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PubMed1993

Degradation of methyl and ethyl mercury by singlet oxygen generated from sea water exposed to sunlight or ultraviolet light.

Photodegradation of methyl mercury (MeHg) and ethyl Hg (EtHg) in sea water was studied by sunlight or ultraviolet (UV) light exposure, and by determining inorganic Hg produced by degradation. Sea water containing 1 microM MeHg or EtHg was exposed to sunlight or UV light. N-Acetyl-L-cysteine was added to the solution for preventing Hg loss during the light exposure. MeHg and EtHg in sea water were degraded by sunlight (> 280 nm), UV light A (320-400 nm) and UV light B (280-320 nm), though the amounts of inorganic Hg produced from MeHg were 1/6th to 1/12th those from EtHg. Inorganic Hg production was greater with increasing concentration of sea water. Degradation of MeHg and EtHg by the UV light A exposure was inhibited by singlet oxygen (1O2) trappers such as NaN3, 1,4-diazabicyclo[2,2,2]octane, histidine, methionine and 2,5-dimethylfuran. On the other hand, inhibitors or scavengers of superoxide anion, hydrogen peroxide or hydroxyl radical did not inhibit the photodegradation of alkyl Hg. These results suggested that 1O2 generated from sea water exposed to sunlight, UV light A or UV light B was the reactive oxygen species mainly responsible for the degradation of MeHg and EtHg.

Ethylmercury Compounds↗
PubMed2001

The rpoS gene in Pseudomonas syringae is important in surviving exposure to the near-UV in sunlight.

The near-UV component of sunlight decreased culturability of the leaf epiphyte and plant pathogen Pseudomonas syringae. Exposure of the wild-type cells for 4 h to UV-A and UV-B in sunlight was ten fold more detrimental than exposure to sunlight with just UV-A. Sensitivity to UV-A especially increased in a mutant of P. syringae lacking the global regulatory sigma factor, RpoS. No RpoS-mutant cells were culturable after 4 h of exposure to near-UV sunlight. These findings suggest that both UV-A and UV-B wavelengths cause damage to the bacterial cell and that the RpoS protein regulates protective measures for the leaf-associated pseudomonad.

Bacterial Proteins↗
PubMed1979

Relative effectiveness of the 300--320 NM spectral region on sunlight for the production of primary lethal damage in E. coli cells.

Cell inactivation by sunlight exposure has been studied in E. coli CSR 603 (uvrA recA phr), a K12 derivative which is deficient in all known repair systems. Under suitable conditions, unfiltered sunlight inactivates these cells to 10(-3) survival within 30 sec. The effects of unfiltered sunlight have been compared with those of sunlight filtered through 1-cm layers of aqueous caffeine solutions ranging in concentration from 1 to 20 mg/ml. In the wavelength region of solar emission below 320 nm, which is most critical for DNA damage, the transmission of these liquid filters changes from 10 to 90% within 8-nm intervals. Thus our results permit minimum estimates for the fraction of lethal lesions produced by the solar spectrum below certain wavelenghts. In an experiment analyzed in this manner more than 80% of primary lethal lesions are caused by wavelengths less than 321 nm, and more than 50% by wavelengths less than 306 nm, while the contribution of wavelengths greater than 380 nm to primary lethal damage is below 1%.

DNA Repair↗
PubMed1990

Natural summer and winter sunlight exposure patterns in seasonal affective disorder.

Twelve subjects with winter depression who lived in the Chicago area recorded their times of going outside during daylight hours for one week during the winter and one week during the summer. These records produced estimates of the duration of daily sunlight exposure and of perceived dawn, dusk and skeleton photoperiod. There was more than twice as much sunlight exposure in summer compared to winter (3.0 vs. 1.2 h/day). The perceived skeleton photoperiod was 4-5 h longer in summer than winter, with a later perceived dusk contributing more to the lengthening than an earlier perceived dawn. The duration of sunlight exposure and perceived skeleton photoperiod in both seasons was much less than what was possible given the available daylight. These results are discussed with reference to the modern urban life style, bright light treatment of winter seasonal affective disorder, and factors which affect the perceived intensity of sunlight.

Adult↗
PubMed1995

An addition to the controversy on sunlight exposure and melanoma risk: a meta-analytical approach.

