[ Clock ticking ] -If you were born in 1900, you could expect to live, on average, just 32 years.

Today, global life expectancy is more than twice that.

It's one of the greatest achievements in human history.

♪♪ -This is the story of the ideas that have in the space of just a century or two changed what it is to be us... by transforming the kind of lives we might live... no longer short and under the shadow of disease, but healthy and long.

I'm David Olusoga, a historian.

I have to say, it does look like the sort of laboratory you see in the "Frankenstein" movie.

-And I'm science writer Steven Johnson.

-The average Black American lives three and a half years less than the average American.

-That, to me, is just really shocking.

-We're investigating the forgotten heroes of global health.

-The scientists, doctors, researchers, and activists who touched billions of lives.

One of their most revolutionary ideas is using data -- the daily tracking of numbers to help stop epidemics in their tracks.

Today, as the world grapples with another deadly pandemic, we reveal how data became one of the most powerful tools we have in the fight for extra life.

♪♪ ♪♪ -I'm in the U.S., and David's in the U.K., and given what's going on in the world, we're meeting online to explore the story of data.

There he is.

-Hey, there.

-Good morning, David.

-How you doing?

-You're looking well.

-Thank you.

If you cast your mind back to the early weeks of the COVID-19 pandemic, what you kept hearing from scientists is how little we knew, that this was a novel virus.

By its nature, we didn't have the information, and it was all about gathering data.

-There was no hope of a vaccine.

There were no therapeutics that could help us.

What we did have were numbers, right?

We had information about where the virus was, where it was spreading.

-When we picked up a newspaper, we didn't look at the sports pages or the stock market.

We just wanted to know data about this disease.

-And that gave us clues about how to potentially protect ourselves.

-I was on a journey around the Caribbean and North America at the time, and we literally -- You would leave one country, and you would look in the airport on your phone at what the infection rates were in the country you were landing at.

So data became the thing that underlied our daily actions.

-This kind of data analysis is something that has been going on quietly behind the scenes for more than a century, looking for patterns of the spread of disease, calculating risk, and using that data to extend our lives.

-And those innovations, just like vaccines and just like drugs, they have inventors and pioneers that very often we've forgotten about.

♪♪ This use of data to fight disease has its roots in the epidemics that plagued Victorian Britain.

It's the year 1866.

Here in the East End of London, in the neighborhoods surrounding the River Lea, there are reports of an outbreak of cholera, and back in the middle of the 19th century, this is one of the most polluted rivers in Britain.

And it runs through one of the most densely-populated neighborhoods in what was then the biggest city on earth.

♪♪ News of cholera is making the headlines.

♪♪ 20 deaths by mid-July.

♪♪ A week later, it's 308.

♪♪ By August, the weekly death toll has reached almost 1,000.

The city is under attack, and people are terrified for their lives.

Cholera is given many nicknames, but some people call it "the blue death," and that's because it turns the skin of its victims a gray blue color.

It begins just like a mild case of food poisoning.

But those affected soon experience extreme bouts of vomiting and diarrhea, and some die within 48 hours of extreme dehydration.

The London of the mid 1800s had already been through three cholera epidemics.

And with so many people dying in childhood, life expectancy is struggling to get above 37 years.

♪♪ Watching as the mortality figures go up and up with each week is a doctor called William Farr, but he's not out treating patients.

He's a medical statistician.

Farr is responsible for keeping records of births, marriages, and deaths in the United Kingdom.

But he...

He has a much bigger agenda because what William Farr understands is the power of numbers when presented in the right way to tell stories and even to solve medical mysteries.

These are William Farr's life tables.

They are raw data, numbers, arranged into columns.

And while all of this information can seem a bit mundane, what it allowed Farr to do was to see the patterns in the numbers.

He doesn't just want to know when someone died.

He wants to know the cause of death.

He wants to know the age of death.

He wants to know their occupation.

And he wants to know where they lived.

And he was able to transform these raw numbers to diagrams like these.

What Farr was doing was revolutionary.

♪♪ No one had gathered and analyzed data in such a sophisticated way, and he hoped to find clues to help him understand the latest cholera epidemic.

