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BIOL 354
Julia Roberts

Biol 354 notesLecture 1Information needed for risk assessment 1Types of toxicants2Toxicant transport and transformation3Exposure of target organism4Response of target organism The does makes the poison and the endpoint makes the experimentCategorizing responses to toxicantsDegree of responseoLethal causing death or sufficient to cause deathoSublethal below a level that directly causes deathTypes of responsesoPopulation density productivity mating success alterations in the genetic structure of the population community diversity characteristic species habitat chemical parametersoWhole organism mortality reproduction lesionnecrosis tumors behavior growthoBiochemicalmetabolic enzyme inhibition Acetyl esterase respirationphotosynthesis immunological suppression DNA adductsdamage endocrine disruption hormone mimics enzyme induction cytochrome 450 induction superoxide dismutase stress protein induction heat shock protein metallothioninesTiming of the responseoAcute a stimulus contaminant inducing a rapid response Brief intense exposure that lasts less than 4 daysoChronic effect after prolonged exposure a stimulus that lingers or continues for a long period of time usually more than 10 of the life spanoSubacute a stimulus that Is less severe than acute stimulus and produces a response in a longer period of timeoCumulative toxicity brought about by successive additions at different times or In different waysLife stages is important in sensitivity to toxicants Life cycle study lethality growth reproduction development over the entire life cycle of an organismCritical life stage testing toxicity at an important life stage eg neonate growth or reproductionEarly life stage test subset of the critical life stage test early in development is often the most sensitive test Weakest link incongruity when critical life stage used extrapolation of the environment can be of concern not all of population will be at this stage leading to overestimation of riskBioassay strategiesTimetime required for a given organism to respond to a given toxicantoUsually hours to days at one concentrationToxicant dose or concentrationthe amount of toxicant contaminant required for the average organism to respond within a specified length of timeoUsually molL mgL ppm responding vs concentrationsigmoid shape can calculate LC50the peak has cumulative response all respondingadditional dead vs concentrationresults in normal distribution curveTest type oStatic toxicity testoStatic renewaloFlow through testsThe dose or concentration response curveoHow to quantify the effect of contaminantsoCan be done used on time or concentration
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