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CHM243EnvrChm > Chemical Pollutants and Structures > Flashcards

Chemical Pollutants and Structures Flashcards

1
Q

What is an Organochlorine?

A

An organic compound which contains one or more chlorine atoms in their structure

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2
Q

What have organochlorines been used for?

A

Used industrially and heavily used as pesticides since 1940’s

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3
Q

What is a Pesticide?

A

Any compound used to kill an unwanted organism

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4
Q

What are the 3 main types of pesticides?

A
  • Insecticides for insects
  • Herbicides for plants
  • Fungicides for fungi
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5
Q

What are the typical properties of organochlorine pesticides?

A
  • Inexpensive
  • High stability against decomposition & biodegradation (called biorefractory)
  • low polarities which = low water solubility ie. Hydrophobic
  • High solubility in non-polar hydro-carbon-like solvents (fatty tissue) ie. Lipophilic
  • Low acute toxicities to mammals but high toxicity to target organisms/pests
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6
Q

What is Hydrophobic?

A

a substance that doesn’t easily mix with water, little attraction to water if any

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7
Q

What is Lipophilic?

A

Strongly attracts to lipids such as fatty tissue

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8
Q

What are some attractive features of pesticides with regards to their use?

A
  • Cheap
  • Little reapplication as they remain active in the environment
  • Low contamination of water supply
  • Safe for workers to handle
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9
Q

Hexachlorobenzene

A

HCB

  • 6 equal c-c bonds
  • Used as fungicide on cereal crops
  • highly soluble in non-polar solvents, but low in H20
  • saturated solution 6.2ppb
  • Doesn’t end up in water supply but ends up in food chain (lipophilic) through bioconcentration
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10
Q

What is Bioconcentration?

A

Selective diffusion and concentration of a chemical into an organism from the envr
- Leads to concentration of pesticides in fatty tissue which may be millions of times greater than the concn in the water

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11
Q

Bioconcentration Factor (BCF)

A

Tendency to bioconcentrate

  • Ratio of the concn of the compound in fatty tissue of fish to the concn in the surrounding water if diffusion is the only mechanism operating
  • equilibrium ratio of the concn of a specific chemical in a fish relative to that dissolved in the surrounding water if diffusion mechanism is the only source of that substance in the fish
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12
Q

Reasonable method to estimate the BCF?

A

1-Octanol test
- Chemical is allowed to equilibrate between the liquid layers in a 2 phase system made of H20 and 1-Octanol CH3(CH2)6CH2OH

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13
Q

What is the Kow?

A

The octanol-water partition coefficient
Kow=[s]octanol/[s]water
Where s is the substance and [ ] in mol/L or ppm

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14
Q

Why is 1-Octanol used to estimate the BCF?

A

1-Octanol is an adequate surrogate for the fatty tissue of fish

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15
Q

What does DDT stand for?

A

para-DichloroDiphenylTrichloroethane

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16
Q

When was DDT 1st synthesized and by who?

A

1939 by Paul Muller who received a Nobel prize for the discovery that it had potent insecticidal properties with low toxicity to humans

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17
Q

What is DDT especially effective against?

A

Mosquitos - Malaria
Body Lice - Typhus
Fleas - Plague
- Powerful neuortoxin to insects

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18
Q

What is Biomagnification?

A

the increasing concentration of a chemical in organisms as a food chain is ascended

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19
Q

What are the 2 main mechanisms by which bioaccumulation occurs?

A
  • Bioconcentration

- Biomagnification

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20
Q

What are some main facts about DDT?

A
  • Powerful neurotoxin in insects
  • Used heavily in WWII
  • Called ‘Miracle Compound’ by Winston Churchill
  • Used in enormous quantities after WWII to drive Malaria out of U.S.
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21
Q

What is the issue caused by DDT and who is credited with the discovery?

A
  • Biorefractory as it bioconcentrates and magnifies up food chain and affected bird of prey ability to metabolize Ca to produce eggshells (too thin to incubate)
  • Discovered by Rachel Carson and outlined in 1962 book Silent Spring
22
Q

What is the real problem with DDT?

A
  • It is metabolized in animals to DDE (DichloroDiphenylDichloroethene) by the elimination of an HCl group
  • DDE is what interferes with Ca metabolism in birds of prey
  • DDE is mechanism by which insects build resistance to DDT and is metabolized by insects and is not a neurotoxin (based on diff structure)
23
Q

Example of DDT food chain ascension

A
  • Zooplankton 0.01ppm
  • Forage fish 1ppm
  • Lake Trout 4ppm
  • Herring Gull 6ppm
24
Q

Dioxin structure

A

-Structure based on simple p-Dioxine where 2 oxygens are in the para position in the ring or just a structure with 2 O’s in Para position

25
Q

How were Dioxins discovered?

A

Produced as a side-product of an herbicide, 2,4,5-Trichlorophenoxyaceticacid which was produced along with 2,4-dichlorophenoxyacetic acid after WWII
- Herbicides still used presently against broad leaf weeds and defoliant

26
Q

Where were 2,4,5-T and 2,4-D used and what was the mixture called?

