Pesticides application and it effects on the environment

Good day everyone. I guess we are steeming. In my last two post, the first one and this second one.

In the first post, I started discussing about how pesticides can be effective in ending food crisis by dealing with agents contending with crops on the farm. I also talked about classification of these under discussion, and from there I gave detail discussion on organochlorines, which then span through the second part of the post.

However, in this episode, I will proceed to another group of the topic under discussion which is organophosphates. I referred to it in the second post that it's more acceptable in the environment than it's organochlorines conterpart.

Thanks for staying tuned. Let us now look at what organophosphates are. They are collection of chemicals purposely made to affect the activities of an enzyme called acetylcholinesterase which is responsible for catalyzing some chemicals which function as neurotransmitters in the body of animals

These group of chemicals known as organophosphorus pesticides forms an average percentage of the entire known chemical pesticides that terminate insects.

The Organophosphates operates by constraining the activities of this enzyme called acetylcholinesterase. This enzyme can be affected by organophosphates through unrepairable covalent restriction and in that process, initiate poisoning of the insect. The poisoning process start like this: the nerve endings, supposed to receives neurotransmitters (are chemical materials liberated at the base of a nerve fibre as a result of an approaching nerve impulse) from the brain, and this is exactly what organophosphates prevent from taking place.

So we can see that organophosphate operate through the interruption of the enzyme activities.

The enzyme Acetylcholinesterase dissect the acetylcholine neurotransmitters which transmit out message to contemporary nerve endings all over the body. It's this process stated above that makes our body and that of animals including insects to operate normally.

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From here, let me move to the different types of Organophosphates. I will be discussing each types showing their structures, prepation, properties and environmental impact. Sit down and enjoy.

Let's start with Parathion:

Parathion are Organophosphates, and it is deleterious to insects and highly dangerous to human. The compound terminate any organisms by prompting the respiratory system to collapse. At unadulterated state, this compound appears white in crystalline form. Has a brown colouration during distribution in the market and stinks like a bad egg. Though stable, but appear brown in contact with sun rays.

Parathion::By Smokefoot - Own work, Public Domain
Incase this compound is ingested by mistake, atropine is a good counteragent. Also, Parathion toxicity can be lessen in the presence of an alkaline medium

The pesticides is widely administered by sprinkling. It's mostly use on cotton, rice and on the tree of some fruit.

On consumption of parathion, the double bonded sulfur is replaced with an oxygen by oxidase to yield paraoxon.

(C2H5O)2P(S)OC6H4NO2 + 1/2 O2 → (C2H5O)2P(O)OC6H4NO2 + S

The industrial synthesis of this compound require the chlorination of diethyl dithiophosphoric acid which gives diethylthiophosphoryl chloride. In a double decomposition reaction of the salt formed (diethylthiophosphoryl chloride.),the salt is reacted with sodium 4-nitrophenolate .

The equation of the entire reaction is shown here:
2 (C2H5O)2P(S)SH + 3 Cl2 → 2 (C2H5O)2P(S)Cl + S2Cl2 + 2 HCl
(C2H5O)2P(S)Cl + NaOC6H4NO2 → (C2H5O)2P(S)OC6H4NO2 + NaCl.

Unlike the organochlorines, Parathion degrade to products which are hydrophilic. The means by which this compound is deactivated is hydrolysis and the reaction site is on the aryl ester bonding site which then results to two soluble molecules called diethyl thiophosphate and 4-nitrophenol as shown in the reaction here

(C2H5O)2P(S)OC6H4NO2 + H2O → HOC6H4NO2 + (C2H5O)2P(S)OH
However, in anaerobic situation, (absence of air), the nitro group present on the Parathion molecule is diminished to an amine as described in the equation below.

(C2H5O)2P(S)OC6H4NO2 + 6 H → (C2H5O)2P(S)OC6H4NH2 + 2 H2O

Vulnerability to Parathion happen mostly when the compound is been use as insects killer on farm crops. It is eminently toxic from acute breathing in, oral and skin interaction with the compound. So in case you are using this compound, be careful with it's handling. When human being is exposed to this insecticide on a short term basis, the organs affected most are the skin, eyes, blood , respiratory and nervous system.

