Diffuse-direct ultraviolet ratios with a compact double monochromator

Photodegradation of the Novel Herbicide Pyraquinate in Aqueous Solution: Kinetics, Photoproducts, Mechanisms, and Toxicity Assessment

Pyraquinate, a newly developed 4-hydroxyphenylpyruvate dioxygenase class herbicide, has shown excellent control of resistant weeds in paddy fields. However, its environmental degradation products and corresponding ecotoxicological risks after field application remain ambiguous. In this study, we systematically investigate the photolytic behaviors of pyraquinate in aqueous solutions and in response to xenon lamp irradiation. The degradation follows first-order kinetics, and its rate depends on pH and the amount of organic matter. No vulnerability to light radiation is indicated. Ultrahigh-performance liquid chromatography with quadrupole-time-of-flight mass spectrometry and UNIFI software analysis reveals six photoproducts generated by methyl oxidation, demethylation, oxidative dechlorination, and ester hydrolysis. Gaussian calculation suggests that activities due to hydroxyl radicals or aquatic oxygen atoms caused these reactions on the premise of obeying thermodynamic criteria. Practical toxicity test results show that the toxicity of pyraquinate to zebrafish embryos is low but increases when the compound is combined with its photoproducts.

Efficiency of ocular UV protection by clear lenses

Ocular UV doses accumulate all-day, not only during periods of direct sun exposure. The UV protection efficiency of three clear lenses was evaluated experimentally, validated by simulation, and compared to non-UV protection: a first spectacle lens with a tailored UV absorber, a second spectacle lens, minimizing UV back reflections, as well as a third spectacle lens, combining both. A tailored UV-absorber efficiently reduced overall UV irradiance to 7 %, whereas reduction of back-reflections still left UV irradiance at 42 %. Thus, clear lenses with a tailored UV absorber efficiently protect the eye from UV, supplementing sun glasses wear to an all-day protection scenario.

Distributions of Direct, Reflected, and Diffuse Irradiance for Ocular UV Exposure at Different Solar Elevation Angles

To analyze intensities of ocular exposure to direct (E_o,dir), reflected (E_o,refl), and diffuse (E_o,diff) ultraviolet (UV) irradiance at different solar elevation angles (SEAs), a rotating manikin and dual-detector spectrometer were used to monitor the intensity of ocular exposure to UV irradiation (E_o) and ambient UV radiation (UVR) under clear skies in Sanya, China. E_o,dir was derived as the difference between maximum and minimum measured E_o values. E_o,refl was converted from the value measured at a height of 160 cm. E_o,diff was calculated as the minimum measured E_o value minus E_o,refl. Regression curves were fitted to determine distributions of intensities and growth rates at different wavelengths and SEAs. E_o,dir differed from ambient UVR exposure. Linear, quadratic, and linear E_o,dir distributions were obtained in SEA ranges of 14°–30°, 30°–50°, and 50°–90°, respectively, with maximum E_o,dir at 32°–38° SEA. Growth rates of E_o,dir with increasing wavelength were fitted with quadratic functions in all SEA ranges. Distributions and growth rate of E_o,refl values were fitted with quadratic functions. Maximum E_o,diff was achieved at the same SEA for all fitted quadratic functions. Growth rate of E_o,diff with increasing wavelength was fitted with a linear function. E_o,dir distributions were fitted with linear or quadratic functions in different SEA ranges. All E_o,refl and E_o,diff distributions were fitted with quadratic functions. As SEA increased, the E_o,dir portion of E_o increased and then decreased; the E_o,refl portion increased from an initial minimum; and the E_o,diff portion first decreased and then increased. The findings may provide data supporting on construction of a mathematical model of ocular UV exposure.

Prevalence and sunlight photolysis of controlled and chemotherapeutic drugs in aqueous environments

This study addresses the occurrences and natural fates of chemotherapeutics and controlled drugs when found together in hospital effluents and surface waters. The results revealed the presence of 11 out of 16 drugs in hospital effluents, and the maximum detected concentrations were at the μg L(-1) level in the hospital effluents and the ng L(-1) level in surface waters. The highest concentrations corresponded to meperidine, morphine, 5-fluorouracil and cyclophosphamide. The sunlight photolysis of the target compounds was investigated, and the results indicated that morphine and codeine can be significantly attenuated, with half-lives of 0.27 and 2.5 h, respectively, in natural waters. Photolysis can lower the detected environmental concentrations, also lowering the estimated environmental risks of the target drugs to human health. Nevertheless, 5-fluorouracil and codeine were found to have a high risk quotient (RQ), demonstrating the high risks of directly releasing hospital wastewater into the environment.

