Just the facts

On average, six rail cars a week carrying 90 tons of chlorine, one of the most lethal gases in the world, pass within 20 blocks of the U.S. Capitol

If terrorists attacked the rail cars, escaping gas could kill or injure tens of thousands — about 100 people a second

Depending on wind patterns, a chlorine spill would be lethal to people within two to five miles and would endanger people within 14 miles

The chlorine passing through Washington, D.C. is not even for use here in the city

The rail cars are not protected; moreover, they carry large, colorful placards announcing that they carry hazardous cargo — including the specific code for chlorine

Rail cars are vulnerable to attack. A rifle shot is capable of penetrating a tanker. Even an open valve would be catastrophic

Rail cars and trestles are covered with graffiti; if graffiti artists (typically teenagers) can get to the rail cars, so can terrorists

Jay Boris of the Naval Research Laboratory said the worst-case scenario would be an accident along the rail line that runs four blocks from the Capitol. If a big event were taking place on the Mall when such an accident occurred, he said, 100,000 out of 500,000 people might be killed. If an attack were to happen at rush hour, he estimated, the death toll could be 17,000

Richard Falkenrath, former deputy homeland security adviser to the White House, has testified before the Senate that “of all the various remaining civilian vulnerabilities in America today, one stands alone as uniquely deadly, pervasive and susceptible to terrorist attack: toxic-inhalation-hazard industrial chemicals”

In response to the seriousness of that threat, eight weeks after 9/11, the Washington, D.C. Blue Plains sewage treatment plant stopped using chlorine and began using a substitute chemical

-read more in Sally Quinn’s Washington Postarticle