Testing Pesticide Residues on Fruit

[jjmax]

Hello,
I am writing to ask if anyone has ideas for a relatively simple method for testing for the presence of pesticides on fruit (apples specifically). This is for a 6th grade science fair project to compare the effectiveness of different washing methods (e.g. vinegar, bakings soda, commercial wash) at removing pesticides.

I have found a few testing kits online but most seem rather complicated and are specific to only a few pesticides, which may or may not be present on my samples (although my local farmers market may be able to tell me the type of pesticides they use). I also considered applying a specific pesticide and then testing for it after washing but am not sure if that will be safe or if the tests would even be sensitive enough to detect small levels of change between methods.

Another option I have considered is whether I can use a substitute for a pesticide that is easier to test, perhaps qualitatively if not quantitatively.

I reviewed previous posts on this topic but most were older and I didn't see a definitive answer. Also I read a recent journal article (https://pubs.acs.org/doi/ipdf/10.1021/acs.jafc.7b03118) which seems to describe my project perfectly but with a much more sophisticated testing method. Is my project even feasible for a sixth grader?

Thank you!

[lynnsamuelson]

Hello jjmax,

You have picked an interesting and very relevant topic to your science fair project. There are however a lot of variables in pesticides and testing methods. I like that you have already done a lot of research into this project and given thought about the methods. As you have discovered, that well there are robust methods for testing for pesticides on foods, these are complicated often require specialized equipment.

First, for any methods you plan to limit your exposure to any chemicals involved, learn about the potential hazards of what you are working with and always have an adult assist you with the experiment.

I see two ways you could set-up this experiment:

1) Since you are interested in looking at the best washing method for fruit, try to do the experiment in two parts. First, test a method for detecting the pesticide on the apples. This may not be easy and could require trying a few things before you are able to detect anything. You could limit the amount of work on this part by getting an idea of the most common pesticides and finding a kit that looks at a broad range of things. Like you said, there are a lot of kits available and each detects different chemical groups.

Then, when you can use this method that detects the pesticides on the fruit, you can perform the experiment before and after washing the fruit. You can draw some conclusion about the best washing methods by comparing the difference in the amount of pesticide detected between the dirty and clean fruit.

2) Another way you could approach this problem would be to use testing strips for pesticides in water. For this method, device a method where you wash the apples in different solutions and then test the dirty water for the presence of pesticides. From my quick search, it looks like there are many different testing strips available for detecting pesticides in water and they are easier to use than the multi-solution procedures in the first option. if you choose this approach be aware that the different cleaning solutions have different pH's and I am not sure if this will have an effect on the strips you choose to use. You can test for this by treating the strips with each cleaning solution alone before you do the larger experiment.

Happy experimenting and follow-up with other questions as you get into the project and analyzing the results.

[jjmax]

Thank you so much for taking the time to reply. This is very helpful. I feel so much less overwhelmed. I will explore these approaches and I'll keep you posted.

Thanks again!

[jjmax]

Thank you for your earlier response. I decided to use a water test kit to try to detect pesticides on the washed produce since it seemed like an easier approach. Unfortunately, in researching the test kits, I learned that all of the kits were designed to detect only two pesticides, atrazine and Simazine. Although these are the most common pesticides in drinking water (as they are used in corn production), they don't seem to be used directly on most produce, including apples which I was planning on testing (using a mixture of zested skin and distilled water). Therefore I suspect even my control unwashed, non-organic apple will likely be negative for pesticides (atrazine and Simazine), along with the rest of my washed test subject.

Since I am several months into the project (science fair is in April), I'm not sure if I should go ahead and simply conduct the experiment and then explain why I was unable to obtain relevant results or if I should modify my project slightly. One project I saw online was to compare the shelf-life of organic versus non-organic produce but I am not sure if this is challenging enough for a 6th grade project. Also I would need to learn more about how/whether pesticides act as food preservatives.

I would greatly welcome your advice on whether I should stay the course or not. If I were to change, would the project I suggest above be viable or is there something more interesting (yet related) I could do in a relatively short time (one month).

Thank you for your help!!!!

JJMax

[jjmax]

Hi - I wanted to share an update on my project. I am proceeding as planned in testing the effectiveness of different washing methods in removing pesticides using the available at home water test kit. I understand it is very unlikely it will yield results due to the limitations of the available at home test kits (only testing two pesticides that are not widely used on fruit). Do you have any recommendations for how to present the data when the hypothesis was not necessarily wrong but the testing method was inadequate?

There is one way I could modify the experiment to get actual results but it would require using a small amount of pesticide (atrazine or simazine) to apply to my fruit (apple). I fear this may not be safe and therefore not worth the risk.

Any final suggestions or resources you would point to on either question above? It is frustrating to have done so much work and learn the limitations of the testing right before I was to start the experiment.

Thank you.