Naturally occurring radon and its short lived progeny are the second leading cause of lung cancer after smoking, and the main risk factor for non-smokers. The radon progeny, mainly Polonium-218 (²¹⁸Po) and Polonium-214 (²¹⁴Po), are responsible for the highest dose deposition in the bronchial epithelium via alpha-decay. These alpha-particles release a large amount of energy over a short penetration range, which results in severe and complex DNA damage. In order to unravel the underlying biological mechanisms which are triggered by this complex DNA damage and eventually give rise to carcinogenesis, in vitro radiobiology experiments on mammalian cells have been performed using radon exposure setups, or radon analogues, which mimic alpha-particle exposure. This review provides an overview of the different experimental setups, which have been developed and used over the past decades for in vitro radon experiments. In order to guarantee reliable results, the design and dosimetry of these setups require careful consideration, which will be emphasized in this work. Results of these in vitro experiments, particularly on bronchial epithelial cells, can provide valuable information on biomarkers, which can assist to identify exposures, as well as to study the effects of localized high dose depositions and the heterogeneous dose distribution of radon.

We describe a school science outreach initiative that introduced learners to applied nuclear physics research by means of a two-day workshop that involved learners and teachers from 5 schools in the Western Cape province of South Africa. During this workshop, the participants were introduced to the naturally occurring, inert, colorless, and tasteless radioactive gas radon (²²²Rn). During the first day of the workshop, the participants were informed about the detrimental health impacts of inhaling radon and its daughter radionuclides and were shown how indoor radon activity concentrations can be measured using the electret ion chamber (EIC) technology. The learners were then each supplied with a short-term electret (E-PERM, Radelec, Frederick, MD, USA) and associated ion chamber to enable them to make radon measurements in their homes. The teachers in turn were supplied with EICs to enable them make radon measurements in their schools. The participants returned the EICs on the second day of the workshop, one week later. Here, the drop in the potential difference across each electret was measured in order to calculate the average indoor radon activity concentration. A total of 49 indoor radon concentrations were measured. The average indoor radon concentrations were 36 ± 26 Bqm⁻³ in homes and 41 ± 36 Bqm⁻³ in schools, while the highest concentration was found to be 144 Bqm⁻³. These levels were compared to predictions from a model that uses input information about the uranium content associated with the surface geology at each measurement location. The predictions compared well with the measured values.

Radon activity concentrations (in water and in air) were measured at 13 selected locations at the Avalon Springs thermal spa resort in Montagu (Western Cape, South Africa) to estimate the associated effective dose received by employees and visitors. A RAD‐7 detector (DURRIDGE), based on alpha spectrometry, and electret detectors (E-PERM®Radelec) were used for these radon measurements. The primary source of radon was natural thermal waters from the hot spring, which were pumped to various locations on the resort, and consequently a range of radon in-water analyses were performed. Radon in-water activity concentration as a function of time (short term and long term measurements) and spatial distributions (different bathing pools, etc.) were studied. The mean radon in-water activity concentrations were found to be 205 ± 6 Bq L⁻¹ (source), 112 ± 5 Bq L⁻¹ (outdoor pool) and 79 ± 4 Bq L⁻¹ (indoor pool). Radon in-air activity concentrations were found to range between 33 ± 4 Bq m⁻³ (at the outside bar) to 523 ± 26 Bq m⁻³ (building enclosing the hot spring’s source). The most significant potential radiation exposure identified is that due to inhalation of air rich in radon and its progeny by the resort employees. The annual occupational effective dose due to the inhalation of radon progeny ranges from 0.16 ± 0.01 mSv to 0.40 ± 0.02 mSv. For the water samples collected, the ²²⁶Ra in-water activity concentrations from samples collected were below the lower detection limit (~0.7 Bq L⁻¹) of the γ-ray detector system used. No significant radiological health risk can be associated with radon and progeny from the hot spring at the Avalon Springs resort.

Probing university students’ understanding of direct-current (DC) resistive circuits is still a field of active physics education research. We report here on a study we conducted of this understanding, where the cohort consisted of students in a large-enrollment first-year physics module. This is a non-calculus based physics module for students in the life sciences stream. The study involved 366 students enrolled in the physics (bio) 154 module at Stellenbosch University in 2015. Students’ understanding of DC resistive circuits was probed by means of a standardized test instrument. The instrument comprises 29 multiple choice questions that students have to answer in ~40 min. Students were required to first complete the standardized test at the start of semester (July 2015). For ease of reference we call this test the pre-test. Students answered the pre-test having no university-level formal exposure to DC circuits in theory or practice. The pre-test therefore served to probe students’ school level knowledge of DC circuits. As the semester progressed students were exposed to a practical (E1), lectures, a prescribed textbook, a tutorial and online videos focusing on DC circuits. The E1 practical required students to solve DC circuit problems by means of physically constructing circuits, algebraically using Kirchhoff's Rules and Ohm’s Law, and by means of simulating circuits using the app iCircuit running on iPads (iOS platform). Each E1 practical involved ~50 students in a three hour session. The practical was repeated three afternoons per week over an eight week period. Twenty three iPads were distributed among students on a practical afternoon in order for them to do the circuit simulations in groups (of 4–5 students). At the end of the practical students were again required to do the standardized test on circuits and complete a survey on their experience of the use of the iPad and iCircuit app. For ease of reference we refer to this second test as the post-test. The students’ average score on the post-test was found to be ~25% higher than their pre-test score. The results of the iPad use survey show that the majority of students felt that the iCircuit app enhanced their learning of DC circuits.