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The average liter of bottled water has nearly a quarter million invisible pieces of very small plastic known as nanoplastics, a recent study says.
最近的一项研究表明，平均每升瓶装水中含有近25万块看不见的纳米塑料。
Researchers found the nanoplastics with a microscope using dual lasers.
研究人员用双波长激光显微镜发现了纳米塑料。
Scientists long figured there were lots of these very small plastic pieces.
长期以来，科学家一直认为存在大量这种非常小的塑料碎片。
But until researchers at Columbia and Rutgers universities did their calculations, they never knew how many or what kind.
但直到哥伦比亚大学和罗格斯大学的研究人员进行了计算，他们才知道有纳米塑料的数量和类型。
Looking at five samples each of three common bottled water brands, researchers found particle levels ranged from 110,000 to 400,000 per liter.
研究人员研究了三种常见瓶装水品牌的五个样品，发现每升瓶装水中纳米塑料的含量从11万到40万块不等。
The average was around 240,000, the study said.
该研究称，平均每升瓶装水中纳米塑料的含量约为24万块。
The research appeared recently in the publication Proceedings of the National Academy of Sciences.
这项研究最近发表在《美国国家科学院院刊》上。
Nanoparticles are particles that are less than a micron in size.
纳米颗粒是尺寸小于一微米的颗粒。
In comparison, a human hair is about 83 microns wide.
相比之下，人类的头发大约有83微米宽。
Previous studies have looked at slightly bigger microplastics that range from 5 millimeters, which could be seen by human eyes, to one micron.
之前的研究关注的是尺寸略大一些的微塑料，从人眼可以看到的5毫米到1微米不等。
About 10 to 100 times more nanoplastics than microplastics were discovered in bottled water, the study found.
研究发现，在瓶装水中发现的纳米塑料大约是微塑料的10到100倍。
Much of the plastic seems to be coming from the bottle and the filtration system to clean the water itself, said the study's lead writer Naixin Qian of Columbia University.
这项研究的主要作者哥伦比亚大学的钱乃欣说，大部分塑料似乎来自瓶子和清洁水的过滤系统。
She would not name the three brands because researchers want more samples and they want to study more brands.
她不愿透露这三个品牌的名字，因为研究人员想要更多的样本，他们想要研究更多的品牌。
Still, she said they were common and bought at a Walmart, a popular store in the U.S.
不过，她说，这些瓶装水很常见，是在美国颇受欢迎的沃尔玛商店购买的。
Researchers still cannot answer the big question: Are those nanoplastic pieces harmful to health?
研究人员仍然无法回答一个大问题：这些纳米塑料碎片对健康有害吗？
"That's currently under review. We don't know if it's dangerous or how dangerous," said study co-writer Phoebe Stapleton of Rutgers University.
这篇研究论文的合著者、罗格斯大学的菲比·斯台普顿说：“目前正在对此进行评估。我们不知道这是否危险，也不知道有多危险。”
"We do know that they are getting into the tissues (of mammals, including people) … and the current research is looking at what they're doing in the cells."
“我们确实知道它们正在进入（包括人类在内的哺乳动物)的组织中，目前的研究正在研究它们在细胞中做了什么。”
The International Bottled Water Association said in a statement: "There currently is both a lack of standardized (measuring) methods and no scientific" agreement on the possible health effects of nano- and microplastic particles.
国际瓶装水协会在一份声明中说：“关于纳米塑料可能会对健康造成的影响，目前既缺乏标准化的测量方法，也没有科学共识。”
The statement added, "Therefore, media reports about these particles in drinking water do nothing more than unnecessarily scare consumers."
该声明还称，“因此，媒体对饮用水中含有这种颗粒的报道只会不必要地吓唬消费者。”
The American Chemistry Council, which represents plastics manufacturers, declined to immediately comment.
代表塑料制造商的美国化学理事会拒绝立即置评。
The Associated Press spoke with four co-writers of the study.