So, this one is an attempt to plot all the deaths in England from cholera each day of the year.

And this this shape, this curve, we're very familiar with that.

And it's called Farr's Curve, because it was William Farr who discovered that epidemics rise and fall in a symmetrical pattern.

And so today, when we talk about the curve of an epidemic, when we talk about flattening the curve, we are harking back to the work that William did in the middle of the 19th century.

♪♪ The strange thing about Farr's work, though, is his great invention, the curve, is terrifying.

-The terror that comes from exponential growth, that that upward curve of an outbreak that Farr documented, the speed with which an outbreak can go from two people sick to 200 people sick to 2,000 people sick.

-I think one of the particular horrors of that moment in 1866 is that no one's got any delusions now about just how awful this could be, because this is the fourth of the great Victorian cholera epidemics.

There's all sorts of doubt and questions about the nature of this disease, but there's absolute certainty about one thing, is it is a killer.

-And in 1866, he's doing a different kind of investigation here in the sense that he's using data in real time to investigate an outbreak as it is unfolding.

And in this way, it's very similar to the use of data in the COVID-19 pandemic.

He's looking for evidence that can show who was getting sick, who was dying, and most importantly, where is the disease coming from?

-The cholera epidemic of 1866 is a medical mystery, and it comes as a shock because during the previous decade, the disease had been largely dormant in London.

But it is also unexpected because during that decade, enormous defenses had been built to protect the city from disease.

♪♪ Following the last cholera epidemic a decade earlier, a vast system of tunnels had been built beneath the city to rid London of its foul-smelling, disease-causing sewage.

♪♪ Those defenses consisted of machines like this giant pumping engines, and they were connected to 82 miles of underground sewers, and building all of this was an epic feat of sanitary engineering.

This was the biggest, most sophisticated sewage system in the world.

Since the discovery that cholera could be caused by drinking contaminated water, it was thought that ridding London of its sewage would also rid it of the disease.

There was real hope that this, all of this, surely that was enough to ensure that there would not be another epidemic of cholera.

♪♪ Farr was puzzled that the outbreak was still growing.

♪♪ What Farr now knows for sure is that the building of London's sewers hasn't driven cholera out of the city.

What he doesn't know is why.

♪♪ William Farr is determined to solve this mystery, using the thing he loves most -- data.

Knowing that cholera is transmitted in water, he does an unusual thing, he adds a new category of information, the water company that supplies each victim's drinking water.

The data shows a clear pattern.

Far works out that the great majority of the cholera cases are connected to the East London Waterworks Company, and so immediately, he has notices put up in the affected areas, warning people not to drink water unless it's first been boiled.

♪♪ Using the mortality reports to work backwards in time... ...the data reveals the first deaths took place in June, weeks before the peak of the epidemic... ♪♪ ...helping to close in on the source of the outbreak.

♪♪ A laborer named Hedges had been living in a house on the edge of the river in a part of London called Bromley-by-Bow.

A group of investigators are sent to examine the sanitary conditions at the address.

What they find is that the toilet has been expelling wastewater directly into the river.

Contaminating one of the water companies nearby reservoirs, which hadn't been properly isolated from the river.

The result was the deaths of over 5,500 people.

♪♪ Within a few weeks of Farr's investigations, the Waterworks are cleaned up and the source of the outbreak is stopped dead in its tracks.

♪♪ William Farr's meticulous work led to something of enormous significance.

Cholera, King Cholera, the disease the Victorians feared more than any other, the disease that stalked their nightmares was finally driven from the city of London, not by a new vaccine, not by a new medicine, but by data.

And it was never to return.

-The legacy of William Farr is around us everywhere in the age of COVID-19.

-Yeah.

-I remember watching the daily briefings, and the centerpiece of those briefings was Farr's Curve.

-If you look at the curves of outbreaks -- you know, they go big peaks, and they come down.

What we need to do is flatten that down.

That would ultimately have less deaths.

-The most important question in the world at that point was, when was that curve gonna crest?

And whether we could flattened it by washing our hands and social distancing and wearing masks and all of the different interventions we made.

