Radon Mitigation Systems Research Articles

Unintended Consequences of Urban Expansion and Gold Mining: Elevated Indoor Radon Levels in Gauteng Communities’ Neighboring Gold Mine Tailings

The province of Gauteng in South Africa has a rich history of gold mining, which has driven economic growth and urbanization. Gold mining has also created over 270 gold mine tailings (GMT), now surrounded by human settlements due to a housing shortage. These GMT pose a health risk as they harbor elevated uranium, which over time undergoes radioactive decay to produce radon, a known lung carcinogen. This study aimed to investigate the potential correlation between the proximity to gold mine tailings (GMT) and indoor radon concentrations in Gauteng’s residential dwellings. Volume activity of radon (VAR) inside 330 residential dwellings was measured in residential dwellings located proximally (<2 km) and distally (>2 km) to gold mine tailings using AlphaE radon monitors during winter. An interviewer-administered questionnaire was utilized to obtain data on factors that may influence indoor radon activities. Descriptive statistics and bivariate logistic regression analyzed the influence of proximity to gold mine tailings and dwelling characteristics on VAR. Furthermore, VAR was compared to the World Health Organization (WHO) radon reference level of 100 Bq/m3. Residential dwellings near gold mine tailings had significantly higher average indoor radon concentrations (103.30 Bq/m3) compared to the control group (65.19 Bq/m3). Residential dwellings proximal to gold mine tailings were three times more likely to have VAR beyond the WHO reference level of 100 Bq/m3. Furthermore, they had estimated annual effective doses of 2.60 mSv/y compared to 1.64 mSv/y for the control group. This study highlighted a concerning association between proximity to gold mine tailings and elevated indoor radon levels. Public health interventions prioritizing residential dwellings near gold mine tailings are crucial. Educational campaigns and financial assistance for radon mitigation systems in high-risk dwellings are recommended. Residents near gold mine tailings are encouraged to ensure continuous natural ventilation through frequent opening of windows and doors.

Study of the performance and time response of the RadonEye Plus2 continuous radon monitor

The availability of affordable continuous radon monitors opens new opportunities for studying the temporal variations of indoor radon and for more precise exposure estimates based on the actual hours spent in homes and workplaces. These new applications require tests of the monitors characteristics, including their response time. A study of a promising electronic radon monitor with high sensitivity, the RadonEye Plus2, was conducted. It was found that it has excellent linearity up to 3500 Bq/m3. A slight deviation from linearity within 12% was observed in the range 3500–7000 Bq/m3. The reproducibility of measurements with 36 different RadonEye monitors was within 7%, estimated in the range of linearity.A dedicated procedure for time response characterization was developed based on exposure to rectangular activity concentration pulses (spikes). It was applied to the RadonEye and three other commercial monitors. The determined characteristic response times of the RadonEye monitor are about 40 min for reaching 50% of the plateau of a rectangular pulse and 90 min for reaching 90%. They are somewhat higher than the corresponding response times of the AlphaE monitor, which are 20 and 60 min, respectively. The response times of the RAD7 monitor in sniff mode are about 3 min for reaching 50% of the plateau and 10 min for reaching 90%. The AlphaGUARD monitor in flow-through mode has the fastest response — it reaches 95% of the plateau in less than 2 min. The monitor AlphaGUARD PQ2000 Pro Rn/Tn is therefore recommended for follow-up of the activity concentration in time response studies of other monitors. It is demonstrated that by exposure to spikes the response function of a monitor can be obtained and used to model its response to variable concentrations.Overall, the RadonEye’s response is sufficiently fast to follow radon variations even in buildings with active ventilation. This sensitive monitor is suitable for homes and workplaces and can be helpful in the installation and investigation of radon mitigation systems and in studies of the indoor radon dynamics.

