Female Speaker: She is having a hard time walking upstairs, which I couldn't understand because she is an ice-skater, she is an athlete. Dr. Dean Edell: Air, earth and water, all are essential elements to human life. Yet the very component vital to our existence, can also contain toxins that make us sick. Where do they exist? Well, you might not have to look far to find the poisons in our world. It's the first thing we do as we enter the world. Air gives us life, as does food and water. Things that sustain our life can also deliver toxins that might make us sick. Female Speaker: I had to blow my nose all the time. Female Speaker: She'd come home tired all the time, she'd have headaches, she'd get winded going up the stairs. Dr. Dean Edell: What was making this student sick? Her mother says, it was mold in her school. Female Speaker: They tested her and found that she was allergic to aspergillus, well aspergillus I know is one of the mold that's found in the school. Dr. Dean Edell: Alice and her daughter Sydney asked not to be identified. Other students in the Sydney's school complained of problems too. Concerns peaked when a student died following an asthma attack. Raymond Slavin: A child who was allergic to mold and who was encountering it at school would become gradually more and more ill. Dr. Dean Edell: Though the death could not be linked to the mold, experts came to investigate. Raymond Slavin: Mold is everywhere. But it will only grow with water damage. Dr. Dean Edell: A musty smell can be a sign of mold, as can water intrusion and mold growth itself. Symptoms can also be assigned like asthma, burning eyes, nose, and chest irritation. Raymond Slavin: It doesn't cause any long-lasting effects and if the individual is removed from that environment, they'll do really quite well. Alice disagrees. Female Speaker: I watched her go from a very healthy child to a sickly child. Dr. Dean Edell: In Herculaneum, Missouri parents are worried about a different type of exposure. Jack Warden: When I walk out of my front door every morning, the first thing I see is a smokestack. Dr. Dean Edell: This is lead, Jack Warden scooped right off the street. Jack Warden: There was a lead contamination there. Dr. Dean Edell: Herculaneum is home to the nation's largest lead smelter and children here have some of the highest lead levels in the country. Jack Warden: My nephew tested it, blood-lead level of 26 at the age of three. Dr. Dean Edell: The CDC says 10 is safe. But lead expert Herbert Needleman has a different opinion. Herbert Needleman: It looks like there maybe no safe amount of lead in the blood. Dr. Dean Edell: He compared lead levels of delinquent kids in Pittsburgh to well-behaved kids. Herbert Needleman: We found that the bone lead levels in the delinquent subjects were 9 to 11 times as high as they were in the normal children. Dr. Dean Edell: Lead causes delays and mental development, decreased attention span, hearing problems, learning disabilities and headaches. Jack's son Eric is shorter than the average and has ADHD. Jack Warden: It's not fair to any child in Herculaneum. Dr. Dean Edell: Herculaneum and Pittsburgh aren't the only cities at risk. More than 80% of homes built before 1978 contain some lead paint or pipes. Herbert Needleman: The effects of lead are permanent and the outcomes are associated with life's success. Dr. Dean Edell: The people of tiny Fallon, Nevada are struggling to solve another medical mystery. Anna Warneke: I thought I was going to die. Dustin Gross: I was thinking that I hope I get through this. Dr. Dean Edell: Dustin and Anna are two of 16 children in Fallon diagnosed of leukemia; three died. Brenda Gross: Too many children, in too small of a time and too small of an area. Randall Todd: We'd expect to see only about one case every five years. Dr. Dean Edell: The cause was a mystery. The CDC collected blood and urine samples from residents and found high levels of arsenic, uranium and tun