Case control studies on the association between sunlight exposure and melanoma risk show considerable differences in design; this could be responsible for the variation in study results. In an attempt to resolve the controversy between study results, the results of 25 publications on case control studies were evaluated using meta-analytical techniques. Comparison of odds ratios between subgroups of studies revealed that the range of odds ratios was far greater for hospital-based studies than for population-based studies. For the latter type of studies, the odds ratios were homogeneous and the pooled odds ratios were 1.57 (95% confidence interval [CI], 1.29-1.91) for intermittent sunlight exposure and 0.73 (95% CI, 0.60-0.89) for chronic exposure. However, among other problems, the lack of standardized measures for sunlight exposure warrants cautious interpretation of these results. It is concluded that evidence to support the intermittent sunlight theory is still far from complete.

Case-Control Studies↗
PubMed2003

DNA damage by ethylbenzenehydroperoxide formed from carcinogenic ethylbenzene by sunlight irradiation.

Ethylbenzene, widely used in human life, is a non-mutagenic carcinogen. Sunlight-irradiated ethylbenzene caused DNA damage in the presence of Cu2+, but unirradiated ethylbenzene did not. A Cu+ -specific chelator bathocuproine inhibited DNA damage and catalase showed a little inhibitory effect. The scopoletin assay revealed that peroxides and H(2)O(2) were formed in ethylbenzene exposed to sunlight. These results suggest that Cu+ and alkoxyl radical mainly participate in DNA damage, and H(2)O(2) partially does. When catalase was added, DNA damage at thymine and cytosine was inhibited. Ethylbenzenehydroperoxide, identified by GC/MS analysis, induced the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine and caused DNA damage at consecutive guanines, as observed with cumenehydroperoxide. Equimolar concentrations of H(2)O(2) and acetophenone were produced by the sunlight-irradiation of 1-phenylethanol, a further degraded product of ethylbenzene. These results indicate a novel pathway that oxidative DNA damage induced by the peroxide and H(2)O(2) derived from sunlight-irradiated ethylbenzene may lead to expression of the carcinogenicity.

Animals↗
PubMed1997

Exposure of organic extracts of air particulates to sunlight leads to metabolic activation independence for mutagenicity.

Air particulates were collected on Whatman, GFA glass fibre filters using a RADECO constant-flow air sampler from a car-parking basement and an open roadside adjacent to the basement. While the basement was not exposed to sunlight, the roadside from where air samples were collected was exposed to regular daylight in the month of July (peak summer month). The filters were soaked and sonicated in acetone to dislodge the particulates and then a residue was obtained after evaporation of acetone. The residues were either held in dark or exposed to natural sunlight or germicidal UV light before being tested for mutagenicity using the Salmonella tester strain TA98 with and without metabolic activation (S9 mix). The results showed that the addition of S9 mix resulted in only a slight increase in the frequency of histidine revertants/plate in the case of daylight-exposed roadside air samples. On the other hand, a considerable increase in mutagenicity was observed in the case of the basement air samples, particularly at higher concentrations of the organic extracts when S9 mix was added. However, a pre-exposure of the organic extract of air from the basement to sunlight abrogated the need for S9 mix for showing mutagenic activity. A pre-exposure of the same extracts to germicidal UV light failed to produce a similar effect. These results suggested that long wavelengths of natural sunlight could be responsible for the conversion of certain promutagens in air particulates into direct-acting mutagens. The environmental impact of solar radiation as a modifier of air particulate mutagens in high-sun countries like Saudi Arabia needs to be carefully considered for assessment of air pollution-related health risks.

Air Pollutants↗
PubMedDate not supplied

Phototoxicity of quinalphos under sunlight in vitro and in vivo.

The phototoxicity of quinalphos (QP) under sunlight was studied by investigating skin sensitization, mouse tail and ear swelling tests and generation of activated oxygen species (AOS). Quinalphos, at an oral dose of 5 mg/kg to the mouse, did not produce any change in water content of the tail, but produced ear swelling under sunlight (60 min). The pesticide did not produce any skin sensitization reaction when applied on depilated skin of guinea pigs (100-500 microg/cm2) and irradiated under sunlight (60 min). Furthermore, the compound produced a significant amount of AOS such as singlet oxygen (1(O2)) and superoxide anion radical (O2- under sunlight. The production of AOS was both concentration (1-20 microg/ml) and irradiation time (0-40 min)-dependent. The generation of AOS was also confirmed by using quenchers of singlet oxygen (sodium azide and DABCO) and superoxide anion radical (SOD).

Administration, Cutaneous↗
PubMed1997

Sunlight and cancer.