Method for assessing radon Re-Entrainment risks from above ground level discharges from sub-slab depressurization systems

Above ground level (ABL) discharges are commonly employed in northern climates to release radon-containing soil gases from sub-slab depressurization radon mitigation systems. While there are many practical reasons to employ this in cold climates (e.g., to avoid ice build-up), it does inherently elevate the outdoor radon concentrations, and raises the possibility of radon re-entrainment back into living spaces of the emitting house, and its neighbors. A method has been developed for assessing outdoor radon dispersion and re-entrainment risks. It links computational fluid dynamics calculations for evaluating outdoor concentrations, and regional multi-annual meteorological records that give the occurrence probability for different wind speed, wind direction, and atmospheric stability conditions. When combined with assumptions about indoor/outdoor concentration ratios, annual average exposure concentrations to radon can be estimated. Concentrations along surfaces of the emitting house are often quite high close to the exhaust vent, and air exchange into the house from nearby open windows, air intakes, etc., and can result in high indoor concentrations. Re-entrainment into the neighboring house is often less serious, though certain circumstances can lead to radon being trapped in the space between the two buildings, which leads to higher exposure.

Towards a better assessment model of transient radon concentrations in dwellings basements for the study of the effectiveness of soil radon mitigation systems designs

In order to study effectiveness of soil radon mitigation systems in dwellings basements, it is necessary to develop robust numerical models that can estimate time-varying radon concentration in the basements. However, development of such models is a very challenging topic. Indeed, there are three difficult tasks that have to be solved: i°) to characterize soil and foundation materials hydraulic properties, and geometry, length, and position of cracks inside these materials, ii°) to solve discontinuity due to free gas flow in a basement volume embedded within a tortuous porous material, and iii°) to characterize the dwelling occupation mode by the inhabitants. The purpose of this work is twofold: first, to investigate the performance of a meshed-basement model (BM1), compared to classical mass balance models (BM2), in simulating measured fluctuations in time of point-radon concentration in the basement; and second, to study efficiency of soil depressurization systems (SDS) designs in reducing the higher radon concentrations in basements due to higher under-pressurizations.Application of both models to an experimental dwelling showed that BM1 is more efficient than BM2 in that it can better simulate both measured radon concentration and radon-entry-rate. Numerical SDS-scenarios by using BM1 showed that the basement sub-slab depressurization (SSD) alone is a costly solution for radon mitigation. However, scenarios combining SSD with a sump pumping well (SPW) design in the soil adjacent to the wall, showed to be a good alternative because it involves less energy for soil air extraction.

FRESH: Long-Term Outcomes of a Randomized Trial to Reduce Radon and Tobacco Smoke in the Home.

IntroductionTobacco smoke and radon are the leading causes of lung cancer. The FRESH intervention was a randomized controlled trial of 515 homeowners to promote stage of action to reduce radon and air nicotine levels. MethodsWe studied 515 participants, 257 in a treatment group and 258 in a control group. Treatment participants received free radon and air nicotine test kits, report back, and telephone support, and those participants whose homes had high radon levels received a voucher for $600 toward mitigation. Both groups were asked to retest 15 months post intervention. We examined differences in stage of action to test for and mitigate radon and adopt a smoke-free–home policy and in observed radon and air nicotine values by study group over time.ResultsHomeowners in the treatment group scored higher on stage of action to test for radon and air nicotine and to mitigate for radon during follow-up than those in the control group at 3 months and 9 months, but the effect of the intervention diminished after 9 months. We saw no difference between groups or over time in observed radon or air nicotine values. Of homeowners in the treatment group with high radon levels at baseline, 17% mitigated, and 80% of them used the voucher we provided.ConclusionThe null finding of no significant change in observed radon or air nicotine values from baseline to 15 months may reflect the low proportion of radon mitigation systems installed and the decline in stage of action to adopt a smoke-free home policy. Including a booster session at 9 months post intervention may improve the remediation rate.

