Named Pesticides

What are the named pesticides?

• Organochlorines

• Organophosphates

• Pyrethroids

• Neonicotinoids

When were organochlorines introduced?

1940s

What are the properties of organochlorines?

• High toxicity

• High persistence

• High liposolubility

• Bioaccumulates and biomagnifies

What are the advantages of organochlorines?

They have high insect toxicity and low vertebrate toxicity.

They were initially used to control pests (like mosquitoes), then were used as an agricultural insecticide.

What are the disadvantages of organochlorine?

• High toxicity to insects led to the deaths of many non target insects (bees and butterflies)

• High persistence & high liposolubility, so less likely to be washed off fields.

• High liposolubility means its can cross the cell membrane. This allows DDT to bioaccumulate and biomagnify up the food chain.

  This produced levels that were toxic to predatory vertebrates at the top of the food chain like herons and otters (basically it killed a bunch of top predators)

Why was the bioaccumulation and biomagnification of organochlorines bad?

It produced levels that were toxic to predatory vertebrates at the top of the food chain (like herons and otters)

Are organochlorines banned?

Yes

What are the properties of organophosphates?

• Low persistence

• Low liposolubility

• High water solubility

• High toxicity

What are the advantages of organophosphates?

The low persistence and liposolubility mean they don’t bioaccumulate.

What are the disadvantages of organophosphates?

• High mammalian toxicity

• They are neurotoxins and inactivate the enzyme acetylcholinesterase so nerve function is damaged. It was used in WW2 as a weapon

Why is high mammalian toxicity of organophosphates bad?

Farmworkers can be at risk of acute exposure to doses, possibly causing death

What does chronic exposure to organophosphates lead to?

ADHD, Alzheimer’s

What are the properties of pyrethroids?

• Low persistence

• Not liposoluble / do not bioaccumulate / biomagnify

• High specificity / high insect toxicity / low mammal toxicity

• Insoluble in water / low mobility

• Not carcinogenic

Why is the low persistence of pyrethroids good?

It means pyrethroids don’t remain in the environment for a long time, as it degrades quickly

What are the properties of neonicotinoids?

• High specificity/ high insect toxicity / lower vertebrate toxicity

• Relatively persistent

• Water soluble

What are the advantages of neonicotinoids?

• High insect toxicity

• Lower vertebrate toxicity as they cannot cross the cell membrane and blood-brain barrier since they aren’t liposoluble

• Neonicotinoids are broken down rapidly in the presence of sunlight and soil microbes.

What are the disadvantages of neonicotinoids?

• Neonicotinoids are neurotoxins and inhibit the action of the neurotransmitter acetylcholine

• Relatively persistent

• Water soluble.

Why is neonicotinoids being water soluble bad?

• They can leach into rivers and cause harms to fish.

• Leaching into water bodies can cause toxicity if consumed.

• Leaching allows the dispersal of lower concentrations

What do neonicotinoids do to bees?

Their use has been linked to the decline of many bee populations.

They are very toxic to bees

Since they have neurotoxic effects, they reduce the bees’ ability to navigate. Also reduces their immunity to disease.

When does neonicotinoid's impact on non targeted species appear to be increased?

By a synergist action with some fungicides that may be present at the same time.

Long term impacts of neonicotinoids

Some research suggests that neonicotinoids may build up in aquifers, which may cause issues in the future.

What is the most widely used pesticide?

Neonicotinoids