Recent reports of the long-term effects of the Christmas Island nuclear tests suffered by British military veterans bring back the horrors of this grim experience for anyone who has had anything to do with the Bomb. They take me back to a gloomy day in the mid 1970s. A Pentagon official doing a survey called me; after reading out a bureaucratic and monotonal statement about the American Privacy Act, he asked me whether I had participated in the atomic test exercises conducted by the US military between the years of 1946 and 1963.

I gave him the data requested: name, rank, serial number (still easy to remember), military unit, date of the test and my apparent state of health, which was good. This could only be "apparent" because the Department of Defence had recently announced to some 300,000 of us that it was now impossible to know what the ultimate physical results of the tests would be for us - a normal life span, or one stricken by cancer, leukaemia or some other malady. At least one test participant had already died.

This was a substantive change in the department's opinion from the era in which I was a test participant. Another bureaucrat, in a very different time and place, talked to us in a memorable briefing session just before we were to take off for Nevada. "I want to reassure you," he said, "because, after all, you are all free, white and 21." He corrected himself: "Oh, I guess you're not all 21."

Then, fixing his eyes upon some black troops sitting in the first row, he observed: "And I guess you are not all white." Guffaws came on cue from some of the crowd, but not from the African Americans. "And, well, you're in the Marine Corps," he added, and no one could doubt either the statement or his use of a substitute for "free". Later, he was momentarily sombre as he warned us that if we somehow received 800 roentgens of radiation, we would lose all our desire for sex. "Don't worry, though," he smiled, "because at 600 roentgens you're dead." And again there were laughs.

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It was all supposedly very funny, it was seen as a lark by many, and we would be given passes that would permit trips to Las Vegas. We even named our bulldog mascot "Roentgen". The lecturer waxed poetic as he finished, for after explaining just where we would go, what we would do and when we would do it, he described the atomic fireball we would see: "It is a beautiful sight; you'll see every colour of the rainbow; and you'll never forget it." He was right about never forgetting it; and the sad truth is that most of us could never forget it even if we resolutely wished to erase the memory; because Albert Einstein was profoundly right when he said that the Bomb changed everything.

Trucks took most of the men to slit trenches, located at various distances from ground zero. I was with a group standing by our helicopter, and we would remain in the open at a distance of six miles. The "shot", as it was called, went off as scheduled. It was a 13-kilotonne explosion that vaporised part of the tower from which it was dropped. Those in my group faced in the opposite direction, our eyes covered. There was a great flash, a feeling of intense heat in the atmosphere and especially on the back of the neck, and then we turned around to see it. The great mushroom lit up the sky much more gaudily than the lights of Las Vegas, where we had been a couple of nights before; but it was hardly what I would call beautiful. I remember thinking that Armageddon would also be dominated by its hues of black and grey.

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We moved no closer to ground zero, but some groups in other tests marched right across it after the great explosion, or jumped up out of their trenches when they were but a few thousand yards away. How foolish! someone may say. But it should be remembered that we trusted the Government then; and besides, you do what you are told to do in the military service.

We left Nevada the next day from Indian Springs airfield for a flight I remember because so many of the men were complaining about how expensive their visit to Las Vegas had been. They did not realise that the casinos had given them much better odds than the Department of Defence had. And yes, we trusted the Government, but I worried all the same as the years went by and as the department increasingly began to change its tune on the safety of the tests.

Small reminders, I continued to find, could be disconcerting. At my university I attended an international affairs meeting devoted to the effects of testing, and the guest speaker and many of the students wore large, luminous and eerie mushroom-cloud pins that accurately depicted the real thing more than any representation I had seen. It was a photograph displaying the colours in an uncanny and haunting way. Old newsreel films appearing on television and demonstrating the monstrous and fearsome weapon have never been easy to watch, either.

My concerns about the effects of the nuclear experiment escalated through the years - I even wrote an opinion piece on the subject for The Boston Globe in 1978. I also made a special trek to Hiroshima to witness at first hand the after-effects of this brutal weapon. My health remained quite intact until I was told in December 2003 that I had contracted leukaemia. Fortunately, by that time, a miracle pill had been developed that neutralised the effects of the disease and reduced the excessive production of white blood cells. I might not have survived leukaemia had I contracted it earlier; the new drug had come into existence only in 2001. What kinds of cancer or other diseases may still be over the horizon is, of course, difficult to guess.

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It should surprise no one that I have been anti-nuke for a very long time. I believe in the Non-Proliferation Treaty, the Test Ban Treaty and the Anti-Ballistic Missile Treaty, all of which were so casually and unilaterally cancelled by George W. Bush, and I am wary even of the peaceful uses of nuclear power.

I believe that I should, whenever possible, raise consciousness in people that will have some lasting effects. I have never talked much about my own experience with the Bomb, but I devised a "nuclear war threat" game for some of my classes that had, I was told, a ring of truth about it.

Through years of thinking, teaching, reading and arguing about the complexity of nuclear weapons and the even greater complexity and stringency of caveats attached to any effort to de-escalate or de-emphasise what J. Robert Oppenheimer and many others saw as a tragic development for the world, those moments in the Nevada desert continue to sear the heart and burden the mind. A non-nuclear world must be sought as long as any possibility remains of its achievement.

The odds, as some of us realise, may be against us. There is an abundant supply of loose nukes out there, the nuclear club keeps growing, and irrationality can often creep into the minds of power-wielders and policymakers.

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