Drinking hot water from disposable paper cups will lead to the ingestion of a large amount of microplastics? Let's take a look at the research of Zhejiang University scientists

In daily life,

Disposable paper cups are very convenient daily necessities.

But if you say,

Disposable paper cup + hot water,

It will release a lot of microplastics.

Would you still choose?

Image source: Screenshot of the paper

Recently, Jiang Chao's laboratory at the Institute of Life Sciences of Zhejiang University published its latest research results in the Journal of Hazardous Materials, an internationally renowned journal in the field of environment . For the first time, it systematically revealed the tissue-specific accumulation of microplastics released when drinking hot water from disposable paper cups in pregnant mice, as well as their toxic effects on metabolism, reproduction and offspring.

When microplastics enter the body, which organs accumulate the most? What harm will it cause to human health? How to reduce the harm of microplastics?

Mice have the highest levels of microplastics in their bodies

Generally speaking, plastic particles smaller than 5 mm are called microplastics.

Existing studies have shown that, for the environment, the impact of microplastics is reflected in the shortened health status and life cycle of organisms in aquatic ecosystems, the reduction of soil fertility and the destruction of ecological balance; for humans, microplastics may accumulate in the human body through breathing, eating and skin contact.

Although no one will eat plastic directly, a large amount of microplastics will enter people's mouths directly through food packaging bags, plastic bags, plastic bottles, plastic boxes, etc. According to the 2019 research conclusion of the World Wildlife Fund, people consume an average of about 5g of plastic per week, which is equivalent to a bank card.

Some people may ask, if we choose not to eat food packaged in plastic, would it be cleaner to use disposable paper products? The answer is still no.

In recent years, with the popularity of coffee and milk tea, the use of disposable paper cups has gradually increased. However, the latest research from Jiang Chao's laboratory at the Institute of Life Sciences of Zhejiang University shows that after disposable paper cups are brewed in hot water, the microplastics released will accumulate in the body's tissues and have toxic effects on reproduction and metabolism.

"In disposable paper cups, when the hydrophobic film on the inner layer of the cup comes into contact with hot water, it releases a large amount of microplastics. As people drink, the microplastics accumulate in the body." Jiang Chao, a researcher at the Institute of Life Sciences of Zhejiang University, explained to reporters.

The research team first screened disposable paper cups from five coffee brands and selected the brand that released the most microplastics and had the smallest particles for in vivo testing. The research team then brewed the disposable paper cups with hot water, let them stand for 15 minutes, concentrated and extracted the microplastics released from them, simulated the daily use of disposable paper cups by humans, and fed the microplastics to pregnant mice by gavage at different "doses". The study lasted for the entire pregnancy of the mother mice.

Schematic diagram of microplastic accumulation in mouse anatomy; color gradients indicate changes in the density of microplastics in different tissues Source: Provided by the interviewee

The results showed that microplastics had significant dose-related adverse effects on fetal development and maternal physiology, and microplastics were detected in 12 tissues and organs of mother mice and fetuses. "Except for the cecum, the fetus had the highest content, and microplastics preferred to be deposited in the fetus, placenta, kidney, spleen, lungs and heart in a dose-dependent manner," said Chen Qiong, the first author of the paper.

May pose a potential risk to the health of the fetus

Currently, studies have shown that microplastics have been detected in human lung, liver, spleen and kidney tissue samples.

The team also found that there was no significant difference in the number and size distribution of microplastics in the fetus and placenta. This finding suggests that the placenta does not have an obvious filtering effect on microplastics, and microplastics can directly pass through the placenta into the fetus, which may pose a potential risk to fetal health.

"In our study, we found that drinking 3.3 cups of hot water from disposable paper cups every day is enough to significantly change the cecal microbiome, metabolic function and immune health, and increase the risk of miscarriage." Chen Qiong said that microplastics may indirectly affect the development and growth of the fetus by affecting the physiological state of the mother, such as inducing liver hypertrophy. It is worth noting that these effects show a clear dose-dependency, that is, the higher the exposure dose, the more significant the impact.

"We often say that it is meaningless to talk about toxicity without considering the dosage, but these findings suggest that even moderate use of disposable paper cups may lead to significant changes in the composition and function of intestinal microorganisms, thereby affecting the host's metabolic and immune function," said Jiang Chao.

Nowadays, more and more researchers have confirmed the presence of microplastics in multiple tissues and organs of the human body, but is there evidence to determine that microplastics will have adverse effects on human health?

A few years ago, due to widespread concern about microplastics, the World Health Organization (WHO) specifically reviewed the health risks of microplastics and formed the first summary report on the impact of microplastics on humans. The core content of the report is that microplastics are everywhere, including in the ocean, fresh water, drinking water, food and air, but no clear evidence has been found that it poses a risk to human health.

At present, there are limited tests on the health effects of microplastics on the human body. Jiang Chao said that in recent years, there have been many research reports on microplastics at home and abroad. Although there is no sufficient evidence to show that such microplastics can cause human diseases, given their increasing discovery in the environment and human body, combined with the results of this study, it is necessary to further evaluate and respond to these potential health hazards.

Pregnant women

It is not recommended to drink beverages packaged in disposable paper cups

Although it has not yet been confirmed whether microplastics can directly cause human diseases and how harmful they are to human health, we can take precautions against them and take measures at the source.

In order to prevent human internal organs from becoming "plastic products", the best way is to reduce intake. Jiang Chao suggested that people should try to reduce the choice of plastic-packaged food and drinks, use glass or non-plastic tableware, and use less plastic containers and paper cups to heat food and hold hot food.

"Expectant mothers who are preparing for pregnancy or are already pregnant need to pay special attention. According to the results of this study, they are very likely to be a high-risk group for potential risks of microplastics. In daily life, you should try to avoid excessive contact with microplastics to protect your own and your baby's health. It is not recommended to drink beverages packaged in disposable paper cups, such as milk tea and coffee." In addition, Jiang Chao also reminded that oily foods may further increase the release of microplastics, so try to avoid ordering high-oil foods when ordering takeout.

Gene benchmark dosage model analysis shows that the safe daily dose for pregnant mice is 2-4 cups. Image source: provided by the interviewee

Jiang Chao said that through research, he also hopes to raise public awareness from a popular science perspective. Microplastics have quietly integrated into our daily lives, and their presence is much closer than many people imagine.

He stressed that although the specific impact of microplastics and their dose-effect relationship still need further exploration, it is crucial to establish such awareness in advance. He also hopes to encourage all sectors of society to pay sufficient attention to this issue, thereby promoting the formulation and improvement of relevant food safety regulations.

It is understood that Jiang Chao's laboratory at the School of Life Sciences of Zhejiang University mainly conducts multidisciplinary cutting-edge research on the diversity, function, evolutionary dynamics, and environmental interactions of the exposure group and microbiome in various natural and human environments.

There is no doubt that microplastics have quietly penetrated into people's daily living environment and have become an existence that cannot be ignored. Assessing the potential threat of these tiny particles to human health, analyzing their specific mechanisms of harm to the human body, and actively exploring effective response strategies are the goals that Jiang Chao and his team members are working towards.