We were all chasing the shape of that outbreak.

-And we all learned something that those experts already knew, which is that there's a horrible time lag.

And when we see infections rising, we know that there's -- nothing can stop the fact that the death rates will be rising in the future.

-By the time you are tracking the deaths, the outbreak has already been unleashed in the society around it.

So the question is whether we can use the same kind of approach, but using new technology to get earlier in the cycle, not just tracking deaths, not just tracking hospitalizations, but actually tracking emergent infections potentially before the community is even aware that an outbreak is happening.

Because if you can do that, then you can create a kind of early warning system that might actually prevent the outbreak from happening at all.

♪♪ Amazingly, one of the most promising sources of data for detecting outbreaks early is precisely the thing that used to kill us in the days of cholera.

Public health officials and researchers are tracking the spread of COVID by looking for signs of the virus in sewage.

It's a new approach that may actually help us get ahead of William Farr's epidemic curve by detecting rising case loads before outbreaks spiral out of control.

♪♪ This is one of the largest wastewater treatment plants in California... ♪♪ ...handling the sewage of over 740,000 people.

♪♪ Eileen White is in charge of the facility, and she's at the forefront of trialing this new approach to tackling COVID-19.

-When a person gets infected with the coronavirus, they may not feel symptoms for several days or a week, but when they're infected, whether they're symptomatic or asymptomatic, they're gonna shed the virus in their poop.

So when a person uses the bathroom at home, they flush, and all that sewage flows to this main wastewater treatment plant.

♪♪ So, that sample then comes into our lab and then our scientists in the lab put it into our PCR machine that can actually quantify the presence of the coronavirus in the sewage.

So this can give the public health professionals a good week's advance notice of the presence of coronavirus in a region.

-This is an incredible early-warning system revealing hotspots of coronavirus before people even have symptoms.

We should pause here just for a second to appreciate and understand the technology that makes this possible.

One of the relatively new technologies that has been absolutely crucial in fighting COVID-19 and in collecting data about COVID-19 is something called PCR, or polymerase chain reaction, -And that acronym, PCR, along with flattening the curve, that became part of millions of people's lives during the pandemic.

Because if you went for a COVID test, the chances are it was a PCR test.

But that same technology can also be used to analyze sewage.

-You can use it to seek out tiny little snippets of genetic code, and there would be otherwise, like, a needle in a vast haystack.

And what it does is, basically, it makes copies of those little genetic snippets.

It's sometimes called a kind of genetic photocopier.

And by amplifying that code, it brings it up to a signal that's loud enough that it can be detected.

Sewage sampling can identify coronavirus at levels as low as one case per 10,000 people and even different variants.

-We're in the control room, and so we have 1,600 miles of sewer pipe.

We can sample from any one of our large pipes, and that will tell us what's happening in a particular area.

And you can see early on where the case loads were pretty low.

You can see the peaks that we had over the summer And definitely it shows the recent spike that we've seen in early December, after the Thanksgiving holiday.

-The technique can also be used to sample sewage from individual buildings like nursing homes, schools, and student housing.

-When you pick up the sewage signal, that's an indicator to the public health professionals that you want to go in, do individual testing, and then isolate and quarantine people.

And it'll be even more important as the vaccines are rolled out.

We can be using the wastewater surveillance data to find out where are we still seeing the presence of coronavirus in the community and maybe those people aren't getting vaccinated and maybe there needs to be a public outreach effort to inform people of the vaccine.

The public health officers have really seen how wastewater surveillance can be a cost effective tool in managing the global pandemic.

♪♪ -Sewage surveillance is a great way to identify infections in a community before they show up in official figures.

But what about in ourselves?

Is there any way of using data to detect COVID and other viral infections earlier in individuals?

I'm here in the hills above Stanford University.

-Extremely natural.

[ Both laugh ] Dr. Snyder's an expert in health and wearable tech.

♪♪ I've been lucky enough to enroll in his study that's trying to determine if smart devices can be used to detect COVID infection before symptoms appear.

Well, Michael, you are on the cutting edge of all of this technology.

I got to start just by asking how many different devices are you wearing right now, tracking your your body state?

