Luyện nói tiếng Anh bằng Shadowing qua video: Should fluoride be in our water?
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This is the New York City tap water that I drink.
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And for every liter of it, there is 0 .8 milligrams of fluoride in it.
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Fluoride is essential for our oral health.
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It protects us from cavities, which is why it's also in lots of toothpaste and mouthwash and in treatments we get at the dentist.
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And for about 63 % of Americans, it's also why it's in our drinking water.
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Now someone with a lot of views on public health not
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supported by science is being considered to lead one of the country's top public health agencies.
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And one thing he believes is that we should advise all U .S water systems to remove fluoride from public water.
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Putting fluoride in the water has long fueled conspiracy theories.
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But it turns out the science is still evolving.
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And some of it emerged even as we made this video.
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And it's causing some scientists to take another look at this practice and wonder: Do we still need fluoride in our water?
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And if so, how much is safe?
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Fluoride protects us from cavities by remineralizing enamel on our teeth.
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It acts as a protective barrier against the acid that bacteria in our mouths produce.
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When we drink fluoride in water, about half of it sticks around in our bodies.
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Some of it binds to our bones, and some reaches our teeth through our saliva.
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Fluoride occurs naturally in soil and air, and some regions have naturally occurring fluoride levels in their water.
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Almost 100 years ago, dentists figured out that high naturally occurring levels of fluoride in the water was staining children's teeth.
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But it was also preventing tooth decay.
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In 1945, Grand Rapids, Michigan and Newburgh, New York were among the first communities to start fluoridating water artificially.
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and observed that the rate of tooth decay declined by more than 60%.
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So other communities started adopting the practice too.
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And eventually it got added to toothpaste which works topically.
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The goal of adding it to water was to make sure that everyone had access to fluoride's protection, regardless of whether they used fluoridated products or had access to dental care.
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One way to figure out how well the fluoride in our
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water is still working is to look at what happens in communities who have stopped adding it.
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Supporters of water fluoridation point to studies like this one that looked at what happened in Calgary, Canada after they stopped fluoridating their water in 2011.
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The rate of tooth decay in children's baby teeth was already on the rise, but after they took the fluoride out of the water, that rate spiked.
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that added fluoride to their water, and could only determine that it may have led to a slight reduction in tooth decay.
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The study authors found that prior to 1975, there was a clear and important effect on prevention of tooth decay in children due to water fluoridation.
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But because of the increased availability of fluoride in toothpaste since then, it is unlikely that we will see this effect in all populations today.
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So fluoride in the water did help us have healthier teeth in the past.
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And it still might in some communities.
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But because of how widespread topical fluoride is, the effect might not be as dramatic as it was historically.
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And in recent years, a handful of scientists have been looking into another question: how much fluoride is safe?
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Fluoride as an additive to water is usually in the form of liquid fluorosilicic acid,
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and the World Health Organization recommends a dosage no higher than 1 .5 milligrams per liter of water.
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you To put that in perspective, that's about one gallon for an Olympic swimming pool amount of water.
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The CDC recommends 0 .7 milligrams per liter of water, or a little less than a half gallon per swimming pool.
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Municipalities set their own fluoride doses, and most set it around this amount, like my New York City tap water.
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This CDC recommendation is solely based on an amount
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that balances the protection from tooth decay while limiting the risk of dental fluorosis, the mostly harmless tea staining first observed in communities with high natural fluoridation.
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But scientists studying these dosages today are looking at how fluoride affects developing brains, both in utero and as young children, primarily by measuring IQ.
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What we've learned about the developing brain is it's probably one of the most sensitive indicators of toxicity.
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And so we typically begin there.
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Bruce Lamphere is a professor of health sciences at Simon Fraser University in Canada and studies environmental neurotoxins like lead, pesticides and mercury.
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Some of the first studies to show a link between fluoride intake
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and IQ were from villages in China with high natural amounts of fluoride starting in 1989 through the 2000s.
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that children who grew up in a village where the water had high levels of fluoride and compared them to villages
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Without high levels of fluoride.
