I bet you’ve heard about our problem with lead contamination. Here in the US, we began phasing out one of the largest sources of lead in gasoline in the mid-1970s. But for decades, our vehicles had spewed this toxic exhaust into the atmosphere. So where did that residual lead go? I'm an investigative reporter, and almost a decade ago, when I began digging into this issue, I realized there's a huge misconception about lead. We talk about it like the problem was solved decades ago, but it's still happening right now. Lead contamination isn't just a problem in the water of Flint, Michigan. It's in the soil, too. And not just in Flint, but around the world and almost certainly where you live. Today, we know that no level of lead is safe in children's bodies, yet lead is detected in the blood of all children. Most people associate lead with water and paint. What they don't realize is that this invisible poison could be in the very soil where their children are playing. Take Santa Ana, California, a city of more than 300,000 people. In the 1960s, the tiny Mexican-American barrio of Logan was one of the poorest neighborhoods in Santa Ana. Squeezed between two railroad tracks, next to a highway and surrounded by all sorts of industry. It had also been a segregated neighborhood. It was, as they say, on the wrong side of the tracks. But for the children of Logan, it was home. Kids would race through the neighborhood, collecting barrels, crawl into them, and then get carried away by the Santa Ana winds that would blast them across the school playground. Everywhere the wind blew the children went. But they didn't know what that wind carried. Tiny, invisible particles of toxic lead dust that were floating in the air and landing in the soil in Santa Ana and cities across the country. We now know that decades of build up from leaded gas, paint, industrial emissions and other sources have created invisible mountains of lead in our urban cores. Because lead contaminants can remain in the soil for decades, even centuries, this poses a threat for areas hit by climate change, for example, drought and flooding, which can remobilize that toxic soil. Soil lead mapping across the country and around the world shows that soil lead contamination is widespread and pervasive. Here you can see how soil tests by scientists have found hotspots in our inner cities. But most people don't read the scientific journals showing this problem. I first encountered the dangers of soil lead contamination in 2014, when I was reporting on young Latino boys who were disproportionately incarcerated and were being turned over to immigration authorities by probation departments across California and then deported. And as I reported that story, interviewing the mothers of these young boys, I saw some similarities. Their sons had trouble learning in school. They couldn't focus, they couldn't sit still, and they had been diagnosed with attention deficit hyperactivity disorder, ADHD. Around the same time, I serendipitously came across a magazine article about lead and a hypothesis about the link between lead and crime, how the rise and fall of leaded gas use in cars had likely contributed to the rise and fall of violent crime in America. And, intriguingly, for my work, a connection between ADHD and lead exposure. And I had an epiphany. I realized I was examining everything in these boys' environment: the poverty, the violence, the high police presence in their neighborhoods. But I wasn't considering the actual environment, the soil, as a factor that might be impacting their behavior. The neighborhoods where these young boys were growing up, on the wrong side of the tracks, was determining their destiny. Once they entered the juvenile justice system, keeping them out was tough. Suspensions led to expulsions, which led to juvenile hall and then worse. César Gaspar was eight years old when I first met him while reporting on incarcerated youth in his neighborhood. He had just been diagnosed with ADHD, and because his parents had pressed the school, he was receiving the services he needed to stay on track. But his mom and dad still worried that he would end up in the school-to-prison pipeline. What was happening to César was happening to other young Latino boys in Orange County and across California. As a journalist and as a Mexican-American, a working class kid who had gone to college on scholarships, I knew that your zip code, where you grow up, can determine where you end up in life. My immigrant parents dreamed big for me, but if I hadn't grown up in Santa Barbara with top teachers and a healthy environment, would I have been able to forge a path to a career in journalism? I wondered, what if we could help children not only succeed in school, but also keep them out of the criminal justice system? What if we could create healthier neighborhoods for everyone by removing the threat that's right under our feet, and ensuring that neighborhoods are free of one of the most well-known and harmful toxic metals known to humans? Lead. So I decided to test the soil for lead contamination in Santa Ana. Now, I'm not a soil scientist. I don't have a PhD in geochemistry. I grew up in California, working alongside my parents, helping my mom clean homes on the