塑料不光污染环境,最终也污染了人类自己。

一则人类血液中首次发现微塑料的消息引发网友热议,一度登上知乎热榜第3,微博阅读量更是达到2.4亿。

这项最新研究来自荷兰阿姆斯特丹自由大学、荷兰三角洲研究院,是环境领域的顶尖研究机构。

科学家们收集了22个志愿者提供的血液样本,其中有77%发现了微塑料颗粒,平均浓度为每毫升1.6微克。

这成为塑料进入人体全身血液循环的首个量化证据,其中光是可量化检测到的塑料就有三种。

50%的人体内含有PET(聚对苯二甲酸乙二醇酯),常见于可乐果汁矿泉水等饮料瓶、还有部分药瓶。

36%的被试体内含有PS(聚苯乙烯),常见于泡沫饭盒等食品包装。

还有23%的被试体内含有PE(聚乙烯),也就是塑料袋的主要原料了。

 

另外还有PMMA(亚克力、又名有机玻璃)、PP(聚丙烯,常用于医疗器具和编织袋等)也有检测出来,只是未做到量化。

人类血液中出现塑料引人担忧,最严重后果或许是可以突破血脑屏障破坏大脑。

韩国科学家曾发现,小于两微米的颗粒几天之内就能在小鼠的神经系统小胶质细胞中积累,导致细胞凋亡。

 

这样下去,若干年以后骂人或许就不说“脑子进水了”,而是改成“脑子进塑料了”。

 

微塑料都有什么危害?

自上世纪50年代开始,人类大规模生产与丢弃塑料。大块塑料对环境的污染、对动物的危害显而易见。

直径小于5mm的微塑料,也逐渐成为学界一个热点研究方向。

实际上不光血液,肝与肠道等人体器官、胎盘、人类粪便中都先后检测出微塑料颗粒的存在。

据维也纳医科大学统计,一个人平均每周进入肠粘膜的塑料颗粒的总重量相当于一张信用卡。

 

塑料颗粒难以被人体代谢吸收,未能排出的部分会在体内积累,造成细胞损伤、引发局部炎症和免疫反应。

在消化系统中微塑料颗粒会减少肠道菌群多样性、特别是有益菌的数量,引发肥胖症、糖尿病等代谢疾病。

饮料瓶的主要材料PET中,含有环境荷尔蒙(Xenohormones),是一种致癌物。

有研究发现婴儿体内的PET含量是成年人的14倍,或许与热水冲泡奶粉让塑料瓶中的颗粒加速释放有关。

 

而织物纤维类型的微塑料进入呼吸道,也可能引发炎症反应和呼吸道损伤。

总的来说,关于微塑料对人类危害的研究刚刚起步不久,还缺乏关键性的体内证据。

但动物体内研究已证实,海水中微塑料会让鱼类和螃蟹出现认知障碍,让寄居蟹更慢找到合适的壳。

微塑料如何进入人体血液

据最新荷兰论文作者表示,微塑料进入血液的方法至少有三种,分别是通过皮肤/粘膜接触、口服、吸入。

第一种皮肤或粘膜接触,但不是指健康皮肤直接接触,而是受损的皮肤或粘膜。

例如,像纹身工具、医疗塑料(植入、注射等)这种,在使用和操作时会对皮肤和粘膜造成破坏,就可能导致微塑料颗粒进入体内。

第二种口服,指微塑料颗粒通过肠道上皮细胞被吸收,进入体循环。

理论上,塑料有几率通过肠道黏膜并被人体吸收,最终进入血液。包括外卖等食物药品包装、日用品(牙膏洗面奶等)、食物链(海洋河流污染鱼类,被人类食用等)、种植牙填充物,甚至是饮用水,都可能让各种微塑料颗粒进入体内。

 

