Chemical Pollutants and Structures Flashcards
What is an Organochlorine?
An organic compound which contains one or more chlorine atoms in their structure
What have organochlorines been used for?
Used industrially and heavily used as pesticides since 1940’s
What is a Pesticide?
Any compound used to kill an unwanted organism
What are the 3 main types of pesticides?
- Insecticides for insects
- Herbicides for plants
- Fungicides for fungi
What are the typical properties of organochlorine pesticides?
- 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
What is Hydrophobic?
a substance that doesn’t easily mix with water, little attraction to water if any
What is Lipophilic?
Strongly attracts to lipids such as fatty tissue
What are some attractive features of pesticides with regards to their use?
- Cheap
- Little reapplication as they remain active in the environment
- Low contamination of water supply
- Safe for workers to handle
Hexachlorobenzene
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
What is Bioconcentration?
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
Bioconcentration Factor (BCF)
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
Reasonable method to estimate the BCF?
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
What is the Kow?
The octanol-water partition coefficient
Kow=[s]octanol/[s]water
Where s is the substance and [ ] in mol/L or ppm
Why is 1-Octanol used to estimate the BCF?
1-Octanol is an adequate surrogate for the fatty tissue of fish
What does DDT stand for?
para-DichloroDiphenylTrichloroethane
When was DDT 1st synthesized and by who?
1939 by Paul Muller who received a Nobel prize for the discovery that it had potent insecticidal properties with low toxicity to humans
What is DDT especially effective against?
Mosquitos - Malaria
Body Lice - Typhus
Fleas - Plague
- Powerful neuortoxin to insects
What is Biomagnification?
the increasing concentration of a chemical in organisms as a food chain is ascended
What are the 2 main mechanisms by which bioaccumulation occurs?
- Bioconcentration
- Biomagnification
What are some main facts about DDT?
- 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.
What is the issue caused by DDT and who is credited with the discovery?
- 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
What is the real problem with DDT?
- 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)
Example of DDT food chain ascension
- Zooplankton 0.01ppm
- Forage fish 1ppm
- Lake Trout 4ppm
- Herring Gull 6ppm
Dioxin structure
-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
How were Dioxins discovered?
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
Where were 2,4,5-T and 2,4-D used and what was the mixture called?
Used in USA and Vietnam as a defoliant
- 50:50 mixture named ‘Agent Orange’ (came in orange barrels)
What health problems are associated with Dioxins?
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
What is Chloracne
Severe acne-like condition associated with over exposure to organochlorines
What was used to poison the ukraine president in 2004?
Dioxins
- Approx 100mgs
- Survived but displays chloracne
What is the biggest concern with Dioxins and some examples
- 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
LOD50
Lethal Oral Dose
- The dose required to cause 50% death response
- Huge range dependent on body weight of creature
Acute Toxicity
High Dose, short-term effect
Chronic Toxicity
Low level doses over long period of time (many years)
How many possible Congeners are there for a basic Dioxin?
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)
What is a Congener?
Molecules with the same basic structure but differ in the # and/or position of a given substituent (such as chlorine)
What is PCDD’s?
PolyChlorinatedDibenzo-p-Dioxins
What are some sources of PCDD’s in the Envr?
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
PCB’s
PolyChlorinatedBiphenyls
- industrial chemicals
- 1st used in 1930s
- several million tonnes produced
- envr problems meant production was discontinued in N.A. in 1977
Structure and Synthesis of PCB’s
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)
PCB Nomenclature
- 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
What are properties of PCB’s?
- White solids or high bpt. liquids
- oily liquids as mixtures
- hydrophobic and virtually insoluble in water
- lipophilic
Attractive features of PCB’s?
- chemically unreactive
- difficult to burn
- low vapour pressure
- inexpensive
- excellent electrical insulators
Main uses of PCB’s
- 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
Do PCB’s magnify?
Yes
Furan’s
-Contaminate PCB’s when strongly heated with O2 = DiBenzoFurans
PCDF’s
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)
PCDF reaction for creation
Biphenyl heated in presence of O2
- x,y (2Cl or Cl + H) is replaced by 1 O connected to both phenyl groups
PCDF Nomenclature
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?
PCB toxicity
- Particularly high acute toxicities
- Factory workers did not experience higher overall death rates than general population
- Most common complaint: Chloracne
- birth defects
How was it determined that PCB’s had long-term detrimental health effects?
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
PCB poisoning in food
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
