Associated Press Writer

Chemical agents are everywhere. A variety of chemicals commonly used in industry also could also be used to mount a terror attack.

Much of the nation's attention has focused on the threat of biological attacks that would use anthrax, smallpox or other pathogens. But just last month, the deadly poison ricin was found in a north London apartment. Ricin is one of the world's deadliest toxins and has been linked to both Iraq and the al-Qaida terror network.

Attorney General John Ashcroft cited the London incident Friday in announcing that the national terror alert was being raised from yellow to orange, the second-highest level.

"These indications demonstrate al-Qaida's interest in carrying out chemical, biological and radiological attacks," Ashcroft said.

Used as weapons, many chemicals could maim, kill and pose risks to the public, although a review of the chemical terror threat concluded that specialized knowledge would be needed to acquire and deliver most of them effectively.

"In most cases terrorists would have to overcome significant technical and operational challenges," the General Accounting Office, Congress' investigative arm, said in 1999 testimony.

But not always, the GAO said: "Some chemical agents are commercially available and require little sophistication or expertise to obtain or use."

For instance, toxic industrial chemicals such as chlorine, phosgene and hydrogen cyanide are readily available. These are among the earliest chemical weapons and were used by troops in World War I. Today, they are commonly used in commercial manufacturing and "could be easily adapted as terrorist weapons," the GAO said.

Cyanide, for instance, is commonly used in electroplating, where metals are attached to each other, and jewelry manufacturing. It's readily available and has been used to attack the public before: In 1982, cyanide-laced capsules of Tylenol Extra Strength killed five people and terrorized the nation.

"Cyanide is obviously a very lethal material that acts very rapidly," said Dr. Philip Edelman, acting associate director for terrorism preparedness and response at the National Center for Environmental Health at the Centers for Disease Control and Prevention.

There is an antidote for cyanide, but it must be administered quickly.

It's not alone on the threat list. "There are a number of chemicals that are highly toxic that would bring on their effects very rapidly," Edelman said. "They are out in commerce for various purposes that are completely legitimate."

Commercial pesticides such as organophosphates, commonly available in hardware stores, are far less deadly than nerve agents like sarin or soman, but they produce similar effects in the body by poisoning the nervous system. If someone were exposed to such an agent, the cause of the resulting illness might not be readily apparent, which would make it difficult to detect such an attack. Symptoms include blurred vision, difficult breathing, excessive sweating, weakened muscles, paralysis and seizures.

A chemical attack would be difficult to execute outdoors, since unpredictable winds can blow the agents away from their targets. Chemicals could be delivered relatively effectively, however, through indoor ventilation systems or in food or water.

The most deadly agents in the chemical arsenal are nerve agents, although they are more difficult to obtain. A small amount of sarin or soman can penetrate the lungs or the skin and invade the nervous system. Sarin has been used once before: In 1995, the Japanese cult Aum Shinrikyo released it into the Tokyo subway system, killing 12 and sickening thousands.

The most toxic of chemical weapons is VX, a sticky, colorless liquid that evaporates slowly into a colorless, odorless gas. It interferes with the body's nerve impulses to cause convulsions and paralysis of the lungs and blood vessels. Victims essentially choke to death. A dose of 10 milligrams on the skin is enough to kill.

There is an antidote for nerve agents: atropine.

Considerable work is being done at the state and local levels to prepare for biological and chemical attacks, and a new survey suggests much work is needed at state labs. A survey by the Association of Public Health Laboratories found most state labs rate their ability to respond to a chemical attack very poorly.