Ultraviolet Radiations PDF

 Definition; Ultraviolet (UV) light is part of electromagnetic radiation with a wavelength of 100 – 400 nm (between the color violet of the visible light and x- rays). U V light is an ionizing radiation that can cause chemical reactions both benef...

 Definition; Ultraviolet (UV) light is part of electromagnetic radiation with a wavelength of 100 – 400 nm (between the color violet of the visible light and x- rays). U V light is an ionizing radiation that can cause chemical reactions both beneficial and damaging, on human health such as; painful sunburn, erythema and pigmentation. Ionization  Mercury Sunlight vapor lamp Fluorescent lamp Sources of Germicidal UVR lamp Halogen lights Tanning Artificial bathes Sources Some LASERs  Vacuum UV; 100- 190 nm UVA; Far UV; 320-400 190-220 nm nm Types UVB; of U V UVC; 290-320 220-290 nm nm 1. UVC, far UV and Vacuum UV; (220-290 nm) a. are NEVER observed in nature, b. absorbed completely in the ozone layer of the atmosphere, c. It is an ionizing radiation producing germicidal effect. d. PRODUCED from germicidal lamps. e. In humans, U V C is absorbed in the outermost layers of the epidermis. f. Accidental overexposure to UVC; i. corneal burns, ii. severe sunburn: it is very painful but heals up in few days. 2. UVB: (290-320 nm) a. Partially absorbed in the ozone layer of the atmosphere. b. UVB is needed for vitamin D synthesis. c. It is the MOST DESTRUCTIVE form of UV radiation reaching earth. d. It causes photochemical damage to cellular DNA. 2. UVB: (290-320 nm) e. Other harmful effects; i. erythema (sunburn), ii. cataracts, and iii. skin cancer. f. UVB produce beneficial effects e.g., vitamin D synthesis. 3. UVA: (320-400 nm) a. It is the MOST COMMONLY found type on earth. b. It is minimally absorbed in the atmosphere. c. Its exposure has an initial pigment-darkening effect (tanning) followed by erythema. d. It is needed for vitamin D synthesis. e. Harmful effects; i. Skin toughening, ii. Suppression of the immune system, and iii. Cataract.  UVR Production; 1. The sun: a. UVR is produced by high-temperature surfaces, e.g., incandescent sources like the sun. b. Most of the ultraviolet radiation in sunlight is absorbed by the ozone. c. 95% of UVR that reach the Earth’s surface, is UVA radiation. Mercury vapor lamps; Quartz tube 2. Mercury vapor lamps: a. Mercury-vapor lamp is made of a quartz tube that is filled with mercury under low pressure and two electric poles at each end of the tube. b. When a high voltage electric current is passed through the quartz tube, the mercury becomes vaporized which result in elastic collision between mercury ions and free electrons. 2. Mercury vapor lamps: C. The result of collision between free electrons and mercury ions is the formation of more free mercury ions and more free electrons that result in; i. Ionization: completely separating an electron out of its orbital energy level within the atom, OR ii. Excitation: pushing the electron to higher orbital energy level in the atom. Ionization Excitation d. When atoms return to their original energy levels after being ionized and/or excited they emit UVR in broad range of wavelengths. e. The quartz tube will prevent the passage of certain range of UVR that are highly destructive. f. This process needs high voltage at the beginning of operation and continues at lower voltages. 3. Fluorescent lamps: a) They are low-pressure mercury vapor tubes with phosphor coating on the insides which absorbs short UV (UVC and UVB) and emit them as UVA (FLUORESCENCE). b) The emitted waves depend on the composure of the phosphor which is usually a mixture of phosphate, borates, and silicates. c) These lamps are used in Physical Therapy to produce UVA and traces of UVB but no UVC.  Low penetration of 1 mm in skin. Its direct effects include skin erythema, PHYSIOLOGICAL pigmentation, skin EFFECTS OF vitamin D hyperplasia, UVR: synthesis, sunburns, skin aging and carcinogenic changes. Penetration depends on; 1. Wavelength, i.e., U V A has deeper penetration than UVC. 2. Intensity of radiation reaching the skin, which depends on; a. Distance from the source. b. Duration of treatment. c. Angle of incidence. 