Implication for photosensitive patients of ultraviolet A exposure in vehicles

BACKGROUND: Photosensitive patients sometimes report disease flares during journeys by car. Window glass blocks all UVB but not all UVA. All car windscreens are made from laminated glass. Side and rear windows are usually made of nonlaminated glass. OBJECTIVES: To determine which types of glass provide most protection from UVA with particular reference to the implications for patients with polymorphic light eruption (PLE). METHODS: The percentage transmission of UVA was determined for a selection of glass, both laminated and nonlaminated, and with differing colour tints. RESULTS: Laminated glass transmits less UVA than nonlaminated glass. Tinted glass transmits less UVA than clear glass. Nonlaminated clear glass transmitted the highest percentage of UVA (62.8%) and grey laminated glass the lowest (0.9%). A dose of 5 J cm(-2) UVA, enough to trigger PLE in some patients, could be transmitted through clear nonlaminated glass in 30 min but would take 50 h through grey laminated glass. CONCLUSION: Patients with severe UVA-induced PLE and other photosensitivity disorders may have disease flares from solar UVA transmission through side-window glass. Protective measures such as wearing long-sleeved clothing, keeping the arm beneath the bottom of the window aperture, or choosing tinted and laminated car windows may be helpful.     

Change in ultraviolet (UV) transmission following the application of vaseline to non-irradiated and UVB-exposed split skin

BACKGROUND: Topical preparations such as emollients used in combination with phototherapy can interfere with such treatment. OBJECTIVES: This study was performed to investigate the impact of vaseline on the ultraviolet (UV) transmission of non-irradiated split skin and on split skin previously exposed to UVB radiation. METHODS: Split-skin specimens were obtained from 20 patients. In each case, one sample was taken from an area of non-irradiated skin, while the second was taken from an area that had been previously exposed to UVB. The transmission was spectrophotometrically measured with split skin placed in specially designed quartz glass cuvettes before and after the application of two different amounts of vaseline (2.5 and 17.5 mg cm-2). RESULTS: Application of vaseline to skin previously exposed to UVB caused significant (P < 0.0001) changes in UV transmission in certain wavelength ranges. In the UVA range, a greater increase in transmission was achieved with 2.5 mg cm-2 vaseline, whereas in the UVB range, a greater increase was achieved with 17.5 mg cm-2 vaseline. The thicker the layer of vaseline applied, the lower was the difference in transmission between non-irradiated split skin and UVB-exposed split skin. CONCLUSIONS: Application of the correct amount of vaseline can enhance transmission in either the UVA or UVB range, and would enable dose reduction during a course of phototherapy.     

Erythema marginatum in rheumatic fever: Early diagnosis by skin biopsy

A randomized double-blind clinical trial involving twenty-two volunteers was conducted in two locations (Orlando, FL, and St. Paul, MN) to test the efficacy of the newly designed ultraviolet monitor badges (Sun Timers), described in another paper by us in this issue of the Journal,¹ and to establish the relationship between spectral band exposure dose and the biologic responses of erythema and pigmentation. Individuals with skin types II, III, and IV, exhibiting differences in reactivity to solar radiation, were exposed to varying doses of full-spectrum sunlight through templates mounted on the lower portion of the back. Simultaneously, on the upper portion of the back, the same volunteers were exposed through two different types of polyester filters that transmitted ultraviolet A (UVA) and visible radiation. Using templates with windows, exposures to full-spectrum sunlight, UVA, and visible radiation were carried out to 1, 2, 3, 6, and 9 sunburn units (approximately 30–270 millijoules/cm² between 10:30 a.m. and 3:30 p.m. daylight time in mid summer), measured with the aid of a Robertson-Berger meter and an IL700 International Light radiometer. Erythema and pigmentation resulting from these exposures were graded (double-blind) immediately after exposure, at 24 hours, and after 5 days. Numerical skin response ratings at each exposure dose for different spectral bands were then averaged and plotted. It was found that the UVB monitor response was predictive of a 24-hour erythema response and 5-day pigmentation response within 30% of the biologic average for skin types II, III, and IV. UVA radiation stimulated melanogenesis. The minimal melanogenic dose (MMD) for skin type II was the same as the minimal erythemogenic dose (MED). The MMD for individuals of skin types III and IV was distinctly less than their MED. Thus, melanogenesis can be stimulated with a suberythemal dose of UVB or UVA radiation. The sun protection factor values of melanin for melanized skin have been estimated to vary from 1.0 (skin type II) to 4.3 (skin types V and VI).     

