跟读练习: Should fluoride be in our water? - 通过视频学习英语口语
正在创建课程...
1
This is the New York City tap water that I drink.
2
And for every liter of it, there is 0 .8 milligrams of fluoride in it.
3
Fluoride is essential for our oral health.
4
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.
5
And for about 63 % of Americans, it's also why it's in our drinking water.
6
Now someone with a lot of views on public health not
7
supported by science is being considered to lead one of the country's top public health agencies.
8
And one thing he believes is that we should advise all U .S water systems to remove fluoride from public water.
9
Putting fluoride in the water has long fueled conspiracy theories.
10
But it turns out the science is still evolving.
11
And some of it emerged even as we made this video.
12
And it's causing some scientists to take another look at this practice and wonder: Do we still need fluoride in our water?
13
And if so, how much is safe?
14
Fluoride protects us from cavities by remineralizing enamel on our teeth.
15
It acts as a protective barrier against the acid that bacteria in our mouths produce.
16
When we drink fluoride in water, about half of it sticks around in our bodies.
17
Some of it binds to our bones, and some reaches our teeth through our saliva.
18
Fluoride occurs naturally in soil and air, and some regions have naturally occurring fluoride levels in their water.
19
Almost 100 years ago, dentists figured out that high naturally occurring levels of fluoride in the water was staining children's teeth.
20
But it was also preventing tooth decay.
21
In 1945, Grand Rapids, Michigan and Newburgh, New York were among the first communities to start fluoridating water artificially.
22
and observed that the rate of tooth decay declined by more than 60%.
23
So other communities started adopting the practice too.
24
And eventually it got added to toothpaste which works topically.
25
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.
26
One way to figure out how well the fluoride in our
27
water is still working is to look at what happens in communities who have stopped adding it.
28
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.
29
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.
30
that added fluoride to their water, and could only determine that it may have led to a slight reduction in tooth decay.
31
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.
32
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.
33
So fluoride in the water did help us have healthier teeth in the past.
34
And it still might in some communities.
35
But because of how widespread topical fluoride is, the effect might not be as dramatic as it was historically.
36
And in recent years, a handful of scientists have been looking into another question: how much fluoride is safe?
37
Fluoride as an additive to water is usually in the form of liquid fluorosilicic acid,
38
and the World Health Organization recommends a dosage no higher than 1 .5 milligrams per liter of water.
39
you To put that in perspective, that's about one gallon for an Olympic swimming pool amount of water.
40
The CDC recommends 0 .7 milligrams per liter of water, or a little less than a half gallon per swimming pool.
41
Municipalities set their own fluoride doses, and most set it around this amount, like my New York City tap water.
42
This CDC recommendation is solely based on an amount
43
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.
44
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.
45
What we've learned about the developing brain is it's probably one of the most sensitive indicators of toxicity.
46
And so we typically begin there.
47
Bruce Lamphere is a professor of health sciences at Simon Fraser University in Canada and studies environmental neurotoxins like lead, pesticides and mercury.
48
Some of the first studies to show a link between fluoride intake
49
and IQ were from villages in China with high natural amounts of fluoride starting in 1989 through the 2000s.
50
that children who grew up in a village where the water had high levels of fluoride and compared them to villages
51
Without high levels of fluoride.
52
They measured levels as high as 2 .3 gallons per swimming pool of water.
53
These early studies had plenty of issues, but they did raise a big red flag.
54
And what they found is comparing the high versus the low populations, they saw about a seven IQ point difference.
55
When it's that large, it's hard to sort of just dismiss.
56
For the average person, a few points difference in IQ doesn't have a huge impact, and it might not even be measurable.
57
The former director of the National Institute of Environmental Health Sciences explained this to me using lead as an example.
58
Thanks.
59
You can't prove that in an individual, but you look at a population.
60
And we know that if you shift the population's IQ, You have more people needing special services, you have fewer geniuses.
61
The results of those early studies inspired some researchers to try
62
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,
63
or even at the lower levels we fluoridate our water in the U .S.
64
Over the years, some studies have found an association between IQ and lower fluoride levels.
65
Some haven't.
66
Leaving scientists, particularly in the dental and epidemiological communities, divided on the issue. But
67
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.
68
In it, a small number of high -quality studies from outside the U .S found an association between lower IQ
69
and water fluoride levels below 1 .5 milligrams per liter.
