How Is Radiation Exposure Measured

How Is Radiation Exposure Measured? Radiation Exposure is mostly measured using the conventional unit rad or the SI unit gray (Gy), whereas the biological risk of exposure to radiation is measured using the conventional unit rem or the SI unit sievert (Sv).

When dealing with ionizing radiation, the fundamental term used to describe the radiation-induced energy transfer to any type of material is the amount of energy D (Dose) that is ‘absorbed’. Energy D is defined as the amount of energy E transferred to a small amount of material.

This is expressed thus:

D = dE/dm. where m is the mass of material.


D – Dose

dE – Energy

dM – Mass of Material

What Is Radiation Dose

Radiation dose quantifies the amount of ionizing radiation absorbed by living tissue or a material. It is measured in units such as the gray (Gy) or the sievert (Sv), indicating the absorbed energy or accounting for biological effects. Exposure sources encompass medical practices, environmental influences, and work-related activities. Dosage is a critical factor in determining the balance between the advantages of procedures such as X-rays and the potential risks associated with them.

Monitoring equipment, including dosimeters and geiger-muller counter devices, assist in the evaluation and restriction of exposure. Precision dose management guarantees the health of individuals in a variety of settings, including healthcare settings, industrial settings, and the implementation of radiation protection measures for both individuals and the general public.

Radiation Measurement Units – How Is Radiation Exposure Measured

Aside from the measurement unit mentioned at the beginning of this article, radiation exposure can be measured using various units and instruments depending on the type of radiation and the context in which it is being measured. The common units and instruments used for measuring radiation exposure include:

1. Roentgen (R): This is a unit of exposure to X-rays or gamma rays. It measures the ionization of air caused by these types of radiation.

2. Rad (Radiation Absorbed Dose): The rad is a unit of absorbed radiation energy. It measures the amount of energy deposited by ionizing radiation in a specific material, typically human tissue.

3. Gray (Gy): The gray is the SI (International System of Units) unit equivalent to the rad. One gray is equal to one joule of energy absorbed per kilogram of tissue.

4. Rem (Roentgen Equivalent Man): The rem is a unit used to quantify the biological effect of different types of ionizing radiation. It takes into account the type of radiation and its potential to cause damage to living tissue. The rem is now being replaced by the Sievert (Sv) in the SI system.

5. Sievert (Sv): The sievert is the SI unit for measuring the equivalent dose, which accounts for the biological effects of different types of radiation. One sievert is equal to one joule of absorbed energy per kilogram of tissue, with a weighting factor that reflects the relative biological effectiveness of the specific type of radiation.

6. Dosimeter: A dosimeter is a device worn by individuals who may be exposed to radiation as part of their work or in certain environments. It measures the accumulated dose of radiation over time. Common types include film badges, thermoluminescent dosimeters (TLDs), and electronic personal dosimeters (EPDs).

7. Geiger-Muller Counter: This is a handheld device that detects ionizing radiation. It is commonly used to measure radiation levels in the environment. It works by counting the number of ionizing events in a specific period.

8. Scintillation Detector: This type of detector uses a scintillating material that emits light when exposed to ionizing radiation. The amount of light emitted is proportional to the radiation dose, and this can be measured to determine the level of radiation exposure.

It is important to note that different units and instruments are used for different purposes, and the choice depends on factors such as the type of radiation, the context of exposure, and the desired measurement outcome (e.g., exposure to the general public, occupational exposure, medical exposure).

After stating all these, let us have a little review of what Radiation is, it types and health effects; why we need to measure it.

READ: Incident Energy Analysis: The Most Important Tool in Radiation Safety?

What is Radiations

According to CDC, Radiation is energy that comes from a source and travels through space at the speed of light. This energy has an electric field and a magnetic field associated with it, and has wave-like properties. You could also call radiation “electromagnetic waves”.

Radiation is an unavoidable part of our daily lives. The sun, microwaves in our kitchens, and radios in our vehicles are some of the most common sources of radiation. Most forms of radiation do not pose a risk to human health, however, some do. Generally, radiation has a lower risk at low doses, however, higher doses may be associated with a higher risk. Depending upon the form of radiation, various strategies must be employed to protect human health and the surrounding environment from its consequences, while also allowing for its numerous uses.

Types of Radiation

  • Ionization radiation:

Ionising radiation is the energy produced from natural or artificial sources. It has more energy than non-ionising radiation, enough to cause chemical changes by breaking chemical bonds. This effect can cause damage to living tissue. It is called ionization radiation because it occurs due to the fact the electron in the atom has acquired enough energy to break away from the atom resulting to the formation of two charged particles or ions: the molecule with a net positive charge, and the free electron with a negative charge.

There are three types of ionization radiation;

  • Alpha particles, which include two protons and two neutrons
  • Beta particles, which are essentially electrons
  • Gamma rays and x-rays, which are pure energy (photons).

Ionization radiation can pose severe health effects, especially when exposed to high dose, you need to follow safety precautions when working with ionization radiation.

  • Non-Ionization Radiation:

Non-ionizing radiation refers to any type of electromagnetic radiation that does not carry enough energy to ionize atoms or molecules, i.e, to completely remove an electron from an atom or molecule. Instead of producing charged ions when passing through matter, non-ionizing electromagnetic radiation has sufficient energy only to trigger the movement of an electron to a higher energy state. Non-ionizing radiation is not a significant health risk.

Examples of non-ionization include: Visible light, Infrared (IR), Microwave (MW), Radio frequency (RF), and Extremely low frequency (ELF).

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