establish whether compact fluorescent lamps constitute any higher risk than incandescent lamps.[74] "
As I read this next quote, I realised I need to discuss this matter with my workplace, as we have begun using poorly – shielded compact fluorescent lamps in the desk – lamp fittings with which we illuminate our personal workspaces, so there is excessive exposure to UV, during the work day. See:
“Ultraviolet radiation risk
Some fluorescent lamps emit ultraviolet radiation that in some circumstances can exceed safe levels. The Health Protection Agency of the United Kingdom has conducted research that concluded exposure to some compact fluorescent lamps (CFLs) for 1 hour per day at a distance of less than 30 cm can exceed safe levels. Touching the exposed bulb results in equivalent exposure to ultraviolet radiation as that of being in direct sunlight.[13]
In 2009, Natural Resources Canada released a report [14] describing the UV exposure due to lamps of several types. The report states that at 3 cm distance, the recommended daily exposure to ultraviolet radiation for skin and eye damage was attained between 50 minutes and 5 hours depending on the type of lamp; the report observes that such a close distance is unlikely in actual use. The report states that most bare spiral lamps tested gave off more UV than the 60 watt incandescent lamp tested, but that the double-envelope CFLs emitted less UV. At 30 cm distance, the recommended maximum daily exposure was attained between 3 hours and 6 hours, with little difference between the studied 60 Watt incandescent lamp and any bare-spiral CFL. The report states that the Threshold limit values used represent otherwise healthy individuals who are not experiencing any hypersensitivity conditions or exposed to substances that increase UV sensitivity. Outdoor sunlight can supply the maximum recommended daily UV exposure in 20 to 100 minutes.”
The first sort of lamp that alarmed me was the “Halogen” lamp; an incandescent lamp that runs at much higher temperature than the old – style incandescent lamps which emitted a yellow light, with less of the high energy radiation that is greater risk to us. Unfortunately, these old style lamps are being phased out, as experts consider they use too much electricity for the amount of light emitted. Such globes can still be purchased in odd sizes and fancy shapes. I have several stored; I hope that stock suffices until better choices are available. I hope that LED lights may provide us with better choices, once they are available in shops.
See:
http://en.wikipedia.org/wiki/Halogen_lamp
Some halogen lamps do emit UV, or "near UV" radiation, able to cause sunburn. In a modified halogen lamp, the tungsten filament emits UV but the glass, and maybe other layers of filters, block UV from reaching users. You need to find out if these safety filters are in place. I have long considered halogen lamps unsafe for use near the skin, after I read a warning about them, many years ago; before I knew I had Gorlin Syndrome. See:
"High temperature filaments emit some energy in the UV region. Small amounts of other elements can be mixed into the quartz, so that the doped quartz (or selective optical coating) blocks harmful UV radiation. Hard glass blocks UV and has been used extensively for the bulbs of car headlights.[12] Alternatively, the halogen lamp can be mounted inside an outer bulb, similar to an ordinary incandescent lamp, which also reduces the risks from the high bulb temperature. Undoped quartz halogen lamps are used in some scientific, medical and dental instruments as a UV-B source."
and:
"Spectrum
Like all incandescent light bulbs, a halogen lamp produces a continuous spectrum of light, from near ultraviolet to deep into the infrared. Since the lamp filament can operate at a higher temperature than a non-halogen lamp, the spectrum is shifted toward blue, producing light with a higher effective color temperature."
and
"Additionally, it is possible to get a sunburn from excess exposure to the UV emitted by an undoped quartz halogen lamp. To reduce unintentional UV exposure, and to contain hot bulb fragments in the event of explosive bulb failure, general-purpose lamps usually have a UV-absorbing glass filter over or around the bulb. Alternatively, lamp bulbs may be doped or coated to filter out the UV radiation. When this is done correctly, a halogen lamp with UV inhibitors will produce less UV than its standard incandescent counterpart."
The next type of lamp I expect to see sold widely is based on light-emitting diodes (“LED”). The physics involved in generating the photons (light energy) is harder to understand, so just focus on the safety statements, unless you are a physicist; see the last 2 sentences here:
"White LEDs can also be made by coating near ultraviolet (NUV) emitting LEDs with a mixture of high efficiency europium-based red and blue emitting phosphors plus green emitting copper and aluminium doped zinc sulfide (ZnS:Cu, Al). This is a method analogous to the way fluorescent lamps work. This method is less efficient than the blue LED with YAG:Ce phosphor, as the Stokes shift is larger, so more energy is converted to heat, but yields light with better spectral characteristics, which render color better. Due to the higher radiative output of the ultraviolet LEDs than of the blue ones, both methods offer comparable brightness. A concern is that UV light may leak from a malfunctioning light source and cause harm to human eyes or skin."
So, if you want a LED - based lamp for "white light" as in lighting a room, or for reading, you may be offered a lamp that emits UV ... or you may not; we still need to be careful, when buying "white" LED lamps. They will need UV – absorbing filters.
It is hard to keep up with all the issues.
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