Chemical dosimetry

Eor virtually all radiopharmaceuticals, the primary safety consideration is that of radiation dosimetry. Chemical toxicity, although it must be considered, generally is a function of the nonradio active components of the injectate. These are often unreacted precursors of the intended radioactive product, present in excess to faciUtate the final labeling reaction, or intended product labeled with the daughter of the original radioactive label. 

Andersen ME, Krishman K. 1994. Relating in vitro to in vivo exposures with physiologically-based tissue dosimetry and tissue response models. In H. Salem, ed. Current concepts and approaches on animal test alternatives. U.S. Army Chemical Research Development and Engineering Center, Aberdeen Proving Ground, Maryland. 

A common approach for personal dosimetry is collection of pollutant on, e.g., silica gel, organic resins or activated charcoal in small tubes worn on the operator s lapel (Table 9.2). Silica gel is useful for polar chemicals charcoal finds wide use for non-polar substances. The pollutant is then solvent-extracted or thermally desorbed for subsequent analysis by, e.g., chromatography. 

James A. 1987. A reconsideration of cells at risk and other key factors in radon daughter dosimetry. In Hopke P, ed. Radon and its decay products Occurrence, properties and health effects. ACS Symposium Series 331. Washington, DC American Chemical Society, 400-418. 

Passive dosimetry, which proved useful for the pursuit of better workplace hygiene in agriculture during the past 40 years (Durham and Wolfe, 1962), yields unvalidated and excessive amounts of worker exposure (Krieger, 1996). Currently, our approach with respect to indoor and agricultural exposure assessments has been the evaluation of exposure estimates using well-known, studied chemicals to first understand the work task and at a later time develop chemical-specific studies as required in the regulatory arena. 

Krieger, R.I., Bernard, C.E., Dinoff, T.M., Fell, L., Osimitz, T. G., Ross, J.I., and Thongsinthusak, T. (2000) Biomonitoring and whole body cotton dosimetry to estimate potential human dermal exposure to semivolatile chemicals, /. Exposure Anal. Environ. Epidemiol., 10 50-57. 

In this chapter we will consider the following as examples of radiation chemical applications (1) dosimetry, (2) industrial synthesis and processing, (3) irradiation of food, waste, and medical equipment, and (4) low-energy ion interaction with matter. Dosimetry is of fundamental importance for yield calculations and also for personnel exposure. Industrial processing would include... 

Since 1925, The International Commission on Radiation Units and Measurements at Bethesda, Maryland has been publishing reports updating the definitions and units for measurements of various radiation-related quantities. Of these ICRU Reports, special mention may be made of reports no. 19 (1971) [radiation quantities and units], 33 (1980) [radiation quantities and units], 36 (1983) [microdosimetry], 47 (1992) [thermoluminiscent dosimetry], and 51 (1993) [radiation protection dosimetry]. A succinct description of various devices used in dosimetry, such as ionization chambers, chemical and solid-state dosimeters, and personnel (pocket) dosimeters, will be found in Spinks and Woods (1990). In this section, we will only consider some chemical dosimeters in a little detail. For a survey of the field the reader is referred to Kase et at, (1985, 1987), McLaughlin (1982), and to the International Atomic Energy Agency (1977). Of the earlier publications, many useful information can still be gleaned from Hine and Brownell (1956), Holm and Berry (1970), and Shapiro (1972). 

A large variety of aqueous and a few nonaqueous solutions have been used or proposed as chemical dosimeters with respective dose ranges for use (Spinks and Woods, 1990 Draganic and Draganic, 1971). Of these, a special mention may be made of the hydrated electron dosimeter for pulse radiolytic use (l(h2 to 10+2 Gy per pulse). It is composed of an aqueous solution of 10 mM ethanol (or 0.7 mM H2) with 0.1 to 10 mM NaOH. Concentration of hydrated electrons formed in the solution by the absorption of radiation is monitored by fast spectrophotometry, which is then used for dosimetry with the known G value of the hydrated electron. 

Interaction with a chemical indicator Can be highly specific, if suitable indicator. Can measure total exposure over time (dosimetry), if a non-reversible reaction is used. Can allow operation at a convenient wavelength, when gas has no convenient absorption in that spectral range. Poisoning can occur, and is easily fouled. Sensitive to groups of chemicals, e.g. acid gases, rather than to a specific gas. May exhibit non-reversible behaviour, which, in many cases, may be undesirable. May need water vapour present, to act as a catalyst, if dry reaction is too slow. 

To develop a better understanding of the potential health consequences of radiocerium in our environment, it is important to know the possible sources and physical and chemical forms of its release. The metabolism and dosimetry of internally-deposited radiocerium are highly dependent upon the forms of the material presented to the body and the mode of exposure as discussed in Section 3—Metabolism of Cerium in Mammalian Species. 

In a study conducted at the Lovelace Inhalation Toxicology Research Institute (ITR1), rats were exposed for up to 30 months, 7 h/day, 5 days/wk, to diesel exhaust containing 0, 0.35, 3.5, or 7.1 mg soot/m3 of air. The diesel engine exhaust was generated as indicated in the section of this paperon "Physical/Chemical Characteristics of Diesel Soot." The lowest exposure concentration, 0.35 mg soot/m3, is directly relevant to some occupational exposures and is 10 to 100 times higher than any current or anticipated environmental exposures. Observations of the animals were made at 6-mo intervals and included measures of dosimetry (mg soot/g lung),... 

Epidemiological and Human Dosimetry Studies. The potential for occupational exposure exists in the use of 3,3 -dichlorobenzidine in the synthesis of 3,3 -dichlorobenzidine-based pigments for printing ink applications and to a lesser extent in paints. Workers exposed to 3,3 -dichlorobenzidine (and simultaneously to other chemicals) have complained of gastrointestinal upset, upper respiratory infection. 

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