Xeroderma Pigmentosum Society, Inc.
437 Snydertown Rd.
Craryville, NY 12521

 
 
 

UV Notes

For the XP patient, even short exposure to UV can ap up and lead to early death from cancer. It is not just children that have XP. Because of improving early diagnosis and better understanding of how to protect the child from the devastating effects of the sun, we are now seeing more XP patients living into adulthood.

Persons with XP can enjoy a relatively satisfactory quality of life if they are protected from UV by following our guidelines. Protection does not require extreme (and expensive) measures. Use window tinting and other inexpensive window coverings, low-wattage incandescent lighting, and wear adequate protective clothing for the short periods it is necessary to be out-of-doors for important travel. These simple steps can allow a fairly active lifestyle. The protective clothing can be long-sleeved denim jackets, broad-brimmed hats, sun glasses, and sunscreen. However, the XP Society does not approve of the use of any kind of protective garment for outdoor activity in full sunlight. We made Camp Sundown UV-safe by following the same simple techniques we suggest for home and school.

None of this is meant to minimize what is clearly a devastating disease. There are many severe consequences from XP, including neurological problems. We offer the following resource to help the patient or caregiver to understand UV and its relationship to XP.

Contents

Regarding UV and the XP patient

Know your light sources

UV Measurement

Selecting a UV Meter for XP Patients

Risk of UV from wood burning fires?

What is risk of UV radiation from TV and computer screens?

Regarding UV and the XP patient

by Patrick Mannix, Technical (non-medical) Consultant and XP Society Webmaster

Each of us involved in some way with XP knows the importance of ultraviolet radiation. But how much do we really understand about ultraviolet (UV)? In my case, I had the knowledge that one might expect of an engineer/technician who had graduated over forty years ago. Which meant that more study was required! The objective of my study is to help the XP Society provide guidance about UV as it relates to XP. I hope this article serves as a first step.

Ultraviolet is defined as being situated beyond the violet end of the visible spectrum. The word spectrum may bring to mind the image of the colors of the rainbow . . . a good image to keep in mind as we delve further. Visible light and ultraviolet are but part of a much broader spectrum: that of electromagnetic radiation (Figure 1). Electromagnetic radiation is described in terms of waves of electric and magnetic field intensity. Visualize the effect when a pebble is dropped in a pond. The waves thus formed have wavelength: the distance from crest to crest. They also have amplitude or height. Before leaving this example, visualize what happens as the waves propagate from the source. At some fixed point ( say, a reed in that pond ) the crest, then the trough, then the crest again pass by. The number of full cycles (one crest and one trough) that appears to pass in one second represents the frequency of the wave, in cycles per second. The shorter the wavelength, the higher the frequency.

Wavelength of electromagnetic waves is most often expressed in terms of the meter (1 meter = 3.28 feet). Radio waves range from the hundreds of meters to fractions of a meter. As we progress to the much shorter wavelengths of visible light and ultraviolet, the nanometer (nm) is a more practical unit. One nanometer is 0.000 000 001 meter.

Other units of length, such as the Angstrom (1 Angstrom = 0.1 nm), are also seen. UV radiation metrics will vary with the discipline involved (i.e., physics, photobiology, astronomy, etc.).

Other artifacts of variation by discipline are observable in Figure 1. The UV portion of the spectrum is further defined by a variety of subset spectra, which overlap and have variations in the end points. When the biological effects of UV radiation (UVR) are being discussed, the terms UVA, UVB and UVC are used most often. Where wavelength is critical, the author will usually be specific.

 

The XP Society is the international authority and resource for XP family support and ionformation in making intelligent decisions regarding the caregiving of the XP family member.

 

 

Graphical depiction of the optical portion of the electromagnetic spectrum

Optical spectrum

Figure 1 - Electromagnetic spectrum

  • Gamma rays, X-rays < 10 nm
  • Ultraviolet 10 nm to 380 - 400 nm
    • Vacuum UV 10 nm to 200 nm
    • Extreme UV 10 nm to 100 nm
    • Far UV 100 nm to 200 nm
    • Far (if no extreme) 20 nm to 200 nm
    • Miple UV 200 nm to 300 nm
    • Germicidal 220 nm to 300 nm
    • Mercury (Hg) line at 253.7 nm
    • Near UV 300 nm to 380 - 400 nm
    • Near (if no miple) 200 nm to 400 nm
    • Black Light 330 nm to 380 nm
    • UVC 100 - 250 nm to 280 - 290 nm; CIE, 1987: <280 nm
    • UVB 280 - 290 nm to 315 - 320 nm; CIE, 1987: 280 to 315 nm
    • UVA 315 - 320 nm to 380 - 400 nm; CIE, 1987: 315 to 400 nm
      • UVA II 315 - 320 nm to 340 nm
      • UVA I 340 nm to 400 nm
  • Visible Light 380 - 400 nm to 760 - 780 nm
  • Infrared 760 - 780 nm to 1 mm
  • Radio Waves > 1 mm

 

 

A graphical depiction of the UV portion of the spectrum:

UV spectrum

Note: The graphics above are based upon figures in the International Light Handbook.

