Henry F. Lucas

Improved Low‐Level Alpha‐Scintillation Counter for Radon

A low counter background is obtained by use of steel for the shell and quartz for the counter window, while marked improvement in the stability is obtained by coating the window with an electrically conducting layer of tin oxide. The distribution of radon and its daughters within the counter under various conditions was determined by comparison of observed and calculated counting efficiencies. A stable counting efficiency of 5.58±0.05 cpm/μμc radon and a background counting rate of 0.08 cpm is obtained. The usefulness of this counter is augmented by adsorbing the radon on charcoal. The radon is then easily transferred to the counter with a small volume of helium and a Sigmamotor pump. This system is suitable for the analysis of samples of radon as small as 10−14 c or concentrations in air smaller than 10−16 C radon/liter.

Dose-response relationships for radium-induced bone sarcomas.

The incidence of bone sarcomas among 3055 female radium-dial workers who entered the dial industry before 1950 was used to determine dose-response relationships for the induction of bone sarcomas by radium. Two subpopulations were analyzed: all measured cases who survived at least 5 yr after the start of employment and all cases who survived at least 2 yr after first measurement. The first constituted a group based on year of entry; it contained 1468 women who experienced 42 bone sarcomas; the expected number was 0.4. The second comprised a group based on first measurement; it contained 1257 women who experienced 13 bone sarcomas; the expected number was 0.2. The dose-response function, I = (C + alpha D + beta D2)e-gammaD, and simplifications of this general form, were fit to each data set. Incidence (I) was in units of bone sarcomas per person-yr; (D) was the quantity (muCi) of radium that entered the blood. Two functions, I = (C + alpha D + beta D2)e-gammaD and I = (C + beta D2)e-gammaD, fit the data for year of entry (p greater than or equal to 0.05); both these functions and I = (C + alpha D) fit the data for first measurement. The function I = (C + beta D2)e-gammaD was used to predict the number of bone sarcomas in all other pre-1950 radium cases (medical, laboratory and other exposures); fewer were actually observed than the fit of this function to the female dial workers predicted.

NATURAL THORIUM IN HUMAN BONE.

AbstractThe 232Th concentration in rib bone from 38 humans ranged from <0.1 to 72 ng/g ash. Values increased with age and were fitted by the expression: Y = (0.16 ± 0.02)T, where Y is the 232Th concentration in ng/g bone ash and T is the age in years. Evaluation of the retention of the 228Ra produce

The determination of 226Ra and 228Ra in water and solids by the least squares gamma spectrometric method

Abstract An extremely simple, fast and accurate method for the simultaneous analysis of both 226 Ra and 228 Ra in water, sludge, sediments, soil and other types of samples has been developed. This method differs from the standard US Environmental Protection Agency methods for radium analysis in that it is used for all types of environmental materials. The radium from a 10- to 100-liter water sample is adsorbed on to a special high-radium-retaining resin, placed in a sealed container and counted on a sodium iodide detector system. The resultant gamma-ray spectrum is analyzed by a least squares method to determine the nuclides present. For a 20-liter water sample, the accuracy approaches ± 4% at radium concentrations of 90 mBq2 liter −1 (2·5 pCi liter −1 ). For 20-liter water samples processed in the system at Argonne National Laboratory, the lower limit of detection (4.66σ background) for 226 Ra and 228 Ra are 130 mBq (6·5 mBq liter −1 ) and 240 mBq (12 mBq liter −1 ), respectively. However, systematic errors increase this limit to about 20 mBq liter −1 for both radionuclides. The lower limits of detection for natural uranium and thorium series nuclides in secular equilibrium in sludge, sediments and other types of solid samples are 240 mBq and 190 mBq, respectively. Thus, only 50- to 100-g quantities of sludge, sediments, soils and other types of solid samples are required and these samples are processed non-destructively. A single operator can process up to 20 water or solid samples per day. When these samples are counted on an analysis system with completely automatic sample changing, a single counting system can process up to 3500 samples per year.

