Hello everyone. So right now we will introduce the topic
of how pesticides can be classified by the chemical makeup. My name is Zohir Chowdhury.
So four major classes of pesticides and insecticides are derived from organic
chemicals and they are organophosphates or OPs, organocarbamates also called carbamates,
organochlorides also known as organochlorines, and finally pyrethroids which are derived from
pyrethrins. because they do not appear to persist in the environment pesticides from the first group
which is the organophosphates group are among those that are chosen most widely for agricultural
purposes yet at the same time ops are among the most common sources of pesticide poisoning
similarly another group of so-called non-persistent pesticides are the
carbamates groups although pesticides of the op class are implicated frequently in fatal
poisoning incidents carbamides are rarely a source of mortality from poisoning
most of the pesticides from the third group group organochlorines have been banned in the u.s
because of their propensity propensity because of their likelihood to remain in the environment
so they stay in the environment for a very long time the fourth group
pyrethrins refer to an organic insecticide obtained naturally from from natural sources and
this pesticide is derived from natural sources are also called botanicals and
mimicking this natural pesticide in the laboratory we have been able to also synthesize
chemicals that look alike and these synthesized chemicals are known as parathroids
so we'll go into details one by one for all of the four different classification of pesticides
so starting off with organophosphates so pesticides from the op group appear in a
wide variety of products such as sprays baits indoor and bombs flea collars fat shampoos
powders animal dips and granules the agricultural uses of organophosphates are for control of insect
pests on crops in fields orchards and vegetable plots non-agricultural uses you include control of
insects in homes offices and outdoor for example opi pesticides are used for mosquito and turmeric
one example of organophosphate is malachion which is approved for direct application to
food crops such as fruits in apples and grapes raw crops as well as vegetables such as tomatoes
the popularities of organophosphate pesticides arises from the facts that they are one
inexpensive in comparison to alternatives two can be used to control a wide range of insects thus
eliminating the need for multiple applications of different pesticides three have not been
weakened by the resistance of insects and four uh organophosphates tend to only persist in the
environment for one to two week maximum which is relatively shorter as compared to some other
pesticides especially organochlorines which was the third group of chemicals
so how do organophosphates work in controlling pets in pests in here you can see the mode of
action so organophosphate pesticides act on the nervous system of insects and higher organisms
by disrupting the transmission of nerve impulses from uh one neuron to the other
this effect occurs when organophosphorus reduce the ability of the enzyme cholinesterase ache
to regulate the neurotransmitter acetylcholine or ach which aids in cell to cell transfer of nerve
impulses in this chart you can see exactly where op are acting in blocking the signal
which essentially causes the neurotransmitter to start over firing
so health effects of organophosphates despite despite the benefits that op pesticides provide in
control uh in the control of damage by insects to food crops and in the abatement of insect vectors
they also present several north of noteworthy hazards two of these hazards are the potential for
uh for harm to the persons who apply the pesticide and more generally the potential for harm to the
entire population particularly children the extensive use of organophosphate pesticides
worldwide increases the likelihood of pesticide poisoning especially in the developing world
and thus is a major concern for environmental health officials work for public health
departments and other environmental agencies organophosphates causes neurotoxic effects
and they can produce both acute effects and long-term effects so acute effects essentially
nerves and muscles may become uncoordinated producing respiratory paralysis and weaknesses
neurological symptoms may also include seizures and lung and loss of consciousness
including cramping of the abdominal area and in extreme cases death also
long-term effects on the other hand um uh occur when the exposure to organophosphate pesticides
occur for a long time and typically relatively low dosage for a long time
and it leads to polyneuropathy which is manifested by numbness loss of sensory abilities and weakness
clinicians believe that in most cases this delayed form of neuropathy is irreversible
the second group of pesticides are known as organocarbonates or carbamates and these are close
relatives of organophosphate pesticides as is true of organophosphates carbonates dissipate quickly
from the environment as a result of breaking down into other substances farmers use based pesticides
as insecticides fungicides and herbicides some varieties are also in use around the home an
example being the carbamide insecticide carbil which is known by its trade names
said in here you can see the picture which is used to control garden pests such as wabs wasps hornets
and snails and is an ingredient in some products applied to furry pets to control ticks and fiends
the third group of pesticides are known as organochlorides and these are derived from
chlorinated hydrocarbons which is a genetic terms given to compounds containing chlorine
carbon and hydrogen organochlorines include a wide range of chemicals that contain carbon chlorine
sometimes several other chemicals as well a range of organochlorine compounds have been produced
including many herbicides insecticides fungicides as well as industrial chemicals such as poorly
coordinated biphenyls or pcbs the compounds uh under this group are characteristically stable so
they last in the environment for a very long time they are fat soluble that means they accumulate
in fatty tissues of animals and humans and uh they bio-accumulate which means they start accumulating
in the body of animals and humans uh through repeated exposure examples of organochlorine
pesticides are ddt linden chloradine murex hexachlorobenzene methoxychlor to name a few
so a metabolite of ddt is dde and dde is formed when ddt is ingested for example fish convert ddt
to dde when they consume ddt that is present in lower occurring organisms in their habitat in the
u.s widespread use of organochlorine pesticides such as ddt began during the early 1940s and
reached a maximum during the 1960s due to concerns about the possible adverse effects of ddt upon the
health of humans and wildlife application of ddt was prohibited in 1972 in the u.s
although most developed nations around the globe at present do ban the use of ddg some countries
continue to use this pesticide especially especially in developing countries and they use it
to stop malaria or mosquito proliferation the last group of pesticides is peripherals pyrethrin is
an insecticide derived from natural sources namely certain variety varieties of chrysanthemum flowers
pesticides from this group have great ability to paralyze and kill flying insects although some
insects may recover because of their own defensive detoxifying enzymes the paralyzing action of
paraffins occurs through interference with the transmission of neural impulses by action on
sodium channels on the right side of the slide you can see the extraction of pyrethrins from flowers
which the flowers are showing here and then the extraction process of the pesticides
so synthetically manufactured chemicals that have a composition similar to pyrethrins which are
the group of chemicals that i just introduced earlier are called pyrethroids although more
than one thousand types of parathroids have been synthesized only a few are in use as insecticides
in the united states the most common pyrethroid is permethrin with over 1 million pounds applied
in the united states pyrethrin-based insecticides having low concentrations of active ingredients
are used inside the home in aerosol cans in sick bombs as well as insecticide pad shampoos
and for treatment for lies applied directly to humans and in mosquito repellents
uh these pesticides degrade rapidly by the action of sunlight and are not very toxic
when applied to humans people may inhale this insecticides as a result of spraying
and may also ingest them when applied to food in here you can see this ortho brand
um pesticide which says three in one and uh it contains uh pyruvates
so thank you for listening um uh and hope to see you soon please remember to subscribe thank you