Unlike the waves in a pond, electromagnetic waves propagate (travel) through space (vacuum). The sun is the most significant source of infrared, visible light and ultraviolet radiation reaching the earth. Energy is transmitted in this way. But first, another concept requires discussion.

While electromagnetic radiation conforms to wave theory, the energy is conveyed as discrete quanta. These quanta, known as photons, increase in energy (electron volts or eV) as the wavelength decreases. Each quantum (photon) of ultraviolet radiation at 250 nm has twice the energy of visible light at 500 nm. This concept is vital when we investigate the effects of various portions of the UV spectrum on the xp patient. Sometimes tables and graphs will use units of energy (eV or Joule) in place of wavelength. (Visible light is 1.6 to 3.1 eV, ultraviolet is greater than 3.1 eV.)

Graphical representation of a spectrum is a powerful way to present data. Of course one should understand the terminology; but, equally important is the scale for the (usually) y axis. Whether in terms of relative values or specific units, it is important to note if the scale is linear or logarithmic.

In the case of action spectra, where the effect of UV radiation (UVR) at each wavelength is plotted, values that are one ten-thousanph that at the maximum can still be significant. For example, if the plot of some biological phenomena shows the effect at a wavelength in the UVA band is 10^-4 below that of a wavelength in the UVB region; but we see that the plot of irradiance from the sun is about 10^4 greater in the UVA range than in the UVB, then the net effect is potentially equal. If you are not used to logarithmic presentation, take extra care when comparing graphs.

Note:

The ^ symbol is used here to denote exponentiation (x raised to power y is x^y).

Sunlight consists of the direct rays as well as scattered (sky) radiation. With the sun overhead, at sea level, low ozone content and cloudless UV is 5% of total global radiation and UVA is 95% of that. Presented on a linear scale this might lead one to ignore the 0.25% remaining UVB as inconsequential. It is not. When translated to uW/cm^2 (microwatts per square centimeter) it is more than enough to be of concern to the normal person. To the xp patient, it is dangerous.

When UV photons from the sun collide with a DNA molecule in someone's skin, there is an increase in the likelihood that he or she will develop skin cancer. When that person has xp, with reduced DNA repair capability, the risk is very much greater.

Another factor not directly apressed thus far is dosage. The duration of exposure must be considered. An example, straight from a lighting manufacturer, is the data which leads to the conclusion that fluorescent lighting in the workplace presents no hazard: Put in perspective, the exposure over one eight hour workday is equivalent to just over a minute of mipay solar exposure on a clear July day in Washington, DC. For the normal person, it is a reasonable conclusion. For the xp patient it raises serious concern; particularly when cumulative effects are taken into account. No informed XP patient or parent of a child with XP would allow even a minute of full sun exposure.

Then there is the question of UVR sources other than the sun. Any element heated to sufficient temperature produces some radiation in the UV range. Common household incandescent lamps radiate relatively little. Fluorescent lamps, because they generate UV internally to excite the phosphor that produces the visible light, are a greater risk. Quartz-halogen lamps, not protected with an outer glass bulb or plate, radiate potentially harmful UV.
Commercial, municipal, and industrial lighting fixtures are another unknown. Certain of these light sources are likely to use a mercury vapor arc as the source. Without proper filtering and shielding this is a source for UVC that isn't even present in sunlight.

What are we to do? The XP Society strategy is to:

  1. Recommend maximum protection (inside, with windows tinted or covered and lowest practical incandescent lighting levels). Minimize risk when required to travel during daylight (sunscreen, protective clothing, etc.).
  2. We have procured UV instrumentation as funds allow. (A UVA meter, and several UVA+B meters are on hand.) We have measured the widest possible range of environments to provide comparison to known safe home environment. We are using these measurements to provide guidelines to xp families.

