Becquerel: one nuclear disintegration per second, equal to 2.7 X 10-11 curie.
Gray (Gy): 1 J/kg, equal to 100 rad.
Rad: 100 erg/g, equal to 0.01 Gy.
Rem (radiation-equivalent man):
a rad (radiation-absorbed dose) adjusted for a quality factor (q) reflecting the biological "effectiveness" (that is, destructiveness) of the radiation and situation. That is, q is a function of radiation type, its energy, and the material affected.
Sievert: 100 rem.
Person.sievert (or person.gray): a unit of population exposure obtained by summing dose-equivalent values for all exposed persons.
The explosions and fires that wrecked the Chernobyl nuclear reactor 10 years ago last April brought on what is universally recognized as a catastrophe. Besides the immediate fatalities and human upheaval, which left hundreds of thousands disoriented, anxious about their own health, and bitterly concerned about their children, the accident inflicted incalculable material losses. In economic terms alone (though not in terms of casualties), Chernobyl was the greatest peacetime industrial disaster of all time. Its 10th anniversary was a fitting occasion for stocktaking--for determining what has been and has yet to be learned about the event, and for improving efforts to help the victims.
The one salvageable benefit is vital new information on how ionizing radiation affects human health. Already, to be sure, that relationship is better understood than the effects of most industrial pollutants, in both qualitative and quantitative terms. Further, unlike other contaminants, radiation doses are easy to reconstruct from the trails left by radioactive decay. But until now, the most important data on radiation health effects have come from the ongoing studies of survivors of the Hiroshima and Nagasaki atomic bombings. And inferences drawn from those intense exposures to radiation have not always meshed well with the results found when less radiation over a longer time is involved. Chernobyl is the first instance of huge populations being exposed to mostly low doses for many months and years.
As the 10th anniversary of the April 26, 1986, nuclear accident drew near, three major international conferences on its health effects were mounted. The culmination was a large gathering of experts in early April at the Austria Centre in Vienna, which IEEE Spectrum attended. It was sponsored by the International Atomic Energy Agency (IAEA), the World Health Organization (WHO), and the European Commission (EC). Concurrently, the Nuclear Energy Agency, based in Paris, issued an appraisal of the accident's radiological and health consequences. As for the two earlier conferences, one was sponsored by the WHO in Geneva, in November 1995, and the other was sponsored by the EC, Belarus, Russia, and the Ukraine in March 1996 in Minsk, Russia.
The scale of the reevaluations and the large overlap among the specialists taking part encouraged a fair degree of consensus about the accident's health effects so far. Still, first findings are tentative. One U.S. expert at the IAEA conference, radiologist F. A. Mettler, frowned on the Vienna meeting's billing: "Summing Up the Consequences of the Accident." Mettler, a member of the University of New Mexico's School of Medicine, Albuquerque, observed that full comprehension would take not 10 but 50 years.
Vastly complicating analysis is the crisis afflicting the former Soviets since the breakup of the USSR. In Russia, where national output is thought to have dropped by 50 percent and industrial production by nearly 75 percent, life expectancy for men has plummeted about seven years (to 58!) since 1986.
Often, too, those responsible for the welfare of victims are tempted to exaggerate, desperate as they are for funds. Belarus, the Ukraine, and Russia each have had at one time or another a ministry just for Chernobyl relief and monitoring. In Belarus, home to the worst-affected districts, 20-25 percent of the state budget goes to remedying Chernobyl's effects. Small wonder that Angela Merkel, Germany's environmental minister and the president and keynote speaker of the Vienna conference, agreed with Mettler that Chernobyl's consequences "cannot be summarized conclusively even today, 10 years after the accident."
That said, three early results stand out: