Hydroquinone predicted concentrations

Species Extrapolation. The Medinsky model used species-specific information to outline the model parameters little extrapolation of information between mice and rats was required. Based on the parameters derived for mice, metabolism of benzene after inhalation by humans was simulated. The results indicate that at concentrations below 10 ppm, metabolism and formation of metabolites is linearly related to inhaled concentration, and that hydroquinone conjugates are the predominant metabolite. At concentrations above 10 ppm, the model predicts a change in the metabolic profile, with increased proportion of phenyl conjugates, associated with detoxification processes. 

Predicting Time, temperature, and solution concentration are all important factors in the developing process. What would be the consequence of leaving the film too long in the hydroquinone developer (Hint the developer is a reducing agent.)... 

The positive value of suggests that the oxidation of hydroquinone by soluble Fe should occur spontaneously xn6sr standard-state conAitxom. However, the standard-state activities of dissolved ions (in this case Fe ", Fe, and H" ) of unity correspond to concentrations that are absurdly high for soil solution (on the order of 1 molar). The standard-state potential, then, has little use in predicting the favorability of the reaction under conditions likely to prevail in soil solutions. It is necessary to use the Nemst equation (see Chapter 7) to calculate the adjusted redox potential, E, for more realistic reaction conditions ... 

Dixon et al. (2001) described a preliminary PB-PK model to predict JP-8 concentrations in Air Force fuel-cell maintenance workers. The model used data from PB-PK models of naphthalene inhalation in mice and rats and nonane inhalation in rats. In addition to inhalation, a pathway of dermal exposure and a skin compartment were included. For highly exposed people, the PB-PK model was generally in agreement with exhaled-air naphthalene concentrations however, predictions for the low-exposure scenarios were grossly underestimated, especially in female workers, by a factor of 10. The model did not predict blood and urinary concentrations. The major limitation of the Dixon et al. (2001) study was the lack of appropriate human data (e.g., metabolic measures, blood and tissue partition coefficients, and diffusion rates). The Dixon et al. (2001) model predicted a rapid decline in naphthalene concentrations in all compartments after exposure except liver, fat, and brain. The model predicted accumulation in liver, brain, and fat tissues for a 7-day period that included 4-hr exposures on 5 days. Competition for enzyme does not occur only from interactions of different inhaled compounds. Interactions can also occur between inhaled compounds and metabolites formed in the body that require similar enzymes for biotransformation. Detailed kinetic studies with both benzene and -hexane show inhibition of later metabolic steps, phenol to hydroquinone or methyl -butyl ketone to 2,5-hexane dione, by high concentrations of inhaled benzene or hexane, respectively (Medinsky et al. 1989 Andersen and Clewell 1984). 

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