Developing a Secure Low-Cost Radon Monitoring System.

Radon gas has been declared a human carcinogen by the United States Environmental Protection Agency (USEPA) and the International Agency for Research on Cancer (IARC). Several studies carried out in Spain highlighted the high radon concentrations in several regions, with Galicia (northwestern Spain) being one of the regions with the highest radon concentrations. The objective of this work was to create a safe and low-cost radon monitoring and alert system, based on open source technologies. To achieve this objective, the system uses devices, a collection of sensors with a processing unit and a communication module, and a backend, responsible for managing all the information, predicting radon levels and issuing alerts using open source technologies. Security is one of the largest challenges for the internet of things, and it is utterly important in the current scenario, given that high radon concentrations pose a health risk. For this reason, this work focuses on securing the entire end-to-end communication path to avoid data forging. The results of this work indicate that the development of a low-cost, yet secured, radon monitoring system is feasible, allowing one to create a network of sensors that can help mitigate the health hazards that high radon concentrations pose.

Long term durability of radon remedial measures in a sample of UK homes.

A study to determine the long term effectiveness of commonly used radon remedial methods over a 15 year period is discussed. The overall failure rate for remediation systems was 63%, with roughly equal rates for passive and active type systems. The fans used in active systems performed better than expected, with many of them exceeding manufacturers' stated life spans by several years. The study found that all types of remedial measure can last more than ten years, but also found examples for all measures that failed in less than five years. This supports HPA advice that homes should be retested every 5-10 years. It was also noted that householders found it difficult to detect failures in passive systems. The need for a follow-up study is discussed, in light of likely changes in building practices and materials during the last twenty years.

Study on the effect of air purifier for reducing indoor radon exposure.

We investigated the effect of air purifier for reducing the indoor radon exposure by continuously measuring the radon (Rn), attached radon decay products (DaRn) and unattached radon decay products (DuRn). The results showed that the air purifier can effectively reduce the concentration of DaRn and DuRn except Rn. The results showed that the air purifier can be a helpful supplement to the existing radon mitigation methods.

Sorption of 226Ra from waste effluents using Syrian bentonite.

In view of environmental concern, sorption of radium on natural bentonite mineral (Aleppo, Syria) was investigated using a batch-type method. Data were expressed in terms of distribution coefficients. An attempt to increase the selectivity of bentonite for radium was made by preparing M-derivatives. Loss of mineral crystallinity in acidic media and the formation of a new phase, such as BaCO3, in Ba-derivative were evidenced by XRD characterizations. Of the cationic forms, Na-bentonite showed the highest affinity. Mechanisms of radium uptake were studied using M-derivatives and simulated radium solutions. The obtained results indicated that surface sorption/surface ion exchange were the predominant processes. The distinct sorption behaviour observed with the Ba-form was, possibly, a reflection of radium coprecipitation with barium carbonate. The competing order of macro components, likely present in waste streams, was investigated by studying different concentrations of the corresponding salt media. Sodium was found to be the weakest inhibitor. The performance of natural bentonite and the most selective forms, i.e. Ba- and Na-derivatives, to sorb radium from actual oil co-produced waters, collected form Der Ezzor Petroleum Company (DEZPC), was studied. This showed the influential effect ofpH compared with other parameters.

Radon remediation of a two-storey UK dwelling by active sub-slab depressurisation: effects and health implications of radon concentration distributions.

Radon concentration levels in a two-storey detached single-family dwelling in Northamptonshire, UK, were monitored continuously throughout a 5-week period during which active sub-slab depressurisation remediation measures were installed. Remediation of the property was accomplished successfully, with both the mean radon levels and the diurnal variability greatly reduced both upstairs and downstairs. Following remediation, upstairs and downstairs radon concentrations were 33% and 18% of their pre-remediation values respectively: the mean downstairs radon concentration was lower than that upstairs, with pre- and post-remediation values of the upstairs/downstairs concentration ratio, R(U/D), of 0.81 and 1.51 respectively. Cross-correlation between upstairs and downstairs radon concentration time-series indicates a time-lag of the order of 1 h or less, suggesting that diffusion of soil-derived radon from downstairs to upstairs either occurs within that time frame or forms a relatively insignificant contribution to the upstairs radon level. Cross-correlation between radon concentration time-series and the corresponding time-series for local atmospheric parameters demonstrated correlation between radon concentrations and internal/external pressure difference prior to remediation; this correlation disappears following remediation. Overall, these observations provide further evidence that radon concentration levels within a dwelling are not necessarily wholly determined by the effects of soil-gas advection, and further support the suggestion that, depending on the precise content of the building materials, upstairs radon levels, in particular, may be dominated by radon exhalation from the walls of the dwelling, especially in areas of low soil-gas radon.

New technique for the determination of radon diffusion coefficient in radon-proof membranes.

