13 - Sources of Radiation: Natural and Man-Made

Sources of Radiation

• Radiation sources are natural and man-made, including the electromagnetic spectrum.

Natural Radiation

• Cosmic radiation comes from space, contributing significantly to radiation exposure outside Earth.
• Terrestrial radiation comes from the land and ground, including radiation from Radon gas.
• Internal radiation is from inhaled or ingested radioactive substances, such as Radon gas.

Man-Made Radiation

• Weapons can cause weaponized nuclear radiation.
• Energy sources like nuclear power plants pose handling and control challenges.
• Medical radiation is a significant source, including fluoroscopy (C-arm and mobile mammograms), CT scans, SPECT scans and Gamma cameras.
• Medical radiation includes radiotherapy for cancer treatments like external beam radiotherapy, stereotactic radiosurgery/radiotherapy (SRS/SRT), and brachytherapy.
• Global radiation sources are around half from natural sources and half from man-made sources.
• The annual average radiation dose is estimated at 3 mSv, with most coming from Radon. Most Radon is buried under the soil and measured in houses through basements.

Electromagnetic Spectrum

• The electromagnetic spectrum consists of different wavelengths, including visible light, X-rays, and radio waves.
• Medical rays include ultraviolet, X-ray, and Gamma Ray.
• Wavelength and frequency have an inverse relationship.
• UV radiation is considered medical due to potential skin cancer risks from sun exposure.

Effects of Radiation on Health

• Pre-1960s understanding of radiation dangers stemmed from WWII experiences in Hiroshima and Nagasaki.
• General effects of radiation are categorized into stochastic and non-stochastic effects.
  • Stochastic effects occur by chance and are all-or-none, including cancers and congenital birth defects.
  • Non-stochastic effects have a threshold dose and are cumulative, such as skin erythema, sterility, and cataracts.
• Acute effects result from single, sudden exposure, with symptoms depending on the radiation dose received
  • Lower doses result in nausea, vomiting, and diarrhea
  • Higher doses cause somnolence, headache, and dizziness.

Conditions Caused by Radiation

• Thyroid cancer can results from radiation exposure, especially in young patients.
• Leukemia, or cancer of the blood cells, is known to be caused by radiation.
• Polonium poisoning is exemplified by Alexander Litvinenko's case, who was poisoned with polonium-210
  • Symptoms included weakness, nausea, and inability to eat or sleep.

Radiation Therapy Side Effects

• Breast cancer treatment using radiation can cause wet desquamation (skin removal) or dry desquamation, where skin is removed with no oozing if radiation exposure stops.

Relative Doses from Radiation Sources

• Whole-body CT scans emit more radiation than background radiation
• The recommendation is not to have too many diagnostic studies done.

Contamination vs. Exposure

• Contamination involves radiation in liquid, gas, or powder form
  • Can be external (spillage) or internal (ingestion/inhalation)
  • Spillage requires removing clothes, thorough showering (30+ minutes), and washing hair multiple times, clothes should be washed, or discarded..
• Exposure involves radiation in beam or ray form, such as X-rays or external beam radiotherapy
  • Prevent undue radiation exposure

Principles of Radiation Safety

• Justification involves the need for the medical radiation procedure and its timing.
• Optimization is selecting the best study for the condition.
• Dose limitation follows ALARA ("As Low as Reasonably Achievable")
• Limit dose, by reducing amount of radiation that the patient is exposed to, if one scan is enough, there is no reason for two scans

Cellphone Safety

• Cellphone signals fall on the left side of the electromagnetic spectrum
• Non-ionizing radiation is not a proven cause of cancer
• WHO reports that there are no adverse health effects associated with cellphones.
• FCC sets safety limits with a 50-fold safety margin
• Radio frequency energy near cell towers is thousands of times less than safe exposure limits.

Question and Answer Portion

• Radiation exposure for workers is monitored with OSLs; exceeding limits requires leave and investigation
• Mammogram recommendations vary: some suggest starting at 40, others at 50, depending on risk factors.
• Dental clinics should have precautions: dentists can use LEAD line screen for conducting X-rays.
• Contaminated clothing should be disposed of in orange radioactive waste bags, disposed of in radioactive waste section.
• Yearly chest X-rays required in UP Manila due to high tuberculosis prevalence.