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PubMedDate not supplied

Photosynthetically active sunlight at high southern latitudes.

A network of scanning spectroradiometers has acquired a multiyear database of visible solar irradiance, covering wavelengths from 400 to 600 nm, at four sites in the high-latitude Southern Hemisphere, from 55 degrees S to 90 degrees S. Monthly irradiations computed from the hourly measurements reveal the character of the seasonal cycle and illustrate the role of cloudiness as functions of latitude. Near summer solstice, the combined influences of solar elevation and the duration of daylight would produce a monthly irradiation with little latitude dependence under clear skies. However, the attenuation associated with local cloudiness varies geographically, with the greatest effect at the most northern locations, Ushuaia, Argentina and Palmer Station on the Antarctic Peninsula. Near summer solstice, the South Pole experiences the largest monthly irradiation of the sites studied, where relatively clear skies contribute to this result. Scaling factors derived from radiative-transfer calculations combined with the measured 400-600 nm irradiances allow estimating irradiances integrated over the wavelength band 400-700 nm. This produces a climatology of photosynthetically active radiation for each month of the year at each site.

Altitude↗
PubMed2005

Assessment of laboratory and field assays of sunlight-induced killing of mosquito larvae by photosensitizers.

The effectiveness of light-induced killing of mosquito larvae in the presence of photosensitizers was studied with larvae of Aedes aegypti (L.), Anopheles stephensi (Liston), and Culex quinquefasciatus Say grown in the laboratory and of Cx. quinquefasciatus grown under field conditions. Tested photosensitizers included xanthene, chlorin, and porphyrin derivatives. All the larvae were treated at the fourth instar. Preliminary laboratory experiments showed a light-induced lethal effect of Rose Bengal (RB) on three species of mosquito larvae. Compared with other photosensitizers, RB seemed to be more efficient at even lower concentration than chlorin (e6) and chlorophyllin on Ae. aegypti larvae. Among the four porphyrin derivatives, i.e., chloroquinoline tetraphenyl propioamidoporphine, tetraphenyl porphine tetrasulfonate, hematoporphyrin (HP), and tetraphenylporphinepropionic acid porphine, HP was the only effective photosensitizer on Ae. aegypti larvae. The best conditions for field tests using RB were conducted on Cx. quinquefasciatus in Bobo-Dioulasso, Burkina Faso. The mortality induced by RB varied from 80 to 96% obtained with unfiltered cesspit water to 0.4 to 6.7% in cesspits with a heavy load of organic materials, thus providing the basis for further developments of this technique under field conditions.

Aedes↗
PubMed1976

Skin cancer, melanoma, and sunlight.

Recent theoretical studies suggest that the earth's ozone layer which filters ultraviolet radiation may be depleted by a fleet of supersonic transports or by continued use of chlorofluoromethanes. It is now generally accepted that short wavelength ultraviolet radiation leads to the development of skin cancer. In this report we demonstrate an approach to estimating the increase in skin cancer incidence associated with increases in skin cancer incidence associated with increases in ultraviolet radiation. The purpose is to demonstrate the logic used and the assumptions that must be made when such estiamtes are made or cited. We emphasize that such estimates should be considered crude until the many assumptions can be investigated.

Environmental Exposure↗
PubMed1978

Sunlight and incidence of cutaneous malignant melanoma. Effect of latitude and domicile in Sweden.

The relationship between tumour incidence rate and habitation patterns was investigated in 3289 patients registered between 1959 and 1968 as cutaneous malignant melanoma in the Swedish Cancer Registry. A linear correlation analysis between latitude and melanoma incidence rate in various regions showed a coefficient, r, was -0.74, which implies a decreasing incidence with increasing latitude. This result supports the hypothesis that ultraviolet irradiation is the predominant cause of melanoma. However, considerable deviations from the regression line were seen in some regions. Moreover, a comparison between town and country indicated melanoma incidence increased with population density, an increase not explained by overdiagnosis and thus not in agreement with the working hypothesis of UV-irradiation as the predominant cause of melanoma. Increase of foreign travel, as estimated by passport issue, may explain the overrepresentation of melanoma in some regions namely city and county of Stockholm, city of Malmö and Göteborg county. As foreign travel in Sweden generally means sunshine trips, this town versus country paradox may also be explained on the basis of increased irradiation, as may the anomalies observed in some counties. A regression analysis of the epidemiological index for UV-irradiation and melanoma incidence, adjusted for foreign travel, demonstrated a close agreement with the results of the latitude gradient analysis.

Female↗
PubMed1994

Epidemiological studies of sunlight and cataract: the critical factor of ultraviolet exposure geometry.

Despite the large body of laboratory evidence that ultraviolet radiation (UVR) is cataractogenic, epidemiological studies of the relationship between age-related cataract and chronic UVR exposure have provided apparently conflicting results. An explanation for these conflicting results could be related to errors in dosimetry. Failure to account for the biophysical, physiological and behavioral factors, as well as ground reflectance, which determine the level of UVR exposure of the lens can lead to completely wrong assignments of lifetime exposure. It is argued that by overlooking these factors, past epidemiological studies of UVR and cataract could readily be expected to produce conflicting results.

Cataract↗