I believe that microplastics are exposed to the digestive system , including stomach acid and digestive enzymes. Then they will either fragment into smaller particles or release harmful chemicals, such as bisphenol A and phthalates, rather than fully degrading. These changes could probably demonstrate how microplastics can persist in the human digestive system, but  still lead to long-term chemical exposure, physical damage to tissues, and interference with nutrient absorption, ultimately increasing health risks over time.

Microplastics are plastic fragments that are less than 5mm in size that are really small. They come from larger plastic waste being shredded or are manufactured for industrial purposes like cosmetics or textiles. The widespread number of microplastics in water, air, and food has become a critical ecological and health hazard. The main way in which humans come in contact with microplastics is through ingestion, which is substantiated by the findings of microplastics in drinking water, seafood, table salt, and even processed food. They can now be found in our water supply, seafood, table salt, and even some pre-packaged foods. Microplastics can either pass through the digestive tract or get sedimented in the tissues. It is harmful to the body in both cases. Microplastics can cause direct cell damage, impair digestion and nutrient absorption, and also cause imbalance in the gut microbiome. Furthermore, many seasoned plastics hold perilous additives that can seep into the bloodstream and lead to immune system problems – like Bisphenol A (BPA) phthalates, or heavy metals. The unhealthy consequences of hormone disruption and elevated disease risk are now unavoidable. Researchers are aware that microplastics have made their way into human stool samples which testify the consumption of microplastics, but the grave concern for many is discovering the long term health consequences for humans. This study seeks to analyze the properties of microplastics, such as their interaction with digestive fluids, whether microplastics are broken down into smaller pieces, or if they release any harmful chemicals that can have a negative effect on human digestion and health.

Material

• Vinegar (Acetic Acid, ~5%)
• Lemon juice or diluted hydrochloric acid (HCl, ~0.1M)
• Baking soda (Sodium bicarbonate)
• Papain or Bromelain (Digestive enzymes from papaya or pineapple)
• Bile salts (Optional, can be sourced from supplements)
• Plastic microbeads (from cosmetic products or craft beads)
• Shredded plastic from water bottles or food packaging
• Synthetic fibers (Nylon or polyester strands from clothing)
• Glass beakers or clear plastic containers
• Petri dishes or microscope slides
• Magnifying glass or microscope
• Digital scale (optional)
• Stirring rods or spoons
• Timer or stopwatch
• Labels and markers

Procedure 

1. Prepare all of your digestive solution in one beaker mix vinegar to simulate stomach acid 
2. Then in another beaker mix baking soda and water to simulate the intestinal fluid environment.
3. After dissolve Papain or Bromelain enzyme in water in a beaker mimic digestive enzyme activity
4.  Collect different types microplastic like microbeads, shredded plastic, and synthetic fibers 
5. Weigh each sample on a digital scale and record initial mass 
6. Observe and record the initial appearance under a magnifying glass or microscope.
7. Place equal amount of each micro plastic into each beaker 
8. Stir the solution periodically to simulate the real digestive system 
9. Let the sample sit for around 24 to 48 hour to observe changes 
10. After the exposure period  remove the microplastic  and place them on the  microplastic slide after put them onto the petri dish
11. Observe the changes in shape,size,colour,texture using a magnify glass or microplastic 
12. Note the visible fragmentation and structural degradation 
13. If possible, weigh the samples again to detect mass loss.
14. If resources allow, use pH strips to check for acidity changes, which may indicate chemical leaching.
15. Compare any color or odor changes in the digestive fluids before and after exposure.
16. Record all your observation  including photo  and sketches of the microplastic  before and after the digestive 
17. Compare the result across the digestive fluid  and which had the most change 
18. Conclude whether microplastics degrade, fragment, or release harmful substances when exposed to simulated digestion.

I observed how the shredded plastic that I put in was around 250 grams and in all the mixture there was not a signal trace of the shredded plastic it evaporated from the mixture . The micro plastic beads were 4 grams at the start. It lost 1 to 2 grams of weight when in the mixture . The polyester never lost weight but gained it. It had the same weight for detergent,vinegar,and Bromelain. When it came to baking soda it gained 5 grams turning into 9 grams. There was a lot of fragmentation of the plastic like shreds of polyester and holes in the microplastic beads . As shaking the mixture with the plastic releases toxins as you  shake it the biggest change was in the baking soda when all of it white molecules latch on to all the plastic making it heavier .

Shredded Plastic Before And After Experiment Weight Change In Gram 

Micro Plastic Beads Before And After Experiment Weight Change In Gram 

Polyester Before And After Experiment Weight Change In Gram 

I conclude that microplastics undergo fragmentation and weight loss under digestive conditions,  indicating that they may not stay whole inside the human body. The weight loss happens because of chemical leaching from the digestive fluids introducing plastic additives, or with physical degradation because of the acid and enzymes acting to weaken the structure of the plastic. Now, that loss may also have been caused by small fragments breaking off, thereby raising the stakes of their potential incorporation into the human body and damage over time. Finding these result  there is a clear need for further research into how microplastics interact with the digestive system and their impact on human health.

The significance of the study will arise in health, environmental science, and food safety, as it shall elucidate the interactions of microplastics within the human digestive system. Insights may be generated for associated health risks: chemical leaching and its effects on gut health. This research could produce findings that will contribute to regulations for food and water safety concerning the behavior of microplastics from contaminated sources during digestion. Additionally, this study would complement gut health studies within medicine and might inform policies to limit human exposure to microplastics by means of better waste management on plastic and regulations for products.

This experiment may have some mistakes like not demonstrating gastrointestinal movement and bacterial activity as it cannot emulate digestion completely. Varying microplastic samples** could change outcomes with particular regard to some pieces sinking while others float. There can be weighing inaccuracies as well because if the changes are undetectable, then microplastics could be a problem. It is impossible to monitor chemical leaching without the equipment that is needed. To increase precision, unifying plastic samples, retaking tests, and applying accurate measuring devices may assist.

Citation 

1. https://hsc.unm.edu/news/2024/04/microplastics-in-organs.html?utm_
2. https://pubmed.ncbi.nlm.nih.gov/34743871/
3. https://www.ehn.org/microplastics-and-gut-health-2665727478.html?utm_
4. https://www.mcgill.ca/newsroom/channels/news/microplastics-are-harming-gut-health-348329?utm_
5. https://www.mdpi.com/1467-3045/46/3/168?utm_
6. https://www.verywellhealth.com/microplastics-colorectal-cancer-11692036?utm
7. https://pubmed.ncbi.nlm.nih.gov/36182891/
8. https://www.mdpi.com/1467-3045/46/3/168?utm
9. https://particleandfibretoxicology.biomedcentral.com/articles/10.1186/s12989-020-00387-7?utm_
10. https://www.wjgnet.com/1007-9327/full/v31/i4/100470.htm?utm

I wanna say thank you to my Science fair Coordinator Greg Neil for selecting my project for judging and helping me on it . I will say thank you to my science teacher Mrs Price for helping me and giving feedback to me about my project . I wanna say thank you to my parents for allowing me to compete in this and driving me up and also helping me. I wanna say thank you to Cysf for hosting such a great event for us kids to participate in . I wanna say thank you for judging me .