-I think seven right now.

-Seven?!

-Yeah.

-I mean, I could see four.

-Yeah.

So, four is smartwatches.

This is actually an exposometer that will measure the various things that I'm exposed to.

I have a continuous glucose monitor on my side here, my smartphone.

Well, that's six, right?

No, that's seven, isn't it?

Yeah.

-So you have to budget like an extra half hour to go through security at the airport.

What's so powerful about your COVID study is this idea that you're able to detect the presence of an infection before people actually experience symptoms.

-Is that right?

-That's right.

Yeah.

So what happens is, when you get ill, your resting heart rate will jump up typically about seven to eight beats a minute.

It's true for COVID.

It's true for other kinds of viral infections, as well, Your immune system becomes activated, and that requires energy, elevated heart rate.

For a normal viral infection, it will jump up about 30 hours early prior to you feeling symptomatic.

♪♪ So this is our very first participant enrolled in the study.

That first red signal is when he felt symptomatic.

And the yellow signal is when we first told him something was up.

It turns out, if you look at the purple day there, that's actually when they're diagnosed with COVID.

The red day is the day before it, when they first had symptoms.

But if you look at the resting heart rate, you'll see it jumps up nine and a half days before they were symptomatic.

So, this person's been ill for nine and a half days without knowing it, spreading the virus, presumably, when he could have been caught with a smartwatch.

-That's incredibly powerful.

Part of what you're picking up is the long period of asymptomatic.

-That's right.

-Which is so distinctive of this virus.

-That's right.

So right now, 20% of the U.S. has a smartwatch -- 50 million people.

And all you have to do is download an app, and the signals of elevated physiology can alert you.

So it can really reach, we think, the entire world, in fact.

♪♪ -This wearable tech can monitor heart rate and rhythm, blood oxygen levels, skin conductivity, and sleep patterns at night, searching the data for anything out of the ordinary and triggering an alert to go see a doctor.

In the future, it's hoped that the tech will be able to distinguish between different viral infections such as COVID-19 and the flu, and even track how people are aging.

-And what we've discovered is actually, by following people over time, that people are aging differently.

It's like a car.

You know, your car gets older as it goes along, but some parts break down first.

Maybe those are the ones you can pay most attention to.

You might exercise more.

You might get checkups and maybe you have something going on where you would like to intervene, possibly with drugs, to actually, you know, better improve your heart health.

I don't know if a wearable will tell you if you have early cancer or not, but believe it or not, we're gonna give that a try, too.

♪♪ -Now, I don't want to get all Pollyannaish about the latest Silicon Valley gadgets.

I mean, the truth is that wearable tech is not gonna be the same level of breakthrough as, say, vaccines.

But if you think about it, conditions like cancer, heart disease, and diabetes are responsible for two thirds of deaths in the United States.

And we know that early detection is key.

So if monitoring wearable data can help us pick up these conditions earlier, that could help us all live longer lives.

♪♪ So, I'm curious where you come down on this, David, I mean, there's this kind of spectrum in the debate between the folks who are willing to share every intimate detail about their health.

On the other hand, you have a growing movement of people who believe that sharing that much information with big tech is potentially an invasion of our personal liberty.

-I think what's been interesting is where people stood on that position before and after the pandemic.

If the collection of data could be shown to lower death rates and infection rates, as arguably it has been in countries like South Korea, where they used mobile phone data to enforce lockdowns, are you willing to have that level of intrusion in your life and in your digital life if it means that you can live in a country where your other liberties, like the liberty of being able to go and have dinner with your family or get on the train or get on a plane, whether that exchange of liberties is worthwhile.

-It's a great point, but it's also about exposing places where the outcomes and particularly in terms of life expectancy, have been severe between one part of a community and another.

-We see these disparities in African-American but also Hispanic communities.

-Right.

-And those inequalities have been stark when it comes to COVID-19.

♪♪ -I'm Dr. Vanessa Apea.

I'm a consultant, and I work in East London.

And a lot of the work that I do in terms of my research is looking at our communities and understanding how health inequalities play out.

