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PubMed1994

Comparative efficacy of sunscreen reapplication regimens in children exposed to ambient sunlight.

Undercompliance with sunscreen reapplication recommendations is a probable factor in suboptimal childhood ultraviolet radiation (UVR) protection. However, improving on the ability of sunscreens to absorb UVR without requiring frequent reapplication is difficult because the models most frequently used to develop and evaluate photoprotectants have only a limited ability to incorporate behavioral and environmental variables that are primarily responsible for loss of sunscreen efficacy. Hence, the objective of the present work was to develop a method to evaluate the efficacy of various regimens of sunscreen reapplication in children, under conditions of unrestricted behavior and exposure to ambient sunlight. Ninety-eight children, ages 7-12, Fitzpatrick skin types I-III, were divided between two study groups. The majority were types I-II, and all types were approximately equally represented between the groups. The children received single or multiple applications of a sun protection factor 25 sunscreen to preassigned lateral halves of the body and engaged in unrestricted activities throughout a 6- (group I) or 8-h (group II) period of sun exposure at a seaside location. The end measurement for these studies was incidence and severity of erythema 18 to 22 h after peak UV exposure. The results obtained showed that 1 or 4 sunscreen applications yielded comparable erythema protection after a 6-hour sun exposure, totaling 13 minimal erythema doses (MED). However, after an 8-h, 21 MED exposure, incidence and severity of erythema was greater at body sites treated with 1 compared with 5 sunscreen applications.(ABSTRACT TRUNCATED AT 250 WORDS)

Acrylates↗
PubMed1994

The role of sunlight and DNA repair in melanoma and nonmelanoma skin cancer. The xeroderma pigmentosum paradigm.

BACKGROUND AND DESIGN: The frequency of melanoma and nonmelanoma skin cancer is increasing rapidly in the United States. However, the linkage of these cancers to sun exposure has been questioned because of differences in anatomic site distribution. To obtain insights into the development of these skin cancers, we examined reports of 132 patients with xeroderma pigmentosum (XP), an inherited cancer-prone, DNA repair-deficient disorder with marked clinical and laboratory UV hypersensitivity. RESULTS: Malignant skin neoplasms were present in 70% of the patients with XP at a median age of 8 years, which is 50 years earlier than in the US white population. Fifty-seven percent of the patients had basal cell or squamous cell carcinoma, and 22% had melanoma. The frequency of melanomas, like the frequency of nonmelanoma skin cancers (basal cell and squamous cell carcinomas), anterior eye cancers, and tongue cancers, but unlike that of internal neoplasms, was increased 1000-fold or more in patients with XP who were younger than 20 years. As in the general population, the anatomic distribution of melanomas was different from that of nonmelanomas in the patients with XP. CONCLUSIONS: These data suggest that (1) DNA repair plays a major role in the prevention of cutaneous cancers in the general population and (2) sunlight exposure is responsible for the induction of melanoma as well as nonmelanoma skin cancer in patients with XP, although acting by different mechanisms for the two types of skin cancer.

Adolescent↗
PubMed1977

[Effect of sunlight penetration on the development of phototrophic sulfur bacteria in marine environment].

Bottles of medium were inoculated with both strains of Chromatiacea and Chlorobiaceae (mixed cultures) and immersed at differnt depths in the marine coastal waters of the Marseilles basin (France). After development, the in vivo absorption characteristics of the cells show the effect of the daylight penetration on the selective growth of photorophic sulfur bacteria. With depth, sunlight selects Chlorobiaceae rich in brown carotenoid pigments to the detriment of Chromatiaceae.

Bacteria↗
PubMed1977

PUVA: using filtered sunlight as an energy source.

In this preliminary report, twenty-two of twenty-three patients with psoriasis had satisfactory clearing with 8-MOP and natural sunlight given through a Mylar screen. The long-term effects and side effects are not known. Whether this program will provide sufficiently lengthy remissions for summer use in less sunny climates is not, as yet, known.

Adolescent↗
PubMedDate not supplied

Sunlight: an environmental toxin for humans. A primer to advise patients.

