Background Ranges

The most important comparison is with concurrent control groups. However, there are occasions when it is necessary to use historical data, that is, information from control animals of the same strain on other studies. This is more relevant if the studies were conducted in the same laboratory under similar conditions and at the same time. The incidence of a particular neoplasm is often different between laboratories and may change with time. Historical data are most useful to get an idea of the variation in the background range of frequency and also to ascertain that rare tumour t)rpes can occur spontaneously. 

For fetal variations that occur frequently, comparison of the incidences with the expected background range in addition to the concurrent control remains valid, but the concurrent control is now of greater importance. 

In samples drawn from the Yenisey River at and upstream of the junction, levels of the neutron activation product60 Co (5.27-year half-life) and of the fission products 137Cs and 152Eu (13.3-year half-life) were much higher than background ranging... 

Tab. 5.5 Mean and maximum values (mg kg" ) of the background ranges reported for trace elements in different soil kinds on the world scale. Adopted from Kabata-Pendias and Pendias (2001) and Tobias et al. (1997)...

Atmospheric mercury in urban areas results from various sources. Stack emissions in California s San Francisco Bay area may have caused the short term peaks of 30 to 50 ng/w observed when the background ranged from 3 to 8 ng/w on days with low and variable winds (7, 26, 27). Most atmospheric mercury in urban areas (Table III, urban) is contributed by processes involving heat which vaporize mercury contained in fuel and other materials (28). Noteworthy are the contributions... 

TABLE IV. COMPARISON OF THE CONCENTRATIONS NEEDED TO ACHIEVE THE RESIDUAL RISK LEVELS FOR THE 14 RADIONUCLIDES WITH TYPICAL U.S. BACKGROUND RANGES AND MINIMUM DETECTABLE CONCENTRATIONS... 

Radionuclide Typical U.S. Background Range Laboratory lE-4 Risk Goal IE-5 Risk Goal lE-6 Risk Goal ... 

The individuals we find at the center have a mixture of educational backgrounds ranging from electrical engineering, industrial design, and multimedia to engineering design. 

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