Estimating the burden of lung cancer and the efficiency of home radon mitigation systems in some Canadian provinces

Lung cancer (LC) is the leading cause of death of cancer in Canada in both men and women, and indoor radon is the second leading cause of LC after tobacco smoking. The Population Attributable Risk (PAR) is used to assess radon exposure risk. In this work we estimate the burden of LC in some Canadian provinces. We use the PAR to identify the radon levels responsible for most LC cases. Finally, we use the PAR function of the two variables, radon action and target levels, to search for a possible optimal mitigation program. MethodsThe LC burden for Ontario, Alberta, Manitoba, Quebec and British Columbia was estimated using provincial radon and mortality data. Then the PAR and LC cases for these provinces were estimated over the period 2006–2009 at different given indoor radon exposure levels. Finally, the PAR function when radon action levels and radon target levels are variables was analyzed. ResultsThe highest burden of LC in 2006–2009 was in Ontario and Quebec. During the period 2006–2009, 6% of houses in Ontario, 9% of houses in Alberta, 19% of houses in Manitoba, 7% of houses in Quebec, and 5% of houses in British Columbia had radon levels higher than 200 Bq/m3 and were responsible about 913, 211, 260, 972, and 258 lives, respectively. Radon mitigation programs could have prevented these LC cases. The BEIR VI assumption for the United States (US) population, 95% of LC deaths in men and 90% of LC deaths in women are Ever-Smokers (ES), can be applied to the Canadian population. The PAR is a linear function in the target radon value with an estimated slope of 0.0001 for Ontario, Alberta, Quebec and British Columbia, and 0.0004 for Manitoba. The PAR is almost a square root function in the radon action level. The PAR is sensitive to changes in the radon mitigation program and as such, any improvement is a worthwhile investment.

Radon Mitigation Approach in a Laboratory Measurement Room.

Radon gas is the second leading cause of lung cancer, causing thousands of deaths annually. It can be a problem for people or animals in houses, workplaces, schools or any building. Therefore, its mitigation has become essential to avoid health problems and to prevent radon from interfering in radioactive measurements. This study describes the implementation of radon mitigation systems at a radioactivity laboratory in order to reduce interferences in the different works carried out. A large set of radon concentration samples is obtained from measurements at the laboratory. While several mitigation methods were taken into account, the final applied solution is explained in detail, obtaining thus very good results by reducing the radon concentration by 76%.

Results of a Test and Win Contest to Raise Radon Awareness in Urban and Rural Settings

Background Radon is a leading cause of lung cancer, but few test their homes to determine radon levels. Purpose The study assessed feasibility and success of a Test and Win Contest to promote radon testing in rural and urban communities. Methods The prospective, quasi-experimental study tested a novel contest to raise radon awareness. Paid and earned media recruited homeowners who received a free test kit and were eligible to win free home mitigation. Urban homeowners with the 5 highest radon levels and rural participants with the 3 highest won free radon mitigation systems. Cross-sectional surveys were completed via Internet or phone at enrollment. Results Most returned the radon test kits (71% urban; 86% rural). Participation was more prevalent in the rural location most likely due to longer media recruitment (6 weeks vs. 11 days) and more money spent on media advertising ($1.86 vs. $0.21 per eligible household). The contest attracted 102 per 10 000 households to test for radon in the rural area compared to 19 per 10 000 households in urban counties. Discussion The contest was a feasible and successful population-based strategy in both locations. Translation to Health Education Practice The Test and Win Contest is a promising health education strategy to promote radon testing.

Indoor Radon Levels and Lung Cancer Incidence on Guam

Abstract Radon (Rn) is a naturally occurring, radioactive gas that impacts air quality world-wide. It is a known carcinogen and considered by the United States Environmental Protection Agency (U.S. EPA) to be the second leading cause of lung cancer after tobacco smoking. Of several known isotopes of radon, 222 Rn is the most stable with a half-life of approximately four days. This particular isotope is associated with the uranium ( 238 U) decay series and accounts for most public ionizing radiation exposures. Most global indoor 222 Rn emanates from granitic bedrocks located underneath buildings. While such rocks are absent on Guam, the karst limestone formations that overlay the island's basement volcanics (basalt) are of biogenic origin and are believed to be a significant source of radon. In a recent multi-year survey conducted on Guam by the local EPA, indoor 222 Rn levels exceeded the U.S. EPA air quality standard of 4 pCi/L in ~40% of all buildings tested. Concentrations were log-normally distributed and exceeded 300 pCi/L in two instances. Weighted average indoor 222 Rn levels were generally much higher in villages from the northern half of the island where limestone coverage predominates. The relationship between 222 Rn and lung cancer incidence on Guam was examined in the study reported here. The results were strongly suggestive of a hormetic effect existing between the two variables. Possible confounding effects attributable to smoking and ethnicity were examined and found to be insignificant. In fact, ethnic groups predominantly confined to the northern half of the island (i.e., Filipinos and all other Asians as a collective group) showed considerably lower cancer incidence and mortality rates than the indigenous Chamorro people who are well represented island-wide. The findings of the study lend further weight to numerous other reports that suggest low-level exposures to 222 Rn have a beneficial health effect. They also support a growing critique of the rationale behind the U.S. EPA adopted linear-no-threshold toxicological model, which assumes that any dose of radiation is harmful, no matter how small. Finally, they also imply that the current U.S. EPA action level of 4 pCi/L for indoor radon is overly conservative and needlessly prompting homeowners to install radon mitigation systems into buildings that really don’t need them.

