Ultraviolet exposure effects

Sun worshipers and those who work outside can protect themselves from ultraviolet exposure with skin creams that contain UV-absorbing molecules. The UV-absorbing molecule in the first sunscreens was PABA, para-aminobenzoic acid. However, this compound may have toxic effects of its own. The UV-absorbing components of current sunscreens are derivatives of cinnamic acid and benzophenone. 

Konig K et al (1996) Effects of ultraviolet exposure and near infrared laser tweezers on human spermatozoa. Hum Reprod 11(10) 2162-2164... 

Other human-health effects of ultraviolet exposure include increased risks of developing cataracts and other damage to the cornea, damage to the retina, a suppressed immune system, sunburns of exposed skin, skin allergies, and an accelerated aging of the skin. 

Dozens of phytochemicals are under study for their potential effects in humans. The benefits may be similar to the roles they are known to perform for the plant itself. In plants, phytochemicals defend against disease invaders, ultraviolet exposure, bacteria, viruses, fungi, DNA and cell damage, and destructive free radicals. 

The problems of ozone depletion in the upper atmosphere have led to increased problems of exposure of the skin to solar ultraviolet radiation [74]. Ultraviolet radiation to earth, due to the above effect could gradually affect human s immune system. Ailments like cataract, lung diseases and skin cancer would increase. Approximately 90% of non-melanoma and 65% of melanoma skin cancers have been attributed to ultraviolet exposure. 

Aromatic urethanes have been stabilized by complexation of peroxides in the polymer and the effect of prior y-irradiation has been investigated, on polyurethanes.The ageing of polyurethane coatings has been investigated, and light-stable integral skin foams have been developed for polyurethanes. Creep behaviour of polyurethanes on ultraviolet exposure has also been investigated. ... 

Figures 4-10 to 4-12 show the effects of ultraviolet exposure followed by reaction with alkaline hydrogen peroxide for different times (15 min to 2 h). The effects of the alkaline peroxide on ultraviolet exposed hair are to dissolve parts of the cuticle, providing for even less structural differentiation. Part of the cuticular proteins are solubilized by these combined chemical treatments into gelatin-like glue that is redeposited between the fibers, see Figure 4-11. This effect was produced after only 15 min exposure to alkaline peroxide after photochemical degradation. The total lack of surface structural definition is seen in the most extreme case in Figure 4-12 where no cuticle scale definition exists after 2h of treatment with alkaline hydro-...

Ozone in the stratosphere absorbs ultraviolet radiation. With ozone depletion comes a corresponding increase in the radiation that reaches us and an increase in its harmful effects, which include human skin cancer and cataracts that can lead to blindness. Increased ultraviolet exposure is also harmful throughout the environment. In the oceans, the phytoplankton population is decreased, resulting in a loss of the fish that feed on... 

T. Lundin, R.H. Ealk and C. Felton, Accelerated weathering of natural fiber-thermoplastic composites Effects of ultraviolet exposure on bending strength and stiffness, in The Sixth International Conference on Woodfiber-Plastic Composites, The Madison Concourse Hotel Madison, Wisconsin, 2001, pp. 87-93, Forest Products Society (2002). 

Bums One hazard of ultraviolet exposure is skin bums or erythema (reddening). With extended exposure, blistering can occur. Skin does not absorb aU UV wavelengths in the same way and the erythemal effects vary across the absorbed spectmm. The outermost layer of the skin (the stramm cor-neum of the epidermis) absorbs the wavelength below 280 nm. Deeper layers of the skin (dermis) absorb wavelengths between 280 and 320 nm. The outer layer (epidermis) absorbs wavelength between 320 and 380nm. 

Various compounds such as thiobisphenol were reported to exhibit a pro-oxidant effect in the early period of polyethylene photooxidation, which is accelerated as their concentration is enhanced, while on the later irradiation period the carbonyl build up was retarded [72]. The retardation of the carbonyl accumulation was obtained with a compound based on dodecyl-3,3 -thiodipropionate over the whole period of ultraviolet exposure. Kinetic data showed [72] that the concentration of 0.1 w/w% of thiobisphenols determines the most effective retardation for flie accumulation of carbonyl group in LDPE films. 