♪♪ So if I were going to paint a picture of East London, what I would say is that it's beautiful and vibrant.

We've got Indian populations.

We've got Bangladeshi populations.

We've got Pakistani populations.

We've got Black African, Black Caribbean.

So it's a real mix all living together.

But on top of that, you've got pockets of definite affluence, and then you've got pockets of definite deprivation, as well.

And within that, you will see any walk of life coming through into the hospital.

-Dr. Apea was among the first to study the impact of COVID-19 on different ethnicities.

She followed the outcomes of over 1,700 patients admitted to hospitals in East London.

-So if we look at the top graph, we're looking at days from hospital admission.

So we're looking up to 30 days.

And then when we look at the different curves, what we're looking at is different ethnicities by color.

So Asian is blue.

Black is red.

And green is white.

If we were going to say that all ethnicities had the same outcome, you would expect all the lines to be on top of each other.

So they would all come together and follow the same trajectory.

But when you look at this, there is a difference.

there is a significant gap.

♪♪ When we looked at the survival at 30 days, we saw that for those of Black and those of Asian ethnicity, we saw an increased risk of death.

♪♪ When we look at those of Black and Asian ethnicity, they were younger and fitter and were dying from COVID-19.

And for me, it was extremely sobering.

One of the key questions is, if we are seeing differences in outcomes of COVID-19 between white, Asian, and Black communities, why are we seeing these differences?

There's a natural, immediate tendency of many people to just focus on biology.

This is really reductionist.

It's not me being Black.

It's the racism that I'm experiencing as a result of being Black that affects my health outcomes.

-The idea that these varying outcomes are due to genetic differences between ethnicities is completely refuted by science.

-They grow the DNA and separate its parts so a computer can read its chemical sequence.

It's the human genome, the genetic spelling of man.

-In particular by the work of the Human Genome Project, led by Dr. Francis Collins, who in 2001, published the first DNA map of the human genetic code.

It's our instruction book for human biology, and the notion that we could actually read that book in any of our lifetimes would have been considered unthinkable 20 or 30 years ago.

-I know you're saving the world from a pandemic.

And so... -With a lot of help from a lot of people.

-Let's start with the Human Genome Project.

What has that revealed to us about the connection between health outcomes, genetics, and race?

-Well, it didn't become clear with that first reference human genome, because that was just one actual patchwork of four or five different people.

Now, gosh, there's hundreds of thousands of genomes.

And we've worked really hard to be sure that that's inclusive, including now a lot of genomes from Africa, which is the cradle of humanity.

So here's the bottom line.

We're all 99.9% the same.

We're incredibly similar.

We're one family, and there's more variation within a group, let's say white Americans, than between groups like a single white American and a single African.

-So, given what we know then about the lack of kind of pronounced genetic differences between racial groups, when we see pronounced differences in outcomes, as in the COVID crisis, right.

Where we, you know, see this disproportionate impact on the African-American community in the United States, for instance, how do we interpret that?

-Most of what we see in health disparities is on the basis of something other than DNA variation.

This is primarily on the basis of environmental exposures, and we can see that that's a reflection of their social environment.

-So it's not genetic, but what is driving the differences that we see?

-I believe that the key thing is the social context in which people are living.

Those from Black and Asian communities are more likely to live in a multigenerational household in a smaller space, so your risk of transmission and vulnerability goes up.

♪♪ And Black and Asian and minority ethnic communities, we see that they are disproportionately more in frontline roles, in which people need direct, face-to-face contact.

So it's about high risk of exposure, higher vulnerability.

And then also that's translated into more severe disease and higher rates of death, as well.

-What COVID-19 did was it illuminated, focused their attention on disadvantages based on race that were already there, because the reason for those disparities has got nothing to do with the biology of people of different races from different parts of the world and everything to do with racism.

This is about how racism and racial disadvantage left certain population groups vulnerable, more vulnerable than other people.

-And now we're starting to get a sense of the impact of this on overall life expectancy, right?

So in the first half of 2020, we believe now that overall life expectancy in the United States dropped by just under a year for the entire population.

But for African-American males, it dropped by nearly three years.

So, it's an extraordinary difference, a real gap that you can see in the data.

