A proficiency test is an integral part of any analytical procedure; however, there is no known proficiency test in place for radon-in-water analysis. This led us to conduct a long-term study. Successful preparation of a reusable radon (222Rn)-in-water standard containing a ‘radium (226Ra)-loaded filter paper (the source)’ sandwiched between polyethylene sheeting has been reported. As the source ‘226Ra-loaded filter paper’ is sandwiched between polyethylene sheets, the surrounding water (which is sampled and analyzed) in the bottle remains free of 226Ra. With this type of standards, a previous study reported that at full ingrowth (>30 days), 86% of the 222Rn produced by the source was emanated into the water and remained stable thereafter, and the remaining 14% was retarded by the polyethylene sheeting. We periodically measured radon-in-water in two such standard samples allowing a 40- to 50-day ingrowth interval for more than 6 years (2016–2022). In each measurement, we prepared in duplicate the cocktails in four different ways (in Mineral-oil vs. Optifluor in combination with two different ways of ‘pipetting or sample drawing’ and dispensing into the scintillation vials) and measured the radon-in-water using two different Liquid Scintillation Counting (LSC) assays: full-spectrum (0–2,000 keV) versus Region of Interest (ROI) for radon (ROI, 130–700 keV). A substantial number of repeated results unequivocally show that the reusable standards maintained its characteristics satisfactorily for a 6-year long period. Duplicate measurements were precise in almost all cases. We consistently observed significant differences in measured radon concentration between the two different LSC assays and between the two different scintillation fluids, but not between the two sample drawing methods. With full-spectrum assay (0–2,000 keV), both Mineral-oil and Optifluor grossly underestimated the actual radon concentration, and with ROI assay (130–700 keV), Mineral-oil overestimated the radon concentration; therefore, these should be avoided. Preparing the cocktails with Optifluor and measuring by ROI assay (130–700 keV) was the only method that consistently produced results within the acceptance window (±25% of the known), suggesting that a certain way of preparing and measuring the water samples could yield more accurate results for radon. Thus, our findings demonstrate that a proficiency test for radon-in-water using these reusable 226Ra-free radon-in-water standards is a valid and valuable option, and it should be a part of radon-in-water analysis by the laboratories.

CONTEXT:To determine if radon mitigation is needed to protect occupants of multifamily housing, reliable testing procedures are needed. Yet, protocols on how many ground-contact housing units must be tested vary from 10% to 25% to 100%.OBJECTIVES:To estimate the probability of failing to identify a building containing at least one unit with elevated radon level when all ground-contact units are not tested.DESIGN:Retrospective analysis of previously collected data from licensed (ie, certified) radon measurement professionals using hypergeometric and Monte Carlo statistical methods to estimate the confidence that there are no units with radon levels of 4 picoCuries/liter of air (pCi/L) or more based on various testing percentages.SETTING:Testing data were obtained from 29 US states for 7892 ground-contact units in 687 multifamily buildings, primarily 5 to 20 units per building.MAIN OUTCOME MEASURE:Probability of failing to identify elevated radon levels in untested units.RESULTS:About 15% (n = 1163) of the units had radon levels of more than 4 pCi/L (the EPA action level); 59 units had more than 20 pCi/L (maximum of 96 pCi/L). For building sizes of 5 to 20 ground-contact units, the 2018 federal testing protocols that currently require testing of 10% and 25% of ground-contact units in each building failed to identify 47%-69% and 32%-46% of the units, respectively, depending on building size.CONCLUSIONS:Measurement of 90% of the ground-contact units in buildings with 5 to 20 ground-contact units results in up to 4% of the units with elevated radon levels being missed. To achieve 95% confidence that no units in the building have radon levels of 4 pCi/L or more in buildings up to 20 units, 100% sampling is required. For the vast majority of multifamily buildings, all ground-contact units in multifamily buildings should be tested for radon.

