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Photo Source: rkron / flickr I first put aside my work and washed the plastic lunch boxes and plastic cups on the table. Although there is no penchant for cleanliness, the two scientists asked me to clean up the edges and corners that I didn't pay attention to. Finally, I rinsed it with clean water many times, but I still don't know whether it has been cleaned or not.

In the 1967 film Graduate, there is a scene in which when Mr. Mr. McGuire asks Benjamin Braddock about his post-college thoughts, Benjamin is so impatient that Mr. McGuire says only one word to him: "plastic." Benjamin didn't understand what this meant. "the plastics industry is booming and has a bright future," Mr. McGuire explained. "

This was true in the 20th century. In 1999, when time magazine selected the most influential people in the 20th century, it selected Leo Baekeland, who is known as the "father of plastics" from many chemists.

In 1907, Baekeland produced the first fully synthetic plastic in history in an attempt to develop an insulating material. He found that heating phenol and formaldehyde in the presence of a small amount of alkali (catalyst) produces a meltable, soluble solid. Then the solid is filled with wood chips and other fillers, and then heated and pressurized in iron equipment, a solid molding product is accidentally made. This is the phenolic resin that was widely used later.

Since then, the era of plastics officially began, and the latecomer polyethylene began to "dominate the world" around the 1950s. In 1965, polyethylene shopping bags developed by a Swedish company called Celloplast appeared on the historical stage and soon became popular in Europe, gradually replacing cloth bags and paper bags. Subsequently, this kind of plastic bag also went to other countries in the world, changing human life.

Image source: Patty Ho / wikimedia, CC-BY-2.0 but Baekeland and British scientists Eric Fawcett and Reginald Reginald Gibson, who invented polyethylene, did not expect that the identity of plastics has changed dramatically in the 21st century: plastics have become the "killer" of the earth. According to the World wide Fund for Nature (WWF), plastics used in the last century may still exist on Earth. Scientists estimate that plastic bags take 20 years to decompose, while plastic bottles and cups take about 450 years.

Although many countries have joined the ban on plastic bags since Bangladesh first imposed the ban on plastic bags in 2002, it is not easy to give up the use of plastics completely. because plastic has penetrated into life, industry, scientific research and other aspects. This has led scientists to turn their attention to recyclable and biodegradable plastics to ease the pressure on the environment and health.

Photo: WWF (https://www.wwf.org.au/news/blogs/the-lifecycle-of-plastics) but a new study published in Journalof Hazardous Materials recently suggests that these recycled plastics may not be so "healthy". We may all drink the water that has been in plastic bottles for a day, and sometimes it tastes strange.

Now Selina Selina Tisler and Jan Christensen, two scientists at the University of Copenhagen in Denmark, have found that water in plastic bottles can detect hundreds of chemicals after 24 hours. They think the ingredients in the plastic are migrated to the water. "A lot of people use this kind of plastic bottles to drink water, but few people know that the chemicals in plastic can be transferred to water." Tessler and Christensen wrote.

Plastics are moving outward. In fact, the sensation caused by the "migration of plastics" dates back to 2003. At the time, Patricia Hunt, a geneticist at case Western Reserve University, was studying the process of oocyte differentiation and egg formation when she accidentally found chromosomal abnormalities in supposedly normal eggs in the control group.

Image source: Christopher hipes / flickr didn't find out why until they turned to analyzing the experimental environment-it turns out that a worker used a powerful detergent to clean the floor next to a mouse cage made of polycarbonate, which caused the plastic to release one of the plasticizers called bisphenol A (BPA), or migrate the plastic's BPA to the environment.

The researchers then replaced the cage and the mouse's eggs returned to normal. To prove that the migrated plasticizer affected the differentiation of mouse oocytes, the researchers deliberately exposed mice to BPA (no animal experimental ethics) and found the same oocyte chromosome abnormalities. So they speculated that BPA--, a plasticizer commonly used in the plastic, caused chromosomal abnormalities in mice.

The structural formula and 3D model of bisphenol A. Photo source: Darkeness3560, Edgar181 / wikimedia, public domain, so is it possible for plastic to migrate if it comes into contact with food instead of mice? On December 16, 2021, a study published in Food Additives & Contaminants specifically analyzed the "ability" of polystyrene (PS) materials in contact with food to migrate. In daily life, polystyrene is often used in disposable plastic tableware, disposable foamed lunch boxes (white lunch boxes we often see before), disposable beverage cups, and the outer packaging of foods such as instant noodles and family buckets.

The researchers found that the amount of styrene (the monomer of PS) migrated from PS was related to the food packaged. If meat is loaded, the amount of styrene migrated from PS is the highest; milk causes more plastic migration than water. More importantly, there are more chemicals migrated from plastics in products that are nearing expiration and have a longer shelf life.

It is worth mentioning that previous studies usually discussed known compounds and often considered only one or more, but "for the first time, we used non-target screening methods." all the chemicals that may be contained in drinking water in reusable plastic bottles were analyzed. Tessler and Christensen said.

Selina Tessler tests the water in plastic bottles in the laboratory. Source: what's in University of Copenhagen Water? Tisler and Christensen selected three kinds of reusable polyethylene plastic bottles, all of which can be bought at Danish sporting goods stores and numbered P1 (red), P2 (transparent) and P3 (transparent) respectively. P1 and P2 bottles had been in use for nearly a year before the experiment began, but they belonged to different types of polyethylene, while P3 was newly purchased. They also considered repeating the experiment, so they prepared two for each bottle (but whether this shows the repeatability of the experiment is open to question). In addition, they also prepared glass bottles as the experimental control group. Because they want to test tap water in plastic bottles, there is also a blank group made up of tap water.

