跟讀練習: Should fluoride be in our water? - 通過影片學習英語口語

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This is the New York City tap water that I drink.

And for every liter of it, there is 0 .8 milligrams of fluoride in it.

Fluoride is essential for our oral health.

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.

And for about 63 % of Americans, it's also why it's in our drinking water.

Now someone with a lot of views on public health not

supported by science is being considered to lead one of the country's top public health agencies.

And one thing he believes is that we should advise all U .S water systems to remove fluoride from public water.

Putting fluoride in the water has long fueled conspiracy theories.

But it turns out the science is still evolving.

And some of it emerged even as we made this video.

And it's causing some scientists to take another look at this practice and wonder: Do we still need fluoride in our water?

And if so, how much is safe?

Fluoride protects us from cavities by remineralizing enamel on our teeth.

It acts as a protective barrier against the acid that bacteria in our mouths produce.

When we drink fluoride in water, about half of it sticks around in our bodies.

Some of it binds to our bones, and some reaches our teeth through our saliva.

Fluoride occurs naturally in soil and air, and some regions have naturally occurring fluoride levels in their water.

Almost 100 years ago, dentists figured out that high naturally occurring levels of fluoride in the water was staining children's teeth.

But it was also preventing tooth decay.

In 1945, Grand Rapids, Michigan and Newburgh, New York were among the first communities to start fluoridating water artificially.

and observed that the rate of tooth decay declined by more than 60%.

So other communities started adopting the practice too.

And eventually it got added to toothpaste which works topically.

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.

One way to figure out how well the fluoride in our

water is still working is to look at what happens in communities who have stopped adding it.

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.

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.

that added fluoride to their water, and could only determine that it may have led to a slight reduction in tooth decay.

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.

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.

So fluoride in the water did help us have healthier teeth in the past.

And it still might in some communities.

But because of how widespread topical fluoride is, the effect might not be as dramatic as it was historically.

And in recent years, a handful of scientists have been looking into another question: how much fluoride is safe?

Fluoride as an additive to water is usually in the form of liquid fluorosilicic acid,

and the World Health Organization recommends a dosage no higher than 1 .5 milligrams per liter of water.

you To put that in perspective, that's about one gallon for an Olympic swimming pool amount of water.

The CDC recommends 0 .7 milligrams per liter of water, or a little less than a half gallon per swimming pool.

Municipalities set their own fluoride doses, and most set it around this amount, like my New York City tap water.

This CDC recommendation is solely based on an amount

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.

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.

What we've learned about the developing brain is it's probably one of the most sensitive indicators of toxicity.

And so we typically begin there.

Bruce Lamphere is a professor of health sciences at Simon Fraser University in Canada and studies environmental neurotoxins like lead, pesticides and mercury.

Some of the first studies to show a link between fluoride intake

and IQ were from villages in China with high natural amounts of fluoride starting in 1989 through the 2000s.

that children who grew up in a village where the water had high levels of fluoride and compared them to villages

Without high levels of fluoride.

They measured levels as high as 2 .3 gallons per swimming pool of water.

These early studies had plenty of issues, but they did raise a big red flag.

And what they found is comparing the high versus the low populations, they saw about a seven IQ point difference.

When it's that large, it's hard to sort of just dismiss.

For the average person, a few points difference in IQ doesn't have a huge impact, and it might not even be measurable.

The former director of the National Institute of Environmental Health Sciences explained this to me using lead as an example.

Thanks.

You can't prove that in an individual, but you look at a population.

And we know that if you shift the population's IQ, You have more people needing special services, you have fewer geniuses.

The results of those early studies inspired some researchers to try

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,

or even at the lower levels we fluoridate our water in the U .S.

Over the years, some studies have found an association between IQ and lower fluoride levels.

Some haven't.

Leaving scientists, particularly in the dental and epidemiological communities, divided on the issue. But

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.

In it, a small number of high -quality studies from outside the U .S found an association between lower IQ

and water fluoride levels below 1 .5 milligrams per liter.

But the small number of studies meant

that they weren't able to draw conclusions about the levels that we fluoridate water in the U .S.

I called Bruce Lanphier back up to make sense of the results.

Hello again.

The meta -analysis is really a way to synthesize

and quantify the high -quality studies and the low -quality studies and try to make sense of it.

Because otherwise, what you're left with is, well, these studies, which are my favorite studies, said this, and that confirms my belief.

