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Ecotoxicology > Lecture 1 - DA > Flashcards

Lecture 1 - DA Flashcards

1
Q

Define toxinology.

A

Study of toxic substances produced by living organisms.

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2
Q

Define toxin.

A

Toxic substance produced by a living organism.

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3
Q

Define toxicant.

A

Toxic substance not originating from an organism. Heavy metals and artificial pesticides.

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4
Q

Define pollutant.

A

Agent of pollution.

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5
Q

Are pollutants always toxicants?

A

No.

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6
Q

True or false

Some things are never poisonous, and some things are always poisonous.

A

False

Everything is a poison in the right dose.

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7
Q

What are 5 classes of environmental toxicants? Give an example for each.

A

Metals and metalloids - heavy metals, trace metals
Organic toxicants - hydrocarbons, some pesticides
Inorganic toxicants - fertiliser, some pesticides
Chemical mixtures - effluents
Radioisotopes - radionuclides

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8
Q

For each class of environmental toxicant, what 7 features are needed?

A 
Its forms
Its source of release
Environmental impact
Toxicity
Measurement/detection
Hazard of use
Controlling it
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9
Q

Name some natural and artificial sources of environmental toxicants.

A 
Artificial
-Industrial discharge
-Agricultural/urban discharge
-Sewage, domestic and industrial
Natural
-Stormwater runoff
-Volcanoes and other natural disasters
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10
Q

What are the 5 steps of assessing toxicology?

A
  • Finding the source of the toxicant
  • Observing the toxicant transport and transformation
  • Finding exposure of the target organism(s)
  • Observe response scale, or
  • Spatial scale
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11
Q

Name and describe the four types of responses to toxicants.

A

Acute - stimulus severe enough to elicit quick response.
Chronic - stimulus that elicits response which lingers over long period of time.
Subacute - stimulus which is less severe than acute.
Sublethal - below the level that causes death.

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12
Q

What period of time must the stimulus linger to be considered a chronic response to a toxicant?

A

Greater than 1/10th of the organisms lifespan.

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13
Q

How does a subacute response differ from an acute one? Can a subacute response be considered a chronic response?

A

Subacute is less severe, producing a response over a greater period of time.
Subacute responses are not considered chronic, but may develop into one.

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14
Q

Name and the 6 levels of effects that toxicants can have.

A 
Individual
Population
Cumulative
Delayed
Long term
Short term
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15
Q

Name the level of effect a toxicant can have on an individual.

A

Hormonal, biochemical, and/or physiological.

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16
Q

Name the level of effect a toxicant can have on a population.

A

Affected population structure, such as male:female ratio.

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17
Q

Name the level of effect a toxicant can have cumulatively.

A

Increase in strength by successive additions at different times in different ways.

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18
Q

Name the delayed level of effect a toxicant can have. What can trigger these effects?

A

Symptoms do not appear until a significant amount of time after exposure. Triggered by occurrence of some other stress.

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19
Q

Name the level of effect a toxicant can have in the long term.

A

Chronic, but more indefinite.

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20
Q

Name the level of effect a toxicant can have in the short term.

A

Acute, but more indefinite.

21
Q

Define modifying factor.

A

Any characteristic of the organism or the surrounding environment that affects the toxicity of a given toxicant/pollutant.

22
Q

Define resistance. What median factor is often used for this?

A

Ability of an organism to resist a condition, ie. a toxicant which is at a level that is otherwise lethal.
LT50 is often used.

23
Q

Define LT50.

A

Median lethal time.

24
Q

Define tolerance. What median factor is often used for this?

A

Ability of an organism to tolerate a condition indefinitely without dying.
Organisms are tolerant of conditions below incipient lethal level - known as LC50.

25
Q

Define LC50. How does this differ to LD50?

A

LC50 is the median lethal concentration (in the environment) after a single exposure.
LD50 is the median lethal single dose.
The two are very similar, but LC50 measures the concentration when in the environment, LD50 measures the dose or absolute amount required.

26
Q

Name the four types of mixture toxicity.

A

Additive effect
Syndergistic effect
Potentiation
Antagonism

27
Q

Describe the additive effect.

A

Combined effect of the components.

ie. 1+1=2

28
Q

Describe the synergistic effect.

A

Combined effect much greater than the individual component sums.
ie. 1+1=5

29
Q

Describe potentiation.

A

A chemical that is only toxic in the presence of another chemical.
ie. 0+1=4

30
Q

Describe antagonism.

A

A chemical that interferes with the action of another chemical, resulting in decreased toxicity.
ie. 2+3=4

31
Q

What are the 3 phases of toxic action?

A

Exposure
Toxicokinetics
Toxicodynamics

32
Q

Describe toxicokinetics (4).

A

Absorption, distribution, metabolism, excretion.

33
Q

Describe toxicodynamics.

A

Effect of molecules at toxic action site.

34
Q

How can toxicants be classified in toxicodynamics?

A

By mode of action, and whether inter or intra-species differences seen in sensitivity.

35
Q

Define concentration-response testing.

A

When organisms are exposed to a concentration of a toxicant to elicit a response.

36
Q

Define dose-response testing.

A

Organism is exposed to a discrete dose of a toxicant to elicit a response.

37
Q

Name 4 exposure routes.

A

Oral
Injection
Topical
Respiratory

38
Q

When measuring tolerance, how are dose/concentration and time defined?

A

Dose/concentration - variable

Time - constant and specified

39
Q

When measuring resistance, how are dose/concentration and time defined?

A

Dose/concentration - constant and specified

Time - variable

40
Q

Define TL50, LT50, LC50, and LD50. Are they the same thing? How do these values differ to ET50, EC50, and ED50?

A

TL50 - median tolerance limit
LT50 - median lethal time
LC50 - median lethal concentration
LD50 - median lethal dose
TL50 is the same as LC50, but both differ to LD50, and LT50.
ET50, EC50, and ED50 are the same as their counterparts above, but measure instead a response other than death, E = effective rather than L = lethal.

41
Q

What are 3 measures of tolerance?

A

TL50, LC50, and LD50.

42
Q

What is a measure of resistance?

A

LT50.

43
Q

What can LC50 be used for?

A

Assessing toxicity of pure chemicals, comparisons for relative toxicity.

44
Q

What can EC50 be used for? What does it allow for?

A

Toxicity of industrial effluents. Allows for end of pipe regulation.

45
Q

Define NOEC.

A

No observed effect concentration.

Highest concentration at which no significant effect is observed relative to controls.

46
Q

Define LOEC.

A

Lowest concentration at which a significant effect was observed relative to controls.

47
Q

What is a bioassay?

A

Test in which the quantity or strength of a material is determined by a reaction of a living organism.

48
Q

What do lethal toxicity tests reveal?

A

If toxic, how its toxic, and how toxic relative to other materials.

Ecotoxicology (22 decks)

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