Radium removal by a home water softener

Abstract The efficiency of radium removal by a home water softener was evaluated in a manually-operated unit that had been in service for about 10 years. The concentrations of calcium, magnesium, and radium in the water provided during a 100-day period averaged 70·2 ± 0·6 mg liter −1 , 24·8 ± 0·6 mg liter −1 , and 0·355 ± 0·007 Bq liter −1 , respectively. The concentration of radium in the effluent remained at 1·3 ± 1·0% of the input level throughout the entire 100-day period. In contrast, the concentration of magnesium began to increase by 30 days. By 40 days, the hardness had increased so much that the homeowner would have initiated another recharge cycle. However, the experiment was allowed to continue until the magnesium content had reached 80% of the influent level. There is no indication that the efficiency of radium removal by this water softener was affected by age or past use. Radium was removed even after the effluent had become hard and a recharge cycle was needed.

Radon and radium retention by the bluegill.

The fractional radon retention by the bluegill has been followed over a 1OOOday period, and is described by the equation F = O.O1to.”. The data were compared to observations in mice that have a comparable bone mineral fraction of 68%. The fish displayed a remarkably low radon retention at 1 day post-injection, due presumably to a smaller bone crystal size (the large amorphous calcium phosphate component). Radon retention by the bluegill increased much more rapidly with time after injection than did radon retention by the mouse. The *=Ra retention for bluegills was described by the equation R = 0.8t-’.I5. FRACTIONAL radon retention in mice, rats, dogs, and man has been shown to increase with time after exposure (Bi75; Ev54; Ev66; Ho44; Ma63; Ma70; Ma75; Mi64; Mi65; No54; No55; Sc33; Va58). Rowland has shown that retention of radon by bone fixed in alcohol is nearly the same as that for the living animal, and an increase in radon retention after heating of the bone was attributed to an increase in the crystal size (Ro58). Mays has predicted the variation in the fractional radon retention with shape and size of bone crystal (Ma%). However, the relative importance of the mineral fraction in bone, its crystal size, and removal of crystal imperfections has not been established. The skeletons of most bony fish (teleosts) have several features that make it possible to approach these questions in a critical manner. First, fish bone lacks osteocytes, and because *Work performed under the auspices of the United States Department of Energy. ?Present address: Washington University School of Medicine, Division of Orthopedics, St. Louis, MO 63 110.

The estimation and potential radiobiological significance of the intake of 228Ra by early Ra dial workers in Illinois.

Undergraduate Research Participant from Emmanuel College, MA. it is acellular, canaliculi are not present. Second, it has nearly the same overall mineral fraction as adult mammalian bone (68%), but its complement of amorphous (very small crystal size) calcium phosphate is much larger (0.32 g/cm3 crystalline apatite, 0.83 g/cm3 amorphous calcium phosphate in eels) (Lo70; Mo63; Po69). Thus, if the pattern of radon retention in fish were compared with that of the higher taxa and found to be different, it would be possible to assess the relative importance of bone crystal size (and mineral fraction) on radon retention. This approach has been tested in the present study, and we have, in addition, examined the variation in radium retention with time.

The effect of meteorological variables upon the vertical and temporal distributions of atmospheric radon

We made radiochemical determinations of 226Ra and the 228Ra-decay product, 228Th, in samples of bone from former Ra dial workers who belonged to a major cohort of Ra-exposed persons under study for health effects at our institution. Most of the former workers were long-term residents of two communities supplied with drinking water containing elevated natural levels of 228Ra and 226Ra, so determinations also were made of radioactivity in samples of bone from long-term residents not occupationally exposed to Ra. The 228Th activity of the bones of the former workers, after correction for the presence of natural radioactivity, showed that some had significant occupational intakes of 228Ra, contrary to published reports that 228Ra was never used by the Illinois company that had employed the cohort of early workers. For 14 workers hired in the years 1920-23, the calculated ratio of the occupational intake of 228Ra to 226Ra activity averaged 0.15 (coefficient of variation 0.65), whereas for three workers hired in 1924, it was not significantly different from zero (mean 0.05, coefficient of variation 1.5). The risk of radiogenic cancer for the typical worker hired before 1924 may have been nearly twice that incurred in the absence of the 228Ra component of the Ra intakes.