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Ecotoxicology > Lecture 3 - RH > Flashcards

Lecture 3 - RH Flashcards

1
Q

What are the classes of metal?

A

Class A - oxygen - seeking metals

Class B - Sulfur or nitrogen - seeking (these are typically highly toxic)

Borderline

These classes are based on lewis acid-base properties

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2
Q

What are metals like in relation to essentiality and non-essentiality?

A

Essential metals are needed in small amounts and toxic in large amounts

Non-essential metals are tolerable up to a certain amount but toxic at a large amount

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3
Q

What must be a characteristic of a chemical for it to be considered as a toxicant?

A

It must be bioavailable

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4
Q

What is the reference toxicant for inorganic chemicals?

A

Copper

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5
Q

What is the reference toxicant for organic chemicals?

A

Phenol

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6
Q

What are trace metals?

A

Metals required in trace amounts

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7
Q

How does the body manipulate metal toxicants to diminish their toxicity?

A

Metals can be stored in some body parts using proteins to avoid their toxicity.

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8
Q

What is the issue with inorganic phosphate fertilizer?

A

Causes lots of cadmium to contaminate the soil affecting marine (such as crayfish)

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9
Q

What is the function of metal ions?

A

Enzyme cofactors

Structural components of organic molecules

Ultra trace essentiality (Li, Al, Sn)

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10
Q

What does bioavailability refer to?

A

Portion/fraction of a substance that an organism absorbs or accumulates

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11
Q

What influences the bioavailability of metals?

A

Concentration

pH

Redox potential

Complexation

Organic content

Environmental factors: temperature, salinity, complexing substances

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12
Q

How can temperature affect toxicity?

A

Increased toxicity

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13
Q

How does salinity affect toxicity?

A

Decreased due to complexing with Cl- ions or SO4 ions

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14
Q

How do complexing substances affect toxicity?

A

Decreases toxicity

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15
Q

What are some factors related to speciation that affect metal toxicity?

A

Ionic state (Divalent and trivalent cations are most biologically active)

Molecular state (Toxicity determined by rate of uptake and degradation of the molecule)

Form (organic forms more toxic than inorganic forms)

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16
Q

What does the strength of the bond indicate about toxicity?

A

Stronger bonds result in greater toxicity

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17
Q

How does a divalent/trivalent metal cause toxicity?

A

It binds to functional groups of amino acids or purines/pyramidines in nucleic acids

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18
Q

What are some biological impacts of metal binding reactions?

A

Block essential function of biomolecules

Displace essential metal ions in biomolecules

Alter or modify the configuration of biomolecules

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19
Q

How is lead toxic?

A

Interferes with production of ALAD resulting in impaired haemoglobin synthesis

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20
Q

How is mercury toxic?

A

Interferes with breakdown of catecholamines resulting in CVD and Heart failure

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21
Q

How is arsenic toxic?

A

Disrupts normal aerobic metabolism resulting in oxidative stress and formation of ROS

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22
Q

How can configuration be altered by metals?

A

Tertiary structure can be altered in enzyme proteins

Polynucleotides can alter genetic information

Biomembranes can be altered by binding to lipoprotein membranes (Hg alters axon)

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23
Q

How do organisms typically get rid of toxins?

A

Complexing metal ions with cysteine rich proteins called metallothioneins

Depositing the metals as insoluble granules in tissues

Excretion via faeces

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24
Q

What are metallothionenes?

A

Cysteine-rich proteins used to complex metallic toxins.

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25
Q

Are metals typically biomagnified?

A

No, however organometallic compounds can be biomagnified

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26
Q

What are the methods by which metals are measured?

A

Atomic Absorbtion Spectroscopy

Neutron activation

Mass spectroscopy

Gas chromatography + mass spectrometry

Pulse polarigraphy - gives quantity and ionic state

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27
Q

What are the advantages and disadvantages of investigating total metals?

A

Easy, less expensive however less meaningful

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28
Q

What are the advantages and disadvantages of investigating individual types of metals?

A

Harder, more expensive, however more meaningful and environmentally relevant

29
Q

In what form is Hg mostly released into the environment?

A

Most is released as inorganic Hg

30
Q

Where does environmental Hg come from?

A

Gold production, coal and oil combustion

Major inputs from the chlor-alkali industry

Slimicides used in timber and paper pulp industries to prevent fungal growth

antifouling paint for ship hulls
pesticides

seed dressings

Weathering of mercury bearing rocks, released volcanoes and geothermal vents

31
Q

What are some commercial uses for mercury?

A

Thermometers

Medicine

Dentistry (amalgam in the past)

Fluorescent lamps

32
Q

Which organisms typically contain mercury?

A

Most fish species contain approx 0.15 p.p.m

Birds accumulate mercury in their feathers and livers

33
Q

What caused minamata disease?

A

Mercury pollution of minamata bay in Japan causing accumulation of toxic mercury in the food chains and in turn affecting 2000 people and killing 43 people while injuring 700 others.

34
Q

Where is environmental cadmium sourced from?