Electronic UV dosimeters

Background/aims: The pathogenic role of ultraviolet (UV) in the development of skin cancer, skin ageing and immunosuppression makes it important to monitor human exposure to UV radiation. In a previous study we constructed UVB and UVC dosimeters based on a thermoluminescent phenomenon induced by UV in CaF₂:Dy and CaF₂ crystals. However, these dosimeters were insensitive to UVA radiation and readout was time-consuming. In the present study we aimed to develop an electronic dosimeter suitable for UVA, UVB and UVC. The principle of this dosimeter is a measure of accumulated electric current induced by UV on a photodetector.
Methods: Electric current induced by UV on a photodetector was accumulated in a Plessey's E-cell coulometer. A special reading device was constructed to quantify total charge of the coulometer. Sensitivity for UVA, UVB and UVC was achieved by the use of appropriate filters in front of the photodetector.
Results: The sensitivity of the electronic dosimeter increased with increasing wavelength of UV radiation; therefore, in UVB and UVC dosimeters the use of amplifiers was necessary. A linear response to UVA, UVB and UVC was achieved.
Conclusion: Dosimeters with a linear response to increasing doses of UVA, UVB and UVC have been constructed for personal monitoring of UV exposure.     

Do different ethnic groups need different sun protection?

Background: In the present study, the transmission of sunlight trough the human skin barrier into the living tissue was investigated in the spectral region between 280 and 700 nm.
Methods: The experiments were performed with a fiber-based spectrometer on sliced skin obtained from volunteers with different skin types. One fiber was positioned directly on the skin surface and the second one underneath the skin samples. The distribution of the sunlight under the epidermis was determined.
Results: Significant differences were found in the absorption properties of the different skin types, which were mainly determined by the variations in melanin concentration and distribution. It was found that sunscreens for specific ethnic groups need different combinations of UV filters, if a balanced relation between ultraviolet B (UVB) and ultraviolet A (UVA) protection is to be obtained. On the other hand, it could be demonstrated that the human skin is also well protected against visible and near-infrared light by melanin.
Conclusions: The higher the skin type category, the better the protection in the visible part of the spectrum of the sun. This stimulates the hot discussion at the present time, as to whether sunscreens should also contain protection compounds in the visible and near-infrared parts of the spectrum.     

Environmental UVA radiation and eye protection during PUVA therapy

Experimental and clinical evidence suggests that patients receiving psoralens plus UVA radiation (PUVA) therapy for the treatment of psoriasis or other skin diseases run the risk of developing cataracts. The total exposure to UVA radiation of these patients has been difficult to quantify because they are exposed to UVA radiation in the environment as well as during PUVA therapy. In our studies, the spectral irradiances of possible environmental sources of UVA radiation (sunlight, daylight and cool white fluorescent bulbs, and incandescent bulbs) were measured and compared to the spectral irradiance of a bank of PUVA bulbs. Sunlight and PUVA bulbs were found to have similar irradiances in the UVA waveband. Window glass reduced the UVA irradiance from sunlight. Artificial sources of illumination had a very low UVA irradiance compared with PUVA bulbs and sunlight. These results indicate that patients should protect their eyes from sunlight both outdoors and indoors after ingestion of psoralens; however, protection from incandescent bulbs or cool white and daylight fluorescent bulbs is much less important, and possibly unnecessary.     

