Ionizing Radiation, Nonionizing Radiation, and Magnetic Fields

1. Ionizing Radiation, Nonionizing Radiation, and Magnetic Fields CHM 605 Fall 2003

2. Ionizing Radiation • Electromagnetic or particulate radiation capable of producing ions by interaction with matter. • X-rays, gamma rays, alpha particles, beta particles (electrons), neutrons, and charged nuclei. • Biomolecules can be altered, e.g., ionized atom in DNA molecule can cause cell death or mutation.

3. Radioactivity • Spontaneous emission of particles and/or electromagnetic radiation from an unstable nucleus • Alpha particles • Beta particles • Gamma Rays • Neutrons

4. Types of Radioactivity • Naturally Occurring • Uranium and Thorium decay series • Potassium - 40 • Continually produced : Tritium and 14C • Artificially Produced • Accelerators • Reactors (Byproduct material)

5. Uses of Radioactivity • Radiotracer applications • Activation by particle irradiation • Irradiation and sterilization • Medical diagnosis and therapy

6. Regulation of Radioactive Material • Nuclear Regulatory Commission (NRC) • Byproduct material • Reactors • Special Nuclear Material and Source Material • State Radiological Health (ISDH) • Machine produced • Accelerator produced • Naturally occurring

7. Requirements for Radioactive Material Use • Purdue Training • Completion of Proper Paperwork (A-4) • Adherence to Protocols Previously Submitted by PI (Principal Investigator) • Training by Designated Individual • Keep Track of Material: SECURITY, INVENTORY, SURVEY

8. Available Training • Unsealed Radioactive Material • Sealed Radioactive Sources (Includes irradiator) • Diagnostic X-ray( includes DEXA) • Analytical X-ray • Laser Safety

9. Exposure Limits • Effective dose equivalent - 5 rems • Dose equivalent to any organ - 50 rems • Shallow dose equivalent (skin) or dose to the extremities - 50 rems • Eye dose equivalent - 15 rems • Declared pregnant worker - 0.5 rems • Minor - 10% of adult levels • 1 rem = 1000 millirem

10. As Low As Reasonably Achievable The philosophy that reasonable efforts are maintained to keep radiation exposures as far below the limits as is practical.

11. Methods to Reduce Radiation Exposure • Time - Plan experiments, use as little radioactivity as possible • Distance - Use remote handle devices, remain away from storage areas • Shielding - store stock vials in a shield • Contamination Control - survey work area and self after use, wear PPE

12. Fly from NY to LA 2 millirem Get chest x-ray 10 millirem Move from DC to Denver 75 millirem/yr or certain parts of Brazil 640 millirem/yr Get married 1 millirem/yr Eat bananas and nuts ? Measures to Increase Radiation Exposure

13. Characteristic Continuous Voltage X-rays • X-rays are created by the deceleration of electrons in a target material • Spectrum can be • Continuous • Characteristic

14. Analytical X-ray Systems • System types • Open beam • Closed beam • Cabinet • Uses • Crystal structure analysis • Virus/protein structure analysis • Composite/alloy integrity

15. Analytical X-ray Hazards • Low energy • Less than 40 keV • Very intense x-ray beam • 400,000 R/minute • Very narrow beam • Typically < 1 mm2 • Minimal scatter • Low energy, absorbed readily in air

16. Energy Dependence of Biological Effects • Low energy x-rays (< 50 kVp) • easily absorbed • produce surface (skin) effects • High energy x-rays (> 50 kVp) • capable of penetrating deep into the body • produce internal effects

17. Specific Hazards • Primary Beam • Very intense x-ray beam • Up to 400,000 R/min • Beam diameter < 1cm • Scatter Radiation • Low intensity • Large area • Leaks through tube housing • Scatter from any point in an absorber

18. Ionizing Radiation Safety -- Administrative Controls • Personal dosimetry, area dosimetry • Area surveys • GM meter: Where are the leaks? • Ion chambers: How much is leaking? • Warning signs, warning lights • Standard Operating Procedures (SOPs)

