- Today after decades of study, researchers have identified one factor that can significantly affect a child's development, performance in school, and even increase the risk of criminal behavior: exposure to lead.

Tainted water in communities like Flint, Michigan has attracted a lot of attention.

But for most children, that exposure comes from peeling paint and contaminated dust.

- About half a million children, most of them in poor neighborhoods have elevated levels of lead in their bodies.

Now some of you might be asking, didn't we deal with that decades ago when the U.S. government banned the use of lead in paint and gasoline?

The problems is, we left one question unanswered.

Who would pay for the clean up?

- [Host] In Providence, Rhode Island June Tourangeau is known as the Lead Lady.

(knocking) - I am a Licensed Practical Nurse and I have been working with lead poisoned children for the last 23 years.

Hi Elijah, hey how are you?

- [Host] Lead is an environmental neurotoxin and can cause brain damage, learning and behavior problems in children.

- So we'll do the developmental assessment.

- [Host] Elijah Riske lives in Rhode Island, one of only a dozen states that require blood tests for elevated lead levels in children.

- We go into the home because an important part of seeing the children medically is we need to see what's in the environment.

Once a child is poisoned, that's when action is started.

Do you find he says two or three words together?

- Not three, two sometimes.

- Two, okay.

Elijah, do you want to do my pen, you want to do it?

- [Host] The government says any elevated lead level is dangerous for children.

Elijah's, at 24 parts per deciliter, was off the charts.

Lead is so toxic, we put strict limits on using it in consumer products decades ago.

So why hasn't childhood lead poisoning gone away?

For much of the 20th century, lead was everywhere.

In gas, in exhaust from our cars, in water pipes, and house paint.

Neurologist David Bellinger studies its effects on the brain.

- Lead was viewed as an occupational hazard.

Childhood lead poisoning was first identified around 1900.

- [Host] We use lead despite the known risks.

While some European countries began removing lead from paint in the 1920s, here it was marketed as safe and clean.

- [Television Announcer] The danger of lead poisoning can be easily minimized by being careful to clean one's hands.

- [Host] And in 1925, after a temporary moratorium, the U.S.

Surgeon General resisted calls to remove lead from gasoline.

- [Dr. Bellinger] Much of the research was funded by industry and the thinking was that a child had to show clear signs of toxicity in order be harmed by lead and once a child recovered all would be well.

- [Host] But in the 1940s, independent researchers discovered that wasn't true.

- Most of them failed in school; they got in fights.

They clearly had residual neurological problems from their lead poisoning.

- [Host] As evidence mounted, lead was finally removed from house paint in 1978, and from gas in 1996.

Children's lead levels plummeted.

- The cumulative effect of these interventions has to be regarded as one of the handful of greatest public health successes of the last 50 years.

- [Host] But some were left behind.

Today at least half a million American children age five and under have dangerous amounts of lead in their bodies.

- State of Emergency has been declared in Flint, Michigan after high levels of lead were found in children's blood.

- [Host] Their plight was all but forgotten until the 2015 crisis in Flint, Michigan over lead in the drinking water.

- If you thought America's lead crisis was limited to a single town in Michigan, think again.

The fact is that lead is an epidemic.

- [Host] And most lead poisoning doesn't come from tainted water, it's from old lead based paint.

And one third of American homes with children under age six still have lead paint.

- So our state Capitol is almost directly across the street from where I used to live.

Those four windows right there, those are the four windows that I believe poisoned Sam.

- [Host] When Liz Colon was just 22 years old her family bought their first house, an old fixer upper in Providence, Rhode Island.

- A few months later Sam was diagnosed with lead poisoning.

He went to his routine visit at 12 months old and his blood came back at 36.

There was lead in everything, every painted surface in every room.

The backyard, he soil, the exterior.

We had to cover the windows in plastic, put duct tape on the doorways, anywhere there was a friction surface, just to make it temporarily safe for him to be able to come home.

- [Host] It didn't take long for Liz to become an advocate with the local Lead Action Project.

- 85% of our houses that was built before 1978, so the majority of our housing stock has a lead paint problem.

I wanted to be able to protect other kids from having to go through this.

It only takes this much dust to poison a child for life.

So Sam became the face of lead poisoning.

They had posters in doctor's offices and advertisements on buses.

- [Host] Sam was poisoned nearly 20 years after lead paint was banned.

In all that time, even though there was some federal grants to help home owners who qualified, we never developed a system to deal with all the paint that remained.

- The Department of Housing and Urban Development isn't doing enough to reduce the danger of lead poisoning for children.

- [Newscaster] America is doing little or nothing about it.

- [Newscaster 2] Looking for cost effective answers.

- One of the strictest lead laws in the state is not being enforced.

- There's still quite a ways to go.

Blood lead levels of kids have fallen significantly.

But now we know that essentially any blood lead level in excess of zero is problematic.

- [Host] Economist Ann Aizer analyzed lead tests and school data from Rhode Island children born between 1990 and 2004.

- When you link children's disciplinary infractions and test scores with their own blood lead levels you see a very clear relationship.

Children with an elevated lead level are in fact 20% more likely to have been suspended from school.

They show aggression and difficulty with impulse control and their test scores suffer.

