Today Aladin Rafi's visiting a rowhome in Northeast Philadelphia. It's a brick two-story unit with a white metal awning.

Like any Philadelphia housing built before 1978, this place likely contains lead paint. It has to get certified as safe if the landlord wants to rent to tenants with small kids. That's where Rafi comes in, he's a certified lead inspector.

"What we first do when we get to each particular unit," he says once inside the mirror-walled living room, "we check visually whether there is any paint which is chipping."

He heads upstairs, and stops. "Actually we do have a problem there if you notice," he says. He points to the ceiling where the paint is starting to peel back.

"Usually in houses there is layers over layers of paint," he explains. "The top layer could be fine, but in case it's chipping, it's uncovering a layer which is underneath, which could be actually containing lead. And that would be a disaster. Just a little flake, a little kid who was three-years-old would play with it and put it in his mouth."

I'll admit, I'm kind of a skeptic when it comes to environmental hazards. But lead paint, especially if you're still a developing kid, it's the real deal. Bad news.

"Oh boy," says David Rosner, a lead poisoning historian with Columbia University's School of Public Health, "In the early part of the century, children literally convulsed. The descriptions are horrifying, they became paralyzed, eyes going back in their head. Dramatic neurological symptoms."

Lead paint was everywhere in the early 1900s. Kids were dying from it, and residents and clinicians started to notice. But the lead paint industry was so huge and powerful, lead-based paint wasn't outlawed until 1978. People got more careful, you saw less kids having seizures over lead. But something more sinister was happening.

The 'Tooth Fairy' project 

"In Philadelphia," says Rosner, "a pediatrician named Herb Needleman had his office across from a school. And the school was in a poor neighborhood and the kids were doing badly."

This was the late 50s. Dr. Needleman had noticed before that his lead poisoned patients seemed to have behavioral issues, more than seemed normal. He wondered if lead poisoning might have something to do with the problems at this school. But how could prove that?

"What he did," says Rosner, "was he started this project called the Tooth Fairy project."

Lead only stays around in the blood a little while. But it turns out baby teeth are a great place to look if you want to know about a kid's long term lead exposure.

Needleman measured lead levels in a bunch of kids' teeth. And he also got their school records. He compared the kids with lead in their teeth, to those who hadn't been poisoned. In 1979, he published his findings.

"And what he found," explains Rosner, "was that if a kid had elevated lead levels, even if it wasn't causing what were traditionally the symptoms of chronic lead poisoning, you found that teachers said that these kids had problems in school, they had trouble learning, they couldn't learn to read as a quickly."

Is there a correlation to crime? 

A more recent set of studies looked at crime rates over the past few decades. The researchers found drops in crime correlated to the time when a location outlawed lead in gasoline – another cause of lead poisoning. The logic is that fewer people impaired by lead poisoning means fewer people at risk for criminality.

Rosner's not a big fan of that line of thinking.

"Crime is such a complicated issue and who gets arrested is so socially determined," he says, "To say lead causes a child to be a criminal is kind of missing the point about the injustice of the criminal justice system."

But he says other researchers have found lead poisoning correlates to lower IQ, aggression, impulse control issues.

An 'overlooked' issue 

And here's why I said this situation's so sinister. These days, lead poisoning typically happens in rundown older homes, often rentals where a landlord has failed to repaint. Kids living in these places are already at a socioeconomic disadvantage. Add lead poisoning to the mix, it can set them back even further.

But lead poisoning can affect anyone.

Back in 2007 Heather Femine and her family moved into a two-story rowhome of their own. She says she knew going in, the house had lead paint. But she figured she'd clean regularly, she'd make sure it didn't flake, the kids would be okay.

"But one day," she remembers, "we saw my daughter Stella who was almost two at the time, and I caught her chewing on the bannister. And then I noticed there was at least a dozen more bite marks all up the bannister!"

She took Stella to the doctor. The little girl had just enough lead in her blood that city authorities had to be notified. Inspectors came, and Femine spent the next year stripping old paint from the house.

Stella's now a healthy eight year old. She likes Pokemon and playing dress-up with her little sister, and much to her mom's relief, she's one of the top students in her class. But for a lot of Philadelphia children, lead poisoning has more serious consequences.

"Lead poisoning is still a problem in Philadelphia, absolutely," says Rachael Greenberg, head of the Southeastern Pennsylvania Lead and Healthy Homes Program through the National Nursing Centers Consortium. She says over 85 percent of Philadelphia's housing stock was built before 1978, before lead paint was illegal. That's more older housing than in most big cities.

"Also we have a very high percentage of children under six," she says. "So when you combine those two factors, I do feel like the issue of lead poisoning is being overlooked in Philadelphia."

Does the Philadelphia lead law do enough? 

In 2012 alone, nearly a thousand Philadelphia kids had lead poisoning. Pennsylvania leads the country as far as the percentage of kids with lead in their blood. Greenberg says overall, lead poisoning appears less common than it used to be, but the number of children being tested for lead has been decreased as well.

She says that when it comes to services for preventing lead poisoning, Philly's worse off than it used to be. And other health advocates in the city point out that the city's new lead law doesn't do enough. It only requires landlords to get lead inspections on properties they rent to families with kids six and under. Which could lead landlords to just avoid renting to these young families. And the law does nothing to protect renters with seven or eight-year-old kids.

$1.1 billion lead lawsuit 

This year brought a big victory for the fight against lead poisoning. Six major California cities sued a group of lead paint companies. The cities said the companies knew all along lead paint was dangerous. Now they should be responsible for getting rid of it. The suit succeeded. The lead companies had to pay $1.1 billion towards getting lead off California walls. Lead historian David Rosner testified in the case.

"Here you have California," Rosner says, "which is kind of the bellwether state for all sorts of environmental laws in general, saying that this issue could be addressed through the courts, and that these large large population centers have a right to gain compensation from these companies."  He's hoping other large cities like Philadelphia will follow suit. 

One home at a time 

Back in the northeast Philly rowhome, lead inspector Aladin Rafi heads to the kitchen counter. He sets up six plastic vials.

"Front bedroom floor, front bedroom windowsill, back bedroom floor, back bedroom windowsill," he writes on their labels.

He stops in each room, and uses handy-wipe to wipe a small patch of the carpet and windowsill. The wipes then get put in the vials for testing at a lab.

"We're pretty much done," he finally announces. An easy job? "Yeah it is, it's very pleasant actually," he smiles.

Rafi got the apartment's tests back from the lab the following week. The results? Lead free.