第三种吸入,指空气中的微塑料颗粒透过肺泡等组织进入血液的过程。

研究表明,1nm~20nm之间的空气颗粒被认为是可吸入的,例如长期在充满灰尘中工作的人可能患上尘肺,同样微塑料颗粒也会通过这种方式进入肺部。

当然,人类也会通过咳嗽等方式,排出一部分塑料颗粒,只不过有时候不自觉就吞下去了……然后,再以口服的方式进入肠道……

但值得注意的是,抛开剂量谈毒性也是不合理的。

例如,海洋和河流中的微塑料颗粒样本,很可能来自科学家们调查时自己携带的工具。

斯泰福厦大学最新研究发现,不少科学家们会穿着含有塑料成分的衣服和鞋、拿着塑料瓶,收集环境中的微塑料颗粒样本:

 

然后,这些收集到的样本中,甚至有超过70%的塑料,是来自科学家自己身上的衣服和手里的工具……

 

比起这些,现在也已经有不少科学家开始想办法解决塑料制品。

变砖或给菌们吃掉

一种典型的方法是用细菌or真菌吃塑料。

来自中国、日本、德国等国家的科学家,都研究过如何用细菌吃塑料,例如他们就发现,一种叫做塔宾曲霉的真菌能分泌一种酶,让PU(聚氨酯)快速分解。

此外,包括饮料瓶中经常采用的PET,也已经有科学家发现了对应的细菌能把它分解掉。

不过这些真菌和细菌分解塑料也都需要一定条件,目前还处于进一步研究的阶段。

 

另一种方法是“手动”分解塑料。

最近,瑞士ETH(苏黎世联邦理工学院)的科学家们,就首次成功通过一种溶剂,将一种塑料长链聚合物分解成了简单分子,效率达到92%。

据研究人员表示,这种溶剂是可以回收利用的。

此外还有一些方法,可以实现塑料的二次利用。

例如将塑料变砖、或是用来铺路,甚至还有国家搞出了专门的塑料银行来回收这些制品。

△将塑料做成公园长椅

但无论如何,目前造塑料比分解还是容易多了。

对此,有网友看得比较开,表示说不定人类将来也会慢慢适应进化:

Plastic not only pollutes the environment, but ultimately also pollutes human beings.

The news that microplastics were discovered in human blood for the first time aroused heated discussions among netizens, and once ranked third on the Zhihu hot list, and the number of Weibo views reached 240 million.

The latest research comes from the Vrije Universiteit Amsterdam, the Netherlands Delta Institute, a leading research institution in the field of the environment.

The scientists collected blood samples from 22 volunteers and found microplastic particles in 77 percent of them, with an average concentration of 1.6 micrograms per milliliter.

This has become the first quantitative evidence that plastics enter the human body’s blood circulation, of which there are only three types of plastics that can be quantitatively detected.

50% of the human body contains PET (polyethylene terephthalate), which is commonly found in beverage bottles such as cola juice, mineral water, and some medicine bottles.

36% of the subjects contained PS (polystyrene), which is commonly found in food packaging such as foam lunch boxes.

Another 23% of the subjects contained PE (polyethylene), the main raw material of plastic bags.

 

In addition, PMMA (acrylic, also known as plexiglass), PP (polypropylene, commonly used in medical equipment and woven bags, etc.) have also been detected, but they have not been quantified.

The presence of plastic in human blood is a cause for concern, and the most serious consequence may be that it can break through the blood-brain barrier and damage the brain.

Scientists in South Korea have found that particles smaller than two microns can accumulate in the nervous system microglia of mice within a few days, leading to apoptosis.

 

If this continues, after a few years, the scolding may not say “the brain has entered the water”, but will be changed to “the brain has entered the plastic”.

 

What are the dangers of microplastics?

Since the 1950s, humans have produced and discarded plastic on a large scale. The pollution of large pieces of plastic to the environment and the harm to animals are obvious.

Microplastics with a diameter of less than 5mm have gradually become a hot research direction in the academic circles.

In fact, not only blood, but also human organs such as liver and intestine, placenta, and human feces have successively detected the existence of microplastic particles.

According to the Medical University of Vienna, the total weight of plastic particles entering the intestinal mucosa of a person on an average week is equivalent to a credit card.

 

Plastic particles are difficult to be metabolized and absorbed by the human body, and the parts that cannot be excreted will accumulate in the body, causing cell damage, local inflammation and immune responses.

