Chapter 14

Relative Risk

(draft of 11/13)

© 2001 Richard A. Muller

Dangers of plutonium vs anthrax

The dangers of plutonium are analyzed in detail in a Lawrence Livermore National Laboratory Report that is available on the web at Here are the key facts:

Plutonium is toxic both because of its chemical effects and because of its radioactivity. The chemical toxicity is similar to that of other "heavy metals" and is not the cause for the widespread fear. The dangers are different for ingestiion and for inhalation.

Ingestion. For acute radiation poisoning, the lethal dose is estimated to be 500 milligrams (mg), i.e. about 1/2 gram. A common poison, cyanide, requires a dose 5 times smaller to cause death: 100 mg. Thus for ingestion, plutonium is very toxic, but five times less toxic than cyanide. There is also a risk of cancer from ingestion, with a lethal doze (1 cancer) for 480 mg.

Inhalation. For inhalation, the plutonium can cause death within a month (from pulmonary fibrosis or pulmonary edema); that requires 20 mg inhaled. To cause cancer with high probability, the amount that must be inhaled is 0.08 mg = 80 micrograms. The lethal dose for botulism toxin is 0.070 micrograms = 70 nanograms, a factor of

How easy is it to breathe in 0.08 mg = 80 micrograms? To get to the critical part of the lungs, the particle must be no larger than about 3 microns. A particle of that size has a mass of about 0.140 micrograms. To get to a dose of 80 micrograms requires 80/0.14 = 560 particles.

In contrast, the lethal dose for anthrax is estimated to be 10,000 particles of a similar size.

Botulism: 70 nanograms, injested, is the lethal dose. 100 micrograms per kilogram? 100 ng per human? I have a reference: ref: John S. Urbanetti M.D., FRCP

who says the inhaled LD50 is 3 ng.