70
But the small number of studies meant
71
that they weren't able to draw conclusions about the levels that we fluoridate water in the U .S.
72
I called Bruce Lanphier back up to make sense of the results.
73
Hello again.
74
The meta -analysis is really a way to synthesize
75
and quantify the high -quality studies and the low -quality studies and try to make sense of it.
76
Because otherwise, what you're left with is, well, these studies, which are my favorite studies, said this, and that confirms my belief.
77
And these studies, which did that, don't confirm my belief, and clearly they're wrong.
78
below 1 .5 milligrams per liter were associated with lower IQ,
79
translating to a loss of 1 .6 IQ points per 1 milligram per liter of fluoride in urine.
80
the totality of exposure that people have.
81
And that's how we measure risk.
82
From total exposure, not from one isolated source.
83
Bruce explained that the fluoride we put in our water is just the minimum amount of fluoride we all consume.
84
Black and green tea leaves have high fluoride content.
85
A variety of food like potatoes and canned shellfish has fluoride in it.
86
The pesticides on our food can have fluoride in it too.
87
We consume fluoride if we accidentally swallow toothpaste or mouthwash.
88
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
89
that has natural fluoride concentrations even higher than 1 .5 milligrams
90
per liter you Experts were particularly concerned about infants who drink formula.
91
Almost their entire diet is fluoridated water and dry formula that can have fluoride in it too.
92
And about pregnant people who can pass all of this fluoride intake to a fetus.
93
We oftentimes see exposures that exceed 1 .5, and in some cases in pregnant women during the third trimester.
94
We saw levels much higher.
95
So what do we make of all of this information?
96
First of all, topical fluoride is essential for keeping our teeth healthy.
97
And for non -pregnant adults, there is no evidence that ingesting fluoride is harmful.
98
There is some evidence that pregnant people, babies, and young children should be aware of their overall fluoride intake.
99
to feed their babies to make it with water that doesn't have fluoride on it.
100
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.
101
So it's a confusing time for understanding these risks and benefits.
102
I am a believer in the precautionary principle, which does not say you act in the absence of evidence.
103
It says you act in the presence of concerning evidence.
104
And my reading of the literature is that there is enough data to say there is concern.
📺 同频道
B21
How bite marks made one man a murder suspect | Part 1
IELTS PrepTOEFL PrepUniversity Students
B22
How Vladimir Putin won Republicans' approval
IELTS PrepTOEFL PrepUniversity Students
B28
How to solve problems like a designer
Business EnglishUniversity StudentsWorking Adults
B2Why Latino voters have turned on Trump | America, Actually
Business EnglishDaily ConversationUniversity Students
B26
Five things you need to know for the 2026 midterms | America, Actually
Business EnglishDaily ConversationUniversity Students
B24
Why are weddings so damn expensive?
Business EnglishDaily ConversationUniversity Students
B21
Are headphones destroying our hearing?
Daily ConversationUniversity StudentsWorking Adults
C11
How to be less neurotic | The Gray Area
Daily ConversationUniversity StudentsWorking Adults
B22
We’re already using AI more than we realize
Business EnglishDaily ConversationUniversity Students
B22
The origin of the '80s aesthetic
Daily ConversationUniversity StudentsWorking Adults
B217
Why “Buy one, get one free” isn’t a great deal
Business EnglishWorking Adults
B22
How F1 drivers survive their own cars
Business EnglishUniversity StudentsWorking Adults
B210
Why 350°F is the magic number for baking
Daily ConversationUniversity StudentsWorking Adults
B26
How did pink become a girly color?
Daily ConversationUniversity StudentsWorking Adults
B22
The real reason Boeing's new plane crashed twice
Business EnglishDaily ConversationUniversity Students
B21
Food waste is the world's dumbest problem
Business EnglishDaily ConversationUniversity Students
B21
Why AI art struggles with hands
Daily ConversationUniversity StudentsWorking Adults
B22
How the rich avoid paying taxes
Business EnglishDaily ConversationUniversity Students
B2What's safe to eat now?
Business EnglishDaily ConversationUniversity Students
B25
Zohran Mamdani on his first priorities as NYC mayor (Full video interview)
Business EnglishDaily ConversationUniversity Students
✨ 推荐视频
C1115
16 句
Can Earth Run Out of Water?