An action spectrum for ultraviolet radiation-induced immunosuppression in humans

Background The immune‐suppressive effects of sunlight play a central role in skin carcinogenesis. Ultraviolet (UV) B radiation is highly immunosuppressive even at suberythemal doses, and longwave UVA is now also recognized to cause immunosuppression in humans. The relative contributions of UVA and UVB to immunosuppression by incidental daily sun exposure are, however, unclear. Objectives We previously determined wavelength dependencies for immunosuppression by UVB and UVA wavebands in humans. We now aimed to calculate relative and solar immune‐suppressive effectiveness across the UVB and UVA spectra. Methods We used the nickel model of recall contact hypersensitivity to determine UV immunosuppression dose responses and minimum immune suppression doses (MISDs) at 11 narrowbands from 289 to 392 nm. The relative immune‐suppressive effectiveness of each narrowband was then determined as 1/MISD vs. wavelength. This curve was multiplied by the solar spectrum to show the relative immune‐suppressive effectiveness of each waveband in sunlight. Results We found peaks of immune‐suppressive effectiveness in the UVB waveband at 300 nm and in the UVA at 370 nm. Because of the far greater amount of longwave UVA in sunlight, the relative solar immune‐suppressive effectiveness of UVA was threefold higher than that of UVB at doses equivalent to sun exposure from normal daily activities. Conclusions Longwave UVA, which abuts the visible light spectrum and is less effectively filtered by sunscreens than UVB, is likely to be the largest contributor to immunosuppression resulting from incidental daily sun exposure.     

UV transmission measurements of small skin specimens with special quartz cuvettes

BACKGROUND: The penetration of different wavelengths of UV radiation through human skin is of major importance, especially for the determination of photoprotective properties of sunscreens and UV-protective clothes. OBJECTIVE: In this study we present a new method for the measurement of UV transmission through small skin specimens. METHODS: The transmission measurements were performed by using a UV spectrophotometer with an integrating sphere operating in the wavelength range of 280-390 nm. For the skin samples, special quartz glass cuvettes were developed which allowed measurements for very thin and small skin specimens. Furthermore, the cuvettes prevented dehydration of the specimens and guaranteed, by using an additional diaphragm, that the transmission data were derived solely from the small skin specimen examined. Specimens measuring 8 x 3 mm(2) with a thickness of 0.3 mm (histometric and sonographic control) were taken from the thighs of 10 subjects via shave biopsy. RESULTS: In the UVA range (315-390 nm) we obtained a mean transmission of 4.6% and for the UVB range (280-315 nm) of 0.9%. No significant (p >0.14) difference of UV transmission was found between the individual skin specimens. CONCLUSION: This new method seems to be well suitable for UV transmission measurements of small skin specimens. As UVA radiation has a much deeper penetration depth and in in vivo situations dermal hemoglobin could have an effect on UV penetration, the present method is better suitable for the investigation of UVB-induced biological adaptation mechanisms and the impact of topical agents on UVB transmission of the epidermis.     

Broad-spectrum photoprotection: the roles of tinted auto windows, sunscreens and browning agents in the diagnosis and treatment of photosensitivity.

Since window glass absorbs sunlight below 320 nm, it provides a means of assessing sensitivity to longer wavelengths, i.e. UVA and visible radiation. Positive responses to the query of whether symptoms develop in the auto with the windows up must now be interpreted with regard to the possible presence of tinted plastic film on side and rear windows. These films block nearly all UVA radiation, as does the plastic interleaf of windshields. Thus, occupants of an auto equipped with plastic film receive photoprotection from UVB radiation and well into the UVA region. We define three classes of topical sunscreens: (1) conventional UVB screens, (2) broad-spectrum preparations containing a UVB screen and a UVA absorber and (3) browning agents such as dihydroxyacetone (DHA) that produce a skin coloration that absorbs in the low end of the visible region, with overlap into long-wavelength UVA. By considering responses of photosensitive persons in autos with tinted or untinted windows, coupled with efficacy of appropriate sunscreens, we produced an algorithm defining three photosensitivity subsets. Persons sensitive to long-wavelength UVA and/or visible radiation will benefit from tinted auto windows. In particular, patients with lupus erythematosus (LE) have actively promoted legislation allowing tinted windows. Support for their position is documented by recent reports of induction of lesions in LE patients by exposure to UVA and visible radiation. The brown color produced by DHA is a useful adjunct to the screening action of broad-spectrum sunscreens. Development of a durable color overnight allows application of the DHA preparation in the evening, thus eliminating possible interference with sunscreen use during the day.     

