"For much of the 20th century, carbon tetrachloride was regarded as a miracle chemical: It was used to put out fires, degrease machines, kill bugs, dry-clean clothing and even help stamp collectors detect forgeries.
From the mid-1960s through the mid-1980s, most of those uses were discontinued for health and safety reasons. ...
Despite all of these efforts to eliminate carbon tetrachloride -- classified by the U.S. Environmental Protection Agency as a probable human carcinogen and known to damage the liver, kidneys and brain -- it still shows up at elevated levels around the world, scientists say. That's a testament, they say, to its past widespread use and its tough-as-nails persistence.
USA TODAY found it outside 70 of 95 schools in 30 states it monitored for a week last fall ... yet there were no obvious industrial sources to explain the readings."