Throughout the United States, laboratories use different sampling methods (“Direct Fill” vs. “Submerged Bottle” methods), sample preparations (“Simultaneous Drawing” vs. “Separate Drawing”), scintillators (“Mineral Oil” vs. “Opti-Fluor”), volume of water plus scintillator in the cocktail (“8 mL plus 8 mL” vs. “10 mL plus 10 mL”), and liquid scintillation counting assays (“Full Spectrum: 0 - 2000 keV” vs. “Region of Interest: 130 - 700 keV”) for analyzing radon (222Rn) in water. We compared these and few other variables on the recovery of radon from two “Proficiency Test (PT)” samples and four “Household Well Water” samples from Georgia. The “130 - 700 keV” assay had significantly higher radon recovery than the “0 - 2000 keV” assay. The “Direct Fill” sampling produced significantly lower radon recovery than the “Submerged Bottle” sampling. “Simultaneous Drawing” of both scintillator and water sample yielded higher radon recovery than “Separate Drawing”. Air bubble in the samples resulted in significant loss of radon gas; and such loss became greater as the air bubble was larger. A “10 mL scintillator + 10 sample” combination appeared better than “8 mL scintillator + 8 mL sample”. Mixing scintillator and sample in the laboratory, when compared with doing it on-site, was found superior for better results and practicality of testing radon in private well waters. “Mineral Oil” scintillator provided higher radon activity than “Opti-Fluor”. However, in 10 consecutive measurements of the two proficiency test (PT) samples at 60 days interval (i.e., with full ingrowing), “Mineral Oil” overestimated the radon activity compared to the predicted/assigned value in most cases, whereas “Opti-Fluor” invariably produced results close to the predicted/assigned value. There were noticeable temporal variations in both radon and uranium concentrations in the study wells; nevertheless, uranium and radon concentrations had good positive correlation. Despite this, the use of uranium concentration over 30 ppb (the MCL of uranium in drinking water) as a trigger for recommending test for radon in well water remains questionable because there may be the safe level of uranium but unsafe level of radon in a well and vice versa.

A comprehensive study of the efficiency calibration and calibration verification of Ge gamma-ray spectrometers was performed using semi-empirical, computational Monte-Carlo (MC), and transfer methods. The aim of this study was to evaluate the accuracy of the quantification of gamma-emitting radionuclides in complex matrices normally encountered in environmental and food samples. A wide range of gamma energies from 59.5 to 1836.0keV and geometries from a 10-mL jar to 1.4-L Marinelli beaker were studied on four Ge spectrometers with the relative efficiencies between 102% and 140%. Density and coincidence summing corrections were applied. Innovative techniques were developed for the preparation of artificial complex matrices from materials such as acidified water, polystyrene, ethanol, sugar, and sand, resulting in the densities ranging from 0.3655 to 2.164gcm−3. They were spiked with gamma activity traceable to international standards and used for calibration verifications. A quantitative method of tuning MC calculations to experiment was developed based on a multidimensional chi-square paraboloid.

As part of an environmental surveillance program operated by the New York State (NYS) Department of Health, measurements of various radionuclides in aquatic life (primarily fish) collected from waterways in NYS have occurred for decades. An investigation was undertaken to gain a better understanding of the occurrence, activity levels, and extent of radionuclide variations in aquatic life obtained from local waterways in relation to concentrations reported in fish from sites outside NYS (e.g., Pacific Ocean tuna). The man-made isotopes Cs-137 and Sr-90 were detectable at activities below 1 Bq/kg in the edible portions of fish from most NYS waterways, with the exception of greater activities in fish collected downstream of Brookhaven National Laboratory. Calculated effective doses resulting from eating the fish, estimated as 11 -390 nSv/yr for Cs-137 and 0.3-7.9 nSv/yr for Sr-90, are considered extremely low. (C) 2015 Elsevier Ltd. All rights reserved.

The results are described of an upgrade of the low-background gamma-ray spectrometry laboratory at New York State Department of Health by acquiring sensitivity to low-energy gamma rays. Tuning of the spectrometer and its low-energy response characteristics are described. The spectrometer has been applied to monitor the environment by measuring aerosols and water in New York State contaminated by the 2011 Fukushima accident plume. In addition, the spectrometer has been used to monitor radioactivity in food by performing a study of cesium in Florida milk.

For nearly 20 years the Department of Health has conducted programs to assist in the measurement and reduction of indoor radon concentrations in 186 schools located primarily in Zone 1 areas of New York State. Although many schools had few or no rooms containing radon above 148 Bq/m(3), some rooms had >740 Bq/m(3) and remediation techniques were utilized to reduce exposure. Short-term radon measurements in the schools showed little correlation to basement and first-floor radon results from single-family homes in the towns.