IELTS PrepTOEFL PrepUniversity Students
C11
284 句
Why do people smoke?
IELTS PrepTOEFL PrepUniversity Students
C164
13 句
What the Flu Does to Your Body
IELTS PrepTOEFL PrepUniversity Students
C13
33 句
Should social media platforms censor hate speech? | Nadine Strossen | Big Think
IELTS PrepTOEFL PrepUniversity Students
C14
41 句
The Building Blocks of Everything: Matter & its Properties
IELTS PrepTOEFL PrepUniversity Students
B110
24 句
Phát âm chuẩn cùng VOA - Anh ngữ đặc biệt: New Food Safety Rules (VOA)
American AccentIELTS PrepTOEFL PrepUniversity Students
B22
31 句
Mark Ruffalo on New York State's Environmental Leadership
IELTS PrepTOEFL PrepUniversity Students
C11
114 句
Education in America
IELTS PrepTOEFL PrepUniversity Students
C13
259 句
We've Been Using The Wrong Science In Court For 50 years
IELTS PrepTOEFL PrepUniversity Students
C12
43 句
Rubio: This Is What We're Doing To Protect The U.S. From Ebola
IELTS PrepTOEFL PrepUniversity Students
B2193
28 句
Why should we care about coral reefs?
IELTS PrepTOEFL PrepUniversity Students
C12
42 句
Are We Eating Better – C1 English Listening Test
IELTS PrepTOEFL PrepUniversity Students
为什么要通过这个视频练习口语？
练习口语是学习英语的重要部分，通过与实际的对话或讲解进行模拟，能帮助你更快的掌握语言的使用方式。这个视频围绕氟化物是否应添加到饮用水中展开，提供了丰富的科学知识和公众健康讨论。这种主题的复杂性不仅让你学习到专业词汇，还能帮助你提高逻辑表达能力和口语流利度。通过与视频内容互动，学生能够在真实的语境中实践口语，同时也能增强听力理解能力。
语法与表达方式分析
在视频中，讲者使用了几种重要的语法结构，这些结构可以帮助学习者提升语言表达能力：
- 条件句：例句“如果我们喝的水没有氟化物…”这样的语句可以帮助学习者了解如何表达假设和条件。
- 被动语态：例句“氟化物被添加到水中…”使学习者理解如何强调动作的接受者，而不是执行者。
- 比较级：提到“比以往的牙齿健康情况”，这帮助学习者学习如何进行比较表达。
- 定语从句：例如“科学家正在研究的影响”，学生可以通过学习如何使用定语从句来加深对名词的描述。
常见的发音陷阱
在视频中，有些词汇和短语可能会对学习者造成发音困难：
- fluoride（氟化物）：注意元音的发音和重音位置。
- tooth decay（蛀牙）：发音时两个单词的连读可能会使初学者感到挑战。
- dosage（剂量）：这个词在不同的语境下可能发音会有所不同，弄清楚其在句中的语调很重要。
- remineralizing（再矿化）：这个长单词可能会让学生在发音时感觉走音，特别是在快速讲话时。
通过模仿视频中的发音，你不仅可以提高英语发音，还能有效地提升口语表达能力，成为更自信的英语使用者。运用看YouTube学英语的方式，让你的英语学习变得更加生动和有趣。
视频中的语法
说话人最常用的结构，并附上视频中的原话：
| 结构 | 视频中的用法 |
|---|---|
| 定语从句 who / which + 从句 — 补充说明人或事物 | cavities, which is · children who grew · studies, which are |
| 现在完成时 have/has + 过去分词 — 过去发生但与现在仍有关联的事 | have stopped · we've learned · have found |
| 被动语态 be + 过去分词 — 强调发生了什么，而不是谁做的 | being considered · were associated · is fluoridated |
什么是跟读法？
跟读法 (Shadowing) 是一种有科学依据的语言学习技巧，最初开发用于专业口译员的培训，并由多语言者Alexander Arguelles博士普及。这个方法简单而强大：您在听英语母语原声的同时立即大声重复——就像是一个延迟1-2秒紧跟说话者的影子。与被动听力或语法练习不同，跟读法强迫您的大脑和口腔肌肉同时处理并模仿真实的讲话模式。研究表明它能显着提高发音准确性，语调，节奏，连读，听力理解和口语流利度——使其成为雅思口语备考和真实英语交流最有效的方法之一。