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Introduction to Cancer
Published in David E. Thurston, Ilona Pysz, Chemistry and Pharmacology of Anticancer Drugs, 2021
The UV band, which is invisible to the human eye, constitutes one component of the spectrum of sunlight and represents approximately 3% of all the solar radiation reaching the Earth’s surface. Three types of UV light have been identified. One of these, UV-C (200 to 290 nm), is generally thought to be the most carcinogenic. UV-B (290 to 320 nm) causes the most sunburn, and UV-A (320 to 400 nm), which can be up to 1,000 times stronger than UV-B, is able to penetrate underlying tissues of the skin leading to “photo-aging” damage. For many years it was thought that UV-A could not cause any lasting damage. However, more recent studies strongly suggest that it may also enhance the development of skin cancers. Fortunately, the ozone layer absorbs most of the more carcinogenic UV-C radiation, although there is presently concern that depletion of the ozone layer through the release of chlorofluorocarbons used in the air conditioner and refrigeration industries and in the production of Styrofoam insulation may increase the intensity of UV-C at the Earth’s surface in the future. UV radiation occurs at a similar wavelength to the region of maximum absorbance by DNA (i.e., 260 nm), and the major damage is intrastrand covalent linkage of adjacent pyrimidines (usually thymines) to form so-called thymine dimers. These thymine dimers create distortions in the DNA helix and can block replication and transcription, thus leading to tumorigenesis.
Radiation Toxicity
Published in Frank A. Barile, Barile’s Clinical Toxicology, 2019
The extent of solar injury depends on the type of UV radiation, the duration and intensity of exposure, clothing, season, altitude and latitude, and the amount of melanin pigment present in the skin. In fact, individuals differ greatly in their response to sun. Fair-skinned persons have fewer melanin-producing cells. Consequently, they are more sensitive to UV rays than people of dark-skinned races, although the skin of the latter is still reactive and can become sunburned with prolonged exposure. Also, the harmful effects of UV rays are filtered out by glass, smog, and smoke but enhanced by reflecting off snow and sand. The indiscriminate use of chlorofluorocarbons in aerosol propellants depletes the UV-blocking properties of ozone in the stratosphere, thus allowing a greater intensity of UV rays to penetrate through the protective upper atmospheric layers.
Impact of global environmental issues on health
Published in Richard Lawson, Jonathon Porritt, Bills of Health, 2018
Richard Lawson, Jonathon Porritt
Much confusion exists in the mind of the populace concerning the twin problems of ozone layer thinning and the greenhouse effect, partly because both occur above our heads, and partly because chlorofluorocarbons (CFCs) are involved in both Chloro- fluorocarbons have three vices: they are extremely longlived, each molecule staying in the atmosphere for 100 years or more (this means that keeping the bathroom window closed while spraying your armpit is of no avail); they are efficient greenhouse gases, trapping solar heat many times more effectively than carbon dioxide; and they are the chief villains in the destruction of the protective stratospheric ozone layer.
Detrimental effect of UV-B radiation on growth, photosynthetic pigments, metabolites and ultrastructure of some cyanobacteria and freshwater chlorophyta
Published in International Journal of Radiation Biology, 2021
Mostafa M. El-Sheekh, Eman A. Alwaleed, Aml Ibrahim, Hani Saber
Ultraviet radiation (UV) is emitted from the sun and divided to three wavebands; UV-A has wavelengths between 320–400 nm and is not screened out by the molecular oxygen (O2) and the ozone layer, UV-B has wavelengths between 280–320 nm and is usually reflected by ozone layer, and the most harmful, UV-C is entirely screened out by a combination of molecular oxygen and ozone layer (Yongji et al. 2018). So, the ozone layer is vital to natural life in the globe because of their function in absorption of UV radiation. Additional UV radiation has been entered to the earth biosphere due to depletion in this protective layer. The depletion of ozone layer induced by substances such as chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) (the United States Environmental Protection Agency 2008). Increased UV levels resulted in climate change and is portend to alteration in weather and growth patterns on the earth (Bi and Zhang 2007). Atmosphere pollution as a result of rapid industarlization is the main reason for depletion in this protective ozone layer (Björn 2007). The Antractic ozone hole is the most spectacular example for this depletion (Björn 2007). During 1997 to 2000, at northern multitudes, ozone level depletion was around 6% in relation to 1980 levels, which could cause an increase in UV-B up to 12% (McKenzie et al. 2003; Arróniz-Crespo et al. 2008). So, the influence of UV radiation on life form became a critical affair over the past three decades and could also be vital in the years to come.
A technology evaluation of CVT-301 (Inbrija): an inhalable therapy for treatment of Parkinson’s disease
Published in Expert Opinion on Drug Delivery, 2021
Michael M. Lipp, Anthony J. Hickey, Robert Langer, Peter A. LeWitt
Nebulizers have been available since the beginning of the twentieth century for pulmonary drug delivery. Most inhaled proteins for clinical development have been developed as liquids for use in nebulizers. Modern inhaler therapy has its origins in treating asthma with pressurized metered-dose inhalers (pMDIs) [15,16]. The commercial dominance of pMDIs was first challenged when chlorofluorocarbon (CFC) propellants were subject to international control and ultimately phase-out through the Montreal Protocol in 1987 [17]. The difficulty of reformulation of inhaled drugs for alternative propellants and the concurrent demand for alternative delivery systems for the products of biotechnology prompted development and use of dry powder inhalers (DPIs) [16].
Acute, repeated inhalation toxicity, respiratory system irritation, and mutagenicity studies of 1,1,2,2-tetrafluoroethane (HFC-134) as the impurity in the pharmaceutical propellant 1,1,1,2-tetrafluoroethane (HFA-134a)
Published in Drug and Chemical Toxicology, 2023
Yanjun Zhao, Huimin Sun, Fei Lin, Huiying Yang
Chlorofluorocarbons were used as propellant in MDI formulations in the past but had been phase-out within the globe because they deplete the stratospheric ozone (Brock et al.2006). 1,1,1,2-Tetrafluoroethane (HFA-134a) is most widely replacing dichlorodifluoromethane (CFC-12) as a propellant for pharmaceutical MDI (Alexander et al.1995). The acute and chronic toxicities of HFA-134a are low with an LC50 of over 700 000 ppm (Ritchie et al.2001).