This paper describes a new device and a method to determine the radon diffusion coefficient in damp-proof membranes developed in the Czech Republic. The main advantage of the device is that it enables tests to be carried out in all the known measuring modes used throughout Europe. Two recently developed computer programs are presented for the numerical modelling of the time-dependent radon transport through damp-proof membranes. According to this method, the radon diffusion coefficient is derived from the process of fitting the numerical solution to the measured curve of radon concentration in a receiver container. Numerical simulation and measured data are also compared. Reasons for disagreements between different methods and specific configurations of the measuring device are also discussed.

Geochemical Cycle of Radon and its Bioremediation Opportunity from Water Environment: A Review.

BACKGROUND: The waterborne or airborne radon causes carcinogenesis in the human bodies due to the continuous decay of α- and ß- particles. The health risks related to radioactive radon instigate to develop an advanced technology for its removal from the environment. There are two standard techniques, such as aeration and activated carbon filtration, available for its removal. However, both of them face different technological drawbacks resulting in the processes either inefficient or inappropriate for the purpose. CONCLUSION: There are several technologies utilizing either algae or microorganisms that could be useful in the bioremediation of radon. Some of the algae and microorganisms are examined and found to be tolerated and decontaminated various ionization radiations like α-, ß-, and γ- radiations. In a US patent, the microalgae Coccomyxa actinabiotis isolated from a nuclear facility showed the properties of bioremediation towards radionuclides. They overcome the physiological stress in the extreme environment for their growth due to the evolution under the prolonged influence of high energy radiation. Further, they are stimulated by the process of cloning, genetic transformations and adaptations for the purpose of enhancing the tolerance and decontamination power. Therefore, biotechnological researches have lots of prospects to remove radon from the water environment using algae and microorganisms.

Assessment of the multimedia mitigation of radon in New York.

Although not yet implemented, the 1996 amendments to the Safe Drinking Water Act instructed the states (or local water suppliers) to address radon concentrations in community water systems (CWS). As an alternative to reducing waterborne radon concentrations in the CWS to the maximum contaminant level (MCL) of 11 Bq L(-1), states (or individual CWS) would be permitted to develop a multimedia mitigation (MMM) program, which allowed a greater concentration (148 Bq L(-1)) of waterborne radon in the CWS, if it could be shown that an equivalent health risk reduction could be achieved by reducing indoor radon concentrations. For a MMM program to be acceptable, the U.S. Environmental Protection Agency required the health-risk reduction attained through mitigations and radon-resistant new construction (RRNC) to offset the increased health risk due to radon in community water systems above the MCL of 11 Bq L(-1). A quantitative assessment indicates that the reduction in health risk currently achieved in New York State through radon mitigations and RRNC exceeded the increase in risk associated with an alternative MCL of 148 Bq L(-1). The implementation of a MMM program in New York would result in an overall reduction in the health risk associated with exposure to radon.

Suppression methods of radon emanation from phosphorus fertiliser and diatomaceous earth.

The present paper shows methods to suppress radon emanation from artificial porous materials such as phosphorous fertiliser or diatomaceous earth with a small amount of radium. The basic concept of suppression is making the radon emanation mechanism 'null', which comes from the fact that recoil is the main mechanism of radon emanation at room temperature. Nullifying may be done through removal of water in the pore volume by heating and through removal of pores by melting or filling with sulphur. These radon emanation suppression methods were tried for phosphorous fertiliser and diatomaceous earth with a small amount of radium. The melting method was the most effective of all. Sustainability of these methods was also studied. The melting method was the most sustainable. The heating method was also sustainable for diatomaceous earth in spite of a long-term immersion in water.

Natural radon reduction rate of the community groundwater system in South Korea.

Tank waters from 13 Community Groundwater Systems (CGS) showed average radon reduction rate of 26.5% (varying from -17.9% to 63.3%). When applying the reduction rate of 26.5% to the nationwide CGS, the percentage of CGS having radon level above 100Bq/L decreases from 28.8% to 22.0%. The natural radon reduction method would be applied to the CGS having radon level slightly exceeding guideline of WHO, as an alternative for aeration or GAC.

Evaluating the health benefits and cost-effectiveness of the radon remediation programme in domestic properties in Northamptonshire, UK.