Mechanisms underlying UV-induced immune suppression: implications for sunscreen design

Abstract: The ultraviolet (UV) radiation present in sunlight is immune-suppressive. Recently we showed that solar-simulated UV radiation (UVA + UVB; 295–400 nm), applied after immunization, suppressed immunological memory and the elicitation of delayed-type hypersensitivity to the common opportunistic pathogen, Candida albicans . Further, we found that wavelengths in the UVA region of the solar spectrum (320–400 nm), devoid of UVB, were equally effective in activating immune suppression as UVA + UVB radiation. Here we report on the mechanisms involved. No immune suppression was found in UV-irradiated mice injected with monoclonal anti-interleukin (IL)-10 antibody, or mice exposed to solar-simulated UV radiation and injected with recombinant IL-12. Antigen-specific suppressor T cells were found in the spleens of mice exposed to UVA + UVB radiation. Applying liposomes containing bacteriophage T4N5 to the skin of mice exposed to solar-simulated UVA + UVB radiation or mice exposed to UVA radiation blocked immune suppression, demonstrating an essential role for UV-induced DNA damage in the suppression of established immune reactions. These findings indicate that UV radiation activates similar immunological pathways to suppress the induction, or the elicitation, of the immune response.     

Sunscreen protection in the ultraviolet A region: how to measure the effectiveness

Products containing ultraviolet (UV) radiation absorbing or scattering ingredients provide varying degrees of protection from sunlight (or other UV sources), thus minimizing the deleterious effects on the skin. The "sun protection factor" (SPF) of sunscreen products has become a well recognized indicator of protection against sunburn induced predominantly by ultraviolet B radiation (UVB: 290-320 nm). A similar system of denoting sunscreen protection from ultraviolet A (UVA: 320-400 nm) radiation has not been universally recognized. A variety of test methods have been proposed, both in vitro and in vivo, each with specific virtues and shortcomings. Regulatory agencies and industry have been reviewing the available methods over the past decade in an effort to develop consumer meaningful claims and appropriate substantiation methods. This article reviews these test methodologies, in vitro and in vivo, as well as the biological background that establishes the need for UVA protection, and the UVA content of solar radiation and its variability.     

DNA damage after acute exposure of mice skin to physiological doses of UVB and UVA light

Solar ultraviolet (UV) radiation is an important risk factor in skin carcinogenesis. This has been attributed mainly to the UVB waveband because the high-energetic photons are capable of interacting with DNA and inducing DNA damage. Recently, UVA light has also gained increasing interest in relation to DNA alteration. Although UVA photons are less energetic than UVB, they comprise a major fraction of sunlight UV radiation and penetrate deep into the skin. The study was carried out to compare the acute effects of UVA and UVB light on SKH-1 mice in relation to DNA damage and associated parameters. Mice were exposed to UVA (10 and 20 J/cm(2)) or UVB (200 and 800 mJ/cm(2)) radiation. The number of DNA single-strand breaks (SSB) in lymphocytes, amount of phosphorylated histone H2AX (gamma-H2AX) and apoptosis or DNA fragmentation (TUNEL-positive cells) in skin sections and level of gamma-H2AX, activated caspase-3 and phosphorylated p53 in skin were evaluated after 4 and 24 h. SSB analyzed by alkaline comet assay were found to be 4 and 24 h following UVB and UVA treatment, respectively. TUNEL and gamma-H2AX-positive cell were observed only in UVB exposed animals at both time intervals. The level of activated caspase-3 and phospho-p53 was increased 24 h after UVA and UVB radiation and was more apparent in UVB treated mice. The results indicate that the mechanism of DNA damage caused by acute UVA exposure includes formation of SSB (oxidative damage), but not double-strand breaks.     

