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

This preview shows page 13 - 17 out of 17 pages.

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
Image of page 13
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)
Image of page 14
- 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
Image of page 15
what is likelihood we will encounter exposure that will pass the 10%? 100-93 = 7
Image of page 16
Oct 31 P = i / N + 1 x 100 I = rank What is the probability of that 20%of toxicity will NOT be exceeded? Then use 80%
Image of page 17

You've reached the end of your free preview.

Want to read all 17 pages?

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture