Term
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Definition
| Extrapolation from acute exposure (scientific experiments) leads to "making educated guesses" about the effects of chronic exposure. Tradeoffs have to be made-- which species are we going to protect, and what percentage of that species bears protecting? Rats and mice are sucky analogs for people, so there are a lot of inherent flaws with experimentation. Also, little is known about interactions between toxins. |
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Term
| EPA's stance on appropriate level of protection |
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Definition
| In 1980, the EPA said that aquatic communities can tolerate some stress and occasional adverse effects on a few species. Therefore it is not necessary to protect all of the species all of the time. |
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Term
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Definition
| Toxic effects resulting from short term (48-96 hours) of exposure to toxin. |
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Term
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Definition
| Toxic effects resulting from long term (10% of organism's life span) exposure to toxin. |
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Term
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Definition
1. Reproduction
2. Development or growth
3. Behavior
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Term
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Definition
| Concentration of toxicant at which 50% of organisms have died, also called TL50 or LC50- lethal concentration corresponding to 50% mortality. A measure of acute toxicity. |
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Term
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Definition
| Specified effect (not just mortality) on 50% of the organisms after a certain period. A measure of acute toxicity. |
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Term
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Definition
| Time at which 1/2 of the organisms are able to survive given the level of stress. A measure of chronic toxicity. |
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Term
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Definition
| Infinite survival time, calculated by extrapolating median survival time as a function of stress level. A measure of chronic toxicity. |
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Term
| Sublethal chronic toxicity determination |
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Definition
| Compare reproduction, behavior, development and growth in exposed group vs. control group. |
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Term
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Definition
| Smallest concentration with statistically significant impact vs. control on reproduction |
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Term
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Definition
| Geometric mean of chronic values (root of the product) |
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Term
| EPA Guidelines for Final Acute Value (Aquatic Ecosystem) |
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Definition
| Acute tests on 8 different families, determine mean acute value for each species (geo. mean of reported values-- could be TLm or EC50). Group species by genera, calculate mean acute value for each genus. Rank then and calculate cumulative probability by dividing rank by rank+1. The 4 genera with cumulative probabilities closest to 0.05 are used to calculate slope and determine final acute value. |
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Term
| EPA Guidelines for Final Chronic Value (Aquatic Ecosystems) |
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Definition
| Final Acute Value / Acute:Chronic Ratio |
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Term
| Calculations of Acute:Chronic Ratio |
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Definition
1. Geometric mean if no major trends in acute:chronic
2. if variable, acute:chronic of species with acute value closest to final value
3. Embryos of larva and barnacles, bivalve mollusks, sea urchins, lobsters, crabs, shrimp, abalone -> acute:chronic= 2
4. If acute:chronic < 2, assume 2 |
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Term
| Final Plant Toxicity Value |
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Definition
| The minimun concentration of the toxicant that statistically significantly reduces plant growth |
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Term
| Criterion maximum concentration |
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Definition
| 1-hour average concentration not to be exceeded more than once every 3 years. Is equal to half the final acute value because the final acute value is based on lethal effect, and you want to protect organisms from sublethal stresses. |
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Term
| Criterion Continuous Concentration |
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Definition
| 4-day average concentration not to be exceeded more than once every three years and is equal to the smaller of the final chronic and final plant values. |
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Term
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Definition
1. Toxicity is dependent on environmental conditions (temperature, water hardness)
2. Conditioning and acclimation
3. Interactions between toxicants |
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Term
| No Interaction Between Toxicants |
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Definition
| After TLm, 1.2 organisms are dead |
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Term
| Antagonistic Interaction Between Toxicants |
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Definition
| After TLm fewer than 1/2 are dead |
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Term
| Strictly Additive Interaction Between Toxicants |
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Definition
| Percent dead is exactly what one would expect from doubling the concentration of either toxicant |
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Term
| Supra-additive/ Syngergistic |
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Definition
| The percent of organisms dead is more than one would expect if the concentration of either toxicant was doubled |
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Term
| Infra-additive Interaction Between Toxicants |
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Definition
| The percent of organisms dead is greater than 50 but less than one would expect from doubling the concentration of either toxicant |
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Term
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Definition
| Lower bound to threshold dose that causes some adverse effect, this term is associated with public health/noncarcinogenic effects |
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Term
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Definition
| Upper bound to threshold dose that causes some adverse effect, term is associated with public health/noncarcinogenic effects |
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Term
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Definition
| Maximum acceptable rate of consumption of toxic substance per unit body weight (related to levels above by dividing by the uncertainty factor) |
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Term
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Definition
| Numeric values limiting the amounts of chemicals present in waters: (Reference dose * body weight)/(water consumption rate + fish/shellfish consumption rate * practical bioconcentration factor) |
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Term
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Definition
| Refence Dose * body weight |
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Term
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Definition
| Refers to the highest dose of a radiological or pharmacological treatment that will produce the desired effect without unacceptable toxicity; this term is used in association with public health/carcinogenic effects |
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Term
| Problems with Rodent Experimentation |
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Definition
1. Inbreeding = prone to cancers
2. Response of different rat populations variable
3. Overfeeding
4. Assumption that MTD extrapolates to low doses (no threshold)
5. Hormesis? |
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