Radiation Uses and Safety BI 245

Weise et al Plant Cell 12:1345 A plant cell Sucrose How can you measure sucrose molecules taken in by the cell?

Expose to Epidermal Growth Factor Untreated FibroblastTreated Fibroblast How would you find out what new proteins are synthesized in the treated fibroblasts?

Labeling with Radioisotopes Radioisotopes are isotopes of atoms that decay and release energy in the form of particles or electromagnetic energy. Radioisotopes are isotopes of atoms that decay and release energy in the form of particles or electromagnetic energy. The energy released is a form of electromagnetic radiation (like light), but very energetic (short wavelengths) The energy released is a form of electromagnetic radiation (like light), but very energetic (short wavelengths) This means if you put a radioisotope on a molecule, you can find it with radiation detection instruments or film – just like light. This means if you put a radioisotope on a molecule, you can find it with radiation detection instruments or film – just like light.

Radioactive Materials in biomedical research Most commonly used radioisotopes Most commonly used radioisotopes –H3, C14, P32, P33, S35 -- all beta emitters  In vivo and in vitro labeling –Na22, K40, Ca45, I all beta/gamma emitters  Uptake studies for the ions, in vitro labeling for I125

Weise et al Plant Cell 12:1345 A plant cell Sucrose How can you measure sucrose molecules taken in by the cell? What isotopes would be best to label sucrose? How could you find out how much was in the cells?

Expose to Epidermal Growth Factor Untreated FibroblastTreated Fibroblast How would you find out what new proteins are synthesized in the treated fibroblasts? What isotopes could you use to label newly synthesized proteins? How would you find those proteins?

Gel electrophoresis of proteins

In vivo labeled protein experiment

Suppose you wanted to label a DNA molecule? What isotopes could you use? What isotopes could you use? How could you find the labeled DNA molecule. How could you find the labeled DNA molecule.

The radioactive molecules used in these experiments are sometimes called tracers Sugars, Lipids…C-14 or H-3 Sugars, Lipids…C-14 or H-3 Proteins, C-14, S-35, or H-3 labeled amino acids Proteins, C-14, S-35, or H-3 labeled amino acids Nucleic acids P-32, either as a P32- labeled nucleotide or as P-32 added to one end of the molecule. Nucleic acids P-32, either as a P32- labeled nucleotide or as P-32 added to one end of the molecule.

Radioactivity vs Radiation Radioactivity Radioactivity – – Any spontaneous change in the state of the nucleus accompanied by the release of energy. Alpha, beta, gamma, neutrons Radiation – – Refers to the actual particles or photons emitted and the energy they carry.

Electromagnetic Radiation Ionizing Non-ionizing

What defines the differences in radionuclides and the radiation they emit What type of radiation (alpha, beta, gamma)? What type of radiation (alpha, beta, gamma)? How does that radiation interact with matter? How does that radiation interact with matter? How much energy does the radiation have? How much energy does the radiation have? How long with the radiation last (half-life of the radionuclide. How long with the radiation last (half-life of the radionuclide.

Results of alpha decay process

Alpha particles Move in straight line Move in straight line Lose little energy in each interaction Lose little energy in each interaction But have many interactions in the path But have many interactions in the path Consequently don’t travel very far Consequently don’t travel very far

Results of beta decay process

Electrons and Positrons (betas) Interaction Characteristics: Ionize and excite atomic electrons Few interactions per unit path length – few ions produced and low energy transfer. Path Length > Range Large energy loss per collision Path is not straight Higher energy deposition at end of path (more interactions at end of path)

Energy differences Betas Betas –H3 = MeV –C14 = MeV –P32 = 1.71 MeV Gammas Gammas –Co60 = 1.33 MeV –Cs137 = 0.66 MeV

Half-Lives of Radionuclides H years H years C years C years S-3587 days S-3587 days P days P days Am years Am years

Radiation Risk All higher energy radiation poses some risk to cells. All higher energy radiation poses some risk to cells. –UV – induces thymine dimers in DNA –Betas—induce changes in DNA, potentially breakage –Gammas and alphas -- the same as beta, but generally more energetic, so more potential for damage. –X-rays -- same DNA repair systems are activated, but not perfect. DNA repair systems are activated, but not perfect.

Radiation Risk High Dose (acute) High Dose (acute) – rem –effects blood cell counts, but people usually recover – rem – GI track, and epithelial cells effected. Lower end survive,. Upper end don’t –Above 1400 rem..death likely Atomic Bomb Victims Chernobyl nuclear meltdown Low Dose Low Dose –Risk related to chance of mutation –Above 50 rem, risk proportional to dose –Below 50 rem, risk assessment less clear. –Effects below 10 rem unknown. Primary risk is induction of cancer Primary risk is induction of cancer

What factors influence probability of radiation damage? Radiation Dose Radiation Dose –Type –Activity (how much) –Time of exposure

Types of exposure External Exposure High energy Betas Gammas Internal exposure – requires intake of radioisotope – Alpha, Beta and Gamma

External Exposure Reduction Time: reduce time spent in radiation area Distance: stay as far away from the radiation source as possible Shielding: interpose appropriate materials between the source and the body

Controlling Internal Exposure PREVENT INTAKE! PREVENT INTAKE! –Safe Handling Practices! –Contamination Control   removable surface contamination   airborne contamination Standard Procedures help! – –Personal   No eating, drinking, smoking, make-up application, etc when working with RAM – –Procedures   Work in hood   Wear PPE   Clean up contamination   Survey to make sure no contamination exists   Monitor Air, to make sure procedure doesn’t release dust or volatiles

Required PPE Gloves Gloves Labcoat Labcoat Dosimeters Dosimeters Safety glasses Safety glasses Inappropriate PPE! Appropriate PPE, shielding, and monitoring

Exposures in perspective You are exposed to ionizing radiation all the time. This is called background radiation. You are exposed to ionizing radiation all the time. This is called background radiation.

DOSE LIMITS What’s my risk of getting cancer from a radiation exposure? This is hard to determine. The most quoted estimate is that an exposure of workers to 1 rem of radiation would produce 4 cancers = 0.04%. Consider that in the US as a whole the risk of cancer is about 25%

BUT! The public perception of radiation risk is that it is always “DEADLY RADIATION”! The public perception of radiation risk is that it is always “DEADLY RADIATION”! This graphic shows how the media place stories on radiation out of proportion to risk. nb. There were NO documented deaths due to radiation in the time shown here. This graphic shows how the media place stories on radiation out of proportion to risk. nb. There were NO documented deaths due to radiation in the time shown here.

Situation Cause of death 2.0 mrem cancer from radiation travelling 700 miles by air accident crossing the ocean by air cancer from cosmic rays traveling 60 miles by car accident living in Denver for 2 months cancer from cosmic rays living in a stone building for 2 months cancer from radioactivity working in a factory for 1.5 wk accident working in a coal mine for 3 hraccident smoking 1-3 cigarettescancer; heart-lung disease rock-climbing for 1.5 minutesaccident 20 min being a man aged 60mortality from all causes living in New York City for 3 dayslung cancer from air pollution Some Risk Comparisons One-in-a million chances of dying

How do you find radiation or radioactive materials Radiation Radiation –With an exposure meter (reads the radiation field)..These are called ion chambers Radioactive materials Radioactive materials –With a counter (like a Geiger counter). These measure individual radioactive particles.