Sunlight causes acute toxic effects such as sunburn, local and systemic immune suppression, and long-term adverse effects including photoaging and skin cancer. The degree of damage depends on the overall exposure-dose and individual susceptibility. Various strategies should be employed to minimize sun-exposure damage, including proper use of sunscreens and exposure avoidance. Public education might best be focused on protecting children and promoting awareness of photoaging changes in adults.

Adult↗
PubMed1997

The prevalence of seborrhoeic keratoses in an Australian population: does exposure to sunlight play a part in their frequency?

Although seborrhoeic keratoses (SKs) appear to be very common, there are very few studies reporting details of age-specific prevalence, distribution or possible cause. We report details on the frequency, nature and distribution of SKs in 100 Australian adults in the age groups 15-25, 26-50, 51-75 and those aged more than 75 years. There was an increase in prevalence of SKs from 12% of 15-25 year olds to 100% of those aged more than 50 years. The median number of lesions in those with them also increased with age from six per person in 15-25 year olds to 69 per person in those aged more than 75 years. There was no difference in prevalence or numbers of lesions/person between males and females. SKs on exposed areas were more often flat and more than 3 mm in diameter than those on the non-exposed areas. There was a higher prevalence of SKs on the exposed areas than non-exposed areas when taking into account the surface area. The data in this study demonstrate an increased frequency of SKs compared with those reported from the United Kingdom recently and from Australasia in the past, a phenomenon paralleling the changing frequency of skin cancer in these populations. This fact, plus the finding that SKs were more common as a function of skin surface area on the exposed areas of the body, suggests that sunlight may play a part in their development in those people who are predisposed to develop them.

Adolescent↗
PubMed1999

The multilayered organization of engineered human skin does not influence the formation of sunlight-induced cyclobutane pyrimidine dimers in cellular DNA.

Solar UVB initiates skin cancer mainly by generating highly premutagenic cyclobutane pyrimidine dimers (CPDs) and subsequent mutations in critical growth control genes. It is universally presumed that the upper epidermis in human skin blocks a significant portion of the incident UVB, thereby protecting the cancer-prone basal layer from CPD formation. Using two sensitive techniques for measuring CPD in cellular DNA, we confirmed that the multilayered organization of engineered human skin efficiently shields the basal layer against 254-nm UVC (which is not present in terrestrial sunlight) but, very unexpectedly, provides virtually no protection against environmentally relevant UVB. This underscores the importance of regular sunscreen use, which, in light of our data, may constitute a considerably more important first line of defense against photocarcinogenesis than previously believed.

Biomedical Engineering↗
PubMed1989

Exposure to sunlight and other risk factors for age-related macular degeneration.

As some ultraviolet (UV) radiation is transmitted by the ocular media, there is a growing concern that there may be a possible relationship between long-term exposure to ultraviolet radiation and increased risk of age-related macular degeneration. To address this question, a survey was conducted of 838 Maryland watermen who had well-characterized ocular UV-A and UV-B exposure. Fundus photographs were taken and graded for presence of exudative disease, geographic atrophy, focal hyperpigmentation of the retinal pigment epithelium, and drusen that were large and/or confluent. None of the subjects in these analyses were aphakic. The results suggested that age-related macular degeneration was not associated with cumulative exposure to either UV-A or UV-B. Age and the presence of nuclear opacity were independently associated with an increased risk of macular degeneration. Thus, we found that in phakic subjects, even with high levels of sunlight exposure, there was no evidence of increased risk of age-related macular degeneration associated with UV-B or UV-A exposure.

Adult↗
PubMed1999

A hypothesis concerning deficiency of sunlight, cold temperature, and influenza epidemics associated with the onset of acute lymphoblastic leukemia in northern Finland.

