Observational evidence for chemical ozone depletion over the Arctic in winter 1991-92

Long-term depletion of ozone has been observed since the early 1980s in the Antarctic polar vortex, and morerecently at midlatitudes in both hemispheres, with most of the ozone loss occurring in the lower stratosphere.Insufficient measurements of ozone exist, however, to determine decadal trends in ozone concentration in the Arcticwinter. Several studies of ozone concentrations in the Arctic vortex have inferred that chemical ozone loss hasoccurred; but because natural variations in ozone concentration at any given location can be large, deducinglong-term trends from time series is fraught with difficulties. The approaches used previously have often been indirect,typically relying on relationships between ozone and long-lived tracers. Most recently Manney et al. used such anapproach, based on satellite measurements, to conclude that the observed ozone decrease of about 20% in the lowerstratosphere in February and March 1993 was caused by chemical, rather than dynamical, processes. Here we report theresults of a new approach to calculate chemical ozone destruction rates that allows us to compare ozone concentrationsin specific air parcels at different times, thus avoiding the need to make assumptions about ozone/tracer ratios. For theArctic vortex of the 1991-92 winter we find that, at 20 km altitude, chemical ozone loss occurred only between earlyJanuary and mid February and that the loss is proportional to the exposure to sunlight. The timing and magnitude arebroadly consistent with existing understanding of photochemical ozone-depletion processes

A terapia fotodinâmica com ácido 5-aminolevulínico como modalidade de tratamento para neoplasias cutâneas não-melanoma Topical 5-aminolevulinic acid photodynamic therapy as a treatment modality for nonmelanoma skin cancer

FUNDAMENTOS: A terapia fotodinâmica baseia-se na associação de fonte de luz e fotossensibilizador para destruir seletivamente as células. OBJETIVO: Avaliar os efeitos imediatos e tardios, a resposta clínica e os resultados estéticos da terapia fotodinâmica com ácido 5-aminolevulínico em neoplasias cutâneas não-melanoma. MÉTODOS: Trinta e quatro lesões, sendo 19 disceratoses de Bowen e 15 carcinomas basocelulares, foram submetidas à aplicação tópica e oclusiva do ácido 5-aminolevulínico a 20%, por seis horas, e posteriormente a sessão única de laser de diodo (630nm). RESULTADOS: Foram registrados: sensação de queimação durante as sessões; eritema, edema e erosões, nas primeiras 72 horas; cicatrização em média de quatro semanas; resultados estéticos variáveis de excelentes a bons. Aos três meses, a resposta clínica foi de 91,2%, sendo reduzida, aos 18 meses, para 73,3%, de modo similar tanto para disceratose de Bowen (72,2%) quanto para carcinoma basocelular (75%). Foi evidenciada relação de tendência linear entre a redução da freqüência da resposta clínica e o aumento da dimensão das neoplasias cutâneas não-melanoma (p<0,001). CONCLUSÃO: A terapia fotodinâmica com ácido 5-aminolevulínico tópico mostrou destacadas vantagens: minimamente invasiva no tratamento de lesões múltiplas em sessão única ou em sítios de pobre cicatrização com superioridade dos resultados estéticos. O tipo/subtipo(clínico e histopatológico), a dimensão e o adequado seguimento devem ser considerados para a sua indicação no tratamento de neoplasias cutâneas não-melanoma.<br>BACKGROUND: Photodynamic therapy is based on the association of a light source and photosensitizer in order to selectively destroy cells. OBJECTIVE: To evaluate the short and long-term effects, clinical response, and cosmetic outcome of the photodynamic therapy with 5-aminolaevulinic acid for non-melanoma skin cancer. METHODS: TThirty-four non-melanoma skin cancer - 19 Bowen’s diseases and 15 basal cell carcinomas, were submitted to a single 6-hour topical and occlusive application of 20% 5-aminolaevulinic acid, and were later exposed to 630 nm diode laser single session. RESULTS: Burning sensation during the session; erythema, edema and erosions in the first 72 hours; healing process after 4 weeks on average and excellent or good cosmetic results were observed. After 3 months, tumor-free rate was 91.2% whereas at 18 months,73.3%, similarly in Bowen’s disease (72.2%) and basal cell carcinoma (75%). It was noticed a linear relation between the reduction in complete clinical response frequency and the increase in tumor dimension (p<0.001). CONCLUSION: The 5-aminolaevulinic acid photodynamic therapy showed significant advantages such as minimally invasive for the treatment of multiple lesions in only one session or lesions in poor healing sites with superior esthetical outcome. The clinical and histopathological type/sub-type, the dimension and an appropriate follow-up must be considered to indicate topical 5-aminolaevulinic acid photodynamic therapy for non-melanoma skin cancer