Further work of this nature would best be accomplished by a qualified research facility, perhaps under a grant when sufficient research funds allow. In the meanwhile, we will share what we do know. See XP Society policy statement regarding UV Protection.

We continue to search for practical (low cost, reliable, easy to use) meters which seem most suitable for individual use. We are concerned about the potential for misuse of UV meters and resultant false sense of security. XP Society policy is to NOT endorse specific products; but we do make available any information that might help patients or their families to make an informed decision. Please see the XPS UV-links page where you can find the UV related links grouped for ease of access. Included are comments about the meters that we have used, with at least one that is available for less than $170 (USD) that meets most of our needs. Also, please read the XP Society policy statement regarding UV Protection.

Sources for this article include a broad selection of material found on the Internet. We invite comments of any kind about this article or the subject in general. You can reach the author by following the "Contact Webmaster" link on this page.

Partial Bibliography:

  1. Authoritative Scientific Review of Environmental and Health Effects of UV
  2. Biological Responses to Ultraviolet A Radiation A symposium sponsored by the American Society for Photobiology; Frederick Urbach, Editor; Valdenmar Publishing Company; ISBN 0-9632105-0-5
  3. Solar ultraviolet radiation effects on biological systems; B L Diffey; Review in Physics in Medicine and Biology 36 (3): 299-328.
  4. Hazards of Optical Radiation A Guide to Sources, Uses & Safety; A F McKinlay, F Harlen and M J Whilock; Adam Hilger; ISBN 0-85274-265-7
  5. Six Roads From Newton Great Discoveries in Physics, by Edward Speyer, Wiley, ISBN 0-471-30503-0
  6. The Light Measurement Handbook, by Alex Ryer (PDF)

The XP Society is the international resource and authority for XP family support and information in making ciritcal decisions in the caregiving of the XP family member.

 

Know your light sources

by Patrick Mannix

My first article was an attempt to familiarize the reader with the confusing array of terminology that will be encountered in the quest for information about ultraviolet radiation, its relationship to XP, and its sources.

This article apresses several common man-made sources of UV which you are likely to encounter.

 

 

Quartz Halogen lamps

These are increasingly found in home lighting fixtures. Technically known as Halogen Cycle lamps, you will find various designations - most often with Halogen as part of the name. They range in size (and power) from flashlight bulbs to 1,000 Watt yard security lamps.

Their appeal over the more common incandescent light bulb is the higher output (brighter, whiter light) per unit of power consumed. This higher efficiency is important for conservation of energy resources. There is a downside. Higher filament temperatures mean more UV is produced.

This is further complicated by the necessity for special high temperature glass (quartz). Quartz, because of its purity, allows a greater portion of the UV to pass. For this reason most quartz halogen lamps are housed within a larger (regular) glass bulb or are protected by another glass covering of some sort in the fixture. This reduces the UV significantly. However, if the outer glass is broken or not in place, the risk of exposure to damaging UV is real. Also, there are some desk lamps and under counter fixtures that do not shield the quartz bulb.

For these reasons, I suggest that it would be prudent to avoid quartz-halogen lighting which is in close proximity to XP patients for extended periods. This would include table and desk lamps used for study or other activities. The popular floor lamps which use a halogen bulb within a reflector aimed at the ceiling usually have a glass plate shielding the bulb. These probably do not represent a high risk; but in the Mahar household, the decision was to give the lamp away. My point? It is a judgment call. When you can control the environment why not err on the conservative side?

 

 

Metal Halide and Mercury Vapor Lighting

This type of lighting is not often found in the home. It is used in a variety of industrial and commercial applications, from shops to street and stadium lighting.

The following information is typical of that supplied by the manufacturer of metal halide lighting:

  • It is important to immediately turn power off if an outer envelope is broken to prevent injury which may be caused by ultraviolet radiation of an unjacketed HID lamp.
  • Metal Halide and Mercury lamps should comply with Federal Standard 21 CFR 1040.3, and include the following warning notice:
    • This lamp can cause serious skin burn and eye inflammation from short-wave radiation if the outer envelope of lamp is broken or punctured, and the arc tube continues to operate. Do not use where people will remain for more than a few minutes, unless adequate shielding or other safety precautions are used.