Epidemiologic evidence on the relation between sunlight and cancer is reviewed. Strong evidence implicates sunlight as a cause of skin cancer, although, for melanoma and basal cell carcinoma, the relationship is complex. Both types of cancer are associated more strongly with nonoccupational exposure than with occupational exposure, and the pattern and amount of exposure each appear to be important. Squamous cell carcinoma appears to be related more strongly to total (i.e., both occupational and nonoccupational) exposure to the sun. The evidence that sunlight causes melanoma of the eye is weak. It shows no latitude gradient and the results of case-control studies are conflicting. There is inadequate evidence to suggest that sunlight does or does not cause any other type of cancer.

Australia↗
PubMed2003

Seborrheic keratosis in the Korean males: causative role of sunlight.

BACKGROUND/PURPOSE: Seborrheic keratoses (SKs) are common epidermal tumors in the white population over 40 years. The etiology of SKs is not well known; however, exposure to sunlight was suggested to play a role in the development of them. To our knowledge, no well-designed study has been undertaken in order to investigate the clinical characteristics of SKs in a brown-skinned Korean population. The aim of this study was to assess the prevalence and clinical features of SKs in the Korean males and to investigate the possible relationship of SKs with sun exposure and possible risk factors of developing SKs. METHODS: A total of consecutive 303 male volunteers, aged 40-70 years, were recruited from general community and public health centres. Each volunteer was interviewed regarding demographic data, sunlight sensitivity, lifetime cumulative sun exposure and smoking history. Skin examination was performed except for scalp, buttocks and genitals. All SKs were recorded about the anatomical distribution, the size of each lesion measured with a caliber, color and morphology. RESULTS: The mean overall prevalence of SKs in the Korean males, aged 40-70 years was 88.1%. A considerable increase in the prevalence of SKs was shown from 78.9% at 40 years to 93.9% at 50 years and 98.7% in those over 60 years. The mean number of lesions per person was 5.5 at 40 years, 9.2 at 50 years and 13.4 at 60 years. Seborrheic keratoses were considerably more frequent on exposed areas (0.47 +/- 0.06/percentage of body surface area, BSA) than partly exposed areas (0.04 +/- 0.01/percentage of BSA). The majority of lesions were concentrated on the face (0.98 +/- 0.09/percentage of BSA) and on the dorsum of each hand (0.51 +/- 0.08/percentage of BSA). The size of each lesion on exposed areas also became significantly larger by decade significantly (P < 0.01). The estimated area covered by SKs per percentage of BSA on exposed areas was 5.7-fold larger than that on partly exposed areas at 40 years, 11.2-fold larger at 50 years and 18.3-fold larger at 60 years. Aging by decade showed a 2.08-fold increased risk for SKs (n > or = 6) (95% CI, 1.07-4.08) at 50 years and a 3.47-fold risk (95% CI, 1.67-7.20) at 60 years on exposed areas compared with the 40-year age group, for developing many SKs (n > or = 6). Lifetime cumulative sunlight exposure of more than 6 h per day was associated with a 2.28-fold higher risk of SKs than a sun exposure of less than 3 h per day. A tendency for an odds ratio value reduction was found on increasing Fitzpatrick skin types I-III to VI, V; however, this was without statistical significance. CONCLUSIONS: Seborrheic keratoses are common in the Korean males, aged 40-70 years, and may be a major pigmentary problem. Both aging and cumulative sunlight exposure were found to be independent contributory factors.

Adult↗
PubMedDate not supplied

Occupational sunlight exposure and melanoma in the U.S. Navy.

Melanoma is the second most common cancer, after testicular cancer, in males in the U.S. Navy. A wide range of occupations with varying exposures to sunlight and other possible etiologic agents are present in the Navy. Person-years at risk and cases of malignant melanoma were ascertained using computerized service history and inpatient hospitalization files maintained at the Naval Health Research Center. A total of 176 confirmed cases of melanoma were identified in active-duty white male enlisted Navy personnel during 1974-1984. Risk of melanoma was determined for individual occupations and for occupations grouped by review of job descriptions into three categories of sunlight exposure: (1) indoor, (2) outdoor, or (3) indoor and outdoor. Compared with the U.S. civilian population, personnel in indoor occupations had a higher age-adjusted incidence rate of melanoma, i.e., 10.6 per 100,000 (p = .06). Persons who worked in occupations that required spending time both indoors and outdoors had the lowest rate, i.e., 7.0 per 100,000 (p = .06). Incidence rates of melanoma were higher on the trunk than on the more commonly sunlight-exposed head and arms. Two single occupations were found to have elevated rates of melanoma: (1) aircrew survival equipmentman, SIR = 6.8 (p less than .05); and (2) engineman, SIR = 2.8 (p less than .05). However, there were no cases of melanoma or no excess risk in occupations with similar job descriptions. Findings on the anatomical site of melanoma from this study suggest a protective role for brief, regular exposure to sunlight and fit with recent laboratory studies that have shown vitamin D to suppress growth of malignant melanoma cells in tissue culture. A mechanism is proposed in which vitamin D inhibits previously initiated melanomas from becoming clinically apparent.

