Called the "poor man's weapons of mass destruction," biological and chemical weapons are, unlike nuclear arms, relatively easy to produce, hide, and use. Our chart lists some of the more menacing biological and chemical weapons, how they work and what they can do.

(Note - Thanks to genetic engineering and at least 30 years of devoted efforts to create an incredibly wide variety of lethal agents by the US, Britain, Russia, and other countries, the list below is only the briefest survey of the most common 'off the shelf' agents which might be used in terror attacks on civilians anywhere on the planet. - ed)

Biological Weapons

ANTHRAX

What is it? Bacteria with spore-forming rods; likes to live in the soil

How it works: Humans become infected by coming into contact with spores, either by touch or inhalation. The spore then produces a toxin that can be fatal. The incubation period for inhalational anthrax is 1-6 days.

Lethal amount: One billionth of a gram (the size of a speck of dust)

How long can it survive? Tends to degrade rapidly in sunlight; if kept in the right environmental conditions, anthrax can survive for years.

Symptoms: Flu-like symptoms, high fever, fatigue and cough. Shock and death can occur within 24-36 hours of the onset of severe symptoms.

Treatment: Antibiotics, including penicillin

Prevention: Vaccine

BOTULINUM TOXIN

What is it? Bacterium that develops only in the absence of oxygen.

How it works: By inhalation. Botulinum neurotoxins generally kill by the relatively slow onset (hours to days) of respiratory failure. The individual may not show signs of disease for 24-72 hours. The toxin blocks biochemical action in the nerves that activate the muscles necessary for respiration, causing suffocation.

Lethal amount: One billionth of a gram

How long can it survive? Relatively short life after it's released

Symptoms: Dizziness, dry throat, blurred vision.

Treatment: Anti-toxins can be injected soon after exposure to a lethal dose of toxin

Prevention: Gas mask, protective clothing

Chemical Weapons

VX

What is it? VX, considered one of the most lethal chemical weapons, is a colorless and odorless liquid that turns into a gas on contact with oxygen.

How it works: VX is primarily toxic through the skin, but can also prove fatal when inhaled. VX is fast-moving, virtually undetectable, and can spread through air as well as water. In its liquid state it is roughly the same density as water. It blocks the transmission of impulses along the central nervous system, causing convulsions, respiratory paralysis, and death.

Lethal amount: 10 mg (just a drop)

Symptoms: Increased salivation, coughing, runny nose, headache and nausea.

Prevention: Gas mask, protective clothing

MUSTARD GAS

What is it? Mustard gas is in its pure state a colorless, odorless liquid, but when mixed with other chemicals, it looks brown and has a garlic-like smell.

How it works: Inhaling the vapors causes painful, long-lasting blisters all over the body.

Symptoms: Itchy skin, watery eyes and burning sensation in lungs. The long-term effects on an individual may include chronic lung impairment, chest pain and cancer of the mouth, throat, respiratory tract, and skin. It has been linked to causing leukemia and birth defects.

Prevention: Gas mask

SARIN

What is it? Sarin is a highly toxic gas which attacks the central nervous system.

How it works: It is chiefly absorbed through the respiratory tract; can be absorbed through the skin at higher environmental temperatures. Depending upon concentration of Sarin, toxicity can occur within minutes.

Lethal amount: 100 milligrams

Symptoms: In low levels, it causes severe headaches, increased salivation and constrict air passages to the lungs. In higher doses, it causes coughing, increased perspiration, nausea, vomiting, diarrhea and breathing difficulties. Death can follow due to suffocation.