RADIATION HAZARDS Important characteristics of radiation Wavelength Frequency

RADIATION HAZARDS

Important characteristics of radiation • • Wavelength Frequency Intensity Velocity Straight line propagation Spectrum Inverse square law

Ultraviolet radiation hazards • Common sources: sun, UV lamps (‘black lights’), welder’s arc • Some devices may emit only a small amount of visible light while emitting intense UV radiation • Especially dangerous to the eyes since they do not dilate readily in response to UV -- retinal burns • Photosensitization to UV can occur from certain dermal chemicals and oral drugs (e. g. antibiotics)

Types of UV Radiation Type Wavelength Effect UV-A 315 -400 nm Little effect UV-B 280 -315 nm Skin cancer possible UV-C 100 -280 nm Cornea damage “Black light” Region

Visible radiation hazards • Common sources: sun, all visible lamps • Major damage likely only if intense beam is focused on the retina • Eye usually registers pain before serious damage occurs

Infrared Hazards • Major effect is burns • Eye is not very sensitive so can be damaged if IR is intense • Skin burns possible but usually avoided due to pain from heat before serious injury occurs

Radio-frequency and Microwave Hazards • Sources include analytical instruments (e. g. NMR), cathode ray tubes (including oscilloscopes, TVs, and computer monitors), microwave ovens, and communications devices (e. g. cell phones) • Biological effects to man uncertain • Suggestion of sterility problems, birth defects and cataracts from microwaves • Pacemakers are effected by microwaves

LASER HAZARDS • LASER = Light Amplified by Stimulated Emission of Radiation • Especially hazardous due to very narrow beam which can be very intense • Lens of eye may concentrate energy onto retina by another 100, 000 times

LASER HAZARDS (cont’d) • • Use minimum power laser possible for job Keep laser beam off or blocked when not in use Post warning signs when lasers are in use Never look directly at a laser beam or align it by sighting over it • If possible, use laser in lighted room so that pupils will be constricted • Do not depend on sunglasses for shielding. • Make sure any goggles used are for the wavelength of the laser used and are of adequate optical density

Ionizing Radiation Characteristics Mass Charge Stopped by Alpha 4 +2 4 cm air Beta 0 -1 X-ray 0 0 Gamma 0 0 6 -300 cm air Lowered 10% by 15 -30 cm tissue 50 cm tissue

Ionizing Radiation Units • Curie (Ci) = 37 billion disintegrations/sec • Roentgen (R) = energy which will produce 1 billion pairs/m. L air • Rad = 100 ergs absorbed energy/gm • Rem = absorbed dose in rads multiplied by factor related to type of radiation (1 for beta, gamma, X-ray; 20 for alpha)

Ionizing radiation damage • Tissue burns, minor and/or destructive • DNA breaks leading to cell death or mutation, potentially cancer

Human radiation dose-effect data DOSE (rems) 0 -25 25 -100 100 -200 200 -600 600 -1000 PROBABLE EFFECT No noticeable effect Slight blood changes Vomiting, fatigue (recovery in weeks) Vomiting, severe blood changes, hemmorhage (recovery in 1 -12 mo. ) Survival unlikely

Regulatory mandates on ionizing radiation • Nuclear Regulatory Commission occupational standard (10 CFR 20) is 5 rems/yr for whole body radiation. [Note that a lifetime exposure to 5 rem total is thought to shorten life by 1 -3 weeks. ] • Standard for nonwork environment is 170 mrem/yr.

Ionizing radiation General precautions • Confine radioactive chemicals to small areas which are posted • Cover bench tops with plastic-backed absorbent material • Use trays to catch spills • Wear gloves to protect hands and lab coat to catch splatters • Dispose of contaminated clothes appropriately

Radiation monitoring devices • Film badges – after the fact measurement, developed weekly or monthly • Geiger counter – best for high energy beta, gamma • Scintillation counter – used for wipe surveys