Although previous analysis of health benefits and cost-effectiveness of radon remediation in a series of houses in Northamptonshire suggested that testing and remediation was justified, recent results indicate fewer predicted affected houses than previously assumed. Despite numerous awareness campaigns, limited numbers of householders have tested their homes, only a minority of affected householders have remediated, and those most at risk generally fail to remediate. Moreover, a recent survey shows a wide range of public perception of radon risk, not significantly influenced by public health campaigns. These observations impact our previous analysis, which has been reviewed in the light of these observations. Following the declaration of Northamptonshire, UK, as a radon Affected Area in 1992, a series of public awareness campaigns encouraged householders to assess domestic radon levels and, if appropriate, to take action to reduce them. Despite these awareness campaigns, however, only moderate numbers of householders have taken remediatory action. The costs of such remedial work in a series of domestic properties in Northamptonshire, the radon level reduction achieved, and the resultant heath benefit to the residents, have been the subject of study by our group for some years. Previous analysis, based on estimates of the total number of affected houses derived from the National Radiological Protection Board (NRPB) test data for the area, suggested that a programme of testing and remediation in Northamptonshire could be justified. The NRPB has continued to initiate and to collate radon testing, and published further results in 2003. These results include revised predictions of the numbers of affected houses, now considered to be less than the numbers previously assumed. More recently, the availability of the European Community Radon Software (ECRS) has permitted calculation of individual, rather than population-average, risk, demonstrating that those most at risk are generally those who do not take action. In addition, a recent survey of risk perception shows an extremely wide range of public perception of radon risk, a perception that has not been significantly altered by public health campaigns. These predictions have profound effects, both on our previous analysis, particularly since only limited numbers of householders test their homes and even fewer remediate if they discover raised levels, and also on the public health strategies for this risk.

Dynamic adsorption of radon by activated carbon.

The adsorption of radon on activated carbon has been used in or considered for a number of applications, including in situ decay beds, cyclic decontamination systems, and diffusive samplers. And although there are numerous measurements of the adsorption coefficients of specific activated carbons for radon, each of these applications depends on knowing, in addition to the adsorption coefficient for radon, the mass transfer factors describing its dynamic adsorption. Here we used a standard procedure in gas chromatography and chemical engineering, the spreading of a pulse as it passes through a bed of adsorbent, to determine these mass transfer factors. For this application, this procedure is developed further to correct the radon adsorption data for distortions caused by the decay of radon and by the presence of radon decay products in the detector. The results from eight activated carbons show a wide variation in the mass transfer coefficients for radon, which could affect significantly the suitability of adsorbents, as demonstrated here by the effect that mass transfer has on the performance of in situ decay beds.

Mitigation of a radon-rich Belgian dwelling using active subslab depressurization.

In a radon prone area in Belgium, a dwelling with high indoor radon concentrations was identified through a passive measurement. Next, a continuous, active radon monitoring device was installed for one month. A 20-a retrospective radon assessment was also performed. The house was subsequently mitigated through active subslab depressurization with a radial fan. Afterwards the dwelling was actively monitored for several more months to observe the effects of the mitigation and to study the effect of reducing the fan power. Dose evaluations were made to evaluate the health benefit of the mitigation. It was seen that the results of the three measuring techniques before mitigation all yielded between 1700 and 2000 Bq/m3. Clear diurnal radon variations showed up only after mitigation. After mitigation, the average radon concentration fell to less than 200 Bq/m3. The yearly average dose was reduced from potentially 45 mSv/y to less than 4.5 mSv/y through mitigation. Reducing fan power to 50% did not clearly influence the amount of radon entering into the dwelling.

Analysis of the individual health benefits accruing from a domestic radon remediation programme.

Although radon can be present within buildings at sufficient levels to pose a health risk, levels can be reduced relatively easily. Recent studies on a group of radon-remediated homes, based on assessment of collective population-average risk coefficients, have estimated the benefits and cost effectiveness accruing from remediation and have confirmed that domestic remediation in UK radon Affected Areas would result in significantly reduced cancer risks to the population in those areas. Although the population-average approach used hitherto has applied occupancy and lung-cancer risk factors, these are potentially misleading in assessing discrete populations. The study reported here uses the recently developed European Community Radon Software (ECRS) to quantify individual risks in a sample of householders who remediated their homes following indications that radon levels exceeded the action level. The study proceeds from population-averaged to 'individual risk' evaluation, successfully comparing individual and collective risk assessments, and demonstrates that those who remediate are not representative of the general population. Health benefits accruing from remediation are three times lower than expected, largely because remediators are older, live in smaller households, and smoke less than the population average, leading to the conclusion that the current strategy employed in the UK is failing to target those most at risk.

Radon mitigation in cold climates at Kitigan Zibi Anishinabeg.

Available radon mitigation results were gathered for 85 houses mainly by installing sub-slab depressurization systems (SSDS) with two types of discharge and fan locations: Above ground level discharge with the fan located in the basement (AGL) or above roof line discharge with the fan located in the attic (ARL). A comparative analysis was made of mitigation efficiency and of exhaust icing. Results show that both SSDS scenarios reduced radon levels similarly. The results of SSDS with AGL show that a sealed radon fan having proper fittings and sealed piping was able to reduce the radon to acceptable levels, and that these installations were less subject to obstructive icing of the exhaust in cold climates.