The above warning was written because both metal halide and mercury lamp arc tubes emit enough ultraviolet radiation to cause adverse biological effects. Skin repening and eye damage are both potential problems if someone is exposed to an operating arc tube which is not surrounded by an outer jacket. The extent of injury to the general population depends upon a number of factors: lamp wattage, exposure time and individual sensitivity. This warning is meant to alert users to the possibility of injury if the outer jacket of the lamps were to be broken. When this occurs, a lamp may continue to operate for an extended period of time (usually not more than 100 hours). During this time, however, injuries to individuals could occur. The risk to the XP patient is immeasurably greater

Installed and maintained correctly these lamps do not pose a risk for most of us. However, lacking sufficient data, and given the potential for unintended exposure to UV, I feel that is prudent for the XP patient to avoid exposure to high levels of lighting from this type of light source.

 

 

Discussion

Why hedge? Because this type of lighting at the top of, say, 100 foot high towers in a stadium reduces the potential risk considerably; particularly if the time of exposure is relatively short. This was the case at the softball game during Camp Sundown during our first year. We surveyed the site to the best of our ability, given the information and meters available at the time. My follow on research led me to the manufacturer of the fixtures used at that ball park, Musco Lighting. I found the company to be very forthcoming and, in fact, the company president telephoned me to offer whatever assistance he and his staff could provide, such as sources for meters and related information. We discussed the steps that Musco takes to minimizes UV radiation. These, plus the effect of the inverse square law which describes the reduction of radiation level in proportion to the square of the distance from a point source, serve to greatly reduce the amount of UV. A lamp can be considered a point source. The sun and skylight cannot.

There can be no certainty. There is no absolutely safe level of UV where XP is involved. My purpose in presenting this information is not to frighten. It is to inform. There are other potentially harmful sources of UV besides the sun and unshielded fluorescent lamps.

 

 

What about LED lamps?

The LED (Light Emitting Diode) is a solid-state device. The mechanism for producing visible light is different from incandescent lamps, where the light is produced by heating a filament to a white-hot temperature. The LED uses very low power and generally produces light at a single wavelength. The earliest LEDs emitted light only in the infrared portion of the spectrum (opposite UV). Remote control "clickers" are among the best known uses. Then red LEDs came into use (remember early digital displays on the first calculators?). Recent developments have enabled the economic production of larger (thus brighter) LEDs of various colors. In fact a common use is to replace traffic lights, because they are more efficient and last longer (even if more expensive than the 100 watt incandescents they replace). Today we see increasing availability of "white" LEDs. The LEDs I've described thus far are monochromatic, that is they produce light of a single color or wavelength. To produce white light, we need the mix of at least two colors (usually three or more, as in color TV or computer monitor). So white LED's use various "tricks" to create the appearance of white. One of the techniques is to coat a blue LED with a phosphor that emits yellow light, that combined with blue appears white to our eyes.
In any event, if you know the light source include LEDs only, then there will be no UV (A, B, or C) emitted. Your UVA+B meter should read zero. No UVC.
I qualified my statement saying "if you know the source is LED" because the blue-white light emitted from white LEDs appears the same as the tell-tale blue-white light I often caution as being a sign that an unknown light source might be high in UV. If in doubt, use a meter.

 

 

UV Measurement

One of our goals is to find (or to have developed for us) a UV meter that can be used by XP families to assess relative ultraviolet levels found in the real world of day-to-day living. We can take all the steps to make our homes relatively safe; but how do we measure other environments (inside automobiles, buses, aircraft, shopping malls, schools, etc.). This is a difficult task, as you can imagine after reading the preceding article, Regarding UV and the XP patient.

We have been in contact with experts at major university centers, NASA, the Food and Drug administration, the National Institutes of Health, and lighting manufacturers. In apition, we have consulted with several manufacturers of UV meters.

We know there can not be an exact, one size fits all, set of values, since XP patients vary amongst themselves in their ability to repair damage done by ultraviolet radiation. Lacking specific values, we have tentatively established criteria that, in conjunction with a suitable measurement device, can provide guidance to allow a family to judge the relative safety of an environment for their child with XP.

Using meters capable of measuring UVA and UVB we conclude that a reasonably safe environment for a person with XP represents UVA+B levels of approximately one microwatt per square centimeter or less. These same meters would indicate 5,000 or greater microwatts per square centimeter in direct noon sunlight in summer. Please understand that these figures, while real, may apply only if the same type and brand of meter is used in a similar environment.

We routinely use a SolarMeter Model 5.7 for these assessments

The XP Society is the international authority for XP family support and information in making intelligent decisions in the caregiving of the XP family member.

