[en] The present investigation was undertaken by the Department of Health, Canada, to determine the most appropriate value to use for uranium gastrointestinal absorption (f₁) in setting the guideline for drinking water. Fifty participants, free from medical problems, were recruited from two communities: a rural area where drinking water, supplied from drilled wells, contained elevated levels of uranium and an urban area where the water supplied by the municipal water system contained <1 μg/l^-1. Uranium intake through food, drinking water and other beverages was monitored using the duplicate diet approach. Intake and excretion were measured by inductively coupled plasma-mass spectrometry (ICP-MS) in samples collected concurrently from the same individuals over a 3 d period. The range of f₁ values was between 0.001 to 0.06, with a median of 0.009. These values were independent of gender, age, duration of exposure, daily total uranium intake and allocation of intake between food and water. Consistent with the recommendation of ICRP Publication 69, 78% were below 0.02. (author)

[en] A study of an aboriginal community was conducted to determine if kidney function had been affected by the chronic ingestion of uranium in drinking water from drilled wells whose uranium concentrations varied from <1 to 1,418 ppb. This non-invasive study relied on the measurement of a combination of indicators of kidney function and markers for cell toxicity measured in urine samples collected from 39 females and 15 males. Ages ranged from 12 to 73 years. Correlation of uranium excreted in urine with bio-indicators at p≤0.05 indicates interference with the kidney's reabsorptive function. Because of the community's concerns regarding cancer incidence, cumulative radiaiton doses were also calculated using uranium intake in drinking water over the preceding 15-year period. the average dose was 0.2 mSv and the highest dose, 1.7 mSv with the risk of cancer from the former being 1.4 in 100,000 while that from the latter in 12 in 100,000. Both would be difficult to detect in the community studied (population: 1,480). (Author) 28 refs

[en] A study was conducted in two Canadian towns to determine the feasibility of using urinalysis data to estimate uranium uptake where exposure is through the chronic ingestion of soluble natural uranium in drinking water. Forty-three subjects participated in the study. Uranium levels in drinking water varied from 5 to 376 μg/L, and intakes ranged from 3 to 628 μd/day. Urinary excretion varied from 1 to 10 μg/day. Variation of the gut absorption factor (f₁) correlated poorly with gender, years of residence, and age, while significant negative correlation was obtained with intakes greater than 9.5 μg/day. (author)

[en] To estimate gastrointestinal (GI) absorption (f1) of uranium in humans where exposure is though chronic ingestion, a study was conducted of a rural community in Canada where the residents relied on drilled private wells that delivered water with uranium levels ranging from 2 to 780 μg/L. A comparison was made with an urban centre whose drinking water was supplied by a municipal system and had a uranium content of <1 μg/L. Fifty subjects participated in the study. To estimate daily intake from both water and food as accurately as possible, the duplicate diet approach was used where individuals collected and set aside a duplicate amount of beverage and food that they had ingested over a three-day period. Total intakes from water and through food varied from 0.03 to 570 μg/day. The f₁ values obtained ranged from 0.001 to 0.06, with a mean of 0.012 and a median of 0.009. Variation of f₁ values correlated poorly with gender, years of residence and age at the time of study. Contrary to expectations, the values were found to be in reasonable agreement with values obtained in previous human studies whether the pattern of exposure was acute or chronic. (author)

[en] Soil gas radon and soil gas permeability measurements were conducted at 32 sites across the five most populated communities in the city of Ottawa where indoor radon measurements were available for 167 houses. A soil radon index (SRI) determined from the soil radon concentration and the soil gas permeability was used to characterise radon availability from soil to air. This study demonstrated that the average SRI in a community area correlates with the indoor radon potential (the percentage of homes above 200 Bq m^-3) in that community. Soil gas radon concentrations together with soil gas permeability measurements can be a useful tool for the prediction of the indoor radon potential in the development of a Canadian radon risk map. (authors)

[en] The long-term monitoring of soil radon variations was conducted at two reference sites in Ottawa. The purpose of this study was to determine whether a single soil radon survey could provide a representative soil radon characteristic of the site. Results showed that during the normal field survey period from June to September in Canada, a single field survey with multiple measurements of soil gas radon concentrations at a depth of 80 cm can characterise the soil radon level of a site within a deviation of ±30%. Direct in situ soil permeability measurements exhibited, however, large variations even within an area of only 10 x 10 m². Considering such large variations and the weight of the equipment, soil permeability can be determined by direct measurements whenever possible or by other qualitative evaluation methods for sites that are hard to access with heavy equipment. (authors)

[en] The Bureau of Radiation and Medical Devices has acted as Canada's National Reference Centre for Bioassay and in vivo Monitoring since 1983. The Centre provides quality assurance to organizations performing in vitro radiobioassay, including urinalysis intercomparisons for uranium, tritium, and carbon-14. Evaluation of results has shown that regular participation has resulted in a steady improvement in analytical performance. Bias between the true value and reported results has been reduced, and precision enhanced. (author)

[en] Ottawa is the capital city of Canada. In the previous cross Canada radon survey, Ottawa was not included. There is great interest to know radon level as well as thoron concentration in Ottawa homes. Therefore, radon/ thoron discrimination detectors developed at the National Inst. of Radiological Sciences in Japan were deployed in 93 houses for a period of 3 months. As expected, thoron is present in Ottawa homes. Radon concentrations ranged from 8 to 1525 Bq m^-3 while thoron concentrations varied from 5 to 924 Bq m^-3. The arithmetic mean of radon and thoron concentrations were found to be 110 ± 168 and 56 ± 123 Bq m^-3, respectively. (authors)

[en] The recently developed radon film-badge makes it possible to measure radon indoors, in soil, in water and/or in aqueous media (e.g. mud). As a result of its wide response linearity, this monitor has been successfully used to measure radon in-water with concentrations from 10 to ∼10 000 Bq/L. By exploiting the unique characteristics of this badge, a mini-survey has been carried out by Health Canada in which radon in water was measured from 12 private wells, as well as in tap water originating from the Ottawa River. Due to the widespread interest of different laboratories in using these passive monitors, laboratories were provided with plastic films to construct their own badges by using in-house CR-39 detectors. Monitors were then irradiated by a known radon concentration at the National Institute of Radiation Metrology (ENEA) s radon chamber and sent back to each laboratory for processing and counting. Even though these laboratories have been using different etching- and counting procedures, the film-badge responses varied only within ∼12%. (authors)