Attempted validation of ICRP 30 and ICRP 66 respiratory models.

The validation of human biological models for inhaled radionuclides is nearly impossible. Requirements for validation are: (1) the measurement of the relevant human tissue data and (2) valid exposure measurements over the interval known to apply to tissue uptake. Two lung models, ICRP 30(1) and ICRP 66(2), are widely used to estimate lung doses following acute occupational or environmental exposure. Both ICRP 30 and 66 lung models are structured to estimate acute rather than chronic exposure. Two sets of human tissue measurements are available: (210)Po accumulated in tissue from inhaled cigarettes and ingested in diet and airborne global fallout (239,240)Pu accumulated in the lungs from inhalation. The human tissue measurements include pulmonary and bronchial tissue in smokers, ex-smokers and non-smokers analysed radiochemically for (210)Po, and pulmonary, bronchial and lymph nodes analysed for (239,240)Pu in lung tissue collected by the New York City Medical Examiner from 1972 to 1974. Both ICRP 30 and 66 models were included in a programme to accommodate chronic uptake. Neither lung model accurately described the estimated tissue concentrations but was within a factor of 2 from measurements. ICRP 66 was the exception and consistently overestimated the bronchial concentrations probably because of its assumption of an overly long 23-d clearance half-time in the bronchi and bronchioles.

210Pb in indoor air by total alpha measurement.

210Pb has been measured in indoor air by two methods. Low flow rate pumps and membrane filters were used to collect the samples. The air filter samples were stored for 1.7 y, after which total alpha activity was determined by scintillation counting. 210Pb was then chemically separated and measured by alpha spectrometry. The efficacy of determination of 210Pb by total alpha measurement was empirically proven. The average air concentration determined by total alpha counting was 340 microBq 210Pb m-3 and 360 microBq 210Pb m-3 by radiochemical analysis.

Initial study of 210Pb in indoor air.

An exploratory program was undertaken to determine the feasibility of measuring the indoor air concentration of 210Pb. Low flow rate pumps and membrane filters were used to collect samples in an office. The air filter samples were stored for 1.6 y and 210Po was chemically separated and measured by alpha spectrometry. Unsupported 210Po was also determined in air samples collected at a later time. The average air concentrations were 150 microBq 210 Pb m-3 and 12 microBq 210Po m-3. The average indoor to outdoor ratio of 210Pb in air is estimated to be 0.25.

Measured intake and excretion patterns of naturally occurring 234U, 238U, and calcium in humans.

The normal dietary and fluid intake and urinary and fecal excretion of 234U and 238U were determined in humans under strictly controlled conditions in the Metabolic Research Ward at Hines Hospital. These values formed the basis of the metabolic balances of these uranium isotopes. The major pathway of 234U and of 238U excretion was via the intestine while the urinary 234U and 238U were very low, averaging 2% of the total excretion. The uranium balances were roughly in equilibrium. These data were used in combination with measurements of tissue concentrations of uranium from nonoccupationally exposed humans to calculate steady-state uptake factors for environmental exposure to uranium isotopes during baseline conditions of a normal dietary intake.

The daily intake of 234,235,238U, 228,230,232Th and 226,228Ra by New York City residents.

The daily intake of long-lived alpha-emitting members of the U, Th and Ac series by New York City residents has been estimated from measurements of diet, water and air samples. The total daily intakes from inhalation, food and water consumption in mBq are 18 (234U), 0.7 (235U), 16 (238U), 6 (230Th), 4 (232Th) and 52 (226Ra). From this, we infer that the total daily intakes of 228Th and 228Ra are 4 and 35 mBq, respectively.

Natural U concentrations in soft tissues and bone of New York City residents.

Specimens of lung, liver, kidney and vertebrae from New York City autopsy cases were measured for naturally occurring U. An age dependency in U concentration was found in lung and vertebrae. The bone concentration was found to be a factor of 10 lower than previously reported for this tissue, thus the skeletal burden of U is estimated to be factor of 10 lower than that suggested in ICRP Publication 23.

Measured 234,238U and fallout 239,240Pu in human bone ash from Nepal and Australia: skeletal alpha dose.

Human bone samples from Nepal and Australia were analyzed for isotopic uranium and fallout plutonium. The Nepalese samples were obtained for a 3-yr period (1976-78) while the Australian samples are representative of a single year (1977). The surface air plutonium concentrations for the latitude bands of these countries were either measured and/or estimated from 1954 through 1978. With the plutonium air concentrations and age-dependent breathing rates as input data, the measured human bone results were compared with skeletal estimates derived from the ICRP Task Group Inhalation Model, and the agreement was found to be reasonably good. The measured isotopic uranium concentrations in these samples provide a benchmark against which to assess fallout plutonium based upon a comparison of the skeletal alpha radiation dose from a natural actinide to these populations.