Image source: congerdesign / Pixabay detected nearly 350 chemicals in tap water that had been placed in the new P3 bottle for 24 hours after deducting the results of the blank group by liquid chromatography-mass spectrometry (LC-MS). However, if you rinse the bottle several times and then fill it with water, you can remove about 150 substances, leaving mostly non-polar substances. This is easy to understand, because water is a polar molecule, so according to the principle of similar miscibility, water can also take away some polar matter. In addition, more than 400 compounds are found only in P1 and P2 bottles that have been in use for a year. However, for glass containers that had been rinsed with clean water, few additional chemicals were detected in the water of the glass containers.

Although some of the detected chemicals can be identified according to the existing compound database and quantitative structure-property relationship (QSPR) methods, there are still many uncertain substances. Currently, they can identify plasticizers, softeners, antioxidants, photoinitiators, and diethyl toluamide (DEET) in the plastic. What Tisler and Christensen are most worried about is the photoinitiator and DEET.

Use chromatography to detect the water in plastic bottles in the laboratory. Photo Source: Selina Tessler DEET is a commonly used active substance in mosquito repellent, so how is it migrated from plastic? The researchers believe that DEET may come from an analogue of DEET, such as dodecolactam, which has only six hydrogen atoms less than DEET. Both dodecyl lactam and DEET were detected in P1 and P2 bottles that had been used for 1 year, while only dodecolactam was detected in newly bought P3 bottles, but no DEET was detected.

On food bags, we often come across a plastic ingredient-photoinitiator, which is the main component of ink printed on packaging materials. The photosensitive groups of photoinitiators can produce active components such as free radicals, anions and cations under the action of ultraviolet or visible light, so they are often used to initiate the polymerization of monomers in the process of plastic synthesis. If you pay attention to the food bags around you, some will say "avoid direct sunlight".

Image source: Nicholas Cadwallader / Pixabay Tessler and Christensen found three photoinitiators in P1 bottle water: Irgacure 369,4-methylbenzophenone (4-MBP) and anthraquinone (anthraquinone). Previous studies have shown that Irgacure 369 has endocrine disrupting side effects. 4-MBP shows carcinogenicity, reproductive toxicity and skin contact toxicity in animal experiments, while anthraquinone may also break down toxic and carcinogenic substances.

Although they are not sure whether these substances in plastic bottle water will really cause harm to the human body, Ian Hamilton, founder of the US company AlkaWay (not involved in the new study), is worried about "bottled water in direct sunlight on the street". AlkaWay is a company that develops its own water filtration system. Moreover, about 70% of the toxicological properties of other identified substances are unclear.

Future toxicological studies, Tisler and Christensen, say they will continue to explore the toxicity of the substances detected, but it may not be easy for them. Toxicological studies on BPA have also demonstrated this since Hunter accidentally discovered the side effects of BPA in 2003. Although many scientists have confirmed that BPA has endocrine-disrupting side effects, the US Food and Drug Administration (FDA) does not accept these scientists' view that BPA is not harmful to humans as long as it does not exceed a certain dose, because humans can break down BPA and expel it faster than rodents such as mice.

But in 2012, FDA worked with academics on a project called "CLARITY-BPA" to explore the potential effects of BPA on an organism's brain, heart and other body tissues. If you open the project website now, you will find that the home page says "Project completed" (completed). But the fact is that FDA still adheres to its previous conclusion, and scholars have different opinions. Some scientists have found that BPA can affect the brain and reproductive health of mice, while others have not found the side effects of BPA at low doses.

Timeline of the CLARITY-BPA project. Image source: https://ntp.niehs.nih.gov/ whatwestudy / topics / bpa / index.html Tisler and Christensen also point out that even if hundreds of chemicals are detected in the water in plastic bottles, this is not the same as "water is toxic." However, they themselves "want to replace it with glass bottles". However, for us, after buying a new cup or washing it with detergent, we still have to rinse it with water a few more times and drain it.

If you check the food bags or boxes around you, you may find that the composition of the plastic is hardly clearly written on it. "when we pour water into plastic containers, we may have added hundreds of chemicals to the water." Tessler and Christensen said. They suspect that some of the chemicals are added by manufacturers, and most of them are produced by chemical reactions in plastics during production and use, such as decomposition, hydrogenation, and the introduction of nitrogen and oxygen.

Original text link:

Https://doi.org/10.1016/j.jhazmat.2022.128331

Reference link:

Https://doi.org/10.1016/S0960-9822(03)00189-1

Https://news.ku.dk/all_news/2022/02/reusable-plastic-bottles-release-hundreds-of-chemicals/

Https://www.archyde.com/reusable-plastic-bottles-the-eco-friendly-gesture-potentially-dangerous-to-health/

Https://www.foodpackagingforum.org/news/hundreds-of-chemicals-migrate-from-reusable-plastic-bottles

Https://alkaway-blog.storychief.io/drinking-from-plastic-bottles-just-got-much-much-worse

Https://www.the-scientist.com/news-opinion/a-landmark-study-on-bpa-leaves-scientists-at-odds-65004

Https://medicalxpress.com/news/2018-09-bpa-substitutes-health-issues.html

Https://www.salon.com/2019/03/18/what-a-strange-case-of-scientific-deja-vu-showed-us-about-the-dangers-of-plastics_partner/

Https://www.foodpackagingforum.org/news/several-studies-determine-chemical-migration-from-food-packaging

Https://www.nature.com/articles/153369a0

This article comes from the official account of Wechat: global Science (ID:huanqiukexue), written by Wang Yibo, revision: 27

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