dose response characterization risk characterisation regulatory advise on

Dose response characterization risk characterisation

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dose-response characterization risk characterisation regulatory advise on acceptable risk exposure criterion or guideline; Objective: determine specific “protective” criterion Risk assessment - problem formulation and hazard identification dose response characterization or exposure characterization risk assessment regulatory decision; objective- determine which series of [ ] are causing unacceptable risk Regulatory goals and assessment endpoints - environmental protection, ecological integrity (hard to measure), ecosystem health, generally ambiguous, difficult to define and hard to measure but key to setting RA endpoints Sustainable ecosystems - ecosystems vary in space and time in ecotoxicity, concern for populations, communities in their environments; exceptions: wildlife individual valued by society or threatened/endangered species; goal to ensure populations and communities are sustained in environment (some impact ok), protect from change not just decreases, adverse ecosystem responses often misperceived as always being negative (chemical in the environment not always bad dose makes the poison), increases in population or functional processes ex. Algal blooms may be just as deleterious in ecosystem; maintaining pristine systems (nature reserves) important for highly valued habitats but many habitats managed by economic or social reasons (accept some impacts): agrioecosystems, forests, sewage treatment systems cost of doing business Assessment endpoints : structure (more sensitive than function)- overall species richness, population densities of key ecological spefcies, population densities of indicator species,
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ecosystem functionality- biogeochemical cycles and energy flow; perceived aesthetic value or appearance of ecosystem/landscape- disappearance of species with a popular appeal , symptoms of eutrophication such as algal blooms in lake and clarity of water Ecological concepts in ERA - organisms a part of food chain therefore some individuals expendable Functional redundancy - multiple species are able to perform each critical function, essential to the sustainability of ecosystems, result of selection imposed by fluctuating and unpredictable environmental conditions (biodiversity- form of insurance against any great loss due to disturbance); in soils- nitrate in the rooting zone occurs and ~65% loss of species occurs before function is affected ie. lots of functional redundancy Some effects at the organism and population level can be tolerated provided that: effects restricted on spatial and temporal scales (can’t be devastating), keystone o rganisms not adversely affected (disproportionate response on ecosystem), functions of lost organisms can be taken over by other organisms, repopulation can occur from nearby, unaffected populations Hazard= toxicity x exposure , set of inherent properties of chemical substance or mixture which makes it capable of causing adverse effects when a particular exposure occurs Risk= Toxicity x exposure x probability RA - often conducted in tiers to maximize efficiency- achieved desired and realistic levels of protection with progressively less uncertainty; divided complex tasks into smaller components to reduce complexity and narrow focus to key issues; Advantages- initial uses of conservative
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