CASE STUDY OF VARIOUS RADON MITIGATION SYSTEMS INSTALLATION IN SOUTH KOREA

Background and Aims: Radon is inert gas which causes lung cancer, and it is important to mitigate indoor radon gas as people stay indoors over 80% of their daily life. There are several radon mitigation systems such as Active Soil Depressurization(ASD) and Passive Soil Depressurization(PSD) which have been applied to buildings in America. However, buildings in Korea are different from ones in America due to the different geological structure. For this reason, it was necessary to develop other radon mitigation systems which can be applied to Korean-type of building structure. Methods: According to radon level measured by Natural Radiation Environmental Health Center, Gangwon and Chungbuk area showed higher level than other areas, thus one elementary schools(initial radon level: 10 pCi/L) and one village office(initial radon level: 5.8 pCi/L) were selected considering radon level and positiveness of the leaders. ASD was applied to the elementary school, and Active Soil Pressurization(ASP) was applied to the office. Results: It is not seriously difficult to install soil depressurization system in America, but geological structure in Korea generally shows clay bed, hence it is hard to install pipes and suck radon gas through them. In elementary school case, because radon suction was not successful(radon level after ASD installation: 31.2 pCi/L), instead of depressurizing the underground, ASP that is, positive-pressure was slightly blown into indoors so that underground radon cannot penetrate through the building, was used. Radon level after the installation in the elementary school and the office stayed under 2.0 pCi/L(1.5 and 1.9 pCi/L, respectively). Conclusions: Even though the problem with energy cost can be an issue, it cannot be a problem if indoor radon level can be monitored continuously and connected to the system. Therefore, delicate diagnose and assessment are essential before installing radon mitigation system. Moreover, to perform diagnose and assessment prior to building construction is preferred.

Indoor and soil gas radon simultaneous measurements for the purpose of detail analysis of radon entry pathways into houses

Detailed knowledge of radon transport mechanisms from the subsoil into the indoor environment is essential for the correct interpretation of results of short-term indoor radon measurements and for proper and effective design of radon mitigation systems. Radon transfer factor time variations have been studied based on simultaneous continuous indoor and soil gas radon measurements within the framework of complex radon diagnosis of individual buildings. In this context, the key influencing factors have been identified and analysed in order to provide satisfactory explanation on radon entry variations under different measurement conditions. Moreover, a new significant manner of radon entry into the indoor environment has been identified and will be discussed in detail.

Use of Simulink for Dynamic Air Quality Modeling in Interior Alaska

Interior Alaska has indoor air quality (IAQ) issues similar to those of other far northern communities associated with long cold winters and reduced ventilation rates. We also have some interesting issues associated with elevated radon in homes built in the hills around Fairbanks, as well as elevated particulate levels created by smoke from forest fires that occur in the vast uninhabited portions of the state. To better understand the influences of critical variables such as indoor source strengths and ventilation rates on IAQ associated with forest fires and radon, we have developed a Simulink-based mass conservation model. Using data gathered at two homes in Fairbanks during 2003, we have used this model to predict indoor radon and PM2.5 levels (particles less than 2.5 μm in diameter). We find that we are able to predict both the rise of radon following the shutdown of a radon mitigation system and the variation of indoor PM2.5 by using ventilation rates consistent with what we have measured, PM2.5 sour...