weekends, and working after school in the gardens that my dad landscaped. It was not fun, let me tell you. (Laughter) It's why, as a kid, I vowed that one day I would have a job where I would never, ever have to toil in the soil. (Laughter) And as you can see, that did not work out very well. There I am, testing the soil in Santa Ana, where so many families grow fruits, vegetables, herbs, but most of all, corn. Just like my dad did in our backyard when I was growing up. Santa Ana is a predominantly Latino immigrant city, and data showed that the number of children who were lead-exposed was much higher than any other city in Orange County, and I wanted to know why. Eight years and two investigations later, I had indisputable evidence. These are the results of more than 1,600 soil tests that I conducted across the city. The lighter the dot, the higher the lead level. And as you can see, the highest levels, that hotspot in yellow, are located near the city center on the east side of Santa Ana, where the Logan barrio is located in the 92701 zip code. Altogether, these results show that more than half of the samples in the city's poorest neighborhoods contain levels of lead that the state of California considers unsafe for children. The 92701 zip code not only ranked in the top five ZIP codes with minors booked into juvenile hall, it also had the highest percentage of elevated soil tests and children with elevated blood lead levels. This data galvanized a coalition of residents, university scholars and environmental justice advocates who conducted their own soil tests and met with city planners and spoke up at city council meetings. And ultimately, they convinced the City of Santa Ana to comprehensively address lead contamination. I also tested the soil in César's apartment complex and neighborhood and found lead. Test results showed that he also had lead in his blood. And I wrote about his family's efforts to make sure that he received the early intervention he needed, but despite this, he still ended up in the school-to-prison pipeline. In 2017, he was arrested by school police and charged with two felonies for bringing a pocket knife to school in his backpack. At the age of 12, he faced the potential five years in juvenile hall. So his public defender raised his lead exposure and ADHD issues in juvenile court, and ultimately, the judge decided to place him on informal probation and assigned him to community service work at school. But his case is rare. Most boys like him end up in juvenile hall. The question I had is how many of these youth are lead-burdened? One of the most disturbing things about lead is the way it can come back to haunt you in different ways throughout your life. That's because once lead enters the bloodstream, it gets stored in our bones where it can then be rereleased, for example, when mothers are breastfeeding, the calcium that's transferred from the mother into the fetus. Also, throughout our lives, things like sickness, stress, menopause and aging can also release that lead into the bloodstream. It's also the silent killer that's rarely talked about. A major risk factor for cardiovascular disease, responsible for more than 250,000 deaths every year in the US. And also one of the leading causes of fatal heart attacks in this country. So one of the questions that was driving me in the work that I was doing is, why are we allowing our children to get poisoned by lead? Why aren't we protecting our most important asset? The best thing I could do is share what I've learned along the way with other journalists, so they, too, could make the invisible visible in their communities. That's why I created this reporting toolkit, as a road map to help journalists investigate this issue. The toolkit is also for community members to help raise awareness about soil lead. Researchers have found soil lead contamination in small and large cities. But one of the problems is we don't have a systematic program to map urban soils, to identify lead hotspots and eliminate them. Today, in most cities, we don't know where those invisible mountains are. We have a Clean Air Act, a Clean Water Act, but we don't have a Clean Soil Act. To protect children, experts say we should test the soil and reduce the exposure. The good news is we have solutions. Here in New York City, groups like the Legacy Lead Coalition are spreading the word about ways that people can tap the city's free, clean soil bank to cover unsafe soil. But we can't tackle the problem one child or one house at a time. Because lead knows no boundaries. It's where the wind blows from our cities to the furthest reaches of the Earth and our polar ice caps. The work that I'm doing today is about connecting the past with the present. I'm organizing a global convening to create an action plan to map urban soils, and to find a way to eradicate lead from our environment, to ensure that growing up on the wrong side of the tracks doesn’t derail a child’s destiny, by preventing lead poisoning to protect our most valuable asset, the human mind. And by planting a seed in the soil, just like my dad did so long ago, hoping it takes root, so that one day the world can see for itself what's been right before our eyes all along. Thank you. (Applause)