By Traci Watson
A new conspiracy theory sweeping the Internet and radio talk shows has set parts of the federal government on edge.
The theory: The white lines of condensed water vapor that jets leave in the sky, called contrails, are actually a toxic substance the government deliberately sprays on an unsuspecting populace.
Federal bureaucracies have gotten thousands of phone calls, e-mails and letters in recent years from people demanding to know what is being sprayed and why. Some of the missives are threatening.
It's impossible to tell how many supporters these ideas have attracted, but the people who believe them say they're tired of getting the brush-off from officials. And they're tired of health problems they blame on ''spraying.''
''This is blatant. This is in your face,'' says Philip Marie Sr., a retired nuclear quality engineer from Bartlett, N.H., who says the sky above his quiet town is often crisscrossed with ''spray'' trails.
''No one will address it,'' he says. ''Everyone stonewalls this thing.''
The situation Marie and others describe is straight out of The X-Files. He and others report one day looking up at the sky and realizing that they were seeing abnormal contrails: contrails that lingered and spread into wispy clouds, multiple contrails arranged in tick-tack-toe-like grids or parallel lines, contrails being laid down by white planes without registration numbers.
Believers call these tracks ''chemtrails.'' They say they don't know why the chemicals are being dropped, but that doesn't stop them from speculating. Many guess that the federal government is trying to slow global warming with compounds that reflect sunlight into the sky. Some propose more ominous theories, such as a government campaign to weed out the old and sick.
Exasperated by persistent questions, the Environmental Protection Agency, NASA, the Federal Aviation Administration and the National Oceanic and Atmospheric Administration joined forces last fall to publish a fact sheet explaining the science of contrail formation. A few months earlier, the Air Force had put out its own fact sheet, which tries to refute its opponents' arguments point by point.
''If you try to pin these people down and refute things, it's, 'Well, you're just part of the conspiracy,'' says atmospheric scientist Patrick Minnis of NASA's Langley Research Center in Hampton, Va. ''Logic is not exactly a real selling point for most of them.''
Nothing is ''out there'' except water vapor and ice crystals, say irritated scientists who study contrails. Some, such as Minnis, are outraged enough by the claims of chemtrail believers that they have trolled Internet chat rooms to correct misinformation or have gotten into arguments with callers.
''Conspiracy nonsense,'' snorts Kenneth Sassen, an atmospheric scientist at the University of Utah. ''These things are at 30,000 to 40,000 feet in the atmosphere. They're tiny particles. They're not going to affect anyone.''
The cloud-forming contrails that conspiracy theorists find so ominous
are ''perfectly natural,'' Minnis says. The odd grid and parallel-line
patterns are easily explained as contrails blown together by the wind,