And these studies, which did that, don't confirm my belief, and clearly they're wrong.

below 1 .5 milligrams per liter were associated with lower IQ,

translating to a loss of 1 .6 IQ points per 1 milligram per liter of fluoride in urine.

the totality of exposure that people have.

And that's how we measure risk.

From total exposure, not from one isolated source.

Bruce explained that the fluoride we put in our water is just the minimum amount of fluoride we all consume.

Black and green tea leaves have high fluoride content.

A variety of food like potatoes and canned shellfish has fluoride in it.

The pesticides on our food can have fluoride in it too.

We consume fluoride if we accidentally swallow toothpaste or mouthwash.

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

that has natural fluoride concentrations even higher than 1 .5 milligrams

per liter you Experts were particularly concerned about infants who drink formula.

Almost their entire diet is fluoridated water and dry formula that can have fluoride in it too.

And about pregnant people who can pass all of this fluoride intake to a fetus.

We oftentimes see exposures that exceed 1 .5, and in some cases in pregnant women during the third trimester.

We saw levels much higher.

So what do we make of all of this information?

First of all, topical fluoride is essential for keeping our teeth healthy.

And for non -pregnant adults, there is no evidence that ingesting fluoride is harmful.

There is some evidence that pregnant people, babies, and young children should be aware of their overall fluoride intake.

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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為什麼要通過這個影片練習口語？

練習口語是學習英語的重要部分，通過與實際的對話或講解進行模擬，能幫助你更快的掌握語言的使用方式。這個影片圍繞氟化物是否應新增到飲用水中展開，提供了豐富的科學知識和公眾健康討論。這種主題的複雜性不僅讓你學習到專業詞彙，還能幫助你提高邏輯表達能力和口語流利度。通過與影片內容互動，學生能夠在真實的語境中實踐口語，同時也能增強聽力理解能力。

語法與表達方式分析

在影片中，講者使用了幾種重要的語法結構，這些結構可以幫助學習者提升語言表達能力：

條件句：例句“如果我們喝的水沒有氟化物…”這樣的語句可以幫助學習者瞭解如何表達假設和條件。
被動語態：例句“氟化物被新增到水中…”使學習者理解如何強調動作的接受者，而不是執行者。
比較級：提到“比以往的牙齒健康情況”，這幫助學習者學習如何進行比較表達。
定語從句：例如“科學家正在研究的影響”，學生可以通過學習如何使用定語從句來加深對名詞的描述。

常見的發音陷阱

在影片中，有些詞彙和短語可能會對學習者造成發音困難：

fluoride（氟化物）：注意母音的發音和重音位置。
tooth decay（蛀牙）：發音時兩個單詞的連讀可能會使初學者感到挑戰。
dosage（劑量）：這個詞在不同的語境下可能發音會有所不同，弄清楚其在句中的語調很重要。
remineralizing（再礦化）：這個長單詞可能會讓學生在發音時感覺走音，特別是在快速講話時。

通過模仿影片中的發音，你不僅可以提高英語發音，還能有效地提升口語表達能力，成為更自信的英語使用者。運用看YouTube學英語的方式，讓你的英語學習變得更加生動和有趣。

影片中的語法

說話人最常用的結構，並附上影片中的原話：

結構	影片中的用法
定語從句 who / which + 從句 — 補充說明人或事物	cavities, which is · children who grew · studies, which are
現在完成時 have/has + 過去分詞 — 過去發生但與現在仍有關聯的事	have stopped · we've learned · have found
被動語態 be + 過去分詞 — 強調發生了什麼，而不是誰做的	being considered · were associated · is fluoridated

什麼是跟讀法？

跟讀法 (Shadowing) 是一種有科學依據的語言學習技巧，最初開發用於專業口譯員的培訓，並由多語言者Alexander Arguelles博士普及。這個方法簡單而強大：您在聽英語母語原聲的同時立即大聲重複——就像是一個延遲1-2秒緊跟說話者的影子。與被動聽力或語法練習不同，跟讀法強迫您的大腦和口腔肌肉同時處理並模模擬實的講話模式。研究表明它能顯著提高發音準確性，語調，節奏，連讀，聽力理解和口語流利度——使其成為雅思口語備考和真實英語交流最有效的方法之一。

影子跟讀法: 閱讀完整分步指南 →

跟讀練習: Should fluoride be in our water? - 通過影片學習英語口語

選擇練習模式

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為什麼要通過這個影片練習口語？

語法與表達方式分析

常見的發音陷阱

影片中的語法

什麼是跟讀法？