UV radiation ocular exposure dosimetry

Cataractogenesis by ultraviolet radiation (UVR) has been shown convincingly by a host of different laboratory studies. However, crucial epidemiological evidence linking chronic UVR exposure of age-related cataract appears to be lacking, since different environmental studies have led to apparently conflicting results. This paper explores a possible explanation for these conflicting results: errors in dosimetry. Any epidemiological study depends upon good dosimetry of the subjects' exposures. A careful examination of the biophysical, physiological and behavioral factors which determine the level of UVR exposure of the lens reveals a number of surprises which should explain the apparently conflicting epidemiological results. It is shown that geometrical and behavioral factors related to sunlight are so important, that by overlooking these factors, past epidemiological studies of UVR and cataract could readily be expected to produce conflicting results.

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.

Ocular hazards arising from depletion of the natural atmospheric ozone layer: a review

The processes contributing to the maintenance of the natural, atmospheric, ozone layer, which screens the earth's surface from solar ultraviolet radiation at wavelengths below 300 nm, are described. The possible adverse effects of man-made chemicals such as chlorofluorocarbons (CFCs) on this layer are outlined. Consideration of the flux of ultraviolet light reaching the earth's surface as a function of the ozone concentration and other factors allows the effect of ozone changes on ocular health to be evaluated. It is concluded that the changes of the order of a few per cent that are predicted by current models of the atmosphere, and which are comparable with natural fluctuations in ozone, would have relatively little effect on the incidence of solar keratitis at the cornea. Larger changes, in the order of 50%, would be expected to have a significant effect. There might also be an increase in the incidence of brunescent cataract. Ozone changes would have a negligible effect on the amounts of solar radiation reaching the retina.

Estimating the solar ultraviolet radiation exposure to an intraocular lens implant

A study of the stability of ultraviolet radiation (UVR) absorbers in intraocular lenses (IOLs) upon exposure to UVR is necessary to determine efficacy. Ultraviolet stability is conventionally tested by placing the UV-absorbing IOLs in a solar simulator exposure chamber to determine any degradation of the absorber. To interpret any change requires a method of correlating the UVR exposure rate in the test chamber with the UVR exposure of the IOL in vivo. A method is derived that permits a determination of the upper limit of daily UVR exposure of the in-vivo IOL (or, for that matter, the crystalline lens) based upon knowledge of the ambient outdoor UVR exposure to the head and the threshold for photokeratitis.

Solar ultraviolet irradiation of human cornea, lens, and retina: equations of ocular irradiation

Photochemical damage of ocular tissues by solar radiation depends on the spectral composition of the radiation in the environment, the geometry of the coupling of that radiation to the eye, the spectral transmittances of the ocular components and any auxiliary lenses used, the spectral sensitivity of the irradiated tissue, the accumulated exposure dose, and the action of repair processes. This paper provides formulas for quantitative estimation of corneal, lenticular, and retinal UV irradiances from the sunlit environment under clear sky conditions. Applications of these formulas for ocular irradiation will be presented in subsequent papers for the cornea, lens, and retina, and the results will be evaluated using weighting functions for the sensitivity of ocular tissue.

Lighting for the elderly: a psychobiological approach to lighting

The present paper reviews the role of illumination in shaping the indoor environment of the elderly person. The approach is that lighting has a twofold impact on the individual. One is as a source of information about the environment, i.e., visual, and the other is photobiological through the skin or photoreceptor.

The visually lighted environment is reviewed, discussing first the physiological changes that occur during the aging process, then the effect of aging on visual performance, and finally the importance of qualitative factors in assessing the adequacy of an illuminated environment for the elderly. Special attention is given to application problems in lighting for the elderly, i.e., excessive brightness differences, discomfort glare, veiling reflections, and the importance of color and the spectral power distribution of the light source. The advantages of a full-spectrum light source which simulates natural sunlight for indoor illumination is discussed in light of recent research.

The biologically lighted environment is reviewed in terms of the potential role that indoor illumination can play in regulating important biochemical processes in the elderly population, i.e., neuroendocrine control, vitamin D3synthesis, immunologic mechanisms, and cardiovascular regulation.