Several health condition resulted when this compound is consumed on a large dose, these conditions include impaired RBC cholinesterase agitation, headache, sickness.

Information has not been pinned on this compound as to whether it is capable to disrupt reproductive system neither is there any record showing any deleterious effect on human or animal growth. Also carcinogenic impact on human has not yet been established because of limited data on it

Information available on it concerning animals indicates high adrenal cortical swelling when rats were feed Parathion by mouth.The compound has now been place under Group C human carcinogenic compound.

Let's consider another Organophosphates known as malathion

Melathion:By Benjah-bmm27 - Own work, Public Domain,
Malathion is not different in terms of targets in the body of organisms, because, it also affect acetylcholinesterase and prevent the enzyme from doing it's neurotransmission activities. It's a chemical that is commonly employed in where people resides, used on farm land, employed in cleaning recreation centers, and in addition to get rid of malaria causing agents (moisquitoes).

Some years back now,[ About 3 decades] this chemical, was employed to deal with a particular fly called Mediterranean fruit fly in some countries. And up till now, many countries are still using malathion to deal with infestation of moisquitoes

The chemical operate in the body of the organisms targeted by confining itself permanently to many arbitrary leftovers of serine found on the cholinesterase enzyme and having a leaving group refer to as peroxide. The phosphoester category obtained is fastly joined to the cholinesterase and permanently stopped the activities of the enzyme and as a result, this cause quick add -up at the synapses of acetylcholine

Mechanism of action of acetylcholinesterase:By Sbolmer - Own work, CC BY-SA 3.0,
This compound called malathion is prepared when dimethyl dithiophosphoric acid is added to diethyl maleate. The obtained compound is chiral, however it found it application as a racemate.

The medical application of this compound includes its use for the treatment lice infestation. Report shows that it satisfactorily terminate eggs and matured lice. The claims is taken from US FDA. Though a counter report from the studies carried out in the UK shows that the chemical is about 36% active against lice on the head completely lower in action against eggs.

The claim of the UK study was substantiated when the chemical was used on lice located on school children head in the UK. It was found out that the low efficiency of the chemical to deal with lice on the head was because resistance has been attained towards malathion.

Side effect of using Malathion;

The toxicity capacity of this compound is relatively low, but when consumed orally or penetrate into the skin, it yield more poisonous metabolite called malaoxon

Malaoxon:By Edgar181 - Own work, Public Domain
Studies revealed that persistent exposure by mouth consumption of malaoxon in laboratory rat shows more level of toxicity than malathion long term exposure to rat. It doesn't stay long on the body before been removed. There is no established negative health implications of this pesticides on long term exposure to laboratory rat according to USEPA.

Limited time exposure of high concentrated malathion results into high level of symptoms all over the body whose potency depends on the strictness of rat exposure to the chemical.

There are several symptoms that could indicates the symptoms of high level of exposure and some are listed here.

Skin and eye irritation, cramps, nausea, diarrhea, excessive sweating, seizures and even death.
Source

The good news is that if one mistakenly ingest malathion, the symptoms diminish after some weeks.
If malathion is in unimproved water, malaoxon it's metabolite is what it will result to when the water is in the chlorination stage of improvement. This is a signal that we should not use this compound near water to be taken for drinking purpose.

Summary

Organophosphorus pesticides forms an average percentage of the entire known chemical pesticides that terminate insects.
The group operates by constraining the activities of this enzyme called acetylcholinesterase.
Parathion are Organophosphates, and it is deleterious to insects and highly dangerous to human.
Vulnerability to Parathion happen mostly when the compound is been use as insects killer on farm crops.

Malathion is not different in terms of targets in the body of organisms, because, it also affect acetylcholinesterase and prevent the enzyme from doing it's neurotransmission activities.

Thanks for staying tuned to read the post. Please don't hesitate to drop a comment if you find this post interesting. You can join @steemstem on discord by clicking on Discord

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