-It's a horrible thing, and because those communities have been suffering racial disadvantage for decades, that's taken a toll long before the pandemic arrived.

So they're more likely to be suffering from preexisting conditions.

-That's such an important point in thinking about the long-term story of human health, right.

Because so much of it is about seeing the invisible pathogens, right, seeing the virus under the microscope or the bacterium under the microscope and identifying it as the culprit that is causing people to get sick.

But there's a whole other side to human health, which is about the environment that people live in and the conditions that shape their day-to-day lives.

And in fact, this is a part of the detective work of data collection that dates all the way back to the 19th century, as well.

♪♪ ♪♪ So, it's a block that way.

Here it is.

Almost every major city has multiple monuments to lives lost in military conflicts, but you almost never see memorials to the lives saved thanks to medical or public health breakthroughs.

This little plaque commemorating the work of W.E.B Du Bois is the exception.

Now, Du Bois is famous today for his work as a sociologist and a political activist, but he was also an unappreciated pioneer in the study of human health, thanks to work that he did in the 1890s here, in Philadelphia's 7th Ward.

♪♪ ♪♪ Du Bois was an aspiring sociologist.

And also something of a prodigy.

He was the first African-American to get a Ph.D. from Harvard, and at the time, he was reading this openly racist academic literature that portrayed African-Americans as intrinsically unhealthy or criminal.

♪♪ But Du Bois was determined to delve deeper into the problem, using data.

The opportunity arose when he was invited to study Philadelphia's 7th Ward, an area with a large African-American community, ravaged by poverty, crime, and high child mortality.

♪♪ The white establishment framed these very real problems in racist terms, pointing to alleged deficiencies in African-Americans.

Du Bois moved to Philadelphia and took on the task of documenting the social and health problems of the 7th Ward.

One of the key questions he wanted to answer was why life expectancy in the 7th Ward was so low.

He spent countless hours exploring this neighborhood, visited over 2,000 homes, interviewing their occupants, surveying their living conditions, poring over documents in the library, and amassing a mountain of information.

♪♪ With this data, Du Bois created this extraordinary color-coded map of the 7th Ward, documenting all the homes and dividing them up into different economic classes.

And what the data revealed was very telling.

♪♪ 87% of residents had no access to an indoor toilet.

♪♪ Almost none had hot water.

And overcrowding was rife with as many as 10 people living in a single room.

To make matters worse, landlords were charging higher rents to Black residents, exacerbating their poverty along with their poor health.

It all combined to mean that, in Philadelphia, the likelihood of a Black child dying before the age of 15 was twice that of a white child.

♪♪ Du Bois published that data and the map in a groundbreaking book.

It painted a picture of what today we would call systemic racism.

If the life expectancy of African-Americans was going to improve, the entire environment and economic system around them was going to have to be changed.

♪♪ Du Bois wrote, "The most difficult social problem is the peculiar attitude of the nation towards the well-being of the race.

There have been few other cases in the history of civilized people where human suffering has been viewed with such peculiar indifference."

Du Bois proved that the health problems in the 7th Ward weren't caused by some natural inferiority, but rather that the system itself was rigged to shorten black lives.

♪♪ Then in 1900, Du Bois took an exhibition of his work to the World Expo in Paris, an international showcase of cultural and scientific achievement, where he revealed startling visualizations of the data he'd collected.

♪♪ ♪♪ This towering achievement of brilliantly designed data opened the world's eyes to the reality of Black lives.

♪♪ When I look at these bold and colorful images, it's almost like looking at modern art, but it's art in the service of social progress, not so much speaking truth to power as it is using data to reveal truths to make the invisible visible.

♪♪ Du Bois is such an inspiring figure on so many levels, but in terms of looking at these environmental causes, he was decades ahead of everyone else.

I mean, it's just incredibly visionary work.

-He really believed that if America was forced to confront these inequalities, the contribution and the suffering of African-Americans could be brought to American and world attention, that it would bring about change.

Wouldn't it be wonderful if you could say these data visualizations were the moment in which America confronted the legacy of slavery and racism, and there was a kind of parallel America that never happened, that could have happened.