19. Ionizing Radiation Safety -- Engineering Controls • Housing • Beam shutter • Primary beam stops • Shielding from entry into primary beam • Interlocks

20. Non-Ionizing Radiation Everything else, mainly the rest of the EM spectrum that is not ionizing: RF, MW, IR, VIS, and UV. • Cell phone bases (RF) • Heat Sealers (RF and MW) • Lasers (IR/UV/Vis) • Mercury Vapor Lamps (UV) • Microwave - Ovens, towers • NMR and MRI (RF and mag) • Radar (RF) • Radio & TV (RF, MW) • Satellites (MW) • Electric Power System (mag) • Ultraviolet Radiation

21. LASER • Acronym:Light Amplification by Stimulated Emission of Radiation • A laser produces a special sort of radiant energy by stimulated emission.

22. Laser radiation is different …from normal EM radiation radiation in that it is 1. monochromatic -- of a single wavelength 2. coherent -- photons in phase with each other 3. directional -- beam has very low divergence • Lasers are pulsed or continuous wave

23. Lasers and their use are regulated (ANSI Z136.1) • Guidelines for safe use of lasers/systems • Establishes hazard classes 1, 2, 3a/b & 4 • Lists requirements for medical surveillance and training programs • Addresses ancillary hazards other than radiation • Specifies maximum permissible exposures (MPE) • Determines the nominal hazard zone (NHZ)

24. Laser Hazard Classes Are based on the inherent capability of causing injury, mainly on laser wavelength and accessible power output: ClassDescription I Not hazardous II Hazardous only when stared at for long periods of time III Hazardous for intrabeam viewing and viewing specular reflections IV Hazardous for intrabeam viewingand viewing specular or diffuse reflections

25. I.e., shinysurface like metal, jewelry Laser Reflections Specular (“mirror-like”) No reduction in beam intensity. Diffuse Beam intensity reduced as the inverse square of distance from reflecting surface. I.e., dullsurface like paper, cloth

26. Mechanisms of Eye Injury • Thermal • charring, edema, hemorrhage • Photochemical (blue light and UV) • produces toxins and biochemical changes causing inflammation, lesions and lens opacities • Photoacoustic (short intense pulses) • explosive forces due to expanding gases

27. Eye Hazard vs. Wavelength UVC UVB UVA VISIBLE IRA IRB IRC 100 200 315 400 700 1400 3000 Lens Retina Lens Cornea Cornea Photochemical Thermal

28. Lasers -- Non-Beam Hazards • Electric Shock • Chemical Exposures • Cryogenic materials • Compressed Gases • Explosions • Laser Generated Air Contaminants (LGAC’s) • Other Hazards

29. Laser Safety Control MeasuresNominal Hazard Zone (NHZ) • Specifies the area(s) of the workroom where direct or scattered laser radiation is considered hazardous. • Exposure levels any place outside the NHZ are not considered hazardous.

30. Laser Safety Control MeasuresNominal Hazard Zone (NHZ) NHZ

31. Laser Safety Control MeasuresEye Protection Entry warning • Require eye protection, specific to the laser and , when exposure above the MPE is possible. • Post appropriate warning signs

32. Laser Safety Control MeasuresEntry Controls Must prevent people from inadvertently or casually entering the laser use area. Types of entry control: • Locked entry • Latched entry • Barriers with signs Secondary Barrier

33. Laser Safety Control MeasuresWindow Coverings • Have windows, doorways, and open portals covered to prevent transmittance of beam Opaque Window

34. Laser Safety Control MeasuresOther Controls • Specify controlled area and limit access • Develop and follow SOPs, especially during the alignment process • Review new procedures and new installations • Prevent unauthorized use of laser • Provide training for all users

35. Magnetic fields • Also magnet quench issues… nothing to do with radiation…. • Magnetic field hazards to surgical implants, metal prosthetics, older pacemakers. • RF field hazard to newer pacemakers • High voltage hazards for everyone. • High field hazard with metal objects.

36. Magnetic device safety • Pacemeakers stay out. • Exercise great care regarding metal objects (including gas cylinders). • Know all procedures and what to do in case of emergency, e.g. magnet quench.