Takeaway is a product of the times and is quietly changing the lifestyle of three generations in China. From students in the classroom to white-collar workers in the office to retired people at home, food delivery will always appear. Convenient takeout can save people time from buying groceries, cooking, cleaning the kitchen and disposing of garbage. People only need to move their fingers on their mobile phones to quickly satisfy their food needs. It is undeniable that takeout has brought a lot of convenience to our lives, but there are also food safety issues. Have you paid attention to takeaway food packaging materials and their impact on health ? Real scientific research data will refresh your understanding.
Take-out lunch boxes of different materials release
microplastics and are not affected by temperature
In November 2020, a research team from East China Normal University published a research result entitled "Microplastics in take-out food containers" in Journal of Hazardous Materials (Figure 1)[1]. The study found that whether it is a microwave-heatable polypropylene (PP) lunch box, a polyethylene terephthalate (PET) lunch box that is heat-resistant to 70°C, or a more traditional Polystyrene (Polystyrene, PS) white foam lunch boxes will release microplastics and are basically not affected by temperature .
Figure 1 Research results (Source: [1])
In this study, researchers collected samples of common polymer materials ( Takeaway containers made of PP, PS, PE (Polyethylene), PET) (Figure 2). In order to simulate the takeout mode and delivery process, the researchers conducted two treatments on the containers: directly flushing the inside of each container, or placing 100°C hot water in the container for 30 minutes; then, the microplastics after different treatments were and container surfaces were characterized; human ingestion of microplastics via takeout containers was then estimated based on the abundance of microplastics and frequency of takeout ordering by high-risk consumers (Figure 3).
Figure 2 Experimental materials (Source: [1])
Figure 3 Experimental design (Source: [1])
Lunch boxes of four materials all release microplastics, with the highest PS
In different types of containers, the released Microplastic materials include rayon , acrylic , nylon, polyester, PP, PS, PE and PET; the highest proportion of sheet microplastics released is PS containers (62%), followed by PP containers (32% ), PE containers (22%) and PET containers (3%).
When exposed to heat, all lunch boxes release 8 types of microplastics. The PET container with the highest PS is not heat-resistant and will be directly deformed after being rinsed with hot water. Among the remaining three containers, treatment with hot and cold water does not affect the release of microplastics; hot water After treatment, 8 types of synthetic polymers (rayon, acrylic, nylon, polyester, PP, PS, PE and PET) were detected in the released materials; the proportion of flake microplastics released was PS (77%), PP (25%) and PE (24%).
When treated at different temperatures, PS is most affected.
After being treated at room temperature, the surfaces of PP and PET containers are relatively smooth, with a few occasional protrusions; the surface of PE has wrinkles with a size of 5-15 μm; the surface of PS is rough, with many damaged ones. place, the damage size range is 20-100μm. After hot water treatment, irregular objects with a diameter of about 1-5 μm appeared on the surface of the PP container; the surface of the PE container was even more uneven, and the PE spray film was obviously separated from the bottom; there was almost no change on the surface of the PS.
Each person may ingest 12-203 pieces of microplastics through takeout containers per week
Calculated based on the average abundance of microplastics in takeout containers and the ordering frequency of high-risk groups (white-collar workers), each person may ingest 12-203 pieces of microplastics through takeout containers per week. Insert 12-203 pieces of microplastics.
This study quantified microplastics in takeaway containers. The highest microplastic abundance was found in containers made of PS. PS containers have a loose structure and rough surface, which can easily lead to an increase in microplastics in the container. Depending on the abundance of microplastics in takeout containers and the takeout ordering frequency of white-collar workers, the weekly intake of microplastics per person ranged from 12 to 203 pieces. In addition, this study lacks microplastics in various food packaging and needs further exploration.
NIST: Plastic consumer products release trillions of
microplastic particles into the water at one time, and can be absorbed by the human body.
In May 2022, the National Institute of Standards and Technology (National Institute of Standards and Technology, NIST) research team published in Environmental Science Technology The research results titled "Common Single-Use Consumer Plastic Products Release Trillions of Sub-100 nm Nanoparticles per Liter into Water during Normal Use" (Figure 4) [2]. Research has found that commonly used plastic consumer products such as disposable food-grade nylon bags and low-density polyethylene hot drink cup linings will release nanoscale plastic particles with a density greater than 1012L-1, and the amount of released particles is a function of water temperature. Relationship ; The microplastic particles released into the water from the 300 mL hot drink cup can be absorbed by human cells, and the absorption amount is approximately one microplastic particle for every 7 human cells .
Figure 4 Research results (Source: [2])
Particle size and chemical composition are important parameters for the toxicity of nanomaterials. Particles with a physical diameter less than 100 nm can be internalized by human cells and carry the risk of interfering with cell function. The two most common plastics that come into contact with human food: food-grade nylon films and single-use beverage cups (SUBCs), both produce suspended micron- and nano-sized plastics when they come into contact with liquid food. Therefore, this study Take these two plastics as research objects.