Azathioprine treatment photosensitizes human skin to ultraviolet A radiation

Background  Azathioprine is used to treat a variety of conditions and to prevent graft rejection in organ transplant recipients (OTRs).
Objectives  To investigate clinically our previous finding that azathioprine metabolites interact with ultraviolet (UV) A radiation to form promutagenic oxidative DNA damage and to determine whether this may be causal or contributory to the development of excess skin cancers post-transplantation.
Methods  The clinical corollary of these data were investigated. Five patients were recruited and the minimal erythema dose (MED) for UVB, UVA and solar-simulated radiation (SSR) was determined for each person before, and at least 12 weeks after, starting azathioprine therapy.
Results  In all five patients azathioprine treatment was associated with an increased UVA and SSR sensitivity of the skin and a significant reduction in MEDs for UVA and SSR. We found no change in UVB-induced erythema or MED. In addition, we found that DNA from the skin of patients on azathioprine contains 6-thioguanine (6-TG).
Conclusions  Our findings confirm the presence of DNA 6-TG in the skin of those taking therapeutic doses of azathioprine and provide support for the hypothesis that DNA damage occurs when DNA 6-TG interacts with UVA, resulting in abnormal cutaneous photosensitivity.     

Ultraviolet A transmission by modern sunscreens: is there a real risk?

In recent years it has been realized that ultraviolet A (UVA) is capable of inducing many of the same deleterious events as UVB. In addition to erythema, UVA can cause connective tissue damage and is photocarcinogenic. Recently, concern has arisen that new, higher potency sunscreens allow dangerous amount of UVA to reach the skin, because they allow prolonged outdoor exposure. Such concerns are unfounded. The problem lies in a misunderstanding of the concept of sunlight protection factor. This is purely a multiplication factor and does not indicate that the effect of transmitted UVR is due to UVA or UVB. Action spectra show that UVA is less, but certainly not more injurious to skin than UVB. There is no reason to believe that higher potency sunscreens enhance exposure to dangerous amounts of UVA.     

Installation of solarium--2000 for phototherapy

Sunlight is the cheapest and most easily available source of ultraviolet light for phototherapy. The disadvantage of using sunlight as the source of ultraviolet light includes its variation with time , place and season, lack of privacy, and atmospheric conditions. To ensure correct dose of UV light in spite of variation in irradiation from the sunlight,we used a PMA2100 meter [Figure:2] and 2110 UVA detector ( Solar light Co, Philadelphia). Privacy for the patients was achieved by erecting a solarium and incidental UVB radiation was cut off by using window glass as the roof of the solarium. We recommend the solarium as a less expensive alternative to artificial phototherapy units, especially in places where there is plenty of sunlight.     

Reusable ultraviolet monitors: design, characteristics, and efficacy

Reusable ultraviolet dosimetry badges have been developed that provide a visual indication of daily cumulative ultraviolet (UV) exposure. These two-sided, tapelike devices measure UV radiation emitted by sunlight or an artificial UV light source exposure by means of a photochromic aziridine color change reaction that is UV-integrating but optically reversible. UV radiation falling on the exposure side of the badge generates a color change that can be seen from the opposite or readout side. End points are indicated by a visual match of the photochromic with a surrounding reference. This paper describes the construction, component characteristics, and clinical testing of two versions of a new photochromic dosimeter that selectively responds to either UVB (280-320 nm) radiation or UVA (320-400 nm) radiation of the solar spectrum. One version of this monitor, sensitive only to the mid-range UVB, has a peak sensitivity to 300 nm and has four end point markers revealing color changes corresponding to 0.4, 0.8, 2.2, and 6.5 times the minimal erythema dose of an average Caucasian. A second version, sensitive only to UVA, has a peak sensitivity at 355 nm and can monitor exposures ranging from 0.8 to 10 joules/cm2. Outdoor efficacy testing has shown that the UVB monitor is an effective predictor of UV dose-related 24-hour erythema response induced by sunlight. Following a measurement, these monitors can be rezeroed by exposing the readout side to sunlight for a few minutes. They can be reused for eight to ten times. The limitation of the sunlight-calibrated UVB monitor tag is its failure to predict erythema response produced by artificial UVB sources such as FS40 sunlamps.     

The contributions of UVA and UVB to connective tissue damage in hairless mice

UVA, in high-dose single exposures, can, like UVB, be deleterious to skin. Dermal damage resulting from chronic exposure to UVA has not been studied. To investigate the long-term effects, we irradiated albino hairless mice for 30-34 weeks with UVA radiation, alone, from two sources with differing spectral qualities, and in combination with UVB as solar-simulating radiation. The results were compared to UVB alone. Like UVB, the UVA waveband, especially that with a spectral distribution similar to solar UVA, caused elastic fiber damage, increased glycosaminoglycan levels, and produced hypertrophy of deep dermal tissues. There were, however, striking differences between UVB- and UVA-irradiated skin. A combination of UVA and UVB summated the effects of both wavebands. Substantial protection against these effects was afforded by a broad-spectrum sunscreen.     