美联社采访了该篇研究论文的四位合著者。
All of them said they would cut back on their bottled water use.
他们都表示，他们将减少使用瓶装水。
Columbia chemist Wei Min said he has reduced his bottled water use by half.
哥伦比亚大学化学家魏民表示，他已经将瓶装水的使用量减少了一半。
Stapleton said she now depends more on filtered water at home in New Jersey.
斯台普顿说，她现在在新泽西州的家里更多地依赖过滤水。
But study co-author Beizhan Yan, a Columbia environmental chemist who increased his tap water usage, pointed out that filters themselves can be a problem by introducing plastics.
但该研究论文的合著者、哥伦比亚大学的环境化学家严北展增加了自来水的使用量，他指出，由于加入了塑料，过滤器本身可能是一个问题。
"There's just no win," Stapleton said.
斯台普顿说：“根本没有赢的可能”。
Outside experts, who praised the study, agreed that there is a general unease about the risks of fine plastic particles.
外部专家对这项研究表示赞赏，他们一致认为，人们普遍对细小塑料颗粒的风险感到不安。
Still, it is too early to say anything certain about the risks.
不过，现在就断言风险还为时过早。
"The danger of the plastics themselves is still an unanswered question. For me, the additives are the most concerning," said Jason Somarelli of Duke University in North Carolina.
北卡罗来纳州杜克大学的杰森·索马雷利说：“塑料本身的危险性仍然是一个悬而未决的问题。对我来说，添加剂才是最令人担忧的。”
Somarelli was not part of the research.
索马雷利没有参与这项研究。
He added, "We and others have shown that these nanoplastics can be internalized into cells, and we know that nanoplastics carry all kinds of chemical additives that could cause cell stress, DNA damage and change metabolism or cell function."
他补充说：“我们和其他人已经证明，这些纳米塑料可以内化到细胞中，我们知道纳米塑料携带各种化学添加剂，这些添加剂可能会导致细胞压力、DNA损伤，并改变新陈代谢或细胞功能。”
Somarelli said his own research has found more than 100 "known cancer-causing chemicals in these plastics."
索马雷利说，他自己的研究发现，这些塑料中有100多种“已知的致癌化学物质”。
About 15 years ago, Min invented dual laser microscope technology that identifies specific compounds by their chemical properties and how they respond when exposed to lasers.
大约15年前，魏民发明了双波长激光显微镜技术，通过化学品的化学性质以及它们在激光照射下的反应来识别特定化合物。
Yan and Qian talked to him about using that technique to find and identify plastics that had been too small for researchers using established methods.
严北展和钱乃欣与他讨论了使用这种技术来发现和识别那些对于使用现有方法的研究人员来说太小的塑料。
Kara Lavender Law of the Sea Education Association said "the work can be an important advance in the detection of nanoplastics," but she said she'd like to see other chemists use the technique and get the same results.
海洋教育协会的卡拉·拉文德·劳说，“这项工作可能是科学家在纳米塑料检测方面取得的一个重要进步”，但她说，她希望看到其他化学家使用这项技术并得到同样的结果。
Yan said he is starting to study water supplies in the U.S. cities of Boston, St. Louis, Los Angeles and elsewhere to see how much plastics are in their tap water.
严北展表示，他开始研究波士顿、圣路易斯、洛杉矶等美国城市的供水情况，检测自来水中的塑料含量。
Previous studies looking for microplastics and some early tests suggest there may be less nanoplastic in tap water than in bottled water.
之前寻找微塑料的研究和一些早期检测表明，自来水中的纳米塑料含量可能比瓶装水中的少。
Even with unknowns about human health, Yan said he does have one suggestion: Use reusable bottles instead of single-use plastics.
虽然对人类健康的影响尚不清楚，但严北展表示，他确实有一个建议：使用可重复使用的瓶子，而不是一次性塑料瓶。
I'm John Russell. And I'm Ashley Thompson.
约翰·拉塞尔、阿什利·汤普森为您共同播报。
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