Deadly chemicals may be passing by your home or school as hundreds of thousands of toxic tank loads crisscross the nation on trains each year.
On Jan. 6, 2005, Graniteville, S.C., experienced a toxic train crash that changed the town forever.
Watch "Primetime" tonight at 10
Maggie Adams went to work at 5 p.m. to start her overnight shift at Avondale Mills, a textile plant located near the railroad tracks that run through the center of town.
Adams was a computer operator in the information services building, just yards away from the tracks where trains were traveling at speeds of 50 mph. Not only was the plant near the tracks, but so were homes and a school.
Adams had said to her boss, "If these trains don't slow down, they're gonna end up derailing and landing on top of me."
There were nearly 200 people working on Adams' shift. Steve Stein and Sonny Morris, steam plant workers, were just a few feet away from the track.
They remember suddenly hearing a screeching, thunderous explosion of crunching metal. Two trains had crashed, leaving 16 cars derailed.
One car had a punctured tank of poisonous gas.
Adams remembers smelling smoke and immediately calling 911.
"I thought [the train] was gonna come through the wall behind me," she said.
Witnesses described a rolling yellow-green blanket of poison invading the town like something out of a science fiction movie.
"I thought my eyelashes had come off. If I breathed too deeply, it burned like, I guess, like drinking gas," said Adams, who was trapped in her building at the time.
Calls poured into 911 from the nearby plant and from houses, with people complaining of everything from "We can't breathe" to "He's got blood coming out of his eyes."
Adams remembers praying on her knees, asking, "God, what is this?"
What burst out of the train was chlorine -- 120,000 pounds.
It is widely used in chemical plants, as a bleach and to purify water. The compound is so deadly, it was used as a weapon in World War I.
"It was like breathing in fire … like being buried alive with no air," Morris said.
Desperate for fresh air, people started running for their lives.
Meanwhile, the Graniteville Fire Department had to call for outside help because it had no protective hazmat suits and air packs were in the fire station, which had been engulfed in the deadly chlorine cloud.
Although Adams was told to wait inside for help, she says it got so bad, she couldn't wait any longer.
She left the building. Her car was so engulfed in the chemical cloud that she set out on foot.
"I took my lab coat, and I wrapped it around the bottom of my face and I would take real shallow breaths. I was so scared to go out of that building, but I knew I was dying if I didn't," Adams said.
"I felt like it was the end of the world. There was nobody. No cars."
Finally, after three hours of wandering around, Adams collapsed.
Adams was rescued on the outskirts of town, while co-workers were still on the roof of the nearby steam plant, gasping for air in the noxious cloud.
Fortunately, Morris and Stein were rescued by their supervisor, Tim Friar, who was equipped with a breathing apparatus.
"I hadn't seen anything like it before in my life. I'd never been that scared before in my life," Friar said.
Later that morning, hazmat teams made it to the crash site.
The dead body of Rusty Rushton, Friar's co-worker and friend of 13 years, was found just outside the loading dock of the steam plant, his shirt in his hands.
Rushton was the father of two boys.
Stein also knew Rushton well.
"[He was] a very good man. The type you trust. If you want[ed] somebody on your side, that was the man to have."
All the bodies found shared the markings of the killer chemical.
Items in their pockets were corroded, and their clothes were bleached white.
Friar found two other dead bodies near the creek, Charles Shealey, a father of three, and 24-year-old John Laird.
Both had helped to rescue people earlier that night.
When Friar found the men, he says they were linking arms. "I have no doubt they were trying to help each other get out."
In all, nine people were found dead, including the train engineer and a Vietnam veteran who required the use of a wheelchair and had died in his home.
His home was about 250 yards from the crash.
More than 500 people were injured. Fifty-four hundred were evacuated from the town for nine days.
A year-and-a-half after the catastrophic train wreck, Graniteville still hasn't recovered.
Some people who couldn't escape say they are now suffering from symptoms of the explosion.
Chlorine corrodes the respiratory tract, and can cause severe eye and skin burns, lung collapse and death.
At the time of the wreck, Ashton Davenport was 5 years old and was staying a mile away from the crash at her grandmother's home.
Trees in that neighborhood still haven't come back to life.
Jessica Davenport, Ashton's mother, says her daughter was never sick before the toxic train crash.
"She would ride her bike. She loved riding horses. She loved doing pageants, and she was just a typical child. She could swim in any pool."
After the train wreck, Ashton kept telling her mother that her chest and throat hurt.
Now she's been diagnosed with scarred lungs, breathing problems -- similar to asthma -- and vocal chord damage.
When it's hot and dry, Ashton has to wear a dust mask to go outside to play because she lives on a dirt road. At times, she needs to inhale medication just to help her breathe.
"It's hard to watch your little girl begging for help and there's nothing you can do," Davenport said.
Ashton's family and many others have sued the railroad Norfolk Southern.
What makes this situation even tougher to handle is the fact that this crash could have been avoided.
It all began with a mistake with the switch that determines which track the train will travel.
Left in the proper position, the switch guides a freight train safely out of town.
On Jan. 6, 2005, that switch was left in the wrong position.
When the freight train came barreling down the tracks, it was guided directly into the yard where it slammed into a parked train.
Jamie Holland, an attorney representing some of the victims of the Graniteville crash says, this problem is nothing new.
"That problem has been around ever since the term 'asleep at the switch' came out."
In fact, Norfolk Southern had more than 100 train accidents caused by switches in the wrong place in the last three years.
Holland says all the company had to do was put a warning light on the switch so the train could see it as it approached.
Norfolk Southern chose not to spend the money on the less-trafficked Graniteville line.
In a statement to ABC News, Norfolk Southern said it "deeply regrets the accident" and is it was working on new technology to improve "an already-superior safety record."
The train was running in what's known as dark territory.
Forty percent of the country's tracks, primarily in less-used areas, have no signals and no warning systems.
Every year there are 1.7 million carloads carrying some of the deadliest chemical agents known to man, crisscrossing the nation--- a number that's rising.
"It's a question of when again. I mean it's going to happen again. There are rail crashes almost every week in this country," said James P. Hoffa, the president of the Teamsters Union, which includes the railroad workers.
"They're just rolling the dice that maybe there won't be a rail wreck. Maybe we'll just get by if we go on the cheap, and that's the thinking of the industry."
Last year alone, there were 846 accidents involving trains carrying deadly chemicals -- a number that's gone up over the last four years.
Thirty-six of those accidents involved the release of toxic chemicals into the air.
A lack of signals isn't the only cause of potentially lethal accidents. Human error is the single largest cause of train accidents . In 2004, three people died in Macdona, Texas in a train collision that released deadly chlorine gas. The National Transportation Safety board determined that the probable cause was fatigue of the train crew .
Track defects are the number two cause of train accidents -- accounting for more than one third of all train accidents.
Peggy Wilhide, spokeswoman for the American Association of Railroads, says the industry is trying to deal with a problem that's been forced upon it.
"We are really adamantly pushing Congress and chemical producers to look at using safer chemicals rather than the toxic chemicals that we are required by the federal government to transport now," Wilhide said.
"We have a 99.997 percent safety record. … A 100 percent safety record is what we strive for."
Wilhide says the industry is asking tank-car makers for stronger cars. She also says railroad companies are experimenting with a new high-tech communication system in two test areas.