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They measured levels as high as 2 .3 gallons per swimming pool of water.
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These early studies had plenty of issues, but they did raise a big red flag.
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And what they found is comparing the high versus the low populations, they saw about a seven IQ point difference.
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When it's that large, it's hard to sort of just dismiss.
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For the average person, a few points difference in IQ doesn't have a huge impact, and it might not even be measurable.
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The former director of the National Institute of Environmental Health Sciences explained this to me using lead as an example.
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Thanks.
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You can't prove that in an individual, but you look at a population.
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And we know that if you shift the population's IQ, You have more people needing special services, you have fewer geniuses.
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The results of those early studies inspired some researchers to try
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and find out whether the neurological risk from high fluoride levels could also occur at lower levels, like the WHO maximum of 1 .5 milligrams per liter,
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or even at the lower levels we fluoridate our water in the U .S.
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Over the years, some studies have found an association between IQ and lower fluoride levels.
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Some haven't.
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Leaving scientists, particularly in the dental and epidemiological communities, divided on the issue. But
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while we were working on this video, U .S federal scientists published a rigorous analysis of 74 of the studies on childhood IQ and fluoride.
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In it, a small number of high -quality studies from outside the U .S found an association between lower IQ
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and water fluoride levels below 1 .5 milligrams per liter.
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But the small number of studies meant
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that they weren't able to draw conclusions about the levels that we fluoridate water in the U .S.
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I called Bruce Lanphier back up to make sense of the results.
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Hello again.
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The meta -analysis is really a way to synthesize
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and quantify the high -quality studies and the low -quality studies and try to make sense of it.
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Because otherwise, what you're left with is, well, these studies, which are my favorite studies, said this, and that confirms my belief.
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And these studies, which did that, don't confirm my belief, and clearly they're wrong.
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below 1 .5 milligrams per liter were associated with lower IQ,
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translating to a loss of 1 .6 IQ points per 1 milligram per liter of fluoride in urine.
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the totality of exposure that people have.
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And that's how we measure risk.
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From total exposure, not from one isolated source.
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Bruce explained that the fluoride we put in our water is just the minimum amount of fluoride we all consume.
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Black and green tea leaves have high fluoride content.
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A variety of food like potatoes and canned shellfish has fluoride in it.
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The pesticides on our food can have fluoride in it too.
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We consume fluoride if we accidentally swallow toothpaste or mouthwash.
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And the levels of fluoride we add to water also doesn't capture the roughly 3 million Americans, primarily in the southwest, that use groundwater
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that has natural fluoride concentrations even higher than 1 .5 milligrams
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per liter you Experts were particularly concerned about infants who drink formula.
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Almost their entire diet is fluoridated water and dry formula that can have fluoride in it too.
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And about pregnant people who can pass all of this fluoride intake to a fetus.
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We oftentimes see exposures that exceed 1 .5, and in some cases in pregnant women during the third trimester.
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We saw levels much higher.
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So what do we make of all of this information?
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First of all, topical fluoride is essential for keeping our teeth healthy.
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And for non -pregnant adults, there is no evidence that ingesting fluoride is harmful.
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There is some evidence that pregnant people, babies, and young children should be aware of their overall fluoride intake.
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to feed their babies to make it with water that doesn't have fluoride on it.
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But if we're trying to figure out whether we still need to keep fluoridating our water, or whether it's safe to do so as is, the science still isn't conclusive.
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So it's a confusing time for understanding these risks and benefits.
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I am a believer in the precautionary principle, which does not say you act in the absence of evidence.
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It says you act in the presence of concerning evidence.
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And my reading of the literature is that there is enough data to say there is concern.
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Ngữ cảnh & Bối cảnh
Trong video này, người nói chia sẻ về lợi ích của fluoride trong nước uống và vai trò của nó đối với sức khỏe răng miệng. Từ việc trình bày những thông tin về hàm lượng fluoride trong nước máy ở New York, cho đến việc chỉ ra rằng 63% người Mỹ sử dụng nước có chứa fluoride, video mang đến một cái nhìn sâu sắc về sự phát triển của nghiên cứu liên quan đến fluoride và sự tác động của nó đối với sức khỏe con người.
