Pesticides application in ending food crisis, and it effects on the environment #2

Good day everyone.I hope we are enjoying on the platform. Thanks for always staying tune to read from my stable.In my last post,i started discussion on how pesticides can improve crop yield, but, I didn't stopped there, I took us through different classification of pesticides and I set the ball rolling by laying emphasis on organochlorine pesticides as a type of pesticide classification based on chemical composition.

Can we continue ?..... Okay before we continue, you might be thinking on why you are concerned with pesticides since you are not a farmer. Well, you need to know this ,and pass the information you acquire here to some folks who may not be aware of the danger in using some pesticides. Suffice for you to know that some folks even use some of these pesticides as mosquitoes repellent, fumigant and for many other house hold purpose, they flit their apartment with it and stay indoors!!!!!. This is common in developing countries. Also many frozen foods imported might be laden with metabolites of some pesticides. You ask me how? Then let's find out!

So let's sit tight and enjoy the ride together.
Next under organochlorine pesticides is Aldrin

ALDRIN

Aldrin at sight is a colourless solid. It is effective as a treatment for seed before being planted, and it is also used to treat soil prepared for cultivation.

Aldrin is gotten when hexachlorocyclopentadiene undergoes a reaction called Diels-Alder reaction with norbornadiene to give Aldrin as the adduct product.

Synthesis of Aldrin:By Seuraza at English Wikipedia, CC BY-SA 3.0,

Also, isodrin, which is an isomers of Aldrin is obtained by reacting hexachloronobornadiene and cyclopentadiene together.

Aldrin is beneficial in that it control pests resident in the soil such as termites. It is use on potatoes and corn crops.

The means by which Aldrin operate on soil, plant surface and digestive system of insect is that it is oxidized to epoxide dieldrin, a very strong insecticidal.

Environmental impact of Aldrin

In similar property with other organochlorine pesticides, Aldrin is also lipophilic (lipid loving). It's solubility is just 0.027 mg/L, which heighten it's persistence in the surroundings. Because of this property, many developed nation of the world have banned it use.

Dieldrin

Dieldrin is another type of Organochlorine pesticides. It is closely related to Aldrin in that Aldrin react further to yield Dieldrin like I discussed it in the mode of operation of Aldrin.

It's also an highly persistent organic pollutant. It's degradation is not easily obtained, but rather biomagnify in the food chain.

Long duration exposure had shown it toxicity to various animals, human being not left out. It effects on human and other productive animal surpasses it original target insects.

Dieldrin has been associated with health challenges like Parkinson's, breast cancer, reproductive and damage of nervous system. It is also termed as endocrine disruptor (chemicals that interact with endocrine/hormones system at a particular dosage, and leads to serious endocrine related health diseases). It act as estrogen and antiandrogen and may negatively affect descend of testicles in a foetus if a pregnant woman come in contact with Dieldrin!!

Dieldrin also like Aldrin can be prepared from Diels-Alder reaction between hexachloro-1,3-cyclopentadiene and norbornadiene then followed by epoxidation of the product formed.

Synthesis of Dieldrin :By Dr.T - Own work, CC BY-SA 3.0,
Aldrin decompose to give Dieldrin in biological system , while Dieldrin gives great resistance to chemical and bacteria decomposition process in the environment.
Aldrin does break down to dieldrin in living systems, but dieldrin is known to resist bacterial and chemical breakdown processes in the environment.

Dieldrin is applied on fruit, soil, and seed to control insects that feast on them. Dieldrin remain in the soil for five years after application because that's the half-life in temperate latitudes. Dieldrin volatilized from deposit and redistributed through air current, thereby moving to a far distance and contaminate it. Measurement has been taken in the
Arctic wildlife which indicates wide range of movement from the southern agricultural regions.

Many nation of the world have banned the use of Dieldrin as an insecticide because of it persistence in the environment.

