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Environmental Toxicology midterm.docx

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TOX 2000
Aaron Witham

Environmental Toxicology Persistent organic pollutants POPs organic compounds resistant to environmental degradation through chemical biological or photolytic processes United Nations banned 16 chemicals aldrindieldrin endrin DDTDDE HCHlindane chlordane heptachlor toxaphene Byproducts PCDDs PCDFs HCB PCBsRegulation protocols easy to achieve when there is no political agenda interfering most of the dirty dozen have been banned by most countries far more difficult to reach international consensus when national agendas are at stake focus on issues in the economy Environmental toxicology multidisciplinary field in which effects of chemical biological and physical agents on living organisms is studied Ecotoxicology focuses on effects of chemical on populations and communities Assessment endpoints AEs explicit expressions of actual value to be protected the ultimate focus in risk characterization and act as a link to risk management process and to policy goals ecologically relevant susceptible responsive to the stressor societal value unambiguous specificityminimal uncertainty Keystone species species that has a disproportionately large effect on its environment relative to its abundance functions cant be replaced function of community or ecosystem would be significantly changed in their absence ex Elephants sea otter could be detrimental if lost have ecological relevance Societal relevance paragon falcon not a keystone species ecosystem wouldnt be affected if they were removed but society likes them Wetlands critical for bird migrations buffers for toxins very valuable need more societal relevance Basis for assessment endpoint functional and structural responses structural response can depend on if organism is keystone or food source Structure who is present in the system what we see in the system eg Abundance diversity Function interaction of population with other populations or abiotic environment including energy and nutrient flow biomass production consumption of biomass controlling abundance of other species providing food for predators processing organic detritus Measures of effect a measurable characteristic test endpoint ex Mortality growth reproduction that is related quantitatively or qualitatively to AEs should consider both direct and indirect effects integrate sensitivity and response time have high diagnostic capacity consider practicality issues Ecosystems temporal changes seasonal changes spatial changes stream vs river segments States present state normal function and structure disturbance regime pollutants transient state recovery resilience Regime shift dramaticchanges to new state Bistable ecosystem 2 possible endpoints resilient Multistable ecosystem several endpoints at different levels of complexity resilient Impact vs timeorganism physiological adaptation Population avoidanceemigration toxicity local extinction loss of diversity loss of function loss of ecosystem ex Increased nitrogen in water increased nutrient levels which increased plant growth and caused green water Restoration and recovery ecosystem relocalization populationcommunity habitat conditioning opportunists succession organism immigration Toxicity involves 3 components exposuredose exposure duration time responseExtrinsic property that is dependent on number of molecules presentLC concentration at which is lethal to 50 of the population 50per unit volume QUANTAL dead or alive EC effective concentration amount of substance per unit 50volume that affects 50 of the test population for continuous nonquantal responses NOAEC no observed adverse effect concentration LOAEC lowest observed adverse effect concentration MATC maximum allowable toxic concentration geometric mean of LOEC and NOEC Increaseincrease timeincreasedmortality Direct reciprocity LC on a day 2 isthat of day one 50Incipient lethal level threshold level of exposure to toxic substance beyond which 50 of population or of organisms cant survive Nonquantal responses response measures are continuous can take on fractional values toxicity may be judged by use of severity scales assigned when difficult to determine
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