So it's kind of heartbreaking that his warnings weren't heeded.

♪♪ -Linda Villarosa is a journalist who investigates today's racial inequalities in health.

We've seen with the COVID crisis that Black Americans are far more likely to suffer severe illness or die.

-African-Americans just simply have poorer health outcomes.

In all of the top-10 causes of death, we die younger and more often.

Several months ago, before COVID, I took my mother to Chicago, where she was born, and I had looked at the statistics.

Where she grew up in Englewood, a section of Chicago, people lived to age 60.

That's the average age.

But 9 miles north, in the wealthiest part of Chicago, people lived to age 90.

So, there's a 30-year age gap.

-And that to me is just really shocking.

-This isn't about some inherent disability or something wrong with your genetics.

It's actually a problem of society.

-I think one of the most important new scientific breakthroughs is this idea of weathering, that there's kind of this long-term stress response that leads to these health outcomes.

-Weathering is the idea that your body is fighting against discrimination.

Whether it's discrimination by the police, whether it's discrimination in housing, whether it's discrimination in employment, or everyday insults, your body physiology changes.

The fight or flight syndrome kicks in, which is healthy.

That's good, but it shouldn't kick in over and over.

-Right.

-So you shouldn't be having your heart rate go up.

You shouldn't be having your blood pressure rise.

You shouldn't be having your stress hormones kick in over and over again.

And so those wear away at the systems of the body and make you prematurely age at a cellular level.

-Right.

-It's hard for a society to admit that racism is harming the bodies of people who are discriminated against.

-So add all those things up together, and you get this really disproportionate impact of the disease.

That's that's the crisis, what we need to be focusing on.

-And that is exactly what Du Bois was looking at in 1899.

So the fact that we're still looking at it is alarming, but it's also promising that we understand it more.

We're acknowledging the problem more and that the next generation of health care providers is trying to push back against.

♪♪ -I think we have to assume that in any given age, even our own age, despite all our advanced knowledge, that we have our own blind spots, and that in 10 or 20 years, we're gonna turn around and say, oh, that should have been obvious to us.

And that was how I felt a little bit when I first heard about the theory of weathering.

Something in the society, something in our assumptions about how health works kept us from seeing it.

-But those insights can only come out of data, out of observation, and it's usually observation that's taken place over decades.

And also these ideas emerge into worlds in which they're contested.

They don't stay in peer-reviewed journals or in universities.

They emerge into a political world.

And very often, these ideas have to fight for their existence.

They have to win people over.

♪♪ -It's the late 1950s.

An aspiring young doctor, Herbert Needleman, is working at Philadelphia's Children's Hospital, Needleman begins seeing high numbers of kids admitted with lead poisoning, and he's completely mystified.

Because at the time, it was believed only exposure to very high levels of lead could be harmful.

Needleman's office overlooked a school playground here in Philadelphia, and that vantage point gave him a hunch.

Perhaps even low levels of lead could build up over time in the body, creating hidden chronic health problems.

♪♪ Needleman realized that if his theory was right, a whole generation of kids growing up in crumbling urban neighborhoods, like here in Philadelphia's 7th Ward, were being exposed to a dangerous toxin, most notoriously lead paint.

♪♪ It was especially disturbing that baby cribs were painted with lead paint.

When it chipped or was chewed on, the lead had a sweet taste, making it particularly enticing.

♪♪ If Needleman was right, almost everyone was being exposed in some way.

Environments with lead paint or lead water pipes or lead pollution from gasoline cars could be incredibly damaging for their inhabitants.

And so, like a good detective, Needleman went looking for proof.

He needed data and lots of it.

And the first step was to find a measurement hidden in the human body that could reveal long-term lead exposure.

♪♪ Lead effects many organs in the body, but it accumulates over time in the bones.

You can see the lead in the bones here in these telltale white lines of lead poisoning at the joints.

Which can then leach into the bloodstream and be absorbed by the brain.

♪♪ Shockingly, that led causes areas of the brain to shrink, impairing memory and learning.

♪♪ And because their brains are developing so rapidly, children are particularly vulnerable.

