And for every liter of it, there is 0.8 milligrams of fluoride in it.

而每升水中含有 0.8 毫克氟化物。

Fluoride is essential for our oral health.

氟對我們的口腔健康至關重要。

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.

它能保護我們免受齲齒的侵害，這就是為什麼它也出現在許多牙膏和漱口水中，以及我們在牙醫處接受的治療中。

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

對於大約 63% 的美國人來說，這也是我們的飲用水中含有這種物質的原因。

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.

現在，一個在公共衛生問題上有很多沒有科學依據的觀點的人正在被考慮上司國家的一個頂級公共衛生機構。

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

他認為，我們應該建議美國所有供水系統去除公共用水中的氟化物。

Putting fluoride in the water has long fueled conspiracy theories.

長期以來，在水中添加氟化物一直是陰謀論的導火索。

But it turns out the science is still evolving.

但事實證明，科學仍在不斷髮展。

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

其中一些內容甚至是在我們製作這段視頻時出現的。

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

這讓一些科學家開始重新審視這種做法，他們想知道，我們的水裡還需要氟嗎？

And if so, how much is safe?

如果是，多少才是安全的？

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

氟可以使牙齒上的琺琅質再礦化，從而防止齲齒。

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

它可以作為一道保護屏障，抵禦口腔中細菌產生的酸。

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

當我們飲用水中的氟時，大約有一半的氟會留在我們體內。

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

其中一些會與我們的骨骼結合，另一些則通過唾液到達我們的牙齒。

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

氟天然存在於土壤和空氣中，有些地區的水中也含有天然氟。

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

將近 100 年前，牙醫們發現，水中天然存在的高濃度氟會汙染兒童的牙齒。

But it was also preventing tooth decay.

但它也能預防蛀牙。

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

1945 年，密歇根州的大急流城和紐約州的紐堡成為首批開始人工加氟的社區。

In Grand Rapids, researchers monitored roughly 30,000 schoolchildren over 15 years and observed that the rate of tooth decay declined by more than 60%.

在大急流城，研究人員對大約 3 萬名學童進行了 15 年的監測，發現蛀牙率下降了 60% 以上。

So other communities started adopting the practice, too.

於是，其他社區也開始採用這種做法。

And eventually, it got added to toothpaste, which works topically.

最後，它被添加到牙膏中，在局部發揮作用。

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.

在水中添加氟化物的目的是確保每個人都能得到氟化物的保護，無論他們是否使用含氟產品或獲得牙科護理。

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.

要想知道我們水裡的氟化物還在起多大作用，一個辦法就是看看那些停止添加氟化物的社區會發生什麼。

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.

氟化水的支持者指出了這樣一項研究，該研究調查了加拿大卡爾加里市在 2011 年停止氟化水後的情況。

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.

兒童乳牙的蛀牙率本已呈上升趨勢，但他們從水中剔除氟化物後，蛀牙率驟然上升。

But this 2024 review looked across 21 studies of communities that added fluoride to their water and could only determine that it may have led to a slight reduction in tooth decay.

但是，2024 年的這篇綜述對 21 個在水中添加氟化物的社區進行了研究，只能確定氟化物可能會使蛀牙略有減少。

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.

研究報告的作者發現，1975 年以前，氟化水對預防兒童蛀牙有明顯而重要的作用。

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.

但由於此後牙膏中氟化物的供應量增加，如今我們不太可能在所有人群中看到這種效果。

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

是以，水中的氟化物確實在過去幫助我們擁有了更健康的牙齒。

And it still might in some communities.

在某些社區，這種情況仍有可能發生。

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

但是，由於外用氟化物的普及程度很高，其效果可能不會像歷史上那麼顯著。

And in recent years, a handful of scientists have been looking into another question.

近年來，一些科學家一直在研究另一個問題。

How much fluoride is safe?

多少氟化物是安全的？

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.

作為水的添加劑，氟化物通常以液態氟硅酸的形式存在，世界衛生組織建議每升水的用量不超過 1.5 毫克。

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

從這個角度來看，大約相當於一個奧林匹克游泳池一加侖的水量。

The CDC recommends 0.7 milligrams per liter of water, or a little less than a half gallon per swimming pool.

疾病預防控制中心建議每升水含 0.7 毫克，即每個游泳池含不到半加侖的水。

Municipalities set their own fluoride doses, and most set it around this amount.

各市政當局自行設定氟化物劑量，大多數市政當局設定的氟化物劑量都在此範圍內。

Like my New York City tap water.

就像我的紐約自來水一樣。

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 teeth staining first observed in communities with high natural fluoridation.

疾病預防控制中心的這一建議完全是基於這樣一個量，即既能防止蛀牙，又能限制氟斑牙的風險，而氟斑牙是在自然氟化程度較高的社區首次發現的一種大多無害的牙齒染色現象。

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.

但是，如今研究這些劑量的科學家們主要通過測量智商來研究氟對胎兒和幼兒大腦發育的影響。

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.

我們對發育中的大腦的瞭解是，它可能是對毒性最敏感的指標之一，是以我們通常從這裡開始。

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

布魯斯-蘭費爾是加拿大西蒙弗雷澤大學健康科學教授，研究鉛、殺蟲劑和汞等環境神經毒素。

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.

最早顯示氟攝入量與智商之間存在聯繫的一些研究來自中國天然含氟量較高的村莊，研究始於 1989 年，一直持續到 2000 年代。

Some of them looked at 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.

他們中的一些人研究了在氟含量較高的村莊長大的兒童，並將他們與氟含量不高的村莊進行了比較。

They measured levels as high as 2.3 gallons per swimming pool of water.