Adolescent↗
PubMed2002

Mutation, DNA strand cleavage and nitric oxide formation caused by N-nitrosoproline with sunlight: a possible mechanism of UVA carcinogenicity.

N-Nitrosoproline (NPRO) is endogenously formed from proline and nitrite. NPRO has been reported to be nonmutagenic and noncarcinogenic. In this study, we have detected the direct mutagenicity of NPRO plus natural sunlight towards Salmonella typhimurium. Furthermore, formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), a mutagenic lesion, was observed in calf thymus DNA treated with NPRO plus simulated sunlight. The treatment with NPRO and sunlight induced single strand breaks in the superhelical replicative form of phage M13mp2 DNA. Single-strand DNA breaks also occurred in the human fibroblast cells on treatment with NPRO plus UVA, as detected by the comet assay. An analysis using scavengers suggested that both reactive oxygen species and NO radical mediate the strand breaks. The formation of nitric oxide was observed in NPRO solution irradiated with UVA. We analyzed the photodynamic spectrum of mutation induction and DNA breakage using monochromatic radiation at a series of wavelengths between 300 and 400 nm. Both mutation frequencies and DNA breakage were highest at the absorption maximum of NPRO, 340 nm. The co-mutagenic and co-toxic actions of NPRO and sunlight merit attention as possible mechanisms increasing the carcinogenic risk from UVA irradiation.

Animals↗
PubMed2005

A systematic review of the evidence for 'myths and misconceptions' in acne management: diet, face-washing and sunlight.

BACKGROUND: Lay perceptions that diet, hygiene and sunlight exposure are strongly associated with acne causation and exacerbation are common but at variance with the consensus of current dermatological opinion. OBJECTIVES: The objective of this study was to carry out a review of the literature to assess the evidence for diet, face-washing and sunlight exposure in acne management. METHODS: Original studies were identified by searches of the Medline, EMBASE, AMED (Allied and Complementary Medicine), CINAHL, Cochrane, and DARE databases. Methodological information was extracted from identified articles but, given the paucity of high quality studies found, no studies were excluded from the review on methodological grounds. RESULTS: Given the prevalence of lay perceptions, and the confidence of dermatological opinion in rebutting these perceptions as myths and misconceptions, surprisingly little evidence exists for the efficacy or lack of efficacy of dietary factors, face-washing and sunlight exposure in the management of acne. Much of the available evidence has methodological limitations. CONCLUSIONS: Based on the present state of evidence, clinicians cannot be didactic in their recommendations regarding diet, hygiene and face-washing, and sunlight to patients with acne. Advice should be individualized, and both clinician and patient cognizant of its limitations.

Acne Vulgaris↗
PubMed1994

The family of sunlight-related eye diseases.

Five ocular disorders, independent clinical entities affecting different parts of the eye with distinctive histopathological features, are part of the same family of eye diseases because they share the same causal factors, of which the most important is molecular damage produced by sunlight. This family of eye diseases includes the major sources of impaired vision and blindness in our society, age-related cataract and age-related macular degeneration. Pterygium, photokeratitis, and cancer of peri-ocular skin are also sunlight-related eye diseases. In each condition, solar radiation, oxygen, and heat, acting in combination, are the primary causal factors. Analysis of the action spectra indicates that only the high-energy radiation in the solar spectrum, particularly the ultraviolet (UV), is hazardous to the eye. The evidence in support of these conclusions is summarized. It indicates that the risk of all sunlight-related eye diseases can be diminished by use of eyewear that absorbs the high-energy constituents of solar radiation during exposure to sunlight.

Blindness↗
PubMed1994

Recreational exposure to sunlight and lack of information as risk factors for cutaneous malignant melanoma. Results of an European Organization for Research and Treatment of Cancer (EORTC) case-control study in Belgium, France and Germany. The EORTC Malignant Melanoma Cooperative Group.

