Cs137 Biospheric Contamination from Nuclear Weapons Tests

Journal Article · Thu Jan 01 04:00:00 EST 1959 · Health Physics

DOI:https://doi.org/10.1097/00004032-195901000-00003· OSTI ID:4205321

Langham, W. H.; Anderson, E. C.

Weapons tests to the end of 1957 have produced about 6 and 11 Mc of Sr⁹⁰ and Cs¹³⁷, respectively, of which about 1.9 and 3.4 Mc have been deposited as long-range fall-out. Average surface deposition levels of Sr⁹⁰ and Cs¹³⁷ in the north temperature population belt may be about 20 and 36 mc/mile², respectively, and the stratospheric reservoir may contain an additional 2.3 Mc of Sr⁹⁰ and 4.2 Mc of Cs¹³⁷. Cesium-137 contamination of the atmosphere, and of drinking water, assuming they are in equilibrium with the rate of stratospheric fallout, does not appear to be a serious potential hazard to man's health even though weapons tests continue indefinitely at the past rate. The ingestion of contaminated foods is the principal source of Cs¹³⁷ in the population. At present it is not possible to determine whether cesium is entering the biosphere and man via direct contamination of vegetation or via soil integration and plant uptake. If its mode of entry is through the soil, the potential radiation hazard from continued tests may be a factor of about 4 greater than if it is entering by direct contarnination of vegetation. Because of metabolic similarity of cesium and potassium, cesium levels in the biosphere are conveniently expressed as Cs¹³⁷g K. The average 1957 Cs¹³⁷ level in United States milk was about 32 per mu mu c/g K, and the level in the rest of the diet was about 20 mu mu c/g K. The average 1956, 1957, and 1958 (through July) levels in the United States population were about 41, 44, and 54 mu mu c/g K, respectively. Correlation of Cs¹³⁷ levels in the population with levels in milk suggests a dietary dfscriminntion factor of about 2 in favor of cesium over potassium in going from the diet to the body. Correlation of 1957 Cs¹³⁷ levels in United States milk (expressed as mu mu c/g K per in. of rainfall) with geographic meteorological conditions suggests that the manner in which tropospheric air masses approach or traverse the latitudes of high stratospheric fall-out may be a factor in Cs¹³⁷ and Sr⁹⁰ surface deposition levels. The increase in Cs¹³⁷ levels in milk and in the United States population from 1956 to 1957 was not proportional to the increase in integrated fall-out, suggesting direct contamination of vegetation as its route of entry into the biosphere. However, measured levels presently in the population are compatible with predictions based on ecological considerations. The average 30 year internal plus external Cs¹³⁷ radiation dose in equilibrium with a continuing test rate of 10 MT of fission per year is estimated as about 300 mr, or about 10 per cent of natural background, and the average total 70 year bone marrow dose is estimated as about 500 mr (assuming Cs¹³⁷ enters the biosphere via the soil). Assuming 30 to 50 r as the genetic doubling dose and a non-threshold respomse to radiation, indefinite testing at the rate of 10 MT of fission per year may produce 0.5 to 1 per cent increase in the incidence of mutations as a result of Cs¹³⁷ biospheric contamination. If weapons tests are stopped, the increase in incidence of mutations from Cs¹³⁷ would be about one-tenth of the above estimate. A comparison of the mean bone marrow dose from Sr⁹⁰ and Cs¹³⁷ suggests that Cs¹³⁷ may pose a potential leukemogenic hazard comparable to Sr⁹⁰, if both are entering the biosphere via soil integration and plant uptake. If C¹³⁷ is entering the biosphere via direct contamination of vegetation, its potential leukemogenic hazard is about one-fifth that of Sr⁹⁰. Present knowledge is not adequate to establish the nature of the dose-response relationship for somatic effects of radiation. Therefore, it is not possible at present to estimate the absolute leukemogenic hazard of either Sr⁹⁰ or Cs¹³⁷ fall-out.

• Research Organization: Los Alamos Scientific Lab., N. Mex.
• Sponsoring Organization: USDOE
• NSA Number: NSA-13-022250
• OSTI ID: 4205321
• Journal Information: Health Physics, Journal Name: Health Physics Journal Issue: 1 Vol. 2; ISSN 0017-9078
• Publisher: Health Physics Society
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

61 RADIATION PROTECTION AND DOSIMETRY
ABSORPTION
ATMOSPHERE
BACKGROUND
BODY
BONE MARROW
CESIUM 137
CONTAMINATION
DIET
FALLOUT
FOOD
GENETICS
HAZARDS
LEUKEMIA
MAN
METABOLISM
METEOROLOGY
MILK
MUTATIONS
NUCLEAR EXPLOSIONS
PLANTS
POTASSIUM
RADIATION DOSES
RADIATION EFFECTS
RADIOACTIVITY
RAIN
SAFETY
SOILS
STRATOSPHERE
STRONTIUM 90
TESTING
WATER