(IF YOU DON\'T SEE GRAPH, PLEASE LET ME KNOW) This activity must be answered in
ID: 792256 • Letter: #
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(IF YOU DON'T SEE GRAPH, PLEASE LET ME KNOW)
This activity must be answered in analytico-dissertative form; you may use general or specific examples to illustrate a point, as well as numbers, but you must provide a description of the concepts as opposed to simply stating a formula or equation.
1. The picture illustrates a dose-response relationship for a toxicant T. The small circles in the graph represent determined experimental response from 10 mice used per dose. The curve is obtained from the seven data points shown, and there are no more data points in this entire experiment.
Discuss the extrapolation of the experimental curve towards the region marked by the red circle, and the practical implications that such an extrapolation might have for humans with respect to NOAELs, toxicity threshold, acceptable daily intake, and long- term exposure to the potential adverse effects of toxicant T.
This activity must be answered in analytico-dissertative form; you may use general or specific examples to illustrate a point, as well as numbers, but you must provide a description of the concepts as opposed to simply stating a formula or equation. 1. The picture illustrates a dose-response relationship for a toxicant T. The small circles in the graph represent determined experimental response from 10 mice used per dose. The curve is obtained from the seven data points shown, and there are no more data points in this entire experiment. Discuss the extrapolation of the experimental curve towards the region marked by the red circle, and the practical implications that such an extrapolation might have for humans with respect to NOAELs, toxicity threshold, acceptable daily intake, and long- term exposure to the potential adverse effects of toxicant T.Explanation / Answer
There are two possible scenarios for the extrapolation of this S-shaped dose-response curve for toxicant T. If the line is extrapolated down to the origin, there is no "no-adverse-effect-level" (NOAEL), meaning there is no threshold dose below which there is no adverse effect. However, if the curve is extrapolated to intersect the x-axis at above 0 mg/kg, then that value would be the NOAEL value. This value, divided by the appropriate uncertainty factors, could then be used to calculate a human reference dose, which would be an estimated daily acceptable intake at which there would likely be no appreciable health effects. However, the decision has to be made whether toxicant T is likely to have a threshold effect or not. The appropriate toxicological studies would have to be carried out to determine whether toxicant T is likely to have a threshold dose or whether the toxicant is a possibly carcinogenic. In the case that toxicant T is likely to be carcinogenic, a no-threshold model would be selected to characterize the risk from exposure to toxicant T. This scenario would suggest that there is no level at which long-term exposure to toxicant T does not produce adverse health effects.
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