Chapter 10 - Pesticides Flashcards
How do pesticides affect the specificity of a pollutant
- no pesticides are so specific that they only kill target organisms and are completely harmless to non target organisms
- MDAF is the lowest dose that will kill every member of a population
- LD50 is the dose that kills 50% of the population
How do pesticides affect the persistence of a pollutant
- persistent pesticides may remain in the environment long enough to disperse over larger area and are more likely to have time to bioaccumulate and biomagnify
How do pesticides affect the bioaccumulation of a pollutant
- liposoluble pesticides are those which dissolve into fats
- if organisms are unable to excrete them or break them down fast enough some will accumulate in the body. Over a long period of time exposure, even to small doses, may eventually produce toxic concentrations
How do pesticides affect the biomagnification of a pollutant
- pesticides which have bioaccumulated in one type of organism may become more concentrated when they are eaten by their predators
How do pesticides affect the mobility of a pollutant
- The mobility of a pesticide is controlled by other properties such as persistence, solubility, and ease of vaporisation
- some pollutants may be transported within living organisms to new areas where they may be excreted
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What is toxicity
- this is a measure of how poisonous a substance is to living organisms
- harm is usually caused by damage to proteins especially the inhibition of enzyme action
What direct effects does pesticide pollution have on living organism
- cause harm to non target species by being toxic
- doses which in themselves are not lethal may inhibit metabolic processes and ill health
- higher doses may kill. For example, DDT affected many birds by being concentrated within food chains
—— low doses caused eggs to have thin shells
—— higher doses causes sterility or death
What indirect effects does pesticide pollution have on living organism
- a reduction in the population of one species affects the inter-dependant species ie loss of food supply, pollinations, seed dispersal
- some species populations increase as predation decreases
What are the environment impacts of organochlorines e.g, DDT
- used to control pests which transferred human pathogens
1) high toxicity = deaths of non target species ie bees and butterflies
2) high persistence
3) liposoluble = bioaccumulation and biomagnification
What are the environment impacts of organophosphates
- neurotoxins which inactivate enzyme acetylcholinesterase damaging nerve function
-took over from organochlorines - low persistence and lipsolubility = less bioaccumulation
- high mammalian toxicity = farm workers and risk and non target species
- chronic exposure led to = impaired memory, depression, and behavioural changes
What are the environmental impacts of pyrethroids
- synthetic insecticides
1) high insect toxicity and low mammal toxicity
2) not persistent - so don’t biomagnify or bioaccumulate
3) not liposoluble
4) toxic to fish - don’t use near rivers or fish farm
What are the environmental impacts of neonicionids
- neurotoxin inhibiting acetylcholine
1) high insect toxicity but low vertebrate toxicity
2) persistent and water soluble
3) toxic to bees
4) synergistic action with fungicides causing increased toxicity
What are the methods of reducing pesticide pollution
1) restrict use - some have been banned (eg. DDT) or use is restricted where it may cause problems
2) use of non-persistent pesticides - break down rapidly, and cannot become more concentrated
3) more use of specific pesticides
4) use of systemic pesticides- are absorbed by the crop and translocated within it, don’t need to be sprayed only all surfaces
5) application timing - spraying on still days results in less spray drift onto surrounding habitats