Research to detect new factors contributing to the etiology of acute leukemia (AL) is urgently needed. Located between latitudes 65 degrees and 70 degrees north, the population in northern Finland is exposed to extreme seasonal alterations of ultraviolet-B light and temperature. There is also a seasonal variation of both the 25(OH)- and 1,25(OH)2-D3 vitamin serum concentrations. In the present work, the frequencies of different types and age-groups at diagnosis of AL were compared during the dark and light months of the year, to uncover seasonality. Between January 1972 and December 1986, 300 consecutive patients aged >/=16 years and diagnosed as having AL were enrolled. The observed mean monthly global solar radiation, temperature measurements, and influenza epidemics were compared with the monthly occurrence of AL. Both acute lymphoblastic leukemia (ALL) (p=0.006) and total AL (p=0.015) were diagnosed excessively in the dark and cold compared with light and warm period of the year. There was a tendency for de novo leukemia to increase also in the dark and cold, but for acute myeloid leukemia (AML) patients the excess was not significant. Age >/=65 was strongly associated with the dark and cold season (p=0.003). Significantly more ALL (p=0.005) and de novo leukemias (p=0.029) were observed during influenza epidemics than during nonepidemic periods. However, a seasonality, i. e., the fluctuation of numbers of AL cases, was not determined, either monthly or during different photo- and temperature periods or influenza epidemics; this might be due to the small numbers of patients studied. Nevertheless, it is hypothesized that sunlight deprivation in the arctic winter can lead to a deficiency of the 1, 25(OH)2D3 vitamin, which might stimulate leukemic cell proliferation and block cell differentiation through dysregulation of growth factors in the bone marrow stromal cells, causing one mutation and an overt ALL in progenitor cells damaged during the current or the previous winter by influenza virus, the other mutation.

Acute Disease↗
PubMed2005

Quantitative structure-property relationships on photolysis of PCDD/Fs adsorbed to spruce (Picea abies (L.) Karst.) needle surfaces under sunlight irradiation.

By partial least squares (PLS) regression, quantitative structure-property relationship (QSPR) models were developed for photolysis half-life (t1/2) of PCDD/Fs and PAHs sorbed to spruce (Picea abies (L.) Karst.) needle surfaces and irradiated by sunlight. Quantum chemical descriptors computed by PM3 Hamiltonian were used predictor variables. PLS analysis for the PCDDs and PAHs respectively resulted in no correlation by our statistical methods. The cross-validated Qcum2 value for the optimal QSPR model of PCDFs is 0.722, indicating a good predictive ability for logt1/2 of PCDFs adsorbed to spruce needle surfaces. The QSPR results show that the number of chlorine atoms bonded to the parent structure and (E(LUMO)-E(HOMO))2 has a dominant effect on t1/2 values of PCDFs. Increasing the number of chlorine atoms and (E(LUMO)-E(HOMO))2 values leads to increase of logt1/2 values of PCDFs.

Adsorption↗
PubMed2005

Engineering of a novel ruthenium sensitizer and its application in dye-sensitized solar cells for conversion of sunlight into electricity.

A novel ligand 4,4'-bis(carboxyvinyl)-2,2'-bipyridine (L) and its ruthenium(II) complex [Ru(II)L(2)(NCS)(2)] (K8) were synthesized and characterized by analytical, spectroscopic, and electrochemical techniques. The performance of the K8 complex as a charge transfer photosensitizer in nanocrystalline TiO(2) based solar cells was studied. When the K8 complex anchored onto a nanocrystalline TiO(2) film, we achieved very efficient sensitization yielding 77 +/-5% incident photon-to-current efficiencies (IPCE) in the visible region using an electrolyte consisting of 0.6 M methyl-N-butyl imidiazolium iodide, 0.05 M iodine, 0.05 M LiI, and 0.5 M 4-tert-butylpyridine in a 50/50 (v/v) mixture of valeronitrile and acetonitrile. Under standard AM 1.5 sunlight, the complex K8 gave a short circuit photocurrent density of 18 +/- 0.5 mA/cm(2), and the open circuit voltage was 640 +/- 50 mV with fill factor of 0.75 +/- 0.05, corresponding to an overall conversion efficiency of 8.64 +/- 0.5%.

Journal Article↗
PubMed2006

Translucent thin film Fe2O3 photoanodes for efficient water splitting by sunlight: nanostructure-directing effect of Si-doping.

