Bottled Water Can Contain Hundreds of Thousands of Tiny Plastic Bits瓶装水或含数十万塑料微粒

In recent years， there has been rising concern that tiny particles known as microplastics are showing up basically everywhere on Earth， from polar ice to soil， drinking water and food. Formed when plastics break down into progressively smaller bits， these particles are being consumed by humans and other creatures， with unknown potential health and ecosystem effects. One big focus of research： bottled water， which has been shown to contain tens of thousands of identifiable fragments in each container.

近些年，微塑料逐渐引起人们的担忧——从极地冰川到土壤、饮用水和食物，这种微粒在地球上几乎无处不在。微塑料是塑料在逐步分解的过程中形成的小颗粒，能被人和其他生物摄入，对人体健康和生态系统有何潜在影响尚不清楚。相关研究的一大焦点是瓶装水，已发现每瓶水中含有数万个可辨别的塑料碎片。

Now， using newly refined technology， researchers have entered a whole new plastic world： the poorly known realm of nanoplastics， the spawn1 of microplastics that have broken down even further. For the first time， they counted and identified these minute particles in bottled water. They found that on average， a liter contained some 240，000 detectable plastic fragments—10 to 100 times greater than previous estimates， which were based mainly on larger sizes.

如今，借助改进的技术，研究人员得以涉足鲜为人知的塑料新世界：纳米塑料领域。纳米塑料是微塑料进一步分解的产物。研究人员首次对瓶装水中的这种极小微粒进行了辨别和计数。他们发现，平均每升瓶装水中可检测出的塑料碎片约24万个，是以往主要基于较大尺寸颗粒的估值的10倍到100倍。

The study was published in the journal Proceedings of the National Academy of Sciences.

相关研究成果已发表在美国的《国家科学院院刊》上。

Nanoplastics are so tiny that， unlike microplastics， they can pass through intestines and lungs directly into the bloodstream and travel from there to organs including the heart and brain. They can invade individual cells， and cross through the placenta to the bodies of unborn babies. Medical scientists are racing to study the possible effects on a wide variety of biological systems.

与微塑料不同，纳米塑料小到足以穿过肠道和肺部直接进入血液，然后随血液抵达心脏和大脑等器官。它们甚至能侵入单个细胞，经由胎盘进入胎儿体内。医学家们正在加紧研究纳米塑料可能对各种生物系统造成的影响。

“Previously this was just a dark area， uncharted. Toxicity studies were just guessing what’s in there，” said study coauthor Beizhan Yan， an environmental chemist at Columbia University’s Lamont-Doherty Earth Observ-atory. “This opens a window where we can look into a world that was not exposed to us before.”

“以前，纳米塑料领域是一个盲区。毒性研究也只能猜测里面有什么。”研究论文合著者颜备战表示，他是哥伦比亚大学拉蒙特-多尔蒂地球观测所的环境化学家，“现在，这项研究打开了一扇窗，透过它我们能一窥未曾探索过的世界。”

Worldwide plastic production is approaching 400 million metric tons a year. More than 30 million tons are dumped yearly in water or on land， and many products made with plastics including synthetic textiles shed particles while still in use. Unlike natural organic matter， most plastics do not break down into relatively benign2 substances; they simply divide and redivide into smaller and smaller particles of the same chemical composition. Beyond single molecules， there is no theoretical limit to how small they can get.

目前，塑料的全球年产量直逼4亿吨。每年超过3000万吨塑料被倾倒入水或被丢弃在陆地上，而且许多塑料制品，比如合成织物，在使用过程中也会释放塑料颗粒。不同于天然有机物，大多数塑料不能分解为相对无害的物质，而仅仅是不断分解为越来越小但化学成分保持不变的颗粒。理论上讲，塑料颗粒可以无限分解，直至小到单分子水平。

Microplastics are defined as fragments ranging from 5 millimeters down to 1 micrometer， which is 1 millionth of a meter. （A human hair is about 70 micrometers across.） Nanoplastics， which are particles below 1 micrometer， are measured in billionths of a meter.

微塑料是指直径介于1微米（即百万分之一米）和5毫米之间的塑料碎片。（一根人类头发的直径约为70微米。）纳米塑料是直径小于1微米的颗粒，以十亿分之一米为计量单位。

Plastics in bottled water became a public issue largely after a 2018 study detected an average of 325 particles per liter; later studies multiplied that number many times over. Scientists suspected there were even more than they had yet counted， but good estimates stopped at sizes below 1 micrometer—the boundary of the nano world.

瓶装水里的塑料之所以成为公共议题，在很大程度上是因为2018年的一项研究。该研究发现平均每升瓶装水中含有325个塑料颗粒——后来的研究将该数字翻了数番。科学家们认为实际数量甚至可能超过现有检出量，可一旦跨过1微米这条界线下至纳米领域，就难以获得可靠的估值。

“People developed methods to see nano particles， but they didn’t know what they were looking at，” said the new study’s lead author， Naixin Qian， a Columbia graduate student in chemistry. She noted that previous studies could provide bulk3 estimates of nano mass， but for the most part could not count individual particles， nor identify which were plastics or something else.

“人们开发了不同方法来观察纳米颗粒，但又不清楚自己看到的是什么。”这项新研究的第一作者钱乃馨说道，她是哥伦比亚大学化学专业的研究生。她指出，此前的研究只能批量估算纳米颗粒，多数情况下既无法计数单个颗粒，也无法辨别出是塑料还是其他物质。

The new study uses a technique called stimulated Raman scattering microscopy， which was co-invented by study coauthor Wei Min， a Columbia biophysicist. This involves probing samples with two simultaneous lasers that are tuned to make specific molecules resonate. Targeting seven common plastics， the researchers created a data-driven algorithm to interpret the results. “It is one thing to detect， but another to know what you are detecting，” said Min.

这项新研究采用了受激拉曼散射显微技术，该技术由研究论文的合著者、哥伦比亚大学生物物理学家闵玮共同研发。受激拉曼散射显微技术通过同时发射两束激光对样本进行探测，而这两束激光已经过调制，可使特定的分子产生共振。研究人员还针对7类常见塑料开发了一套数据驱动的算法，用于分析结果。对此，闵玮说道：“检测是一回事，知道检测到的是什么则是另一回事。”

The researchers tested three popular brands of bottled water sold in the United States （they declined to name which ones）， analyzing plastic particles down to just 100 nanometers in size. They spotted 110，000 to 370，000 particles in each liter， 90% of which were nanoplastics; the rest were microplastics. They also determined which of the seven specific plastics they were， and charted their shapes—qualities that could be valuable in biomedical research.