**3.2 High indoor radon levels in South Africa and applicable radon mitigation system**

#### *3.2.1 Gauteng Province*

In South Africa, there are studies of indoor radon measurements, some of which indicate levels of radon higher than 148 Bq/m3 recommended by EPA [24]. In a study done by Radebe [25] for the design of radon chamber, alphaguards that were calibrated measured radon levels above 1000 Bq/m3 from Tudor shaft soil samples.

Tudor shaft, an informal settlement in Krugersdorp, is known to be affected by gold mine shaft, and tailing dam is one of the areas of note that radon mitigation methods must be implemented. The inhabitants of Tudor shaft built their shacks on top of mine dump with radioactive uranium soil as seen in **Figure 7**. Vegetables are

#### **Figure 7.**

*(a) Example of shack interior for Tudor shaft. (b) Children playing on soil that has potentially higher levels of radiation. (c) Shacks built on soil that potentially have higher levels of radiation [26, 27].*

grown on top of soil potentially carry high levels of radioactivity and environment due to polluted air from mine tailings. The community is at risk of radioactive health risk arising from mine dumps. Typical entry points in shacks in Tudor shaft comprise cracks on the floor or ground, holes on mats used to cover the soil, and gaps found on the edges of the interior of the shack between the mat and the shack or poles. It is also noted that when doors and windows are closed, radon accumulates and returns to an average value, while during the day, it reduces indoors.

A radon mitigation system applicable to Tudor-shaft inhabitants for shacks can be a passive sub-slab depressurization system. A passive sub-slab system relies on stack effect, which is a term that defines radon reduction by the reliance on air pressure differentials to extract radon from underneath the foundation to the outdoor air via vent pipes. Mats or floor covers must be checked to any opening and removed for the installation of a high-density polyethylene plastic to retain the radon gas. Then the radon vent pipe can be installed for moving the radon retained by the plastic to the outdoor air as seen in **Figure 8**. Furthermore, when a floor cover or mat is placed on top of the high-density polyethylene plastic, openings or voids must be sealed with caulk or epoxy sealant. Passive sub-slab system together with sealing and natural ventilation application can reduce the radon in informal settlement such as Tudor shaft especially for shacks without electricity means. The government has done a good job in relocating some families affected by mine dumps.

A best solution would be to relocate the community to a better place. A temporary solution would be to apply radon mitigation methods to minimize the risk of lung cancer, also community awareness about reducing emanation of radon via natural ventilation and sealing of openings or cracks is important.

*An Overview of Radon Emanation Measurement System for South African Communities DOI: http://dx.doi.org/10.5772/intechopen.109065*

**Figure 8.** *Passive sub-slab system [28].*

#### *3.2.2 Western cape*

Houses in Paarl, Western Cape province, with a type of crawlspace foundation used for storage by occupants recorded radon levels off up to 800 Bq/m3 as seen in **Figure 9** [30]. Also houses with wooden floor recorded higher radon levels than concrete floor. At the foothill off Paarl Mountain, higher levels of radon levels were found and some of the houses are nearby the foothill. An active sub-slab depressurization system and sub-membrane suction system for crawl space can be applied for houses at Paarl.

Furthermore, methods of foundation crack repair and staples are essential for the reduction of radon in houses, although mitigation systems are the best. Foundation crack repair inhibits the entrance of radon indoors. By utilization of products such as concrete staples or epoxy, which works like a glue, and holes or cracks that are in the concrete or wooden foundation are repaired and reinforced [31], which thus stops the primary entrance of radon in houses.

The houses with walls having stability problems tend to lean or bow; therefore, carbon staples can be used to repair and reinforce the cracked or bowed wall to achieve radon emanation reduction. Epoxy, which comprises epoxy resin and hardener, is essential for closing the cracks in foundation where there is radon entry [31] .

**Figure 9.** *Radon in Paarl crawlspace type of a foundation [29].*
