The History of Pesticides and Their Effects
Organochlorine was one of the first types of pesticides to hit the market in the 1940’s. However, brands, such as DDT or heptachlor, were band in the late 1980’s, due to the effects in had on insects and animals. Since it was a contact insecticide, it had detrimental effects on insects that they weren’t trying to target. What came after, in the 1990’s, were organophosphates. They were originally developed in the 1940’s for chemical warfare as Nerve Agents, like Agent Orange. They then went through a process of refinement and hit the market as a replacement for DDT. Another insecticide to hit the market was neonicotinoids, which became popular due to their systemic nature. This means that it can be placed in the soil with the seed of a plant, and as water hits the chemical, it can be absorbed into the growing plant. This was a huge breakthrough because instead of the chemical reaching all pests, it would only affect those that are consuming the plant. While this seems like a better solution, it has led to many environmental concerns. Since the chemical has now become part of the plant, it is in the pollen. Bees therefore are affected inadvertently. Earthworms are also affected by the chemicals in the soil. Since the chemical is water soluble, it has many downstream effects as well. Many water insects are killed and this decrease in insects is leading to the starvation of the animals that feed on them, such as birds. It also has affected sea life, such as carbs and sea urchins. While the chemicals might not kill animals or insects right away, it destroys their immune systems leaving them more susceptible to diseases, leaves birth defects in their offspring, lowers yearly offspring, and causes genetic mutations, impaired communication, or habits. Since the chemical becomes infused in the plant cells, there is also no way to prevent humans from ingesting some amount of chemicals. Where in the past washing vegetables or fruit would get rid of most of the chemicals they were treated with, there is now no way to separate the two.
Organochlorines, such as pyrethroids, affect the sodium channels along the axon. The pyrethroids keep the sodium channels open allowing positively charged ions into the negatively charged axon. The positive ions continue to flow into the membrane, until equilibrium is reached. At that point, the insect stops seizing and dies. This is even more effect on insects than humans because insects lack the protection of Schwann cells around the axon.
These chemicals affect the insect’s nervous system through AchEI (Acetylcholinesterase Inhibitors). These inhibitors block the enzyme AchE (Acetylcholinesterase) from breaking down Ach (Acetylcholine). AchEI’s bind to the enzymes in the synapse allowing excess amounts of Ach to build up in the synapse. This means Ach constantly stimulates the sodium receptors in the synapse, keeping the sodium channels open. Therefore, a huge influx of sodium is allowed through the neuron, which leads to convulsions and then death of the insect. Neonicotinoids are a type of organophosphate that targets the nicotinic receptors, instead of the muscarinic ones. This means symptoms will reflect tachycardia, hypertension, mydriasis (pupil dilation) sweating, paralysis, muscle weakness and fasciculation vs. muscarinic symptoms of diarrhea, urination, miosis (constriction of pupils), vomiting, bronchospasms, lacrimation (tearing), salivation, bronchorrhea, hypotension, and bradycardia. Carbamate also works in a similar fashion. Carbamate binds to the enzyme both blocking the breakdown of Acetylcholine and keeping the sodium channel open. The only difference is that carbamate molecules will diminish over time, allowing Acetylcholine to bind to the enzyme, so there is a constant cycle of carbamate vs. acetylcholine.
Effects on Humans
Kepone was a chemical similar to DDT. It was manufactured in Hopewell, VA, until it was shut down in 1975. The workers at the plant came in direct contact with the chemical. They would go home covered in 91-92% Kepone, to put that into perspective 2-3% kills insects. The employees started to have severe effects such as neurological tremors, joint pain, difficulty breathing, arrhythmia, and opsoclonus. When blood tests were run on workers, they found that Kepone levels in the blood were as high as 11.8ppm (the warning level today is 0.3 ppm). It was eventually shutdown after 29 employees were hospitalized and 41 severely effected. It also led to the James River being closed to fisherman, until 1988.
In India, 25 children, ages 4-12, died from over exposer to organophosphate in the rice, soy beans, and lentils they were having for lunch. The lunch was given for free by the Mid-Day Scheme. This just goes to show the devastating affects of pesticides on humans and the lack of regulations on such chemicals.
There have also been studies showing the long term effects of the normal exposer the EPA allows. It shows that chronic exposer to the chemicals are damaging to the developing minds of children, especially when exposed prenatal there have been cases of neurological effects, such as ADHD. Also, when these chemicals were tested on pregnant animals in higher doses some of the offspring suffered from autism.
How Much is Used in the U.S.A.
Over 1 billion pounds of pesticides are used in the United States each year and approximately 5.6 billion pounds are used worldwide
US pesticide production is said to reach ~$17.4 billion by 2018
Biopesticides, biostimulatants, and microbial herbicides are the only current solution. These are all natural bacteria’s that fight off insects, weeds, or stimulate plant growth. These companies are growing quickly due to the decrease in restrictions from the EPA. While it is a bit concerning that they might not be getting enough testing before they hit the market, it is comforting that the ingredients are natural. Companies such as Monsanto and NewLeaf Symbiotic are investing in this growing business. While it is time consuming to test thousands of microbes for one that works, it is worth it because the market is expanding. Although right now it is primarily organic companies that use this new strand of natural pesticides, other companies may lean towards it in the near future due to new regulations the EPA is putting on neonicotinoids.
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