Due to their sensitivity and ease of use, alpha-scintillation cells are being increasingly utilized for measurements of radon (222Rn) in natural gas. Laboratory studies showed an average increase of 7.3% in the measurement efficiency of alpha-scintillation cells when filled with less-dense natural gas rather than regular air. A theoretical calculation comparing the atomic weight and density of air to that of natural gas suggests a 6–7% increase in the detection efficiency when measuring radon in the cells. A correction is also applicable when the sampling location and measurement laboratory are at different elevations. These corrections to the measurement efficiency need to be considered in order to derive accurate concentrations of radon in natural gas.

A study to characterize the radionuclide and chemical components in a radium-ore revigator has been completed. Measured activities of dissolved 222Rn, 226Ra, and U isotopes, determined in the water using radioanalytical techniques, exceeded recommended limits in drinking-water supplies. Trace-metal concentrations, determined using inductively coupled plasma mass spectrometry, increased in the water with exposure time and exceeded recommended drinking-water limits for V and As. The contribution to, and dose from, the airborne radon-gas level in a room due to radon emanation from a revigator were evaluated. The annual committed effective dose resulting from consuming the radionuclides in the revigator water were estimated to be ~100 μSv/y for combined uranium and radium.

An air-sampling network that operates continuously as part of New York State’s environmental surveillance program collected radionuclides emitted as a result of the Fukushima nuclear accident. Samples were collected, typically for 7 days each, by drawing ~600 m3 of air through a particulate-collecting filter followed in series by a canister containing activated charcoal. Additional air sampling was implemented at ~3-day intervals at two locations. Gamma-ray spectroscopy was used to confirm the detection of 131I, 137Cs, 134Cs, and 7Be in the particulate phase at all sites, with maximum concentrations near 1,260, 160, 160, and 5,200 μBq/m3, respectively. Gas-phase 131I, collected on activated charcoal, exhibited a maximum concentration of 3,400 μBq/m3 at the sites. Assessment of radionuclide levels in the air samples suggests that there were minimal health impacts from the airborne radionuclides as the activities contributed an insignificant amount to the annual human dose.

Radium-free standards are not readily available for proficiency testing of laboratories that conduct radon ((222)Rn) analyses of water. For this study, 33 identical, reusable, radon-in-water standards were prepared using a (226)Ra-loaded filter sandwiched in polyethylene sheeting. The (222)Rn concentrations in the (226)Ra-free standards were measured by liquid scintillation counting and compared to 10 reference solutions containing (226)Ra. The (222)Rn concentrations measured in the standards were consistent (standard deviation of <2%), but averaged substantially less than concentrations determined in the (226)Ra reference standards. At full ingrowth, 86% of the (222)Rn produced by the sandwiched (226)Ra sources emanated into the water. An intercomparison of radon-in-water standards, performed to examine the accuracy of analyses by commercial, government, and private companies, showed that 18 of the 21 participants reported concentrations within 25% of the known (693 Bq l(-1)). (C) 2010 Elsevier Ltd. All rights reserved.

The manufacture of carbon nanotubes (CNTs) relies on the use of transition metal catalysts. The presence of metals in CNTs has been shown to critically affect the physical, chemical and surface properties of the material for applications in areas such as gas sensors and microcolumns. Once CNTs are released into the environment, the bioavailability of the metals is of concern, in the context of potential human toxicity. In the present study, methods were developed to determine the metals' concentrations in single-walled and multiwalled CNTs (SWCNT and MWCNT, respectively). The metals' concentrations in the SWCNT and MWCNT were determined by inductively coupled plasma optical emission spectrometry (ICPOES) and mass spectrometry (ICPMS), after the CNTs had been pretreated with one of the three extraction/digestion methods: water extraction, dilute acid (1% HNO(3)) extraction, and microwave acid digestion. The total metal concentrations were determined by instrumental neutron activation analysis (INAA). The metals in CNTs were found to have poor solubility in water and dilute acid, suggesting that the role of CNT metals in cytotoxicity may be limited due to their limited bioavailability, and that metals encapsulated in the CNTs could have potential use as tracers for CNTs, in biological or toxicological studies. Microwave acid digestion can achieve a near-complete extraction of metals from the CNTs, and thus is a suitable cleaning method, when high-purity CNTs are desired. Microwave acid digestion followed by ICPOES analysis produced results closer to those obtained by INAA than to those obtained by ICPMS; the latter method was subject to nonspectral interference induced by carbon residues in the sample solution.

