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Environmental Science
Course Code
Silvija Stefanovic
Study Guide

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Lecture 6: Radiation and Human Health
We cannot escape radiation
1. Background radiation: natural radioactivity in Earth by cosmic rays from outer
space, cannot be controlled
2. Manmade radiation: electronic products like X-rays, television sets, microwave
ovens, radar devices, lasers and CAN be controlled
Background and Manmade Radiation
1/8th manmade radiation, others natural
*From artificial sources, main source is medical
Radiation and Human Health
Ionized radiation vs. non-ionized
Ionized radiation have short wavelength but high energy
Non-ionized radiation: low energy, not really considered harmful, but has become a
concern in last few years
Ionized Radiation
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Radioactive material that decays spontaneously produce ionizing radiation
Strips away electrons from atoms which create 2 charged ions
Can break some chemical bonds
Alpha, beta particles, gamma and x-rays all differ in the amount of energy they have
Health Effects from Exposure to Radionuclides
1. Stochastic health effects: chronic (by chance, long period of time)
Long-term, low level of exposure, not certain pattern established
Increase levels of exposure makes these effects more likely to occur but do
not influence type of severity of the effect, carcinogens (20 years)
Ex. professional exposure to microwave or lab instrument
2. Non-stochastic health effects: acute
Short-term, high level of exposure
Increases levels of exposure make these effects more severe
Ex. nuclear explosion
Stochastic Health Effects
Changes in DNA: impact on genetic material
Teratogenic (fetus most sensitive 8-15 weeks of pregnancy, mental retardation,
birth defects…)
Genetic (passed from parent to child)
Cancer: uncontrolled growth of cells, damage at the cellular/molecular level
Non-Stochastic Health Effects
Radiation sickness: hair loss, skin burn, organ function, nausea, premature aging,
Cancer: a disease in which cells multiply without restraint
Tumor invades tissue of origin and metastasis into other tissues
Cancer results from accumulation of mutations: change to DNA of a cell
Key mutations in carcinogenesis include: increase the activity of genes that instruct cell
to divide (oncogenes) or decrease activity of genes that instruct cell to stop dividing
(tumor suppressor genes)
Carcinogen: any agent that increase cancer risk at any stage in the process
Simple view of stages:
Initiation: initial mutation in a cell either enhances instructions to cell to divide;
or decreases instructions to stop dividing
Promotioninitiated cell is stimulated to divide, becoming a benign tumor
Progressionmutations cascading cell division malignant tumor
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Chemical Properties of Radionuclides
Organs can’t distinguish between radioactive and non-radioactive forms of element
Ex. radioactive iodine in thyroid (endocrine gland), calcium, strontium-90, radium-226
accumulate in bones
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