The PTBT isn't terribly heavy on the metaphors, but there is one potent symbol that looms over the entire text not unlike a horrible, dark cloud. You could even say it's a mushroom cloud.

That would be the symbol of toxicity.

Of course, the language of an international peace treaty isn't going to employ the devices of poetry to get its point across, so when we talk about symbolism here, it is in a more abstract sense—it is an idea that is equally embedded within the text as it was in the culture of the 1950s and 1960s. The scene of its writing was a moment in history in which the rate of nuclear experimentation was increasing at the same rate (or faster) than scientists were discovering how truly deadly radioactivity was.

The PTBT is thick with a consciousness about radioactivity and its capacity to poison. This mentality influenced the way in which the treaty was written, and on occasion, it pops out from the text like a vicious pimple. Lines like "[s]eeking to achieve the discontinuance of all test explosions of nuclear weapons for all time, determined to continue negotiations to this end, and desiring to put an end to the contamination of man's environment by radioactive substances" (3) reveal that the authors knew full well the hazards of nuclear energy.

This explains why the treaty includes certain conditions that strive to limit the uncontrollable toxicity of nuclear weapons testing. Take a look at this excerpt from Article I:

Each of the Parties to this Treaty undertakes to prohibit, to prevent, and not to carry out any nuclear weapon test explosion, or any other nuclear explosion, at any place under its jurisdiction or control: [...] in any other environment if such explosion causes radioactive debris to be present outside the territorial limits of the State under whose jurisdiction or control such explosion is conducted. (6-8)

The PTBT is all about anxieties surrounding radioactive toxicity. It's a nuclear-age message for the ages that says, "Don't do this because it's unsafe and really don't do this if you can't control it."The underlying hope is that it always remains a statement of warning and not one that says, "I told you so."