A

Cadmium is produced as a byproduct of zinc smelting

35
Q

Does cadmium biomagnify? Why or why not?

A

No, because the fishes and mammals that ingest it are able to excrete it. However molluscs accumulate cadmium more readily

36
Q

What causes Itai Ita?

A

Cadmium toxicity which causes severe bone deformities (it replaces calcium). Contaminated rice paddies was the source

37
Q

What forms of cadmium are most common?

A

Cd2+>Cd1+ (ranked according to abundance)

38
Q

What are the commercial uses of cadmium?

A

Batteries

Pigments

Plastics

39
Q

What are the sources of lead in the environment now? Rate in order of abundance.

A

Mining

Smelting

Gasoline = Natural weathering

Refining

40
Q

What are the uses of lead today?

A

Dentistry

Medicine

Radiation protection

41
Q

What are the forms of toxic lead?

A

Pb2+ (major problem)

Tetraethyl Pb and tetramethyl Pb these are very bioavailable and cross the blood brain barrier

42
Q

How does lead affect organisms?

A

In aquatic systems 16 different chemical species can occur. Low pH and low water hardness favours Pb2+ and in turn toxicity

43
Q

What are the physiological effects of lead on humans?

A

Children’s mental development is impaired

Neurological defects

Kidney dysfunction

Anemia

44
Q

What causes anemia during lead poisoning?

A

Shortened blood cell life span

Impaired haemoglobin synthesis

45
Q

What causes neurological defects from lead?

A

Blocks impulse transmission and acetylcholine release

46
Q

Which organisms bioconcentrate Lead?

A

Mussels

47
Q

The extent to which toxicity is amplified by hardness and pH is shown in this example:

A

at pH 7.1, hardness 50 mg/L as CaCO3 -> 1.1mg/L

at pH 8.1, hardness 360 mg/L as CaCO3 -> 398 mg/L

48
Q

What are the sources of copper release into the environment?

A

Pesticides (Bourdeux mixture)

Mining and Smelting (3rd most common metal in use)

49
Q

What are some commercial uses of copper?

A

Plumbing, electrical conductors, cookware, coins, medicine

50
Q

What are the forms of copper that can be toxicants? Rate in order of abundance.

A

Cu2+

Cu+

Cu3+

Cu4+

51
Q

What are the biological effects of copper?

A

Copper is essential as an important cofacter in many enzymatic reactions

hemocyanin

52
Q

What are the sources of Zinc?

A

Fungicides

Mining and smelting and 4th most commonly used

53
Q

What forms of zinc are toxicants?

A

Zn2+

ZnO - zinc oxide

54
Q

What are some commercial uses of zinc?

A

Galvanisation

Pigments

Catalyst in rubber manufacture

Medicine

Coins

55
Q

What are the biological effects of zinc?

A

Zinc is an essential element and used as a cofactor in many important enzymatic reactions

56
Q

What are the forms of tin?

A

Sn2+ more commonly than Sn4+

57
Q

What are the sources of tin in the environment?

A

Mining/Smelting

Former use as a marine antifoulant

58
Q

What are the commercial uses of tin?

A

Coating other metals to reduce corrosion

Dentistry

Glass production

59
Q

What are the biological effects of tin? What is an important effect of TBT on snails?

A

Tributyl tin (TBT) is extremely toxic and lethal to a variety of planktonic organisms

TBT causes gross distortion of oyster shells rendering them unmarketable

Female marine snails exposed to TBT developed a penis and sperm duct

This condition is known as imposex due to imposing opposite sexual characteristics

60
Q

What are the forms of Aluminum that are toxic?

A

Al+, Al2+, Al3+

61
Q

What are the sources of aluminum?

A

Mining and smelting

Increased use of Al pots and Al paint

Acidification due to acid rain increasing solubility of Al in H2O causing an increased bioavailability of Al

62
Q

What are some commercial uses of aluminum?

A

Aerospace industry

Various alloys

electrical conductors

Constructio

63
Q

What are some proposed biological effects of aluminum?

A

Implicated in Alzheimer’s disease but no evidence as of yet

Damages plant roots and reduces growth in acid soils due to increased bioavailability of Al3+ ions

64
Q

What are the forms of arsenic?

A

As3-, As0, As3+, As5+, organoarsenicals, AsH3 (arsenic gas which is most toxic)

65
Q

What are the commercial uses of arsenic?

A

Alloys

Agricultural products (pesticides, etc)

Electronics

Pigments

66
Q

What are some biological effects of arsenic?

A

Sublethal toxic effect on reproduction in several fish

Reproductive impairment in crustaceans

Toxic to sensitive algae

Associates with erythrocytes causing rapid membrane breakdown

Enters blood and associates with serum proteins

67
Q

What is biomethylation?

A

A process by which inorganic metal forms change into organic metal forms

68
Q

How does biomethylation affect toxins?

A

Increases toxicity and bioconcentration

69
Q

How does biomethylation occur?

A

Bacteria

Ecotoxicology (22 decks)

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