o RM what should we do about it policy goals specific or general statements

o RM: what should we do about it? - policy goals: specific or general statements about the conditions you would like to have in place Functional Redundancy - a key ecological trait in terrestrial and freshwater ecosystems is functional redundancy o Multiple 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: o Effects are restricted on spatial and temporal scales o Keystone organisms are not adversely affected o Functions of these organisms can be taken over by other organisms o Repopulation can occur from nearby unaffected populations o Thus local extinctions can be tolerated Keystone 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 important Risk = HAZARD X EXPOSURE Hazard = toxicity x exposure Hazard - The set of inherent properties of a chemical which makes it capable of causing adverse effects once exposure occurs Hazard quotient (HQ) - HQ = exposure concentration / effect concentration, or (LC50/NOEC)

- Margin of safety = effect concentration / exposure concentration Threshold 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