The carcinogenic effect of UVA irradiation

The carcinogenic effect of UVA radiation (from Philips black light tubes filtered through a 2 mm-thick glass plate to eliminate the radiation below 320 nm) was studied in 7 groups of 25 lightly pigmented hairless mice. Irradiation with a moderate daily dose of combined UVB and UVA for 3 months induced a tumor incidence of 0.22 after 58 weeks. When the combined UVB and UVA irradiation was followed by filtered UVA for 2, 4, or 6 months, the tumor incidence was marginally significantly increased to 0.42, 0.48, and 0.50 (p less than 0.05), respectively. However, irradiation with the moderate dose of combined UVB and UVA induced a slight but not significantly lower tumor incidence as compared to UVB alone (0.22 vs 0.30, p greater than 0.1). UVA alone induced no tumors. It thus appears that in hairless mice initially exposed to a combination of UVB and UVA, subsequent continued irradiation with UVA increases tumor incidence. While only marginally statistically significant, tumor incidence in these animals seems to increase with duration and hence total UVA exposure. Furthermore, it is suggested that the photoaugmentative carcinogenic effect of UVA irradiation from unfiltered UVA bulbs can be reduced by attenuating the shorter wavelengths of the radiation.     

Prevention of ultraviolet-induced skin pigmentation

BACKGROUND/PURPOSE: Exposure to ultraviolet (UV) radiation increases skin pigmentation and usually results in an even darkening of the skin. However, it may also occasionally lead to the development of hyperpigmented lesions due to a local overproduction of pigment. Skin pigmentation is induced both by UVB and UVA rays. METHODS: The in vivo protection by sunscreens against pigmentation was studied using the determination of a level of protection against pigmentation based on the standardized sun protection factor (SPF) test method. The method includes delayed UVB and UVA pigmentations. The level of prevention against pigmentation was determined 7 days after exposure to solar-simulated radiation by visual assessment. It was calculated using the ratio of the minimal pigmenting dose on protected skin to the minimal pigmenting dose on unprotected skin. Broadspectrum UVB/UVA filters, Mexoryl SX and Mexoryl XL, and complete formula were tested. RESULTS: Protection against pigmentation correlates with the concentration of Mexoryl SX. The levels of protection obtained show a synergetic effect of Mexoryl SX when associated with Mexoryl XL. When different products having the same SPF (same protection against erythema) and different levels of UVA protection are compared, only sunscreen products with a high level of UVA protection show a similar level of protection against sunburn and pigmentation. Products with low UVA protection have a lower capacity of preventing induced pigmentation compared with their efficacy against erythema. CONCLUSIONS: These studies have evidenced that SPF determination was not sufficient to account for the efficiency in preventing pigmentation and that UVA protection was an essential part of this prevention.     

Lack of photoprotection against UVB-induced erythema by immediate pigmentation induced by 382 nm radiation

Immediate pigment darkening (IPD) was induced on the backs of 11 human volunteers of skin types III and IV by exposing the skin to UVA radiation (382 nm). The minimum erythema dose (MED) of UVB radiation was also determined by exposing sites to graduated doses of 304 nm radiation. The order of exposure of distinct anatomic areas was as follow: UVB followed by IPD induction; IPD induction followed by UVB; IPD induction followed 3 h later by UVB; and UVB only. Erythema responses induced by UVB were graded by inspection 24 h later and the MEDs in the 4 areas were compared. The induction of IPD before UVB exposure caused no significant change in the MED compared to sites receiving UVB only, or receiving UVA radiation after UVB, confirming that the IPD reaction does not protect against UVB-induced erythema. There was also no evidence of photorecovery, i.e., an increase in the MED of UVB resulting from exposure to longer wavelength, UV or visible radiation following UVB exposure.