 

Selecting a UV Meter for XP Patients

There are a variety of instruments on the market that are said to measure or monitor UV (ultraviolet) radiation. For the XP patient, whose DNA can be damaged by very small amounts of UV, a meter not sensitive enough to measure these lower levels of UV will fail to warn of the risk of damage that will accumulate, ultimately leading to skin cancers. The XP Society philosophy is to take no risk when it comes to your child's long term health. Damage can occur without immediate visible results (e.g., a burn). That is why the choice of a suitable meter is so important.

There are a number of meters or monitors that are designed to tell people how long they can "safely" stay in the sun (usually based on skin type). These are designed for people without unique health conditions such as XP. The meters of this type that we have experience with are NOT sensitive enough to be used by persons with xeroderma pigmentosum.

You can roughly gauge if a UV meter is sensitive enough by checking for a reading greater than zero under all the following conditions:

  • indoors next to a window, even one that is tinted, during daytime
  • within a few feet of an unshielded fluorescent lamp
  • outdoors in open shade (no direct sunlight)
  • outdoors near dawn or dusk
  • outdoors on a completely overcast day

We have determined that a satisfactory UV meter for XP patients should be capable of measuring as low as 10 microwatts per square centimeter (10 uW/cm²) -- and, better yet, as low as 1uW/cm² for combined UVA+B.

Some meters that might be suitable will be calibrated in different units. Inquire of the manufacturer how their specification compares to microwatts per square centimeter.

The XP Society, as a matter of policy, does not endorse specific products. We do, however, make as much information as possible available so you can make your own informed choice. On our UV Links Web page we list a number of meter manufacturers. We have only had first-hand experience with three or four of these. You will see one that we use routinely at Camp Sundown (SolarMeter Model 5.7) and two others that we have tried: Solar Light Company model 3D and International Light, Inc. model 1400A. The Littlemore Scientific Engineering Company model 763 that we have is no longer in production.

Please note that none of the meters mentioned is a medical device. While useful when used in conjunction with the advice found herein, good judgment must be applied, keeping in mind that sources of UVC will not register on these meters. Remember, there is no published "safe level" of UV for persons with XP. The empirical methods the XP Society has used to arrive at our recommendations must be applied in the spirit offered. There is some trade-off with quality of life; but given the potential fatal consequences, we have tried to err on the side of being conservative, while still allowing some normalcy in the life of an XP patient. We urge caregivers of minor XP patients to always keep in mind the cumulative effect of UV exposure when making a determination with respect to quality of life issues.

The XP Society is the international authority for XP family support and information in making intelligent decisions in the caregiving of the XP family member.

 

Proper use of a UV Meter

UVB meter in useIllustrated using a UVB-only meter similar to the SolarMeter Model 5.7 Actually, on a sunny day, as seen in this illustration, the Model 5.7 would over-range, because at any time there is clear sky and the sun is high enough above the horizon the amount of UVA+B will exceed the 1999 microwatts per square centimeter that is the maximum reading available. This, in order that we be able to detect UVA+B as low as 1 microwatt per square centimeter. The principle of use is the same. Simply aim the meter toward the brightest source of light, be it a window, a lamp, or the sky close to sunrise or sunset (or on a very overcast day). The sensor is at the top of the case. You will see the small hole with a Teflon diffuser behind it. After aiming, press the button and observe the reading. We suggest that you be consistent in the relative position (e.g., slightly above eye level for the sky, at a distance of 6 inches to one foot from a lamp or a window.) We find that readings inside the Camp Sundown facility are zero in most cases, perhaps reading 3 when held high near the flood lamps in the pool area. It is not difficult to protect interior living areas to achieve zero. This should be the objective in any area where the XP patient will spend significant time.

The XP Society is the international authority for XP family support and information in making intelligent decisions in the caregiving of the XP family member.

 

UV-related questions

Risk of UV from wood burning fires?

XPS research activity uncovered some references in the literature which raised a question about the safety of wood fires, such as fireplaces and camp fires, with respect to possible ultraviolet radiation. We asked Dr. Kenneth H. Kraemer about this and he forwarded the question to a colleague in the FDA. This is the e-mail reply received Fri., 30 May 1997, from Dr. Robert H. James:

Dr. Kraemer -
Statement re: UV from fireplaces - R. H. James
(NOT official FDA position)

A fireplace produces an optical radiation output similar to a low temperature `black body', which has a smooth spectral curve with little or no ultraviolet being present, significant infrared presence, and some visible radiation. For a fire, there will be imposed upon this `normal' `black body' type of radiation output some transient effects (hot spots and `flares') based on variations in the fuel source - some having a narrower spectral band output. The type of fire (and physical size of the fire) can have a dramatic effect on the optical output - different types of wood burn with different intensity - gas fireplaces will produce different spectral outputs than wood. At the beginning of the fire's life, the radiation output will be low - it increases as the fire gets hotter, and coals develop - it decreases once again as the fire dies out. An individual can decrease his exposure by simply moving to a greater distance from the fire. All of these parameters make a description of the optical radiation output from a fire very difficult indeed.

