Study Notes for Environmental Health Lecture: Ionizing & Nonionizing Radiation

Introduction to Environmental Health

Lecture 14: Ionizing & Nonionizing Radiation

Date: 27 October 2025
Instructor: Prof. Alasdair Cohen
Course: Virginia Tech | PHS 3014

In the News

  • No lecture today; time dedicated for students to work in project groups.

Learning Objectives (Part I)

  • Define the terms ionizing radiation and nonionizing radiation.

  • Understand the basic science behind electromagnetic radiation and isotopes.

  • Understand the general differences between these two types of radiation.

  • Describe some primary sources of nonionizing radiation and health impact concerns.

What is Radiation?

  • Definition: Energy that travels through space.

Types of Radiation:

  1. Nonionizing Radiation

    • Classified as the form of radiation on the left half of the electromagnetic spectrum.

  2. Ionizing Radiation

    • Definition: Radiation that has so much energy it can knock electrons out of atoms, process known as ionization.

    • Examples:

      • Radioactive elements

      • Cosmic particles

      • X-ray machines.

Radioactivity

  • Occurs during radioactive decay.

  • Definition: Reduction in the activity of a quantity of material by disintegration of its atoms.

  • Key Terms:

    • Isotope: Each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei.

    • Nuclide: Any species of atom that exists for a measurable length of time.

    • Radioisotope: Radioactive isotope.

    • Radionuclide: Radioactive nuclide.

Isotopes & Heavy Water

  • Neutron characteristics in isotopes.

Non-Ionizing Radiation

  • Definition: A type of radiation that lacks sufficient energy to ionize atoms or molecules.

Examples of Non-Ionizing Radiation:

  • Extremely Low Frequency (ELF) Radiation: High tension power lines.

  • Radio Waves: AM, FM, VHF-TV radio waves.

  • Microwave Radiation: Used in microwave ovens.

  • Infrared Radiation (IR): Source of heat in heat lamps used for keeping food warm.

  • Visible Light Radiation.

  • Ultraviolet Radiation (UVA, UVB, UVC).

Health Effects of Non-Ionizing Radiation:

  • Sources of ELF Radiation:

    • Electric power poles,

    • Wiring in buildings,

    • Some electrical appliances.

    • Study Findings: Research on ELF and health has produced conflicting findings, with some suggesting non-definitive results concerning EMF exposure and cancer.

Cell Phone Radiation

  • Cell phones transmit in the range of 900-1800 MHz producing radiofrequency radiation.

  • Higher frequency levels (i.e., radiofrequency and microwave radiation) cause heating of the body.

Sources of Ultraviolet Radiation (UVR):

  • Welders' arcs,

  • Tanning beds,

  • Flood lamps (used in photography),

  • Halogen desk lamps,

  • Lightning,

  • Electrical sparks,

  • Sunbathing.

Ultraviolet Radiation (UVR) Classification:

  • UVA: Long wavelength.

  • UVB: Medium wavelength.

  • UVC: Short wavelength.

  • UV Index: Forecast indicating expected risk of overexposure to UV radiation from the sun on a scale of 0 to 11+ (extreme risk at 11+).

Effects of UV Radiation:

  • Short-Term Conditions: Burns, temporary blinding.

  • Long-Term Consequences:

    • Photoaging of skin.

    • Nonmelanoma skin cancer (NMSC).

    • Malignant melanoma (MM).

    • Retinal damage.

Understanding Ionizing Radiation

  • Definition: A form of energy that removes electrons from atoms and molecules in materials like air, water, and living tissue.

  • Radioactive Decay: Process where radioactive atoms spontaneously emit radiation (energy or particles) to achieve stability.

  • Ionizing activity can damage molecules in body cells potentially leading to health issues (like cancer).

Types of Decay:

  • Alpha (α) Decay:

    • Reduction of protons and neutrons by two.

  • Beta (β) Decay:

    • Transformation of protons and neutrons by converting one to the other.

  • Gamma (γ) Decay:

    • High energy photons exit the nucleus, stabilizing it.

Properties of Radioactive Isotopes:

  • Alpha (α) Particles:

    • Large particles blockable by a sheet of paper.

    • External exposure not harmful, potentially damaging if ingested/inhaled.

  • Beta (β) Particles:

    • Smaller than alpha particles, blockable by clothing but can cause skin burns.

  • Gamma (γ) Rays:

    • High penetration capability, need dense material (like lead) to block.

Natural Sources of Ionizing Radiation

  • Cosmic Radiation: Can easily penetrate the human body.

  • Nuclear Elements:

    • Uranium: Found in North America, Africa, Australia,

    • Radon: Colorless and extremely toxic gas, a Class A carcinogen produced from radium and uranium decay.

Anthropogenic Sources of Ionizing Radiation

  • Medical Sources:

    • X-rays, nuclear medicine, and radiation therapy.

  • Industry Sources:

    • Radioactive substances in various industrial applications.

  • Nuclear Power Plants: Known for potential leakage of radiation.

  • Nuclear Testing: Radioactivity from nuclear weapons tests.

Primary Radiation Exposure Sources in the USA

  • Medical Uses of Ionizing Radiation: Accounts for approx. 40% of radiation exposure, through medical procedures involving X-ray machines and nuclear medicine.

Radiation Measurement Units

  • Curie (Ci): Measure of radioactivity in a sample.

  • Rad: Formerly used unit of absorbed ionizing radiation dose.

  • Rem: Measure of radiation dose relative to biological effect.

  • Roentgen (R): Measures ionizing ability of gamma radiation.

  • Becquerel (Bq): Corresponds to radioactivity.

  • Gray (Gy): Corresponds to absorbed dose.

  • Sievert (Sv): Corresponds to dose equivalent.

Exposure and Dose Measurements

  • Exposure: Describes the amount of radiation traveling through air.

  • Absorbed Dose: Amount of radiation absorbed by an object/person.

  • Effective Dose: Amount absorbed, adjusted for radiation type and organ effect.

Factors Affecting Radiation Exposure:

  • Total exposure time to radioactive source.

  • Distance from the source.

  • Radioactivity degree of material.

Stochastic vs. Nonstochastic Effects

  • Stochastic Effects: Random, associated with low-level exposure over long periods.

  • Nonstochastic Effects: Acute, seen in high radioactive exposure causing burns and sickness (e.g., nausea, weakness, hair loss).

Effects of a Nuclear Explosion

  • Blast Damage: Destruction to buildings and individuals.

  • Heat Effects: Severe temperatures causing injury.

  • Ionizing Radiation Effects: Leading to acute radiation syndromes.

  • Radioactive Fallout: Health risks over time affecting consumables.

Historical Events: Atomic Bombs

  • Hiroshima & Nagasaki:

    • Hiroshima: August 6, 1945

    • Nagasaki: August 9, 1945

Health Outcomes of Survivors

  • Tracking health outcomes of atomic bomb survivors to assess long-term effects.

Nuclear Facility Accidents

  • Three Mile Island Accident (1979):

    • Partial meltdown; serious but with no detectable health effects.

  • Chernobyl (1986): One of the largest nuclear accidents worldwide.

  • Fukushima (2011): Accident in Japan highlighting the risks associated with nuclear power.

Radiocarbon Dating

  • Definition: Method proposed by Willard Libby in 1946 to establish the age of objects by detecting carbon-14’s presence.

  • Principle: Based on measuring the half-life of the carbon isotope to determine age.

References:

  • Sources include educational supplements for the textbook "Essentials of Environmental Health" (2019, by Robert Friis).

  • Additional resources from CDC, EPA, and other health, environmental, and nuclear-related agencies.