5 Câu Chuyện Hàng Ngày Cần Biết
- Fluoride là gì? - Một chất bảo vệ chống lại sâu răng.
- Hàm lượng fluoride trong nước? - Khoảng 0.8 mg mỗi lít nước.
- Lợi ích của fluoride? - Giúp tái khoáng hóa men răng và bảo vệ răng khỏi axit.
- Tại sao nhiều người lo ngại về fluoride? - Những lý thuyết âm thầm và nghiên cứu mới đang nổi lên.
- Liều lượng an toàn của fluoride? - Theo CDC, không vượt quá 0.7 mg/lít nước.
Hướng Dẫn Shadowing Từng Bước
Để cải thiện kỹ năng nói tiếng Anh của bạn qua video này, bạn có thể áp dụng shadow speak hiệu quả bằng cách làm theo những bước sau:
- Xem video lần đầu tiên: Chỉ xem để hiểu tổng thể nội dung và thông điệp chính của video.
- Nghe lại từng đoạn ngắn: Dừng lại sau mỗi cầu để ghi chú lại các cụm từ hay và cách phát âm. Sử dụng phần mềm shadowing để dễ dàng tái bao quát các câu thoại.
- Lặp lại theo giọng nói: Cố gắng nói theo sau khi nghe. Điều này giúp bạn cải thiện phát âm và ngữ điệu.
- Thực hành với người khác: Tìm bạn học hoặc đồng nghiệp để thực hành cùng nhau. Điều này giúp củng cố thêm kỹ năng và tự tin trong giao tiếp.
- Đánh giá bản thân: Ghi âm lại giọng nói của bạn khi thực hành shadowing và so sánh với giọng của video. Nhận diện các điểm cần cải thiện.
Bằng cách áp dụng những bước này, bạn không chỉ nâng cao khả năng giao tiếp mà còn hiểu sâu sắc hơn về nội dung mà các video giáo dục mang lại, từ đó phát triển khả năng luyện nói tiếng anh một cách hiệu quả.
Ngữ pháp trong video
Những cấu trúc người nói dùng nhiều nhất, kèm đúng cụm từ trong video:
| Cấu trúc | Trong video |
|---|---|
| Mệnh đề quan hệ who / which + mệnh đề — thêm thông tin về người hoặc vật | cavities, which is · children who grew · studies, which are |
| Thì hiện tại hoàn thành have/has + quá khứ phân từ — việc đã xảy ra nhưng còn liên quan đến hiện tại | have stopped · we've learned · have found |
| Câu bị động be + quá khứ phân từ — nhấn vào việc xảy ra, không phải người làm | being considered · were associated · is fluoridated |
Phương Pháp Shadowing Là Gì?
Shadowing là kỹ thuật học ngôn ngữ có cơ sở khoa học, ban đầu được phát triển cho chương trình đào tạo phiên dịch viên chuyên nghiệp và được phổ biến rộng rãi bởi nhà đa ngôn ngữ học Dr. Alexander Arguelles. Nguyên lý cốt lõi đơn giản nhưng cực kỳ hiệu quả: bạn nghe tiếng Anh của người bản xứ và lặp lại to ngay lập tức — như một "cái bóng" (shadow) đuổi theo người nói với độ trễ chỉ 1–2 giây. Khác với luyện ngữ pháp hay học từ vựng bị động, Shadowing buộc não bộ và cơ miệng phải đồng thời xử lý và tái tạo ngôn ngữ thực tế. Các nghiên cứu khoa học xác nhận phương pháp này cải thiện đáng kể phát âm, ngữ điệu, nhịp điệu, nối âm, kỹ năng nghe và độ lưu loát khi nói — đặc biệt hiệu quả cho người luyện IELTS Speaking và muốn giao tiếp tiếng Anh tự nhiên như người bản ngữ.