Mohammed Atta, the man named by the FBI as one of the masterminds behind the 9/11 terrorist strikes against the United States, had previously investigated the possibility of carrying out an attack on a chemical plant in eastern Tennessee. Had the facility's tanks holding about 250 tons of sulfur dioxide been blown up, as many as 60,000 people could have been killed or seriously injured by the resulting toxic vapor cloud, the Washington Post reported.

But the nation's chemical security problem is certainly not limited to a handful of plants like the one in Tennessee. An analysis by the Congressional Research Service released two years ago found that there were more than 100 facilities that each place upwards of 1 million people at risk from a toxic chemical release, and more than 400 additional facilities that place between 100,000 and 1 million people at risk.

Many of these dangerous facilities are in the South. In fact, Texas has by far the most plants -- 29 -- where a worst-case release could affect 1 million or more nearby residents. And a list of recent accidents at chemical facilities compiled by the Associated Press found seven incidents since 2006, with most of them taking place in the South.

Responding to watchdogs' warnings, Congress last fall passed a temporary law giving the Department of Homeland Security the authority to regulate the nation's most hazardous chemical plants, and DHS released its new rule earlier this month. But after reviewing that rule, the United Steelworkers union says it fails to adequately protect plant workers and nearby communities.

"The Homeland Security rules for the nation's high risk chemical plants fall far short of what is needed to truly make facilities safe from terrorist attacks," said USW President Leo W. Gerard in a press release. "It's another example of the Bush Administration's attempt to appear as if it is taking care of industrial safety problems. Security actions alone are insufficient to protect workers and communities."

DHS estimates that as many as 66,000 plants nationwide present a potential chemical threat, according to the AP. About a third of those are already regulated by other agencies, and DHS is asking the owners of the remaining plants to complete an online questionnaire within 60 days disclosing what they manufacture, what chemicals they store, in what quantities, and in what type of storage.

Gerard noted that the rule fails to require plants to use safer technologies and less hazardous chemicals. In addition, it does not involve employees in plant safety and offers no protections for whistle blowers.

Another concern raised by the USW is the fact that the new rule could preempt existing state security laws. For example, the new federal rule trumps state laws that gives the public any information DHS considers as making a plant more vulnerable to security risks -- a provision that USW says could deprive workers of the right to know what chemicals they're handling.

DHS Secretary Michael Chertoff told the AP that the federal rules would override only those state rules that directly conflict with the federal ones. Meanwhile, a bill introduced in Congress to ensure more lax federal rules would not eclipse stricter state regulations has stalled.

The law that gave DHS the authority to craft the rule is a watered-down, chemical industry-approved version of a proposal the Bush administration considered back in 2003. The earlier legislative package -- crafted with the help of then-DHS chief Tom Ridge and former Environmental Protection Agency Administrator Christine Todd Whitman -- was thwarted by White House Office of Management and Budget Counsel Philip Perry, who also happens to be Vice President Dick Cheney's son-in-law, according to the Washington Monthly:

A flippant critic might say the father-in-law has been prosecuting a war that creates more terrorists abroad, while the son-in-law has been working to ensure they'll have easy targets at home. But it's more precise to say that White House officials really, really don't want to alienate the chemical industry, and Perry has been really, really willing to help them not do it.

The new security rule does not set a timetable for changes or require the industry to take any specific measures to boost security. The USW suggests that if the feds were really serious about improving security at the nation's chemical plants, they would require the employment of sufficient and qualified personnel to meet the requirements; strengthen the recordkeeping and reporting requirements for process malfunctions or any attempted terrorist attack; define the need for emergency response, safe shut down, evacuation and decontamination procedures in case of an attack or malfunction; and put in place effective training requirements for workers in covered facilities.

The environmental group Greenpeace has also called on the new Congress to pass a strong permanent law that would protect communities from chemical disasters. Last July, the House Homeland Security Committee tried to do just that, but the measure was never allowed to go to the House floor.