Regional and national estimates of the potential energy use, energy cost and CO 2 emissions associated with radon mitigation by sub-slab depressurization

Active sub-slab depressurization (SSD) systems are an effective means of reducing indoor radon concentrations in residential buildings. However, energy is required to operate the system fan and to heat or cool the resulting increased building ventilation. We present regional and national estimates of the energy requirements, operating expenses and CO 2 emissions associated with using SSD systems at saturation (i.e. in all US homes with radon concentrations above the EPA remediation guideline and either basement or slab-on-grade construction). The primary source of uncertainty in these estimates is the impact of the SSD system on house ventilation rate. Overall, individual SSD system operating expenses are highest in the Northeast and Midwest at about $99 y −1, and lowest in the South and West at about $66 y −1. The fan consumes, on average, about 40% of the end-use energy used to operate the SSD system and accounts for about 60% of the annual expense. At saturation, regional impacts are largest in the Midwest because this area has a large number of mitigable houses and a relatively high heating load. We estimate that operating SSD systems in US houses, where it is both appropriate and possible (about 2,6 million houses), will annually consume 1.7 × 10 4 (6.4 × 10 3 to 3.9 × 10 4) TJ of end-use energy, cost $230 (130 to 400) million (at current energy prices), and generate 2.0 × 10 9 (1.2 × 10 9 to 3.5 × 10 9) kg of CO 2. Passive or energy efficient radon mitigation systems currently being developed offer opportunities to substantially reduce these impacts.

Assessment of pressure-field extension below slab-on-grade concrete floors

This paper discusses studies of the sub-slab depressurization performance of radon mitigation systems in four schools after floor replacement, and in one newly built school, in Cornwall, England. Sub-slab pressure-field extension was assessed by means of small bore plastic tubing laid below slab-on-grade concrete floors with ‘standard’ U.K. type radon sump (sub-slab depressurization) systems. A variety of hardcore types and floor constructions were used. Improvements over the pressure-field obtained in normal U.K. floor construction were readily achieved by careful selection of hardcore free from fine material and by avoidance of sand blinding directly on the hardcore. However, the performance achieved in a similar American study was not consistently reproduced. Even with close supervision of labour and correct construction, optimum pressure-field extension was not consistently achieved. The thickness of the permeable layer and the method of laying blinding materials may be critical to success. A polyethylene membrane can keep blinding materials out of the permeable layer and may allow the usual sand blinding to be used. Careful floor construction and selection of hardcore materials could result in new-build properties requiring fewer radon sumps and/or a reduction in fan power consumption. However, this must be balanced against the increased construction costs and current inconsistency in results.

95/04226 Reentry of radon from mitigation system outlets

Some radon mitigation systems draw air with a high radon concentration from under the basement floors of houses and exhaust it outdoors. The objective of this project was to measure the reentry rates of radon released at roof level and at ground level near a house to determine whether exhaust above the roof is necessary. This was done by using a portable mockup of a radon mitigation system exhaust, with sulfur hexafluoride (SF{sub 6}) as a tracer gas. The roof-level exhaust produced maximum indoor sulfur hexafluoride concentrations that were significantly lower than those from the ground-level exhaust. This suggests that the better radon discharge location is on the roof of a house.

Radon Entry Control in New House Construction

People exposed to high concentration levels of radon face an increased risk of developing lung cancer. The risk is directly proportional to the length and level of radon exposure. Because of health reasons, it is safer to build new houses with radon mitigation systems installed in slab-on-grade houses. However, the interrelationships between parameters and factors governing radon entry and control are highly complex. A study performed by the University of Florida has examined the effectiveness of different radon entry control approaches. The analysis was based on 47 houses from three research projects conducted by the University of Florida (14 houses), Florida Solar Energy Center (13 houses), and GEOMET Technologies (20 houses). The evaluation of the performance and effectiveness of improved floor slabs, space conditioning, and ventilating systems were analyzed. Statistical analyses of the interrelationship between various parameters were also performed. Study findings such as the important factors in reducing radon entry and the effectiveness of passive construction approach and active subslab depressurization systems are presented in this paper.