Thin, silicon-doped nanocrystalline alpha-Fe2O3 films have been deposited on F-doped SnO2 substrates by ultrasonic spray pyrolysis and chemical vapor deposition at atmospheric pressure. The photocatalytic activity of these films with regard to photoelectrochemical water oxidation was measured at pH 13.6 under simulated AM 1.5 global sunlight. The photoanodes prepared by USP and APCVD gave 1.17 and 1.45 mA/cm2, respectively, at 1.23 V vs RHE. The morphology of the alpha-Fe2O3 was strongly influenced by the silicon doping, decreasing the feature size of the mesoscopic film. The silicon-doped alpha-Fe2O3 nano-leaflets show a preferred orientation with the (001) basal plane normal to the substrate. The best performing photoanode would yield a solar-to-chemical conversion efficiency of 2.1% in a tandem device using two dye-sensitized solar cells in series.

Journal Article↗
PubMed1990

Potent genotoxicity of halogen lamps, compared to fluorescent light and sunlight.

The light emitted by halogen lamps induced mutations in Salmonella typhimurium and DNA damage in Escherichia coli, as shown by the hypersensitivity of DNA repair-deficient strains. The mutagenicity of halogen lamps was considerably higher than that of fluorescent light and of sunlight, even at much lower illuminance levels. Excision mechanisms and SOS functions were involved in repairing light-induced base-pair substitutions and frameshift errors in bacterial DNA. At variance with solar irradiation, which produces mutagenic effects over a wide UV spectrum, genotoxicity of halogen lamps was almost exclusively due to far-UV wavelengths transmissible through UV-R-250 and UV-R-280 interference filters. The main mutagenic component of fluorescent light (254 nm) were almost 10(4)-fold more mutagenic than near-UV wavelengths (365 nm). All light sources exhibited some residual mutagenicity even following filtration through various cloths. On the other hand, appropriate glass or plastic covers consistently prevented mutagenic effects. This emphasizes the urgent need for a compulsory shielding of halogen and fluorescent lamps in order to prevent unnecessary exposures to genotoxic and potentially carcinogenic UV radiations.

DNA Damage↗
PubMed1983

Aggressive basal cell epithelioma on sunlight-protected skin. Report of eight cases, one with pulmonary and bone metastases.

This report concerns a series of eight patients with large basal cell epitheliomas that occurred on sunlight-protected areas of the trunk. Histologically, the neoplasms exhibited highly "invasive" features and were complicated by recurrences. Five years after removal of one of the neoplasms by surgical excision, regional lymphatic metastasis occurred. This was followed by distant metastases to the lung and pelvic bone.

Adult↗
PubMed2006

Up-conversion fluorescence: noncoherent excitation by sunlight.

We demonstrate up-conversion of noncoherent sunlight realized by ultralow excitation intensity. The bimolecular up-conversion process in our systems relies on the presence of a metastable triplet excited state, and thus has dramatically different photophysical characteristics relative to the other known methods for photon up-conversion (two-photon absorption, parametric processes, second harmonic generation, sequential multiphoton absorption, etc.).

Journal Article↗
PubMed1988

UV sunlight and patch test reactions in humans.

No seasonal influence of UV sunlight on patch test reactions in humans over a period of 9 years of clinical practice was found in this retrospective study of almost 8000 patients. Although the mean UV monthly dose varies seasonally, up in the summer and down in the winter, no significant differences could be identified for patch test reactions, either for the mean number of positive test reactions or for the intensity of the skin reaction or for the id-like spread reactions seen in summer or winter. Furthermore, no short-term influences of UV exposure during the weekend preceding patch testing could be demonstrated. Therefore, reliable patch-test results can be expected at any season of the year from a general population, at least in Belgian-type climates.

Belgium↗
PubMed1982

Spectral character of sunlight modulates photosynthesis of previtamin D3 and its photoisomers in human skin.

The photosynthesis of previtamin D3 from 7-dehydrocholesterol in human skin was determined after exposure to narrow-band radiation or simulated solar radiation. The optimum wavelengths for the production of previtamin D3 were determined to be between 295 and 300 nanometers. When human skin was exposed to 295-nanometer radiation, up to 65 percent of the original 7-dehydrocholesterol content was converted to previtamin D3. In comparison, when adjacent skin was exposed to simulated solar radiation, the maximum formation of previtamin D3 was about 20 percent. Major differences in the formation of lumisterol3, and tachysterol3 from previtamin D3 were also observed. It is concluded that the spectral character of natural sunlight has a profound effect on the photochemistry of 7-dehydrocholesterol in human skin.

Cholecalciferol↗