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For starters, of the four so-called weapons of mass destruction, three are far less massively destructive than good old-fashioned explosives.272 Radiological or “dirty” bombs, which are conventional explosives wrapped in radioactive material (obtained, for example, from medical waste), would yield only minor and short-lived elevations of radiation, comparable to moving to a city at a higher altitude. Chemical weapons, unless they are released in an enclosed space like a subway (where they would still not do as much damage as conventional explosives), dissipate quickly, drift in the wind, and are broken down by sunlight. (Recall that poison gas was responsible for a tiny fraction of the casualties in World War I.) Biological weapons capable of causing epidemics would be prohibitively expensive to develop and deploy, as well as dangerous to the typically bungling amateur labs that would develop them.
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Steven Pinker (The Better Angels of Our Nature: A History of Violence and Humanity)