A

Used in USA and Vietnam as a defoliant

- 50:50 mixture named ‘Agent Orange’ (came in orange barrels)

27
Q

What health problems are associated with Dioxins?

A

Dioxins originally contaminated 2,4,5-T (approx 10ppm later reduced to 0.1ppm but couldn’t entirely eliminate)
- discontinued in 1980’s b/c of birth defects and chloracne

28
Q

What is Chloracne

A

Severe acne-like condition associated with over exposure to organochlorines

29
Q

What was used to poison the ukraine president in 2004?

A

Dioxins

  • Approx 100mgs
  • Survived but displays chloracne
30
Q

What is the biggest concern with Dioxins and some examples

A
  • Chronic toxicity of low level doses over many years
  • Vietnam vets (Agent Orange exposure with inevitable Dioxin contamination) had reproductive problems and liver damage and diabetes
  • Ukraine president poisoning in 2004
31
Q

LOD50

A

Lethal Oral Dose

  • The dose required to cause 50% death response
  • Huge range dependent on body weight of creature
32
Q

Acute Toxicity

A

High Dose, short-term effect

33
Q

Chronic Toxicity

A

Low level doses over long period of time (many years)

34
Q

How many possible Congeners are there for a basic Dioxin?

A

75 different molecules possible

- Can have up to 8 Cl atoms on the rings but remember there are 10 positions total (the 5 & 10 taken by the Oxygens)

35
Q

What is a Congener?

A

Molecules with the same basic structure but differ in the # and/or position of a given substituent (such as chlorine)

36
Q

What is PCDD’s?

A

PolyChlorinatedDibenzo-p-Dioxins

37
Q

What are some sources of PCDD’s in the Envr?

A

Anytime organic material is heated in the presence of an organic or inorganic source of chloringe

  • Coal fired utilities
  • diesel trucks
  • metal smelting
  • waste incineration
  • burning of treated wood
  • bleaching wood pulp with Cl2
38
Q

PCB’s

A

PolyChlorinatedBiphenyls

  • industrial chemicals
  • 1st used in 1930s
  • several million tonnes produced
  • envr problems meant production was discontinued in N.A. in 1977
39
Q

Structure and Synthesis of PCB’s

A

Start: Benzene’s heated with PB catalyst
Product: Biphenyl + H2 gas
Next: add Cl2 or FeCl3 (catalyst)
Product: mixture of many PCB’s
- 10 possible positions for chlorine = 209 congeners
- Typically marketed as mixtures (eg. Monsanto’s ARACLOR)

40
Q

PCB Nomenclature

A
  • 2 rings separately numbered
  • Unprimed ring is that which would give a substituent with lowest numbered
  • Always increasing numbers (so primes are mixed with unprimed numbers
  • 1 always starts at connection bond
41
Q

What are properties of PCB’s?

A
  • White solids or high bpt. liquids
  • oily liquids as mixtures
  • hydrophobic and virtually insoluble in water
  • lipophilic
42
Q

Attractive features of PCB’s?

A
  • chemically unreactive
  • difficult to burn
  • low vapour pressure
  • inexpensive
  • excellent electrical insulators
43
Q

Main uses of PCB’s

A
  • coolant and insulating fluids in industrial electrical transformers and capacitors
  • plasticizers for various plastics (PVC’s)
  • de-inking solvents for recycling newsprints
  • vacuum pump oils
44
Q

Do PCB’s magnify?

A

Yes

45
Q

Furan’s

A

-Contaminate PCB’s when strongly heated with O2 = DiBenzoFurans

46
Q

PCDF’s

A

PolyChlorinatedDibenzoFurans

  • Similar to PCDD’s
  • 8 possible positions where H can be substituted by Cl (So, 125 congeners possible)
  • Cl can be placed anywhere that is not an official part of the Furan bonds (middle part of structure)
47
Q

PCDF reaction for creation

A

Biphenyl heated in presence of O2

- x,y (2Cl or Cl + H) is replaced by 1 O connected to both phenyl groups

48
Q

PCDF Nomenclature

A

9 positions including counting the O

  • not counting the spot where the O bonds to the phenyl groups or the phenyl groups bond together
  • the 5 position is always the O?
49
Q

PCB toxicity

A
  • Particularly high acute toxicities
  • Factory workers did not experience higher overall death rates than general population
  • Most common complaint: Chloracne
  • birth defects
50
Q

How was it determined that PCB’s had long-term detrimental health effects?

A

Great Lakes study by Wayne State University in Detroit (Decades long study)

  • Focused on mothers who ate fish from lake and had elevated PCB levels
  • Found statistically significant effects: babies had lower birth weights and smaller head circumference, children at 11 years age had lower IQ’s, attention spans and lower memory score tests
  • 2 cases of PCB poisoning from contaminated food
51
Q

PCB poisoning in food

A 
Japan 1968 & Taiwan 1979
-Contaminated cooking oil from leaking equipment 
-Heated PCB's =high level of PCDF contamination
Health Problems:
-general malaise
-chloracne
-headaches
-peripheral neuropathy
-thyroid goiter
-reproductive problems
-Lower IQ's in children

CHM243EnvrChm (4 decks)

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