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Scientists Are Defeating Pesticides

by Rachel Korman

October 13, 2015 | News

Today I wanted a snack and chose an apple. As I washed it in the sink, I thought about the pesticides that were flowing down my drain and released into the environment. You would not think that washing a fruit could be so harmful but after an experiment I worked on this summer, I learned to think twice.

Let me give you some background information and couple of definitions first: Parathion, is an insecticide that is highly toxic to non-target organisms including humans, aquatic organisms, and avian species. The active metabolite of parathion is paraoxon, which binds and inhibits the enzyme acetylcholinesterase thereby disrupting nerve impulse transmission through the nervous system. Exposure to paraoxon can result in nausea, convulsions, vomiting, loss of consciousness, lung-edema, and respiratory failure.

In the 1970’s parathion was responsible for about half of the world’s reported pesticide poisonings. The EPA’s Pesticide Incident Monitoring System (PIMS) also recorded 1,283 human parathion poisonings between 1966 and 1980. As a result, parathion was rightfully banned or at least highly limited in several countries.

Now that you have a little context, you can understand the experiment I worked on this passed summer in a biological chemistry lab. Alongside two other students, I created and tested the efficiency of paraoxon hydrolase mutants. Paraoxon hydrolase is an enzyme capable of hydrolyzing organophosphorus compounds like paraoxon. Produced by Pseudonomas, the gene coding for paraoxon hydrolase can be inserted into plasmids to allow expression of mutants of the enzyme.

We followed the procedure of site directed mutagenesis, protein purification and tested the activity of the mutants under a range of temperatures, pH and concentration of a metal ion chelator. We wanted to identify paraoxon hydrolase variants with improved catalytic activity and biochemical properties. In order for bioremediation to be fast and effective, the mutation should be stable under a wide range of pH and temperature and should be resistant to decrease in activity in the presence of a metal ion chelator.

This experiment may seem overdue or out-dated since parathion has been banned. However, like many other pesticides and insecticides, parathion residues can remain in the soil for extended periods of time after its last application. This experiment also has the potential to be applied other insecticides and toxins.

Once I worked with this toxin hands-on and read its intimidating warning pamphlet which mentioned blindness and paralysis, I realized how dangerous pesticides can be. While science is developing mutants to break down these harmful toxins, what are we doing to reduce the impact of pesticides on the environment?

Some people have resorted to going organic and it's no wonder! Chronic pesticide exposure has also been linked to skin cancer, kidney disease and Parkinson’s disease. Of course, we’re worried about what we’re putting in our bodies but the environment can’t suddenly make the choice to go organic.

In an article, “What Pesticides Are on Your Food?”, author and physician Andrew Weil explains how the ongoing use of pesticides and herbicides is responsible for contaminating groundwater and ruining soil structures while promoting erosion. Pesticides have also been considered to be contributors to CCD, colony collapse disorder, which is the sudden die-off of pollinating honey bees. This serves as a serious threat to the American food supply.

The article “Impact of pesticides use in agriculture: their benefits and hazards,” elucidates how pesticides have managed to contaminate every part of our environment. Residues can be found in the soil and air, in surface and ground water across the countries. The pesticides are also very harmful to the ecosystem as non-target organisms ranging from microorganisms to insects, plants, fish and birds. They explain that the realistic solution is to reduce pesticide contamination by using safer, non-chemical pest control methods.

Unlike the environment, we have the decision to go organic but of course, there’s the tug-of-war between eating health consciously and breaking the bank. In the previously mentioned article “What Pesticides Are on Your Food?” EarthTalk ® addresses some concerns people have about the dangers of eating foods that are produced with chemical pesticides and fertilizers. They explain how you don’t have to start buying all organic foods but can make better choices based on the fact that pesticides are for the most part sprayed on the outer layer of a fruit or vegetable. Therefore, groceries that have an outer layer of skin or rind that can be peeled off and discarded are less dangerous. In this case, it makes sense economically to buy conventional produce. However, an apple is a different story. Fruits and vegetables that you would eat directly are better off being organic.

The Environmental Working Group (EWG) has complied a list of the fruits and vegetables that have the highest pesticide retention. They advise people to buy the organic varieties of these foods whenever possible. Apples, celery, strawberries, peaches, spinach, nectarines, grapes, sweet bell peppers, potatoes, blueberries, lettuce and kale/collard greens.

It may be expensive to go full force and buy all organic foods but the suggestions in this article seem realistic and the most beneficial. A healthy balance can exist between helping your body and saving more money. Although pesticide-covered peels and rinds would still be expelled into the environment, we would still be reducing the pesticides release down the drain as we wash our snack time apples.


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