Emanation of radon ( 222 Rn) from several brands of cat (kitty) litter was measured with a continuous radon monitor. Radon emanating from the cat litters, encapsulated in an airtight container, produced equilibrium concentrations below 1.2 pCi/g. The measured radon flux was below 10 pCi/kg-hr for all the cat litters. Although each of the samples emitted a measurable amount of radon, the emanation is too small to raise indoor radon concentrations. The cat litters were measured with gamma-ray spectroscopy to identify and quantify the naturally occurring radionuclides in the samples. Secular equilibrium for the 238 U and 232 Th radioactive-decay series

Decorative stones (32 natural and 18 manufactured) and five ceramic tiles that are used in home interiors were measured with gamma-ray spectrometry, to identify and quantify the naturally occurring radionuclides. Activity concentrations of the radioisotopes varied by more than two orders of magnitude across the stone samples, with maximal levels of 3380, 850, and 2130 Bq/kg, for 238 U, 232 Th, and 40 K, respectively. A radiation index and measurements with a radiation meter established that the annual effective dose rates due to a 1 h/day exposure to gamma rays emitted by the granite samples were often low, but can occur as high as 1 mSv/year.

The standardization of instruments used for radon-in-water measurements typically involves handling and disposal of Ra in solution. To avoid contact with the Class A carcinogen, radium-free solutions were prepared and tested for use as radon-in-water standards. Filters containing known amounts of Ra were sealed in polyethylene and placed in vials filled with distilled water for >30 days to allow the decay products to establish secular equilibrium. Voluntary intercomparisons of the radon-in-water standards were conducted to investigate the accuracy of analyses by commercial, government, and private companies. Various analytical methods were utilized by the participants. Result show that, at radon concentrations of 18,700 and 3850 pCi/L (693 and 143 Bq/L, respectively), most participants reported concentrations within 25% of the known amounts.

Emanation of radon (Rn-222) from granite used for countertops and mantels was measured with continuous and integrating radon monitors. Each of the 24 granite samples emitted a measurable amount of radon. Of the two analytical methods that utilized electret-based detectors, one measured the flux of radon from the granite surfaces, and the other one measured radon levels in a glass jar containing granite cores. Additional methods that were applied utilized alpha-scintillation cells and a continuous radon monitor. Measured radon nux from the granites ranged from 2 to 310 mBq m(-2) s(-1), with most granites emitting <20 mBq m(-2) s(-1). Emanation of radon from granites encapsulated in airtight containers produced equilibrium concentrations ranging from <0.01 to 11 Bq kg(-1) when alpha-scintillation cells were used, and from <0.01 to 4.0 Bq kg(-1) when the continuous radon monitor was used. Health Phys. 96(4):477-482; 2009

Methods currently approved for the measurement of radon (222Rn) in water in New York State are liquid scintillation counting and emanation into alpha-scintillation cells. A passive system using an electret ion chamber (EIC) was evaluated as an alternative for the measurement of radon in water. Over 130 water samples from a community water supply containing 32BqL−1 and 30 standards containing 686BqL−1 were measured using the EIC method over 1- to 4-day exposure times. For comparison, identical samples were measured using liquid scintillation counting. Results of duplicate samples were typically within 5% for liquid scintillation counting and within 10% for the EIC. With respect to accuracy, the EIC produced results that were consistently low by 11–15%.

Over 35 samples of decorative stone, imported into the United States for use as countertops and mantels, were measured for the emission of radon using electrets and continuous radon monitors. The 14 engineered stones emitted little or no measurable radon (≤2 pCi/lb; <0.2 Bq/kg ), while the natural stones emitted up to 42 pCi/lb (3.4 Bq/kg). Pieces of a granite countertop, removed from a local home, emitted an average 170 pCi/lb (14 Bq/kg) of radon. It is estimated that in most cases the contribution of the decorative stone to the indoor radon concentration will be <1 pCi/L, but may exceed 4 pCi/L in rare cases.

The concentrations of selenium, barium, and radium were determined in Brazil nuts grown in four regions: Brazil, Bolivia, Peru, and an unknown locality assigned to northern South America. Results indicated that, regardless of geographic origin, all nuts contained measurable amounts of selenium, barium, and radium. The concentration range of Se (2–20μg/g) and that of Ba (96–1990μg/g) each varied by more than an order of magnitude in the nuts, while 226Ra (17–27mBq/g) and 228Ra (18–31mBq/g) activities were comparable and within a factor of two of one another. The greatest concentrations of the elements were measured in nuts from Bolivia, for Ba; Brazil, for Ra; and northern South America, for Se. Only the northern South American nuts contained 137Cs.