他們測得每游泳池水的濃度高達 2.3 加侖。

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

這些早期研究有很多問題，但它們確實引發了一個大問題。

And what they found is comparing the high versus the low populations, they saw about a 7 IQ point difference.

他們發現，將高智商人群與低智商人群進行比較，發現兩者的智商相差約 7 個點。

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

如果規模如此之大，就很難被忽視。

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

對於普通人來說，幾分的智商差異並不會產生很大的影響，甚至可能無法測量。

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

美國國家環境健康科學研究所前所長以鉛為例，向我解釋了這一點。

You know, Laura, if you'd had less blood lead, maybe you'd have three more IQ points.

你知道嗎，勞拉，如果你的血鉛含量低一點，也許你的智商就會高出三分。

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

你無法從個體身上證明這一點，但你可以從人群中尋找答案。

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

我們知道，如果改變人口的智商，就會有更多的人需要特殊服務，天才就會減少。

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.

這些早期研究的結果啟發了一些研究人員，他們試圖找出高濃度氟對神經系統造成的風險是否也會發生在較低濃度的情況下，比如世界衛生組織規定的每升 1.5 毫克的最高濃度，或者甚至是我們在美國給水加氟的較低濃度。

Over the years, some studies have found an association between IQ and lower fluoride Some haven't, leaving scientists, particularly in the dental and epidemiological communities, divided on the issue.

多年來，有些研究發現智商與低氟之間存在關聯，有些則沒有，這使得科學家，尤其是牙科和流行病學界在這個問題上產生了分歧。

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.

但就在我們製作這段視頻的同時，美國聯邦科學家發表了一份對 74 項有關兒童智商和氟化物研究的嚴謹分析報告。

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.

其中，少數來自美國以外的高質量研究發現，智商較低與水中氟含量低於每升 1.5 毫克之間存在關聯。

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.

但由於研究數量較少，他們無法就美國水的氟含量得出結論。

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

我又給布魯斯-蘭菲爾打了電話，希望他能解釋一下結果。

Hello again.

又見面了

Hello.

你好

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, right?

薈萃分析實際上是一種對高質量研究和低質量研究進行綜合和量化的方法，並試圖使其變得有意義，對嗎？

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

否則，你只能說，我最喜歡的這些研究是這麼說的，這證實了我的信念。

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

而這些研究並不能證實我的觀點，很顯然它們是錯誤的。

What this new meta-analysis was able to conclude is that urinary fluoride levels 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.

這項新的薈萃分析得出的結論是，尿液中氟含量低於每升 1.5 毫克與智商較低有關，即尿液中每含 1 毫克氟就會損失 1.6 個智商點。

Urine, which captures the totality of exposure that people have, and that's how we measure risk from total exposure, not from one isolated source.

尿液可以捕捉到人們接觸到的所有物質，這就是我們衡量總接觸風險的方法，而不是衡量某個孤立來源的風險。

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

布魯斯解釋說，我們在水中加入的氟化物只是我們所有人攝入的最低氟化物量。

Black and green tea leaves have high fluoride content.

紅茶葉和綠茶葉的含氟量很高。

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

馬鈴薯和貝類罐頭等各種食物中都含有氟。

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

食物中的殺蟲劑也可能含有氟。

We consume fluoride if we accidentally swallow toothpaste or mouthwash.

如果我們不小心吞下牙膏或漱口水，就會攝入氟化物。

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.

而且，我們添加到水中的氟含量也無法滿足大約 300 萬美國人的需求，這些人主要居住在西南部，他們使用的地下水中天然氟的濃度甚至高於每升 1.5 毫克。

Experts were particularly concerned about infants who drink formula.

專家們尤其關注喝配方奶粉的嬰兒。

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

他們的全部食物幾乎都是含氟的水和幹奶粉，而幹奶粉中也可能含有氟。

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

還有孕婦，她們會把攝入的氟傳遞給胎兒。

We oftentimes see exposures that exceed 1.5, and in some cases in pregnant women during the third trimester, we saw levels much higher.

我們經常看到暴露量超過 1.5 的情況，在某些情況下，懷孕三個月的孕婦的暴露量要高得多。

So what do we make of all of this information?

那麼，我們該如何看待這些資訊呢？

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

首先，外用氟化物對保持牙齒健康至關重要。

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

對於未懷孕的成年人來說，沒有證據表明攝入氟化物有害。

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

有證據表明，孕婦、嬰兒和幼兒應注意氟的總體攝入量。

Right now, we could be encouraging pregnant women to drink bottled water if their tap water is fluoridated.

現在，如果孕婦的自來水中含有氟，我們可以鼓勵她們飲用瓶裝水。

And we could be encouraging women who are using formula to feed their babies to make it with water that doesn't have fluoride on it.

我們可以鼓勵使用配方奶粉餵養嬰兒的婦女用不含氟的水沖泡配方奶粉。

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.

但是，如果我們要弄清楚是否還需要繼續在水中添加氟，或者現在這樣做是否安全，科學上還沒有定論。

So it's a confusing time for understanding these risks and benefits.

是以，現在是瞭解這些風險和益處的混亂時期。

I am a believer in the precautionary principle, which does not say you act in the absence of evidence.

我信奉預防原則，但這並不是說在沒有證據的情況下就採取行動。

It says you act in the presence of concerning evidence.

它說你是在有相關證據的情況下行事的。

And my reading of the literature is that there is enough data to say there is concern.

而我對文獻的解讀是，有足夠的數據表明存在擔憂。