Dose received

However, there are multiple routes of entry to the body for some materials. When a toxic chemical acts on the body or system, the nature and extent of the injurious response depends upon the dose received, that is, the amount of the chemical actually entering the body or system. This relationship of dose and response is shown in Figure 3. The dose-response curve varies with the type of material and the response. 

Generally a serious exposure refers to a large, single dose received over a short period of time and an immediate response occurs, (acute)... 

Everyone receives small radiation doses every day Figure 8.3-5 illustrates some of the doses received from background and other types of radiation. Note that the scale is logarithmic , and that background and cosmic-ray doses vary over an order of magnitude just with location and elevation. In addition to these natural sources, most people receive some medical and dental doses each year. 

PNL - Pacific Northwest Laboratory, technical analytical DOE laboratory including PSA Population dose - The sum of the doses received by a population. If each person recci cd a dose, and the population is N, it is d N. 

In this chapter we will consider only exposure to chemical agents in the air. We will not address other risks that do not influence the dose received by a worker. 

The response of humans to var> ing doses of radiation is a field tlmt has been widely studied. The obscr ed radiation effects can be categorized as stochastic or nonstochastic effects, depending upon tlie dose received and tlie time period over which such dose was received. Contrary to most biological effects, effects from radiation usually fall under tlie category of stochastic effects. The nonstochastic effects can be noted as having three qualities a minimum dose or tlucshold dose must be rcceii ed before the particular effect is obsen ed the magnitude of the effect increases as the size of the dose increases and a clear, casual relationship can be determined between the dose and the subsequent effects. 

Variability arises from true heterogeneity in characteristics such as dose-response differences within a population, or differences in contaminant levels in tlie enviromiient The values of some variables used in an assessment change witli time and space, or across tlie population whose exposure is being estimated. Assessments should address tlie resulting variability in doses received by members of the target population. Individual exposure, dose, and risk can vary widely in a large population. The central tendency and high end individual risk descriptors are intended to capture tlie variability in exposure, lifestyles, and other factors tliat lead to a distribution of risk across a population. 

The dose received shall not exceed specified limits. As with most hygiene standards these limits vary slightly between nations local values should be consulted. Limits set within the European Community are summarized in Table 10.4. 

The radioactive source need not aiways be introduced into the body. Inoperable brain tumors can be treated with y rays from an extemai source, usuaiiy a sampie of cobait-60. The patient is placed in a position where the y-ray beam passes through the tumor. The patient is moved so that the y rays irradiate the tumor from several angles. In this manner the tumor receives a much higher dose of radiation than the dose received by any surrounding tissues. 

C22-0024. Although X-ray exposures pose little threat to patients, medical technicians must be careful to avoid exposure to the beam. Suppose that an X-ray machine is leaking radiation that exposes the technician to 1% of the dose received by a patient. After how many exposures would the technician begin to show reduced numbers of white blood cells If the technician administers 40 X-ray studies daily and works 250 days per year, would this damage show up ... 

Electron spin resonance (ESR) measures the trapped electron population in a lattice, which is directly related to the amount of ionizing radiation received by the sample since its formation. The total radiation dose received by the sample is estimated from the ESR... 

TX Pharmacoft, 2004. (Provides alphabetical list of drugs with references calculates theoretical infant dose received after maternal use.)... 

Collective dose—The sum of the individual doses received in a given period of time by a specified population from exposure to a specified source of radiation. Collective dose is expressed in units such as man-rem and person-sievert. 

Tissue Dose—Absorbed dose received by tissue in the region of interest, expressed in rad (see Dose, Gray, and Rad). 

Hart 1976), pregnant rats (Hart 1980), calves (Palmer et al. 1979), or dogs (Hart 1980) was noted subsequent to acute (Hart 1980) or intermediate (Army 1978 Hardisty et al. 1977 Hart 1976, 1980) oral administration of diisopropyl methylphosphonate. However, as discussed in Section 2.2.2.1, there is some confusion concerning the concentration units of the diisopropyl methylphosphonate used in the Army (1978) and Hardisty et al. (1977) studies (EPA 1989), and the actual doses received may be lower. 

The radiological impact of being exposed to a given atmosphere is, however, only partly determined by the PAEC, but also by the likelihood of deposition of the inhaled activity at specific sites in the respiratory tract and thus for a given value of PAEC upon the fraction of the progeny in both the attached and the unattached state. Several models for the radiological dose received over a given time... 

It is reasonable to conclude that dose to cells throughout the bronchial tree may contribute to the risk of lung cancer and not just the dose received by certain cells in the large central airways. It is probably also appropriate to evaluate the dose absorbed by cells throughout the depth of bronchial epithelium, i.e. the mean dose,... 

The dose received by cells in the bronchial epithelium from decay of the alpha-emitting radon daughters at the airway surface decreases rapidly with depth in tissue. The data available show that the thickness of bronchial epithelium is highly variable (Gastineau et al., 1972) but the distribution of values can be formalised (Wise,... 

Where sufficient toxicologic information was available, MRLs were derived. MRLs are specific for route (inhalation or oral) and duration (acute, intermediate, or chronic) of exposure. Ideally, MRLs can be derived from all six exposure scenarios (e.g., Inhalation - acute, -intermediate, -chronic Oral - acute, -intermediate, - chronic). These MRLs are not meant to support regulatory action, but to acquaint health professionals with exposure levels at which adverse health effects are not expected to occur in humans. They should help physicians and public health officials determine the safety of a community living near a substance emission, given the concentration of a contaminant in air or the estimated daily dose received via food or water. MRLs are based largely on toxicological studies in animals and on reports of human occupational exposure. 

The application of the Chelex 100 resin separation and preconcentration, with the direct use of the resin itself as the final sample for analysis, is an extremely useful technique. The elements demonstrated to be analytically determinable from high salinity waters are cobalt, chromium, copper, iron, manganese, molybdenum, nickel, scandium, thorium, uranium, vanadium, and zinc. The determination of chromium and vanadium by this technique offers significant advantages over methods requiring aqueous final forms, in view of their poor elution reproducibility. The removal of sodium, chloride, and bromide allows the determination of elements with short and intermediate half-lives without radiochemistry, and greatly reduces the radiation dose received by personnel. This procedure was successfully applied in a study of... 

Accumulation of 2,3,7,8-TCDD is reported in the liver of rats during lifetime exposure to diets containing 0.022 pg 2,3,7,8-TCDD/kg (Newton and Snyder 1978), or when administered orally at 0.01 pg/kg body weight once a week for 45 weeks (Cantoni et al. 1981). Liver residues of rats fed 2,3,7,8-TCDD were 0.54 pg/kg, or about 25 times dietary levels livers of rats dosed orally contained 1.05 pg/kg, or about 2.3 times the total dose received on a unit weight basis. Unlike toxicity, elimination rates of accumulated 2,3,7,8-TCDD were within a relatively narrow range. The estimated retention times of 2,3,7,8-TCDD in small laboratory mammals (rats, mice, guinea pigs, and... 

Genetically significant dose (GSD) A radiation dose that, if received by every member of the population, would produce the same total genetic injury to the population as the actual doses received by the various individuals. 

Ultimately it must be asked whether a health risk exists at these doses, and a second important factor in making this determination is the number of days over which the dose continues. Duration of exposure as well as the dose received from it thus needs to be included in the equation. 

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