L2: Major Classes of Environmental Contaminants

Question 1

Metals Characteristics

Answer 1

Move b/w diff phases in environment
Donate electrons in reactions, are cofactors in enzymes
Change states (state they are in affects uptake and toxicity)

Question 2

Non-metals include

Answer 2

noble gases, halogens, radioactive radon, products of combustion

Question 3

Lead in Drinking Water in Hamilton

Answer 3

Lead-base solders in pipes used up until the late 1980s
Leached into drinking water
Pregnant women, women planning children and children at greatest risk
Can cause nervous system damage, kidney damage, learning disabilities, attention deficit disorder

Question 4

Arsenic (As)

metalloid

Answer 4

Can be naturally high in soils, rocks, groundwater
Link to skin lesions, cancer (skin, bladder, lung)
Used in many products, pesticides, herbicides, preservatives (wood preservative)

Question 5

Tributyltin (TBT)

organometallic

Answer 5

Antifouling agent to prevent the growth of barnacles and other organisms on ships

Caused imposex in gastropods (cause female dog whelks to form male reproduction organs=lower reproduction, pop decline)

Question 6

Chlorinated alkenes

solvents & degreasers

Answer 6

Tetrachloroethylene –dry cleaning solvent
Trichloroethylene –degreaser, solvent, removed caffeine from coffee

Do not mix with water (denser than water)=groundwater and drinking water contamination

Question 7

Polycyclic aromatic hydrocarbons (PAHs)

Answer 7

2-7 fused aromatic rings
Produced by incomplete combustion of wood, coal, oil
Abundant in water, air and soil
Structure determines fate and toxicity

Question 8

PAH sources (3)

Answer 8

Pyrogenic –formed during high temperature combustion (fires—forest fires)
Petrogenic –from petrochemical sources such as oil spills (less common)
Biogenic –produced naturally by plants, fungi, bacteria

Question 9

Polychlorinated benzene use

Answer 9

used as a fumigant, wood preservative, in pesticide synthesis

Question 10

Polychlorinated phenols use

Answer 10

wood preservative and fungicides, for herbicide synthesis, can also be produced during pulp mill operations

Question 11

Polychlorinated biphenyls (PCBs)

Answer 11

Very stable and heat resistant
Used as lubricants, heat insulators/coolants in transformers, plasticizers, etc.
Can contain 1-10 Cl atoms, up to 209 possible congeners
Not easily degraded an environment or metabolized in the body (major concern)
Very soluble in lipids, insoluble in water

Question 12

Organochlorine pesticides

Answer 12

Mainly for controlling insects
Affect sodium channels or GABA receptor, leads to over-excitation or depression of nervous system (leads to death of insect)
Degrade very slowly and environment, soluble in lipids

Question 13

Organochlorine pesticides examples

Answer 13

Cyclodienes (e.g. dieldrin, aldrin, toxaphene, chlordane): toxaphene used to kill unwanted fish species
Diclorodiphenylethane: DDT and metabolites, methoxychlor
Chlorinated benzenes (cyclohexanes): e.g Lindane

Question 14

Organophosphorus pesticides & MOA

Answer 14

More water soluble, less lipid soluble
Degrade faster in environment but more acutely toxic, often involved in human poisonings

Mechanism of action (MOA): inhibition of acetylcholine esterase activity therefore are neurotoxins
- this enzyme system is common in most organisms thus they are very non-specific pesticides

Question 15

Neonicotinoid Pesticides

Answer 15

Affect acetylcholine receptors of insects
Low toxicity for animals, birds, fish
Replacing organophosphate and carbamate pesticides
Concerns about impacts on pollinators

Question 16

Perfluoroalkyl substances (PFAs)

Answer 16

On surfaces of paper, fabrics, carpets, leather to increase water and stain repellency; also in firefighter foams and some insecticides (flame retardant)

Persistent (do not break down easily) Concentrates in food webs –common in wildlife and toxic to animals

Question 17

Polybrominated diphenyl ethers (PBDEs)

Answer 17

Similar structure to PCBs but with Br
Decreases flammability in textiles, plastics and electronic equipment, in many household products (foams in furniture)
Very lipid soluble, degrade very slowly an environment
Link to thyroid disorders and diseases