- [Host] The data also shows who are most affected.

- Families that live in old homes, those are going to be the kids who are most likely to be exposed to high lead levels, and those are going to be poorer children.

- [Host] While the cost of making those old homes safe seems overwhelming Aizer says we're paying anyway by leaving them full of lead.

- We're paying for special education.

We are paying for school resource officers.

We are paying for the juvenile courts and we are going to see the manifestation of that in crime and educational attainment and employment and earnings later in life, unless we take steps to reduce those numbers.

- [Host] But taking those steps is expensive and difficult.

- We're going to test the bathroom.

Anything that comes up 1.0 and above is considered hot.

- [Host] Lead testing is done house by house, room by room.

The most dangerous spots include doors and windows where friction turns old paint to lead dust.

- This is 6.5 so that's pretty hot.

- [Host] Removing lead paint can cost thousands of dollars and even properly covering it up is beyond what many homeowners, landlords, or even states, can afford.

- Rhode Island is going after the makers of lead paint.

- [Host] Looking to fund clean up in 1999, the state of Rhode Island sued paint manufacturers claiming that by selling a dangerous product they had created what is called a public nuisance.

Attorney Bob McConnell represented the state.

- The definition of public nuisance is, it's a harm that society ought not have to bear.

And they kept promoting their paint with the knowledge that is could harm children.

The government just doesn't have enough money to de-lead all the houses.

- It is a public health tragedy that can only be stopped by making them pay.

- We're not asking for past damage, we're not asking to compensate the kids who have been poisoned.

It's forcing the wrong doer to clean up the problem.

- [Host] McConnell's firm, Motley Rice, sued in other states too.

- Several cities, taking a lead from those who have sued the tobacco companies for damages have decided to sue the paint companies.

- [Host] The industry admitted old paint could harm children but insisted the real fault was with homeowners and landlords.

- Once the paint has been sold, the condition of that property was not the responsbility of the manufactures of paint.

- [Host] After nine years of litigation, in 2008 the Rhode Island Supreme Court and courts in several other states, ruled for the paint companies.

- What the courts said is, the manufacturer, you weren't in those homes to decide how they were going to be maintained.

Some chose to maintain their properties, some chose not to.

- The case was over and we were extremely disappointed.

It was a tough pill to swallow.

- [Host] But in California the case continued for 18 years.

Larry Brooks runs the Lead Poisoning Prevention Program in Alameda County.

- In the heart of our county, in the city of Oakland, we actually have a child lead poisoning rate higher than Flint, Michigan.

I know that when they put the lead in the paint they weren't intentionally trying to poison our communities, but once they discovered that the lead in the paint was harming their customers, it was time to start doing something about it.

- [Host] For the first time, the courts agreed.

- A California judge has ordered three paint companies to pay for the removal of lead.

- This was a big victory here in California, but it sure did take a long time.

- The judge, in his order, indicated the paint companies are the cause of the problem and they had a responsibility to help us to address lead paint hazards.

- [Host] But some of the companies continued to fight, appealing the 400 million dollar judgment unsuccessfully to the U.S. Supreme Court.

And while they've now agreed to a settlement in California, they're still defending cases in other states.

- The idea of holding companies responsible for conduct over a century ago is more than troubling.

- [Host] But for Liz Colon the California decision feels like a vindication.

- Someone is actually going to be held accountable for the first time ever, that's big.

- [Host] And while she agrees, June Tourangeau is frustrated that after 20 years children are still getting poisoned in their own homes.

- Children are lead detectors and it's sad that a child has to be poisoned before red flags are raised.

Why should this still exist when this is a preventable disease and people know about it.

- [Host] So she continues teaching parents like Elijah's mother, Jasmine Riske, how to protect their children from further poisoning.

- The only person that I have to help me is my landlord and he's been notified multiple times and there's nothing.

We didn't have the money for like a nice fancy apartment.

Because people have less than somebody else their children deserve to be sick.

How is that fair to anybody?

- [Host] Jasmine worries about the long term effects of lead on Elijah.

- So, I just - No whatever questions please You're always going to watch him, and if you ever feel that he is not doing the things that he should be then you definitely talk to the pediatrician.

We can't change what has happened, but we can go forward.

- Yeah.

- Yeah.

- [Host] Just as Liz once worried about Sam.

- I think it was the direct result of lead poisoning that he was slower in school.

He was impulsive and it was hard for him to process math and reading comprehension, but he did okay because we put a lot of work into providing extra support wherever we could.

Sam today, is 24 years old.

He's really grown up and he's really worked hard.

He now works with adults with disabilities and he's great at his job and he loves it.

- [Newscaster 3] 30% of children in some neighborhoods on Cleveland's east side could have lead poisoning issues.

- 18 cities in Pennsylvania reported higher levels of lead exposure than Flint.

- Now New York Mayor de Blasio ordering lead inspections of nearly 130,000 public housing units.

- [Host] All across the country, communities are still looking for resources to fix the problem of old lead paint.

But it's hard to know where they will find the answer.

- I understand why they want to resist but my hope would just be that the paint companies would work with others and try to address the hazards that they unintentionally created.

It's like addressing an oil spill.

Those companies have to step forward and clean up the accident that they created.