3. Skin thickness and pigmentation. U.V.R. These photochemical events include alterations in cell biochemistry and metabolism, i.e.,; a. It decreases the synthesis of D N A and R N A in epidermal cells for 24-48 hours, which decreases protein and enzyme production. b. This leaves the cell inactive or dead. c. The period of D N A suppression is followed by a period of increased D N A synthesis. is the response of any human tissue to an irritating substance or injury. D N A , R N A and Appear after 8- cell proteins 24 H. Inflammation is Rebuilding starts complete after 24 H. after 30 H.  UVR is absorbed by; Keratinocytes in epidermis Mast cells in dermis Histamine-like substance Increased capillary Vasodilatation permeability Increased capillary permeability produce erythema Plasma proteins pass to dermis WBCs pass to skin to and cause edema phagocytize dead cells  Photosensitization 1. Sunscreens and cosmetics. 2. Antibacterial drugs and antibiotics. 3. Diuretics. 4. Antihistaminic drugs. 5. Tranquilizers. Is the increased deposition of melanin pigments in the skin in response to UVR exposure. Melanin acts as a biologic filter against UVR by scattering, absorbing or dissipating the absorbed energy as heat.  Pigmentation Immediate Delayed  Pigmentation Immediate Delayed It appears immediately Due to darkening of Formation of new melanosomes in the skin. melanosomes from melanocytes in strata It fades out within 1 hour. basal. Hardly seen after 3-8 It is called melanogenesis. hours. It is mostly common in It appear 72 hours after dark individuals. UVR exposure. Normal This will After desquamation; turnover result in Skin growth period shedding of remain high 28-30 days most with 20-40% U V R increases superficial increase in epidermal thickness. layers of skin It fades out in 4- turnover. Starts within 72 in sheets 6 weeks after H. of exposure application.  Long term effects Premature skin aging; Skin dryness, wrinkles, cracking and reduced Skin cancer elasticity. It is more common in white races. Photokeratitis Conjunctivitis Photophobia Cataracts  Vitamin D Production active form is regulate produced UVR transferred calcium by converts to liver, (Ca++) and exposure to Vit-D to kidneys, phosphorus UVB active form bones, (P+4) 1. Increase their absorptioinntefrsotim netshe inte m estatibnoesli,sm 2. Increase their deposiatinodn m inubsocnleess and 3. Increase their concentration in blood. Immunosuppressive effects, dose dependent effect Low dose High dose suppress increases immunity. immunity. Therapeutic Effects of UVR: 1. Vitamin D synthesis: a. Treat disorders of calcium and phosphorus metabolism. b. For example: rickets, osteoporosis and tetany. 2. Skin diseases: a. e.g., acne, psoriasis and eczema. b. It acts through cell damage and desquamation. Therapeutic Effects of UVR: 3. Accelerate wound healing: a. It occurs through cell hyperplasia. 4. Bactericidal effects: using UVC. 5. Improve immunity. 6. Sterilization of operation rooms and utensils: using UVC. INDICATIONS OF UVR: 1. Some skin diseases: e.g., acne, psoriasis, and eczema. 2. Vitamin D deficiency: e.g., Rickets in children and Osteoporosis and osteomalacia in adults. 3. Infected open wounds and bed sores. 4. Sterilization. 5. PUVA Therapy: (Psoralen UV-A) for psoriasis, acne and eczema. 6. Diagnosis of some dermatological diseases. CONTRA-INDICATIONS OF UVR: 1. Absolute contra-indications: a. Areas of recent or potential hemorrhage. b. Loss or impaired sensation. c. Neoplasm or malignancy. d. Ischemia and poor circulation. e. Recent burns and delicate sensitive skin. f. Eyes. CONTRA-INDICATIONS OF UVR: 2. Relative contra-indications: a. Unreliable patients. b. Deep Vein Thrombosis (DVT) and thrombophlebitis. c. Pulmonary, cardiac, kidney or liver disease. PRECAUTIONS OF UVR: 1. Photosensitizing drugs. 2. Skin photosensitivity, e.g., patients with fair skin and colored hair. ADVERSE EFFECTS OF UVR: 1. Burn. 2. Eye damage 3. Adverse effects of PUVA