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oRM: what should we do about it?-policy goals: specific or general statements about the conditions you would like to have in placeFunctional Redundancy-a key ecological trait in terrestrial and freshwater ecosystems is functional redundancyoMultiple species are able to perform the same roles in an ecosystem-Essential to the sustainability of ecosystems-Results from selection forces imposed by fluctuating and unpredictable environmental conditions
Functional redundancy and Ecological Risk Assessment-Some effects at the organism and population level can be tolerated, provided that:oEffects are restricted on spatial and temporal scalesoKeystone organisms are not adversely affectedoFunctions of these organisms can be taken over by other organismsoRepopulation can occur from nearby unaffected populationsoThus local extinctions can be toleratedKeystone Species-They play a unique and crucial role in the ecosystem, they are important-The functions of keystone organisms cannot be replaced-Function of the community or ecosystem would be significantly changed in their absence-Keystone organisms shouldn’t be confused with organisms judged by society to be importantRisk = HAZARD X EXPOSUREHazard = toxicity x exposureHazard-The set of inherent properties of a chemical which makes it capable of causing adverse effects once exposure occursHazard quotient (HQ)-HQ = exposure concentration / effect concentration, or (LC50/NOEC)
-Margin of safety = effect concentration / exposure concentrationThreshold of Toxicity-Cramer (1978) classified over 2500 food flavouring agents into 3 toxicity classes based on chemical structure to identify TTC-The thresholds of toxicological concern (TTC) represents a level of exposure for all chemicals, whether or not there are chemical specific toxicity data, below which there would be no appreciable risk to human health
what is likelihood we will encounter exposure that will pass the 10%? 100-93 = 7
Oct 31P = i / N + 1 x 100 I = rankWhat is the probability of that 20%of toxicity will NOT be exceeded? Then use 80%