A radon generator/delivery system.

A radon-generating system is described in which 222Rn, emanating from 226Ra stored in an aluminum containment vessel, may be pumped into a syringe for subsequent injection into a standard spinner flask containing tissue culture medium. The radium-containment vessel is sealed by an indium gasket and three metal bellows valves, one of which was used to fracture the glass capsule that contained 2.9 GBq of radium salt. A rotating piston pump transfers radon-enriched air from the radium-containment vessel to a delivery loop that includes a transfer syringe. The flow of air and radon through the loop is manipulated by three crossover ball valves, one of which may be set to fill the syringe. A charcoal trap is provided to collect residual radon left in the delivery loop after the transfer syringe has been filled. The protocol used to expose cells to radon and its progeny is described as well as the dosimetry that is used to estimate the dose delivered to the cells. A description of safety precautions taken in fabricating the generator and in conducting radiobiological studies is also presented.

A solvent extraction technique for the measurement of 222Rn at ambient air concentrations.

The high solubility of radon in cold organic solvents is exploited to extract radon directly from a sample air stream into a hexane-based liquid scintillation solution. Up to 10 l. of air is passed through 20 ml of solvent held at -78 degrees C in a bath of dry ice and acetone. The solvent is then transferred to an ordinary glass liquid scintillation vial that has been preloaded with 2 ml of concentrated fluors. A large number of samples can be prepared in a short time with minimal equipment, making it possible for field workers to conveniently collect numerous samples prior to returning to the laboratory. After allowing an interval of at least 3 hr after processing for radon daughter ingrowth, the vials are counted on an unmodified liquid scintillation system with a narrow window set around the radon and polonium alpha peaks. The large sample volume more than compensates for the relatively high alpha background of liquid scintillators. Relevant theoretical considerations and alternate sampling strategies are discussed.

Steady-state response of a charcoal bed to radon in flowing air with water vapor.

Previously we have developed a mathematical model of radon adsorption in active air with water vapor on small U.S. Environmental Protection Agency charcoal canisters that are used for environmental measurements of radon. The purpose of this paper is to extend this mathematical model to describe the adsorption of radon by large charcoal beds with radon-laden air flowing through them. The resulting model equations are solved analytically to predict the steady-state adsorption of radon by such beds.

Mitigation of indoor radon in an area with unusually high radon concentrations.

In an area of unusually high indoor radon concentrations of up to 270,000 Bq m-3, four houses were selected for mitigation of indoor radon. Methods used were basement sealing, soil depressurization, a mechanical intake and outlet ventilation system with heat exchanger in the basement, and a multilayer floor construction using a fan to suck radon from a layer between bottom slab and floor. Basement sealing proved unsuccessful, the radon concentration remained unchanged after the mitigation attempt. The most successful remedial measure was soil depressurization using two fans and loops of drainage tubes to withdraw radon from the region under the floor and outside the walls of the basement and from soil under the part of the house without a basement. This method reduced the basement radon level in winter by about a factor of 200, i.e., from 100,000 Bq m-3 to 500 Bq m-3, and the ground-floor level by about a factor of 400. As regards the mechanical intake and outlet ventilation system with heat exchanger in the basement, it is essential to ensure that ventilation provides increased air pressure in the basement compared to outdoors. Unbalanced mechanical intake and outlet ventilation may decrease the air pressure indoors compared to outdoors, leading to increased radon concentrations. Optimization of this method reduced radon concentrations from 200,000 Bq m-3 to 2,000-3,000 Bq m-3 in winter. In one house with only a very small basement, a multilayer floor construction using a fan to suck radon from a layer between the bottom slab and floor was found to reduce radon concentrations on the ground floor from 25,000 Bq m-3 to about 1,700 Bq m-3 in winter. The results show that even in areas with extremely high radon concentrations, effective mitigation of indoor radon can be accomplished if suitable techniques are used. The evaluation of the different mitigation methods shows good coincidence with the ICRP 65 report.

New methods of energy efficient radon mitigation.

Two new radon mitigation techniques are introduced and their evaluation in a field study complemented by numerical model predictions is described. Based on numerical predictions, installation of a sub gravel membrane at the study site resulted in a factor of 2 reduction in indoor radon concentrations. Experimental data indicated that installation of "short-circuit" pipes extending between the subslab gravel and outdoors caused an additional factor of 2 decrease in the radon concentration. Consequently, the combination of these two passive radon mitigation features, called the membrane and short-circuit (MASC) technique, was associated with a factor of 4 reduction in indoor radon concentration. The energy-efficient active radon mitigation method, called efficient active subslab pressurization (EASP), required only 20% of the fan energy of conventional active subslab depressurization and reduced the indoor radon concentration by approximately a factor of 15, including the numerically-predicted impact of the sub-gravel membrane.