Disquieting revelations of a very present danger--by an experienced Far Eastern correspondent with a familiar surname: he is the son (and, it could be said, the heir) of famed ""Burma surgeon"" Gordon Seagrave. And, to make the danger manifest, he fills in the background: following the widespread use of poison gas in World War I, the 1925 Geneva Protocol was supposed to outlaw chemical warfare; nonetheless, the Nazis developed a second generation of killers, the nerve gases soman and sarin. After World War II, the US Chemical Corps enthusiastically adopted satin and stockpiled half a million tons (most of which is still stored--in a dangerously unstable condition--in various parts of the country). During the Yemen civil war of the late 1960s, the Russians (disguised as Egyptians) field-tested a gruesome new third-generation agent, a yellow or red substance which killed rapidly by inducing massive hemorrhaging. (Seagrave identifies this ""yellow rain"" as a T2 toxin, a derivative of ergot and/or other deadly cereal fungi.) The agent is in use today, he maintains, by the Russian-supplied Afghans and Vietnamese. The Warsaw Pact nations are prepared, therefore, to wage a chemical war--whereas NATO is not. Still, writes Seagrave, the 1968 Nixon ban on chemical weapons was a fraud: the various research facilities merely switched locations or acquired new, misleading labels (becoming labs for ""cancer research"" or the study of ""toxic effects""). And, with chemicals in use for political assassinations (the notorious Markov case being only the latest instance), as well as in local warfare, recent rumbles from the Pentagon--plus an unremarked 1980 budget appropriation--suggest renewed pressure to create binary weapons (in which two relatively innocuous chemicals are mixed after the shell or missile has been fixed, to produce toxic effects only at the target). Seagrave regards the development of binaries as inevitable--but we should first expose the issue to public scrutiny and debate. To that end, a graphic, responsible presentation.