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 TypeWavelengthEffect UV-A “Black light” Region nmLittle effect UV-B nmSkin cancer possible UV-C nmCornea damage

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 MassChargeStopped by Alpha4+24 cm air Beta cm air Lowered 10% by X-ray cm tissue Gamma0050 cm tissue

Ionizing Radiation Units Curie (Ci) = 37 billion disintegrations/sec Roentgen (R) = energy which will produce 1 billion ion pairs/mL 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)PROBABLE EFFECT 0-25No 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