Chlordane

Chlordane is another example of , organochlorine compound used as pesticides. It's employed as pesticides against citrus and corn crops. It's also employed against termites at home. Just like the previous ones earlier discussed, it's a chlorinated cyclodiene. Its also resistant to decomposition in the environment after being applied as a pesticides. In human/animals generally,it accumulate in the lipid since it is a lipophilic compound. Exposure of human to it has been related with cancer and some other serious health challenges.

Technical Chlordane was developed coincidentally by Julius Hyman in 1948.He was a chemist that just synthesis rubber, while he was interested in determining the application of the by-product of the rubber. So he chlorinated the by-product, and that was how he obtained several chlorinated compound.

With 7 chlorine atoms, he got heptachlor, 8 chlorine atoms in
chlordane while combination of 9 chlorine atoms gives nonachlor,these chlorine atoms surround and gives stability to the cyclodienes ring. These compound are all known as cyclodienes. Other examples of cyclodiene family have been discussed earlier.

Like Aldrin and Dieldrin, Chlordane is also formed from a Diels-Alder reaction between Hexachlorocyclopentadiene and
cyclopentadiene to give an intermediate called Chlordene. Chlorination of the intermediate Chlordene gives two isomers of the final product α and β chlordane and other by-products such as transnonachlor and heptachlor.
The β-isomer of chlordane, is popularly refer to as gamma and relatively bioactive.

Synthesis of Chlordane :By Leyo - Own work based on: doi:10.2903/j.efsa.2007.582, Public Domain,

Human gets exposed to chlordane while consuming crops cultivated on soil laden with chlordane. Also people get exposed when they inhales air in homes or landfills treated with chlordane. Ingestion of dairy products, fish and meats that has chlordane accumulated in their fatty tissues also exposed people to chlordane.

Chlordane can penetrate the placenta and become assimilated by fetuses in the womb of pregnant women. Oxychlordane a metabolite of Chlordane build up in the blood and adipose tissue overtime.

Environmental impact of Chlordane

Due to it hydrophobic properties, chlordane is not washed away from the soil, but stick to the soil particles and percolate the ground water slowly, as a result of low solubility (0.009 ppm). It takes some years to degrade. This chemical bioaccumulate in animal fatty-tissues. It toxicity in fish is high with an LD50 (LD is Lethal dose. This means it can kill 50% of the population of fish within a particular or specified time): of 0.022–0.095 mg/kg (oral).

The metabolites of Chlordane that bioaccumulate most are, Oxychlordane (C10H4Cl8O), the primary metabolite of chlordane, and heptachlor epoxide, which is the primary metabolite of heptachlor, and another two mixture of Chlordane, cis-nonachlor and trans-nonachlor. The trans-Nonachlor is highly toxic in comparison with technical chlordane, while the cis isomers is less toxic.

Chlordane and Heptachlor have been classified as persistent organic pollutants (POP) and been banned in the Stockholm Convention on Persistent Organic Pollutants in 2001 ,but still in use by some countries as fumigant against termites
In addition, health implications of exposure to Chlordane or heptachlor or their metabolites are risk factors associated with type-2 diabetes, lymphoma, breast cancer, prostate and testicular cancers and obesity.

SUMMARY

In this post, I discussed the concluding part of Organochlorine pesticides which includes Aldrin, Dieldrin and Chlordane. Though alongside Chlordane, brief discussion of Heptachlor was also made.
The three organochlorine pesticides discussed were all made through Diels-Alder reaction.
The application of the three organochlorine pesticides was discussed and their environmental impact on human and animals was also highlighted. For instance, the mean lethal dose of Chlordane is LD50 with fish, which means that 50% population of fish exposed to Chlordane at 0.022–0.095 mg/kg (oral) concentration will be killed within a specified period of time.

I discussed the effect of indirect ingestion of the metabolites of these compounds too.

In the next post, I will be discussing about organophosphorus pesticides too as they tends to be more acceptable environmentally than their conterpart organochlorine pesticides. Because unlike organochlorine, the organophosphorus pesticides are more readily decomposed on exposure to sunlight ,air as well as soil.

Note that all images are from free source: Wikipedia commons
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