Microplastic particles in the digestive system can reduce the diversity of intestinal flora, especially the number of beneficial bacteria, and cause metabolic diseases such as obesity and diabetes.

The main material of beverage bottles, PET, contains environmental hormones (Xenohormones), which are carcinogens.

Some studies have found that the PET content of infants is 14 times that of adults, which may be related to the accelerated release of particles in plastic bottles by brewing milk powder in hot water.

 

And the microplastics of the fabric fiber type enter the respiratory tract and may also trigger an inflammatory response and respiratory damage.

In general, research on the harms of microplastics to humans is relatively new, and critical in vivo evidence is lacking.

But in vivo studies in animals have confirmed that microplastics in seawater can cause cognitive impairments in fish and crabs, making it slower for hermit crabs to find suitable shells.

How microplastics enter the human bloodstream

According to the authors of the latest Dutch paper, there are at least three ways for microplastics to enter the bloodstream: skin/mucosal contact, oral intake, and inhalation.

The first type of skin or mucous membrane contact, but not direct contact with healthy skin, but damaged skin or mucous membranes.

For example, things like tattoo tools, medical plastics (implants, injections, etc.) that cause damage to the skin and mucous membranes during use and manipulation can lead to microplastic particles entering the body.

The second oral method refers to the absorption of microplastic particles by intestinal epithelial cells into the systemic circulation.

In theory, plastic has a chance to pass through the intestinal mucosa and be absorbed by the body, eventually entering the bloodstream. Including food and drug packaging such as take-out, daily necessities (toothpaste, facial cleanser, etc.), food chain (ocean and river polluted fish, eaten by humans, etc.), dental implant fillings, and even drinking water, all kinds of microplastic particles may enter the body.

 

The third type of inhalation refers to the process of microplastic particles in the air entering the blood through tissues such as alveoli.

Studies have shown that air particles between 1nm and 20nm are considered inhalable. For example, people who work in dusty environments for a long time may suffer from pneumoconiosis, and microplastic particles can also enter the lungs in this way.

Of course, humans also expel some plastic particles through coughing and other methods, but sometimes they swallow them unconsciously… Then, they enter the intestines orally…

But it is worth noting that it is not reasonable to talk about toxicity without dose.

Samples of microplastic particles in oceans and rivers, for example, likely come from tools that scientists carry with them when they investigate.

The latest research from Staffordshire University found that many scientists will wear plastic-containing clothes and shoes, hold plastic bottles, and collect samples of microplastic particles in the environment:

 

Then, even more than 70% of the plastic in these collected samples came from the scientists’ own clothes and tools…

 

Compared with these, many scientists have begun to think of ways to solve plastic products.

Bricked or eaten by bacteria

A typical way is to eat plastic with bacteria or fungi.

Scientists from China, Japan, Germany and other countries have all studied how to use bacteria to eat plastic. For example, they found that a fungus called Aspergillus tabin can secrete an enzyme that makes PU (polyurethane) quickly decompose.

In addition, including PET that is often used in beverage bottles, scientists have also found that the corresponding bacteria can decompose it.

However, these fungi and bacteria also require certain conditions to decompose plastics, and it is still in the stage of further research.

 

Another method is to break down the plastic “by hand”.

Recently, scientists at ETH (ETH Zurich) in Switzerland successfully used a solvent for the first time to decompose a plastic long-chain polymer into simple molecules with an efficiency of 92%.

According to the researchers, the solvent is recyclable.

In addition, there are some ways to realize the secondary utilization of plastics.

For example, plastic is turned into bricks, or used to pave roads, and even countries have created special plastic banks to recycle these products.

△ Plastics are made into park benches

But in any case, it is still much easier to make plastic than to break it down.

In this regard, some netizens see it more openly, saying that maybe humans will gradually adapt to evolution in the future:

 

Some netizens ridiculed, it seems that health care products can use the banner of “removing plastic” in the future:

What do you think?

Paper address: https://www.sciencedirect.com/science/article/pii/S0160412022001258

还有网友调侃,看来以后保健产品可以打出“排塑料”的旗号了:

你觉得呢?

论文地址:https://www.sciencedirect.com/science/article/pii/S0160412022001258

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