This study addressed the impact of exposure to ultraviolet radiation on the risk of cutaneous malignant melanoma (CMM), as well as the behavioral components at stake in its occurrence. We performed a one-to-one unmatched case-control study among subjects aged 20 years or more with naturally non-pigmented skin in Germany, France and Belgium. Four-hundred and twenty consecutive patients with CMM diagnosed from 1 January 1991 on were derived from hospital registries; 447 controls were chosen randomly in the same municipality as cases. Subjects unaware of the dangers of exaggerated exposure to sunlight display an estimated CMM risk of 3.72% (95% confidence interval 2.63-5.26). The number of holiday weeks spent annually in sunny resorts and sunbathing during the hot hours of the day are strong risk factors in the three countries, but not the number of years spent outdoors, as farmers or building workers. Multiple logistic adjustments on the host characteristics increases the CMM risk associated with recreational exposure to sunlight, as well as the adjustment on the unawareness of the dangers of exaggerated exposure to sunlight. Recreational exposure to sunlight and sunburn early in life seem capable of fostering the proliferation of pigmented lesions of the skin. Our data support the hypothesis that most CMM develop from pigmented lesions of the skin containing initiated melanocytes, and that the cell proliferation due to brutal, intermittent exposures to solar radiation amplifies the likelihood of a melanocyte entering into a malignant process.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2001

Occupational sunlight exposure and mortality from non-Hodgkin lymphoma among electric utility workers.

This case-control study examined occupational sunlight exposure and death from non-Hodgkin lymphoma (NHL) and NHL subtypes among 188 cases and 1880 controls selected from a cohort of 138,905 male electric utility workers. Exposure was classified according to work history linked to indices of cumulative sunlight exposure. Odds ratios and 95% confidence intervals were derived from conditional logistic regression models and were conditioned on the matching factors birth year and ethnicity. Mortality from NHL and intermediate/high-grade lymphomas was not related to cumulative sunlight exposure, with odds ratios around the null. For low-grade lymphomas, a dose-response gradient was observed for exposure in the past 12 to 21 years, but this result seemed to be sensitive to cut points for categorization of cumulative exposure. These data do not provide evidence for an association between occupational sunlight exposure and mortality from NHL or NHL subtypes.

Adult↗
PubMed1999

Basosquamous carcinoma after ultraviolet therapy with artificial sunlight.

We report a 63-year-old Japanese man with basosquamous carcinoma developing after ultraviolet therapy with artificial sunlight. Because he had had an eczematous lesion on the right leg five years previously, he had received ultraviolet therapy with artificial sunlight from a mercury-quartz lamp for a total of 30 sessions over a 3-year period. Physical examination revealed an irregular erythematous plaque measuring 5 x 6 cm, with slight eruptions and erosions, on the right leg. A brownish plaque, measuring 9 x 12 cm, surrounded the erythematous plaque. Histopathologically, in the nests of atypical cells in the dermis, nuclear palisading was present at the edge of each tumor cluster. Adjacent clusters exhibited transitions to squamous cells and contained horn pearls. Most of the cells of the epidermis and adnexa were atypical, but cells of the normal adnexal epithelium extended over the atypical cells of the epidermis in an umbrella-like fashion in other lesions. We believe that, in the present case, artificial sunlight therapy caused solar keratosis and that this developed into basosquamous carcinoma. To our knowledge, skin cancer developing after ultraviolet therapy with artificial sunlight without PUVA has not previously been reported in the English literature.

Carcinoma, Basosquamous↗
PubMed2004

Effect of sunlight on the survival of Salmonella on surfaces.

AIMS: To investigate the effect of simulated full-spectrum tropical sunlight on the survival of Salmonella in droplets on surfaces. MATERIALS AND RESULTS: The survival on surfaces of three Zambian strains of Salmonella enterica serovars Enteritidis and Heidelberg was compared with that of a strain of S. enterica serovar Enteritidis phage type (PT) 4 with known characteristics which had been isolated from poultry in the UK. Samples were taken from surfaces every hour for 3 h and after 24 h exposure in either dark or 12 h light/12 h dark cycle conditions. Differences were analysed for significance using a one-way analysis of variance (anova). Results show that there were a significantly higher number of cells surviving on surfaces after 24 h in the dark when compared with populations exposed to a 12 h light/12 h dark cycle. Significantly more cells also survived exposure to sunlight under dirty than clean conditions. CONCLUSIONS: Exposure to sunlight results in a significant decrease in numbers of Salmonella on surfaces. SIGNIFICANCE AND IMPACT OF THE STUDY: Under field conditions exposure of contaminated surfaces to sunlight could be used in place of chemical methods of control as a cheaper way to reduce Salmonella contamination of surfaces.

Animals↗