By: Becca Yeamans & Lewis Perdue
Disposable plastic cups – we’ve all used them! Having a party and don’t want a million dishes to wash? Get out the disposable plastic cups! Moving and haven’t unpacked the kitchen boxes yet? Get out the disposable plastic cups! Getting a drink at the drive thru? Get handed a disposable plastic cup. It’s a very common item in nearly every household and restaurant out there. But, is drinking from these disposable plastic cups safe?
Aside from BPA and other endocrine disrupting chemicals in plastic products, microplastics have also been found to be nearly everywhere and in almost everything.
What are microplastics? Briefly, microplastics are teeny pieces of plastic, less than 5mm in size, which degrade very slowly and have been found in many places in the environment and waterways. Microplastics have been shown to cause significant health problems in animals and other organisms in nature as a result of not only ingesting them, but also from the fact that pathogens or other illness- or infection-causing organisms can attach to them and thus exposure critters in the environment to a whole host of other problems.
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Humans are not immune to ingesting of microplastics either. Once the microplastics are in the environment, they will travel up the food chain and eventually into the products that we humans use and/or eat, thus getting into our bodies and potentially causing health problems for us as well. In fact, studies have shown that microplastics that are smaller than 100nm can actually penetrate the skin, thus ingestion of microplastics isn’t the only way these tiny troublemakers can get into our bodies (think: microplastics in the water or air).
While there have been studies on many plastic products and microplastics, there isn’t much in the research about the disposable plastic cups that are so prevalent in many societies around the world – until recently that is. A recent study, published in the Journal of Hazardous Materials, aimed to examine the release of microplastics from different types of disposable plastic cups, how hot and cold drinks impact the release of microplastics, how shaking around (simulating to-go cups being jostled about in a moving car) impacts microplastic release, and finally the effect of washing the cups was also studied.
[REALLY] Brief Summary of Methods
For this study, the researchers looked at three different types of disposable plastic cups: polypropylene (PP), polyethylene terephthalate (PET), and polyethylene (PE).
Each 500mL cup was filled with 400mL of deionized water and covered with foil to avoid any microplastics in the air from getting in and contaminating the experiment. The cups were then gently “shaken” using a horizontal rotary oscillator for 1 minute. After this time, the cups were either left still or shaken further for the part of the study that examined the effect of shaking that was intended to simulate being driven around by a delivery driver. For the temperature experiments, the water was either warmed to 60oC or 5oC and then gently shaken as before.
Exposure time was also studied. Water in the cups were tested for microplastics after 5 minutes and 30 minutes of exposure time.
To study the effect of washing, the cups were washed prior to adding the 400mL of deionized water (using deionized water only for the washing as well), and then put through the same procedures as mentioned previously.
The number and size of microplastics was measured and analyzed for all treatments.
There were also “blank” samples (untreated) that were used as controls (which resulted in them finding a tiny amount of microplastics in them, indicating the presence of some microplastics in the air).
Major Findings
The results of this study should come as no surprise. Microplastics were found in the water after all treatments. We’ll highlight a few of the major details here:
- Of the three disposable plastic cup types, the PP cups (polypropylene) released the greatest number of microplastics into the water.
- It just so happens that PP is the most abundant type of plastic used in take-out packaging….that’s not good….
- It also happens that PP is the most abundant type of plastic found in human stool, studies have shown…..
- Going from 5 minutes to 30 minutes exposure time, the number of microplastics increased for all three disposable plastic cup types.
- So, the longer the beverage is in the cup, the more microplastics end up in it and thus in your body if you consumed it.
- Shaking the disposable plastic cups, like the take-out/delivery simulation, increased the number of microplastics in the cups.
- So, all that jostling about in the car of the delivery person is just adding more and more microplastics into your beverage/food.
- Interestingly, when the temperature increased from 5oC to 60oC, there was little increase in microplastics present in the water of PE and PP disposable cups, however there WAS a significant increase in microplastics in the PET cups with the warmer water.
- So, it seems some plastics are more sensitive to the temperature of their contents than others, with some leaching more microplastics into the water than others.
- It should be noted that even if the microplastic concentrations don’t change much with temperature, studies HAVE shown that BPA and other endocrine disruptors DO increase with increasing temperature of the contents, so no matter what, having hot beverages in a plastic cup isn’t the healthiest idea.
- If cups were washed prior to experimentation, microplastic concentrations were DECREASED in all plastic cup types. Specifically, microplastic concentrations were reduced after washing by 50.2%, 36.4%, and 35.9% for PET, PE, and PP cups, respectively.
- So, by simply washing the cups prior to use, you can reduce your potential microplastic exposure by over a third to nearly half!
Important Take-Aways (*pun intended*)
Overall, the results of this study found that microplastics get into your beverage no matter what type of disposable plastic cup you are using. So, disposable plastic cups = bad news bears.
Let’s be realistic though. There will be times when you don’t really have a choice – you may have to resort to drinking out of a disposable plastic cup.
What should you do then, if you have to drink out of a disposable plastic cup?
- Well, first, if you have the ability to choose the type of plastic, try to avoid PET (this one is probably the most out of our control).
- Try not to jostle the cup around too much. This really can’t be avoided if you’re getting delivery. Perhaps don’t order a beverage from delivery and just drink water from home.
- Try to avoid hot beverages. Room temperature or cooler is ideal.
- If you must drink out of a plastic cup, WASH IT FIRST!!! This is probably the most important thing you can do – if you have access to the cup before your food or beverage goes into it, then wash it! A reduced exposure to microplastics by 1/3-1/2 is nothing to shake a fist at! WASH WASH WASH!
Long story short, try to avoid disposable plastic cups, and when you must use them, don’t put in anything hot and wash it first!
Find the study here (you may only have access to the abstract): Zhou, G., Wu, Q., Tang, P., Chen, C., Cheng, X., Wei, X-F., Ma, J., and Liu, B. 2023. How many microplastics do we ingest when using disposable drink cups? Journal of Hazardous Materials 441: 129982.