Analysis of the performance of a radon mitigation system based on charcoal beds

Abstract The performance of a commercially available radon mitigation system based on adsorption of radon onto charcoal beds (RAdsorb system) combined with an electronic air cleaner (EAC) installed in a single family house in Massachusetts has been studied. Semi‐continuous measurements were made of the radon gas concentration, potential alpha energy concentration (PAEC), and radon decay product activity‐weighted size distribution with and without additional operating aerosol sources. An automated, semi continuous graded screen array (ASC‐GSA) system was utilized for the measurement of the activity‐weighted size distribution. During the tests without the mitigation system in operation, the conditions in the basement of the house were as follow: the radon concentrations were in the range of 600 to 800 Bq m‐3, the Potential Alpha Energy Concentration (PAEC) was 600 to 700 nJ m‐3, the particle concentration was below 1000 cm‐3, and the fraction of PAEC and 218 Po in the smallest size range, 0.5–1.6 nm were approximately 0.6 and 0.9, respectively. The tests were designed to study the influence on the measured parameters of the combined mitigation system as well as each of the separate components: fan, charcoal bed, and EAC. When all the components of the mitigation system were operating, the radon concentration was below 150 Bq m‐3 and the PAEC was below 104 nJ m‐3 with the smallest sized fraction of PAEC (0.5–1.6 nm) of about 0.4. The tests showed that under certain conditions, the charcoal bed/EAC mitigation systems can be a potentially valuable technique for reducing a health risk due to indoor radon.

An Innovative Radon Mitigation-Energy Conservation Retrofit System For Residential Buildings

Field tests were performed on an innovative radon mitigation system that provides basement pressurization and dilution while conserving heating fuel, improving indoor air quality and human comfort. This year-round radon reduction retrofit device has been successfully installed and monitored in a Wisconsin home that exhibited elevated radon levels. In the design, a secondary heat exchanger for a conventional-type residential furnace is modified to provide heated fresh air exchange and intermittent pressure regulation. Experiments have shown that the average indoor radon level can be reduced by 97 percent and that employment of this system during the heating months exhibits a zero operational cost. Measurements of radon reduction levels, fuel usage and environmental factors that affect radon migration are documented. A state-of-the-art PC-data acquisition system with accompanying instrumentation for radon measurements is also described.

Modeling Air Flow Dynamics in Radon Mitigation Systems: A Simplified Approach

Subslab air flow dynamics provide important diagnostic information for designing optimal radon mitigation systems based on the subslab depressurization technique. In this paper, it is suggested that subslab air flow induced by a central suction point be treated as radial air flow through a porous bed contained between two impermeable disks. Next, we show that subslab air flow is most likely to be turbulent under actual field situations in houses with subslab gravel beds, while remaining laminar when soil is present under the slab. The physical significance of this model is discussed and simplified closedform equations are derived to predict pressure and flows at various distances from a single central depressurization point. A laboratory apparatus was built in order to verify our model and experimentally determine the model coefficients of the pressure drop versus flow for commonly encountered subslab gravel materials. These pressure drop coefficients can be used in conjunction with our simplified model a...

Evaluation of Radon Mitigation Systems in 14 Houses Over a Two-year Period

Fourteen single-family detached houses in Spokane, Washington, and Coeur D'Alene, Idaho, were monitored for two years after high concentrations of indoor radon had been mitigated. Each house was monitored quarterly using mailed alpha-track radon detectors deployed in each zone of the structure. To assess performance of mitigation systems during the second heating season after mitigation, radon concentrations in seven houses were monitored continuously for several weeks, mitigation systems in all houses were inspected, and selected other measurements were taken. In addition, occupants were also interviewed regarding their maintenance, operation, and subjective evaluation of the radon mitigation systems. Quarterly alpha-track measurements showed that radon levels had increased in most of the homes during many follow-up measurement periods when compared with concentrations measured immediately after mitigation. Mitigation-system performance was adversely affected by (1) accumulated outdoor debris blocking the outlets of subsurface pressurization pipes; (2) fans being turned off (e.g., because of excessive noise or vibration); (3) air-to-air heat exchanger, basement pressurization, and subsurface ventilation fans being turned off and fan speeds reduced; and (4) crawl-space vents being closed or sealed.