(intense music)
- 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 Seventh Ward,
were being exposed to a dangerous toxin.
Most notoriously, lead paint.
(gentle music)
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.
(babies chattering)
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.
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 affects 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.
(dynamic music)
Shockingly, that lead 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 longterm 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.
(chiming music)
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 four points lower in IQ tests.
(menacing music)
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 longterm 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,
the 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
in 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.