Ozone s presence in the atmosphere (amounting to the equivalent of a layer 3 mm thick under ordinary pressures and temperatures) helps prevent harmful ultraviolet rays of the sun from reaching the earth s surface. Pollutants in the atmosphere may have a detrimental effect on this ozone layer. Ozone is toxic and exposure should not exceed 0.2 mg/m (8-hour time-weighted average - 40-hour work week). Undiluted ozone has a bluish color. Liquid ozone is bluish black and solid ozone is violet-black. 

Geotextiles may be woven, nonwoven, or knitted. AH types, woven, nonwoven, or knitted, are susceptible to degradation owing to the effects of ultraviolet light and water. Thus stabilizing agents are added to the base polymeric material to lessen the effects of exposure to ultraviolet light and water. 

The ECPI approach has been adopted by the European Commission in their "Technical Guidance Document on the Risk Assessment of Notified New Substances" as the model for assessment of environmental exposure from additives in plastics. It is important to note, however, that due to the effect of ultraviolet degradation and microbial attack, a significant proportion of the emissions from flexible PVC consists of plasticizer degradation products. In these instances, therefore, the level of plasticizers appearing in the environment will be significantly less than indicated by the plasticizer loss data. 

Durability. Grass-like surfaces intended for heavy-duty athletic use should have a service life of at least eight years, a common warranty period provided by suppHers. Lifetime is more or less proportional to the ultraviolet (uv) exposure (sunlight) and to the amount of face ribbon available for wear, but pile density and height also have an effect. Color is a factor generally uv absorption is highest with red fabrics and least with blue. In addition, different materials respond differendy to abrasive wear. These effects caimot be measured except in simulated field use and controlled laboratory experiments, which do not necessarily redect field conditions. 

Wea.ther lbillty. One of the more destmctive elements is exposure to sunlight specifically, ultraviolet (uv) light. AH sealants are affected by weathering, but there is much difference in the effect of weathering on different sealants. Most sHicones are stable with respect to uv exposure. Urethanes and polysulfides show effects of uv exposure, but can be formulated with uv absorbers to provide reasonable lifetimes in most appHcations. However, there are exceptions in aH classes of sealants and specifiers must be carehil to look for test data that has proven a specific sealant s durabHity. The source of the test data is also important data from an independent testing laboratory is generaHy apt to be more reHable. 

An important effect of air pollution on the atmosphere is change in spectral transmission. The spectral regions of greatest concern are the ultraviolet and the visible. Changes in ultraviolet radiation have demonstrable adverse effects e.g., a decrease in the stratospheric ozone layer permits harmful UV radiation to penetrate to the surface of the earth. Excessive exposure to UV radiation results in increases in skin cancer and cataracts. The worldwide effort to reduce the release of stratospheric ozone-depleting chemicals such as chlorofluorocarbons is directed toward reducing this increased risk of skin cancer and cataracts for future generations. 

The energy available in various forms of irradiation (ultraviolet, X-rays, 7-rays) may be sufficient to produce in the reactant effects comparable with those which result from mechanical treatment. A continuous exposure of the crystal to radiation of appropriate intensity will result in radiolysis [394] (or photolysis [29]). Shorter exposures can influence the kinetics of subsequent thermal decomposition since the products of the initial reaction can act as nuclei in the pyrolysis process. Irradiation during heating (co-irradiation [395,396]) may exert an appreciable effect on rate behaviour. The consequences of pre-irradiation can often be reduced or eliminated by annealing [397], If it is demonstrated that irradiation can produce or can destroy a particular defect structure (from EPR measurements [398], for example), and if decomposition of pre-irradiated material differs from the behaviour of untreated solid, then it is a reasonable supposition that the defect concerned participates in the normal decomposition mechanism. 

Griseofulvin Beneficial effects may not be noticed for some time tiierefore, take the drug for die full course of dierapy. Avoid exposure to sunlight and sunlamps because an exaggerated skin reaction (which is similar to a severe sunburn) may occur even after a brief exposure to ultraviolet light. 

Hydroquinone inhibits melanin production when applied to the skin. The effect is reversible by exposure to ultraviolet light. 

Skin lighteners, freckle and age spot removers, and other remedies for hyperpigmentation are not actually bleaches like the products listed so far. The active ingredient is hydroquinone, which inhibits melanin formation when applied to the skin. Since the effect is easily reversed by exposure to sunlight or ultraviolet light, a sunscreen is usually included in the formula. 

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