Table 1.
List of selected studies of radon mitigation intervention with relative effectiveness.
| Study Design, Citation, location | Population, Sample, Measures, Duration of follow up/Timeline | Interventions, Comparison | Baseline Radon Before Mitigation (Bq/m3) | Outcome After Mitigation (Bq/m3) | Effectiveness* (*measured as the percentage of difference between pre- and post- remediation radon level) |
|---|---|---|---|---|---|
| Quantitative-comparative study by Stanley et al. (2017) in Calgary, Canada. | 2382 residential homes tested for radon for at least 90 days (median 103 d) between 2013 and 2016. High radon level homes were remediated and retested to determine the efficacy of radon reduction techniques. | Sub-slab depressurization mainly but in a minority of cases, radon-impermeable membrane installed. | Average 126 (range >15–3441); 1135 homes had >=100; 295 homes had >= 200; 90 homes had average 575. | Mitigated 90 homes with av. 575 radon and noted reduced av. levels of 32.5. The house with the highest radon level of 3441 was reduced to 86 | Highest mitigation efficacy recorded was 97.5%; Mitigation was effective in reducing radon levels to below 100 Bq/m3 in all cases and typically reduced levels by 92%. |
| Experimental study by Boardman and Glass (2015) in Wisconsin, USA | A single-zone air infiltration model was calibrated to measure tracer gas, soil moisture, and air exchange rate. | Active soil or sub-slab depressurization system (AS/SSDS) | 321.9 ± 5.18 | 11.1 ± 7.4 | 96.5% efficiency in radon reduction; >75% reduction in moisture |
| Quasi-experimental study by Brossard et al., (2015) in Canada. | Mitigated nine houses by installing SSDS with two types of discharge and fan locations: Basement or roof-discharge. | Sub-slab depressurization systems (SSDS) with fans at two levels | 322–1931 | Below <15 to 196 | 91+_6% at ground level and 94+_5% at the attic level |
| Quasi-experimental study by Brossard et al. (2015) in Quebec, Canada. | Above ground level (AGL) discharge with the fan located in the basement and above roof line (ARL) discharge with the fan located in the attic. | Sub-slab depressurization systems (SSDS) | Above 300 | ARL (Avg%, SD) = 75.3 ± 13.6; and AGL = 74.3 ± 20.8 | ARL 89%, AGL 95%. |
| Quantitative-comparative study by Groves-Kirkby et al. 2006 in Northamptonshire and neighbouring counties, UK. | After measuring radon levels, 73 post constructed houses remediated with fan-assisted sump pump and compared with 64 houses remediated during construction with protective radon membrane only. | Fan-assisted sump-pump and protective membrane used as damp-proof; included a cavity tray to seal the membrane together with weep-holes in it for drainage. | Post-construction houses: 516; During construction houses: 458 | Post construction houses: 60; During construction houses: 107. | With active sump-pump 100% and with protective membrane only 89% |
| Quantitative-comparative study by Groves-Kirkby et al. (2008) in the UK | Radon concentration data collected from 170 homes situated in Radon Affected Areas in Northamptonshire and neighbouring counties. | Conventional sump-pump technology by a commercial organization | 487.6 | 64.6 | 100% of remediated homes achieved reduction to below the Action Level of 200 Bq/m3 and more than 75% of the sample exhibiting mitigation factors of 0.2 or better. |
| Experimental study by Marley and Phillips, 2001 in Northamptonshire, UK. | Studied four model single story buildings with construction design similar to local houses. | Air-Conditioning (AC) and Central Heating without AC | 96–1083 | Much lower than the UK action level of preceding level. | 40–100% |
| Quantitative-comparative study by Long et al.,(2013 in three counties of Ireland. | Radon level tested in houses of North Cork (n = 152);South and West Cork (n = 105) counties. | Homes exceeding the reference level remediated with active sump technique. | North Cork: Max 3300; 126 houses >200; 26 houses >800. South and West Cork: Max 1000; 105 houses >200 and 3 houses >800 | <200 | 92% |
| Quantitative-comparative study by Huber et al., 2001in western Tyrol, Austria, | Five years after mitigation, five different remedial actions were examined in five houses for their efficiency | House 1: A mechanical intake and outlet ventilation with heat exchanger combined with a SSDS. House 2: SSDS with two fans and loops of drainage tubes to withdraw radon from the area below the floor. House 3: A multilayer floor construction, with a fan to suck radon from a layer between bottom slab and floor. House 4: A basement sealing. House 5: A waterproof basement. | 25,000 | 1,200 | 50–95% |
| Experimental study by Maringer et al. (2001) in the federal state of Upper Austria. | Studied 5 houses in high radon; for the first time used an extended Blower Door method to determine building tightness and radon levels. | Two farm houses mitigated with active SSDS and a single-family house mitigated with passive SSDS | Radon level varied from 150 to 900 (Avg. 457) depending on location and seasons | 48 and 233 | 90% and 50% |
| Quasi-experimental study by Paridaens et al. (2005) in Belgium | A house in radon prone area with very high indoor radon concentrations was identified with passive measurement. | Active sub slab depressurization with a radial fan. | 1790 | <200 | 90% |
| Quasi-experimental study by Vázquez et al. (2011) in Spain | Evaluated four construction models in two locations (underneath the basement slab and outside the foundation wall) and two ventilation (natural and forced) techniques studied for no less than one month. | Sump depressurization with passive and active ventilation | Same for all 4 models: Basement 39400 and ground floor 6860 | Combination 1 (C1): 1740 and 603; C2: 16600 and 3210; C3: 409 and 368; and C4: 327 and 480. | 93–95% |
| Experimental study by Akbari and Oman (2013) in Stockholm, Sweden. | A two-storey house renovated to conserve energy; a multizone dynamic simulation model developed using an Indoor Climate and Energy (ICE 4.0) tools and validated using measurements of energy for heating, ventilation and total energy use. | HRV (Heat Recovery Ventilator) | 3582 | 27 (at the highest HRV performance level) | Almost 100% radon mitigation with 74% energy saving |
| Experimental study by Yasuoka et al., 2009 in Kobe, Japan. | In a 5 t h floor apartment having high radon concentration from the building material was tested for radon. Mitigated for radon with and without using the air cleaner as the case and control case. | Mitigated with two types of radon filters: a high efficiency particulate air filter (HEPA-filter) and a deodorizing activated carbon (carbon-filter). | Mean radon concentration, EEC andEF were 86 ± 10 36 ± 4 and 0.42, respectively. | In both cases reduction of radon (<15) was significantly lower (0.01 and 0.05 level) | Effective 95–99% |
| Experimental by Gao et al. (2008) Hong Kong, China. | Anti-radon coating was experimented in a newly constructed building. | Anti-radon coating for radon mitigation | Maximum and average radon level 130,000 & 86,000; and 100,000 & 63,000 for the case & control | Below the set action level 142 & 174 | 99.85%, |