Body burden toxicological

The absorption, distribution, and accumulation of lead in the human body may be represented by a three-part model (6). The first part consists of red blood cells, which move the lead to the other two parts, soft tissue and bone. The blood cells and soft tissue, represented by the liver and kidney, constitute the mobile part of the lead body burden, which can fluctuate depending on the length of exposure to the pollutant. Lead accumulation over a long period of time occurs in the bones, which store up to 95% of the total body burden. However, the lead in soft tissue represents a potentially greater toxicological hazard and is the more important component of the lead body burden. Lead measured in the urine has been found to be a good index of the amount of mobile lead in the body. The majority of lead is eliminated from the body in the urine and feces, with smaller amounts removed by sweat, hair, and nails. 

Studies of the effects of lead on bone metabolism indicate that, in addition to being a reservoir for the lead body burden, bone may also be a toxicological target (Hamilton and O Flaherty 1994, 1995). 

Traditional, default approaches for toxicological risk assessment are not based on specific understanding of modes of action and tissue dose metrics (e.g., tissue concentrations, body burdens, AUCs). In recent years, PBPK/PBTK modeling has found frequent application in risk assessments where PBPK models serve as important adjuncts to studies on modes of action of xenobiotics. 

No relationship was found between the measured body burden of thorium and complete blood count parameters (e.g., hemoglobin, red and white blood cells) in humans occupationally exposed to thorium (see Section 2.2.1.2). Further studies may reveal thorium-specific biomarkers that may alert health professionals to thorium exposure before toxicological effects occur. 

Sijm, D. T. H. M., M. Schipper, and A. Opperhuizen, Toxicokinetics of halogenated benzenes in fish Lethal body burden as toxicological end point , Environ. Tox. Chem., 12,1117-1127 (1993). 

The similarities in response of humans and experimental animals to similar body burdens of CDDs and related chemicals (Table 2-10), along with our understanding of common mechanisms of actions of CDDs in humans and experimental animals lends support to both the relevance of experimental animal toxicology to humans and the use of experimental animal data for establishing MRLs (see Section 2.4.3 for more information on the animal-to-human extrapolations). Acute, intermediate and chronic MRLs for... 

Health professionals cannot use a hair analysis result to compute a body burden, an internal dose, or other parameter that would enable a meaningful toxicologic evaluation of a hair analysis result. ... 

Bowman RE, Heironimus MP, Allen JR. 1978. Correlation of PCB body burden with behavioral toxicology in monkeys. Pharmacol Biochem Behav 9 49-56. 

It is well known that the effects of narcosis type chemicals are completely concentration additive [92, 134-136]. Intrinsically, these chemicals are equally toxic. In other words body burdens at a certain effect are the same for all compounds within this toxicological class . The differences in aqueous effect concentrations of chemicals with base-line toxicity are only due to differences in... 

Cadmium occurs only in one valency state (2 ) and does not form stable alkyl compounds or other organometallic compounds of known toxicological significance. Cadmium initially is distributed to the liver and then redistributes slowly to the kidney as cadmium-metallothionein (Cd-MT), with 50% of the total-body burden in the liver and kidney after distribution. Cadmium and several other metals induce the expression of metallothionein, a cysteine-rich protein with high affinity for metals such as cadmium and zinc. Metallothionein protects cells against cadmium toxicity by preventing the interaction of cadmium with other proteins. 

Neubeit, D., Borchert, G., Gericke, C., Hanke, B. and Beckmann, G. (2001) Toluene Field Study Group Multicenter field trial on possible he di effects of toluoie. I. Toluene body burdens in woikers of the rotogravure industry. Toxicology 168 (2001), 139 -157. 

It is clear that the body burden increases as absorption increases and excretion decreases. Since toxicology studies often involve libitum feeding or bolus administration into the GI tract, where complete absorption is assumed, they inherently evaluate the excretion rate in dermal exposure, absorption is the prominent variable in the evaluation ( 2). 

Based on these principles, quantitative and qualitative toxicology data on pesticides are generated from animal studies and extrapolated to sian. The extrapolation, however, is usually not direct and stay include several assumptions. Species susceptibility, species metabolism differences, and extrapolations of dose response relationships below the experimental range should be considered (7 ). In a work situation, the husian body burden is determined by the exposure, absorption, and excretion rates. The same is true in animal studies, although continuous exposure is usually incorporated in the study design. Absorption is usually considered relatively complete. Excretion rates are usually specific to the physico-chemical properties of the chemical and the species however differences in excretion rates are not usually incorporated into extrapolations to man ( ). 

Sijm, D. T. H. M., Schipper, M. and Opperhuizen, A. (1993) Toxicokinetics of halo-genated benzenes in fish lethal body burden as a toxicological endpoint. Environ. Toxicol Chem., 12, 1117-27. 

The actual body burden of dioxin-like compounds at a given point in time is the important qnantity in defining the toxicological risk to that individnal a single acute dose and an average daily dose mean very different things. Approximately similar body hardens of dioxins conld... 

Ellis K, Yasumura S, Vartsky D, and Cohn S. (1983). Evaluation of biological indicators of body burden of cadmium in humans. Fundamentals and Applied Toxicology, 3, 169-174. 

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