Pesticides

Question 1

Point sources

Answer 1

• a discrete source of pollution
• discharge pipes, effluent
• sewage plants

Question 2

non point sources

Answer 2

• cannot be precisely narrowed to a single source
• surface run-off, atmospheric deposition, fireplaces
• residential neighbourhoods

Question 3

pesticide

Answer 3

-any substance or mixture of substances intend for preventing, destroying, replying, or mitigating any pest

Question 4

pesticide use in history

Answer 4

• use gradually increasing
• Sumerians-used sulphur
• Rigvdea-poisonous plants
• 1500s-1900s-heavy metal salts, arsenic salts
• 1800s-today-natural pesticides (nicotine, rotenone-kill fish, pyrethrins-kill mosquitos and ticks)

Question 5

Synthetic pesticides example DDT

Answer 5

• Paul Hermann Muller
• eradicate mosquitos, vectors for malaria
• Received nobel prize

Question 6

Organochloride insecticides

Answer 6

• DDT
• aldrin
• Hecptoachlor
• Toxaphene
• Lindane

Question 7

DDT

Answer 7

• banned in 1972 in the US
• banned in Canada in 1985
• banned worldwide in 2001-Stockholm convention
• still used in some countries with malaria

Question 8

Insecticides

Answer 8

• neurotoxins
• not very selective
• preferentially kill because insects are much smaller
• acute toxicity in humans-occupational exposures, accidental poisonings, suicides
• chronic exposure-residues on food, water source contamination, spraying crops

Question 9

DDT mode of action

Answer 9

• nerve action potential is produced by pumping Na+ ions to the inside, K+ outside
• neuron fires, lets the Na+ ions back in through sodium channels to create a wave of depolarization, flows down the nerve axon
• sodium channels quickly close to allow the neuron to go back to its resting status
• DDT binds to the sodium channels and keep them open
• causes repetitive firing of neuron

Question 10

DDT toxicity

Answer 10

• repetitive firing leads to spastic paralysis
• moderately toxic
• persistance and biomagnify
• chronic exposures
• possible carcinogen

Question 11

DDT endocrine disruptor

Answer 11

• alter hormone signalling
• DDE (breakdown product of DDT) inhibits androgen signalling (IC50)
• DDT activate estrogen receptors (IC50)
• may contribute to breast cancers, possible carcinogen

Question 12

IC50 values

Answer 12

• concentrations at which a molecule can bind to a receptor as an agonist or antagonist
• stronger binding

Question 13

pyrethrin and pyrethroids

Answer 13

• made in the plant
• bind to sodium channels and keep them open
• very liable and low persistence due to cleavage of ester bond
• make synthetic variants
• LD50 values high
• more infinity

Question 14

pyrethrin and pyrethroids examples of uses

Answer 14

• flight sprays in airline industries
• used to prevent the spread of potential pests
• disinsection

Question 15

organophosphates

Answer 15

• 50% of insecticides used today
• high acute toxicity
• function as acetylcholine esterase inhibitors

Question 16

acetylcholine esterase inhibitors

Answer 16

• transmit nerve signals between neurons and neuromuscular junctions, acetylcholine is released, binds to a receptor
• acetylcholine esterase destroys the acetylcholine
• acetylcholine isn’t removed, receptor will continue to be activated, propagating the nerve signal

Question 17

inhibition of acetylcholine esterase

Answer 17

• regular reaction mechanism acetylcholine is transferred onto a serine of AChE enzyme
• acetyl group is hydrolyzed, can be used in another reaction
• OPs transfer their phosphoric group onto the serine taking hours to days to hydrolyze, stopping AChE activity

Question 18

organophosphates-malathion and mosquito fogging

Answer 18

• mammals have an enzyme (carboxyl esterase) that rapidly breaks down malathion
• exposure barely makes it to our nervous system
• not carcinogenic
• may be endocrine disrupting

Question 19

organophosphates-chemical weapon

Answer 19

-more toxic to humans
-chemical warfare agents
examples are sarin or VX gas

Question 20

herbicides

Answer 20

• poison plant-specific processes

- persist in the environment

Question 21

glyphosate

Answer 21

• herbicide, kills all plants
• EPSP synthase-makes aromatic amino acids
• monsanto-mutant version to make them round up ready and used to kill weeds
• not very toxic to humans

Question 22

paraquat

Answer 22

• herbicide
• steals electrons from photosynthetic transport chain and NADPH to make reactive oxygen species
• most acutely toxic
• accumulates in lung and kidney cells
• ROS destroy membranes (pulmonary edema and fibrosis)

Question 23

Parkinson’s disease

Answer 23

• death of dopamine-generating cells
• pesticide exposure increases risk
• paraquat and organochlorines
• factors also genetic, life history

Question 24

Pesticides and economics

Answer 24

• saves a lot of money from crop losses
• farming is the most water intensive activity
• major greenhouse gas producing industry
• number of undernourished people has been declining

Question 25

environmental costs of pesticides

Answer 25

• egg shell thinning from DDT

- neonicotinoids-partially responsible for collapse in bee populations

Question 26

Pesticides in the Red River

Answer 26

• Anti-epilepsy drug-Selkirk
• Neonics are heavily used on Canola, soy bean, and grain crop-Headingley, St. Norbert, and Emerson
• Atrazine is used heavily on corn crops-Emerson

Question 27

Plant produced pesticides

Answer 27

• plants produce compounds that are insecticidal and fungicidal
• Cause mutations in bacteria
• Potential endocrine disruptor