Researchers purchased nylon film food bags and 335 ml SUBCs in retail stores, and washed them with room temperature ultrapure water (UPW) to remove possible adhesion during the manufacturing, storage, transportation and palletizing processes. or adsorbed substances. For SUBCs, load 300 mL of 100°C or room temperature UPW into the SUBCs for testing, and immediately cover the SUBCs with a clean watch glass . The SUBCs sample containing UPW was naturally cooled in room temperature air for 20 min. Finally, separate the low-density polyethylene (LDPE) film of SUBCs; for the nylon film food bag, fill it with 1 L of room temperature UPW and seal it. Place it in the slow cooker and maintain the temperature condition at 22°C or 90°C for 1 hour. Subsequently transfer the sample to a clean 1L glass bottle (Figure 5). By detecting the particle density of air aerosol , the particle density in aqueous solution and scanning electron microscope images, the diameter of plastic particles (Diameter, Dm), the number density of particles in water (Number density in water, NW) and the mass concentration of particulate matter in water are evaluated. .
Figure 5 Experimental design (Source: [2])
Results found:
Nylon membranes and SUBCs both release hundreds of billions of microplastic particles that can be absorbed by the human body at normal and high temperatures, and rising temperatures can increase the release concentration by 50%.
uses UPW as a blank control. The average Dm of UPW atomized particles is 26±2 nm, and the NW is about 7*1011L-1. At 22℃ and 90℃, the nylon film Dm is 70±2 nm and 83±2 nm respectively, and the NW is about 2.4*1013L-1 and 3.5*1013L-1 respectively; at 22℃ and 100℃, the SUBC Dm is respectively are 30±2 nm and 44±2 nm, and the NW is approximately 2.8*1012L-1 and 5.1*1012L-1 respectively. The increase in temperature causes the NW of both to increase by about 50% (Fig. 6).
Figure 6 Mass concentration of plastic Dm, NA and particles in water (Source: [6])
The amount of microplastic particles released by nylon material into hot water is about 7 times higher than SUBC
The liquid contained in 300 ml SUBC enters The body is equivalent to ingesting one microplastic particle for every seven cells
Researchers said that although microplastic particles will migrate into water, the migration of food-grade plastic particles into water is far lower than the safe human consumption amount specified by FDA. Common plastic consumer products are a significant source of human ingestion of microplastic particles that have been identified as posing a potential risk to the health of biological systems.
There are many ways to prevent microplastics from entering the body.
Biological toxicity is diverse.
In the age of plastics, no one can escape the fate of microplastics entering the body! Research from the University of Newcastle in Australia shows that people around the world may ingest 5 grams of microplastic particles every week, equivalent to the weight of a credit card. The main source of these microplastics is tap water and bottled water [3]. In March 2022, Dutch scientists discovered microplastics in human blood for the first time. These microplastics can enter human organs through blood circulation [4].
There are many ways for microplastics to enter the body, making it difficult to prevent them.
From the deepest ocean to the highest mountains, from the invisible air to the tangible soil, microplastic fragments invisible to the naked eye have appeared in every corner of the earth. Microplastics can enter the human body through various life activities such as eating and breathing. Microplastics that enter the human body through ingestion and respiration can accumulate in the intestines and lungs and may be transferred to other organs and tissues. Studies have shown that various human cells can absorb microplastics. Microplastics reaching the lungs and intestines are absorbed by lung epithelial cells and small intestinal epithelial cells respectively through passive diffusion, cell infiltration or active cellular uptake. Similar to the way in which exogenous substances such as nanoparticles are absorbed, cells actively internalize microplastics mainly through pinocytosis and phagocytosis.
Microplastics have diverse biological toxicity and are unavoidable
Microplastics are micron and nanometer level particles. After being absorbed by cells, their size, surface charge and other physical and chemical properties will have toxic effects on cells. Microplastics adsorbed on the surface of cells can enter the cells by damaging the cell membrane and further cause toxicity to the membranes of mitochondria, endoplasmic reticulum and other organelles. Exposure to microplastics can cause varying degrees of oxidative stress reactions in a variety of organisms and human cells. The reason may be that because of their large specific surface area, many oxidizing substances (such as metals) will be adsorbed on their surfaces, and these substances will release reactive oxygen species . In addition, reactive oxygen species will also be released during the process of inflammatory response ; Microplastics The toxic mechanisms also include disturbances in energy balance and metabolism; in addition, exposure to microplastics may also cause genotoxicity in cells.
Human beings who create countless plastics are also at the top of the food chain, and they will eventually suffer the consequences. There are some inexplicable diseases, which may be inseparable from microplastics . What we, ordinary people, can do is to reduce the consumption of plastic products as much as possible in our daily lives, leaving an extra piece of pure land for ourselves and future generations!
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Reference:
[1]Du F, Cai H, Zhang Q, Chen Q, et al. Microplastics in take-out food containers. J Hazard Mater. 2020 Nov 15;399:122969. doi: 10.1016/j.jhazmat.2020.122969. Epub 2020 May 26. PMID: 32526446.
[2]Zangmeister CD, Radney JG, Benkstein KD, et al. Common Single-Use Consumer Plastic Products Release Trillions of Sub-100 nm Nanoparticles per Liter into Water during Normal Use. Environ Sci Technol. 2022 May 3;56(9):5448-5455. doi: 10.1021/acs.est.1c06768. Epub 2022 Apr 20. PMID: 35441513.
[3]https://phys.org/news/2019-06-consume-credit-card-worth-plastic.html
[4]Leslie HA, van Velzen MJM, Brandsma SH, et al. Discovery and quantification of plastic Environ Int. 2022 May;163:107199. doi: 10.1016/j.envint.2022.107199. Epub 2022 Mar 24. PMID: 35367073.
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