Lesson Objective

To understand that the term “low dose” encompasses both unavoidable everyday radiation and radiation from medical procedures—which we, as a society, choose to undergo based on their proven benefits. To recognize that certain medical procedures (such as CT scans) involve receiving, in a single instance, an amount of radiation equivalent to three or four years of natural background radiation. To acknowledge that CT scans involve radiation doses far lower than those classified as “high dose,” where the associated risks are well-established. To identify the three different models regarding low doses: linear, threshold, and hormesis. To understand the basic mechanisms underlying these three models.

Context

Radiation “phobia” is undesirable, as it would make life unbearable. In fact, it is impossible to live without being exposed to radiation; it is emitted by the soil, by food, and even reaches us from distant galaxies. However, following the discovery of radiation, society chose to accept the associated risks in exchange for the benefits. Today, exposure to “low-dose” radiation—defined as doses below 100 mSv—is widely accepted. Historically, the term “low dose” was applied to the exposure experienced by the “Radium Girls.” Years later, some of these women developed cancer; the radiation levels they were exposed to are now classified as an intermediate dose. Ultimately, “low dose” serves as a label for a level of radiation exposure we accept due to its tremendous benefits, even though there is no scientific consensus regarding its specific effects.

Moments	Description
Exposure	Radiation emission is a natural phenomenon. Some elements emit more radiation and are termed radioactive. Explain the various benefits associated with radiation. Present the radiation doses emitted by everyday objects, cosmic radiation, uranium mines, and X-rays. Propose expressing the 0 to 1 Gray range in mSv to facilitate discussion. Compare radiation doses from different situations and identify which is higher.
Activity	True/false activity (Part 1) to consolidate the presentation. Click to download the PDF of the complete Activity 3.
Exposure	Highlight the difficulties in studying the effects of low doses, given that the potential outcome is cancer—a disease with multiple causes. Discuss the meaning of “low doses” with them; historically, the concept refers to doses that produce no perceptible effects. Present the case of the “Radium Girls.” Introduce three models currently used to describe low-dose radiation.
Activity	Activity (Parts 2 and 3) for the initial understanding and description of low-dose models. You need only write down the fundamental thesis of the model.
Exposure	Present an analogy that explains two aspects present in all low-dose models: the effect of radiation and the repair performed by the human body.
Activity	Activity Part 4, which consists of students developing an analogy to explain the models.