I believe that little or no ultraviolet radiation can be expected from wood fires. The most significant output from wood fires is in the infrared, with some visible radiation also present. I do not know of any measurements of wood fires which have detected any ultraviolet radiation output at reasonable viewing distances from the fire.

I know this is not very detailed, but if you wish to discuss this further, please let me know.
Bob

Dear Dr. James
Thank you very much for this information. I will pass your letter on to the people in the Xeroderma Pigmentosum Society who originally asked the question out of concern for their children who are very sensitive to ultraviolet radiation. I am sure they will be grateful for your efforts.

Best wishes.
Ken Kraemer

Kenneth H. Kraemer, M.D.
Laboratory of Molecular Carcinogenesis
National Cancer Institute
Building 37 Room 3E24
Bethesda, MD 20892
301-496-9033 FAX: 301-496-8419
e-mail: kraemerk@nih.gov

 

 

What is risk of UV radiation from TV and computer screens?

Cathode Ray Tubes

crt

Cathode Ray Tube, the type of vacuum tube used in computer monitors and television receivers (color or monochrome).

This question was directed to an expert in this field, Dr. Carlo Infante. He is a member of the Society for Information Display and was gracious enough to give his permission to post his reply dated 8/15/95:

Re. your question about UV radiation from CRTs

I know a little bit about the subject, having worked with those devices for many years. I designed one of the first CRT-based Office Word Processors in the late '70s. It used a 14 in. monochrome CRT and was produced by Xerox.

We were concerned at the time about the entire gamut of radiation, from infrared up to and including X-rays. We specifically worried about UV. Those worries resurface from time to time. Let me try and put you at ease.

In the first place, phosphors used in CRTs convert the electron-beam energy (which ranges from 10 keV to 30 keV) into visible light. The output of these phosphors falls very drastically in the blue. Not only is the eye relatively insensitive to blue, it also loses much of its spatial resolution at the shorter wavelengths. Thus no useful information is carried by having phosphors emit in the blue and UV regions of the spectrum.

Furthermore, for mechanical strength, CRTs employ a fairly thick glass faceplate between the phosphors and the viewer. UV radiation is strongly attenuated by even thin glass (so-called "leaded glass" is used to reduce X-rays).

Finally, in a push to make color CRTs brighter, the "blueness" of the blue phosphors has been reduced by pushing their color point to more of the center of the Color Chart. This further reduces any amount of UV radiation.

This issue has never been a problem in any monitor that I know of. There are some fairly strict rules on the amount of UV radiation that is allowed; but the amount of UV is unmeasurable in CRTs for the reasons above.

I hope this eases your concerns, please feel free to contact me if you have any more questions.

Sincerely,

Dr. Carlo Infante
CBI Consulting
9433 N 87th way
Scottsdale, AZ 85258
602-951-0808 Tel
602-951-6083 Fax

The XP Society is the international authority for XP family support and information in making intelligent decisions in the caregiving of the XP family member.

 

Flat Panel Screens

Newer thin or flat panel computer monitors and all laptop/notebook computer screens are Liquid Crystal type displays (LCDs). Televisions are now available with screens using both LCD and plasma technology. Neither should be confused with the similar-sounding term: "flat screen" which almost always are CRTs (see above) that have a flat screen face.

We have attempted to measure any UV that might be radiated from LCD screens (we have not yet measured plasma screens) and were unable to detect any UVA or UVB using meters capable of measuring as low as 1 microwatt per square centimeter in the UVA and UVB spectrum.

The XP Society is the international authority for XP family support and information in making intelligent decisions in the caregiving of the XP family member.

Conclusion

Television and computer displays using either CRT or LCD technology do not pose a UV risk for persons with xeroderma pigmentosum.

This does not apress photosensitivity. Persons, including those with XP, who experience symptoms when exposed to visible light may have to take measures such as turning down brightness or sitting farther from the screen.

 

The XP Society is the international authority for XP family support and information in making intelligent decisions in the caregiving of an XP family member.