PM2.5 in takeout
Next to the gate of Beijing Wangjing Science Park, there are several tables dedicated to takeout. Every day at noon and evening, it may take employees 3 minutes to find their own among the piles of takeout and the crowds of people.
Returning to the desk, opening various plastic lunch boxes and eating is the norm in office buildings. It has become a lifestyle for young people to order takeout at home on weekends. However, there are some unknown "little things" that go into the mouth with the food.
To eat a takeaway, it is inevitable to use a plastic lunch box or a paper box container with a waterproof coating. At present, there are 4 common lunch box materials on the market: polypropylene (PP) plastic, polystyrene (PS) plastic, paper and aluminum foil. The research report "Depicting the Environmental Impact and Policy Effectiveness of China's Takeaway Food Industry" wrote that the use rate of PP plastic lunch boxes exceeds 60%, making it the most commonly used food container. In terms of packaging bags, high-density polyethylene (HDPE) plastic bags dominate, with a usage rate of about 90%.
In 2020, China's food delivery industry generated a total of 17 billion food delivery orders, with an average of 3.44 lunch boxes per order, of which nearly 70% were plastic lunch boxes. Plastics such as PP and PS are likely to bring microplastics into the human body.
"Microplastics" refer to plastic fragments and particles with a diameter of less than 5 mm. In 2004, Thompson and others from the University of Plymouth in the UK first proposed the concept of microplastics in the journal Science. These particles, which are widely present in the marine environment and difficult to distinguish with the naked eye, are also called "PM2.5 in the sea."
Microplastics have always existed in the environment, transferring from one organism to another. Bottled mineral water has a shelf life because the plastic containers that hold water will leach chemicals after a period of time.
In recent years, more and more studies have found that microplastics are everywhere. Microplastics have been detected in the bodies of marine organisms, thousands of meters deep on the seabed, floating in the air, and in 40% of food. According to a statement recently released by the World Wildlife Fund (WWF), a recent study conducted by the University of Newcastle in Australia found that the average weekly intake of plastic by each person in the world is equivalent to eating a credit card. In 2022, scientists detected microplastics in human blood and living lungs for the first time.
There are countless occasions for humans to ingest microplastics. A study led by the National Institute of Standards and Technology (NIST) found that the non-stick coating of food-grade baking tools releases nanoparticles into hot water; hot drinks in disposable coffee cups cause their waterproof coating-the lining of low-density polyethylene (LDPE) to release trillions of tiny plastic particles into the beverage.
A study by East China Normal University shows that whether it is a microwave-heated polypropylene (PP) lunch box, a heat-resistant polyethylene terephthalate (PET) lunch box up to 70буC, or a more traditional polystyrene (PS) white foam lunch box, it will release microplastics and is basically unaffected by temperature.
Microplastics have become one of the four major new pollutants that have attracted widespread international attention. However, the total consumption of disposable plastics in the takeout industry is still increasing. In 2021, China's online takeout industry accounted for 21.4% of the catering industry, an increase of 4.5 percentage points from 2020. It is estimated that by 2025, the total consumption of disposable plastics in the takeout industry will increase to 2.5 million tons.
Thousands of years ago, there were no plastic products in takeout food boxes. The effect of ceramic food boxes with hollow layers of hot water insulation may be no less than the insulated boxes and plastic lunch boxes in the back seat of the contemporary takeout brothers' cars. As early as the Northern Song Dynasty, there were "idle men" who were responsible for "ordering prostitutes to buy things, taking and sending money and things." "Dongjing Menghualu" records: "The families of market brokers often only buy food and drink in the market, and do not buy vegetables at home." "Along the River During the Qingming Festival" also has the image of "takeaway boys"; restaurants in the Northern Song Dynasty provided fast food and meal services that were "called on demand at any time" and "can be done with a slap."
Today, when takeout emphasizes low prices, fast delivery, no spillage of food, and light weight, traditional food boxes cannot compete with plastic food boxes.
It is unlikely that the traditional food boxes of the Song Dynasty will be reused, but new environmentally friendly alternatives are being developed. Disposable tableware such as bamboo knives, forks, spoons, straws, cups and plates can replace traditional plastic products. However, for a 25-gram disposable food box, the cost of bamboo is 2-3 times higher than that of plastic. In the short term, plastic will still be the mainstream of food boxes.
The impact of microplastics on human health is currently unknown. Scientists have found that microplastic particles smaller than the submicron range can exist in large quantities in intestinal cells and liver cells, but these particles are either directly attached to the cell membrane or trapped in small bubbles in the cell membrane. American scholar Philip Demokritou found that the presence of microplastics can have a negative impact on health due to fat absorption, allowing more fat to enter the blood. In addition, the absorption of micronutrients such as vitamins is also affected. However, these preliminary findings need further experiments to confirm.
Zhao Anqi