♪♪ To prove that lead was building up in children over time, causing long term harm, Needleman needed a way to measure the level of lead in their bones.

But there was a problem.

Taking bone samples from a living person is an invasive and painful procedure.

Then he had an idea.

Needleman's data came from something that kids leave under their pillows all the time -- baby teeth.

He collected the teeth directly from the kids themselves and from dental clinics, ultimately amassing such a large supply that he became known locally as the Tooth Fairy.

♪♪ It allowed him to track children's lead levels over many years -- something that had never been done before, The data, published in 1972, was shocking.

Needleman discovered that inner-city kids living in older buildings and exposed to greater traffic pollution had five times more lead in their bodies than kids from the suburbs.

Now Needleman needed to prove that lead exposure caused harm.

He analyzed the teeth of over 2,000 children looking at lead levels, and then he gave a battery of tests to the children with the highest and the lowest levels -- IQ tests, verbal tests, surveys of their teachers about the kid's behavior.

The data was clear.

Children whose exposure to lead was highest scored 4 points lower in IQ tests.

♪♪ And when he continued to study the children as they grew up, he found greater high school dropout rates, poorer hand-eye coordination, and other persistent problems even a decade later.

-The data showed conclusively that lead was harming the long-term health of children.

So, this should be the tipping point, the moment the industry is forced to remove lead from household products and petroleum.

♪♪ But rather than accept all this, that lead industry instead decided to try and discredit Dr. Needleman, and they did this by attacking his most important asset -- his data.

♪♪ Needleman testified that he had made a small mistake in one of his mathematical calculations.

This was in the years before computers were used to process big data sets.

But that mistake didn't change his findings.

But then his own university launched an investigation.

They locked him out of his files and prevented him from accessing his own research.

♪♪ -I'd like to now call forward to testify Dr. Herbert L. Needleman.

-When I last testified here in 1979, there was considerable disagreement about the impact of lead at low dose on children.

There's been an explosion of scientific knowledge from human studies and from the animal laboratories about the effects of lead.

-Needleman's name was eventually cleared.

His research, along with all of the other studies that relied on it, became accepted as scientific consensus.

And we now know that there is no safe level of lead in the human body.

His data ultimately resulted in the removal of lead from paint and other household goods.

-And there is a broad consensus on the part of everybody except the lead industry and its spokesmen, that lead is extremely toxic at extremely low doses.

-Thank you so much.

-But it took until 1996, over three decades after his research had begun, for the sale of leaded gasoline to finally be banned in the US.

It was not banned in the U.K. until the year 2000.

More than 400,000 people a year in America are dying because of lead that they ingested when they were children.

Now, they wouldn't be dying if at the beginning of this journey, the industry had got behind Needleman, rather than refuting his claims or attacking his personality, they'd listened.

The story of Needleman and the lead industry is in some ways very similar to another story of the 20th century, which is the tobacco industry's long-delaying strategy, fighting against data, fighting against medical research that showed first that cigarette smoking is unhealthy, then showed strong links to cancer.

-We saw very clearly at the beginning of the COVID-19 pandemic.

I mean, we had political leaders in the United States who did not want to test for the presence of the virus because somehow the rising caseload would make us look bad.

And that was just such a fundamental mistake, and and it betrayed the whole history of the role of data in extending our lives.

-And what would be really worrying if we see history repeating itself and data once again disguised or dismissed as opinion.

We've got a battle about air pollution.

We've, of course, got a global fight against the climate crisis.

Data is not our enemy.

-The truth is, you can't begin to think about solving problems, whether those problems are coming from natural threats, like viruses, or manmade threats, like pollution or smoking.

You can't begin to imagine a solution to the problem until you see the problem, and you can't see the problem without data.

-As the world grapples with another deadly pandemic, we reveal how changing our behavior became one of the most powerful tools that we have in the fight for extra life.

-At the molecular level, soap breaks everything apart.

At the level of society, it helps us to hold everything together.

-"How To Have Sex In An Epidemic."

-This is an historic document.

-Yeah.

-This is arguably the biggest story in human history, how we doubled our life expectancy.

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