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24the teeth of 6,000 children and found that childrenborn soon after the Chernobyl catastrophehad 10 times more Sr-90 in their teethcompared with children born in 1983 (Ecologist,2000).Problem of Americium-241. The powerful alpharadiation emitter Am-241, formed as a resultof the natural disintegration of Pu-241, isa very important factor in the increasing levelsof contamination in many areas locatedup to 1,000 km from the Chernobyl NPP.The territory contaminated by Pu today, wherethe level of alpha radiation is usually low, willagain become dangerous as a result of the futuredisintegration of Pu-241 to Am-241 inthe ensuing tens and even hundreds of years(see also Chapter III.9). An additional dangerof Am-241 is its higher solubility and consequentmobility into ecosystems compared withPu.1.6. Lead ContaminationDuring operations to quench the fires inthe fourth reactor of the Chernobyl NPP, helicoptersdumped 2,400 tons of Pb into the reactor(Samushia et al., 2007; UNSCEAR, 2000);according to other data, the figure was 6,720tons (Nesterenko, 1997). During several subsequentdays, a significant part of the Pb wasspewed out into the atmosphere as a result of itsfusion, boiling, and sublimation in the burningreactor. Moreover, Pb poisoning is dangerousin itself, causing, for example, retardation inchildren (Ziegel and Ziegel, 1993; and manyothers).1. Blood Pb levels in both children and adultsin Belarus have noticeably increased overthe last years (Rolevich et al., 1996). In theBrest Province of Belarus, for example, of213 children studied, the level of Pb was0.109 ± 0.007 mg/liter, and about halfof these children had levels of 0.188 ±0.003 mg/liter (Petrova et al., 1996),whereas the World Health Organization(WHO) norm for children is no more than0.001 mg/liter.2. In Ukraine in the Poles’e District of KievProvince,levelsofPbintheairbreathedby operators of agricultural machinerywas up to 10 times or more, exceedingmaximum permissible concentrations. Increasedlevels of Pb were apparent in thesoil and atmosphere and in the urine andthe hair of adults and children in Kievsoon after the explosion (Bar’yakhtar,1995).3. Pb contamination added to radiationcauses harm to living organisms (Petinand Synsynys, 1998). Ionizing radiationcauses biochemical oxidation of free radicalsin cells. Under the influence ofheavy metals (such as Pb) these reactionsproceed especially intensively. Belarussianchildren contaminated with both Cs-137and Pb have an increased frequency ofatrophic gastritis (Gres and Polyakova,1997).1.7. Evaluation of Chernobyl’sPopulation DosesThe International Atomic Energy Agency(IAEA) and WHO (Chernobyl Forum, 2005)estimated a collective dose for Belarus, Ukraine,and European Russia as 55,000 persons/Sv. Byother more grounded estimates (see Fairlie andSumner, 2006) this collective dose is 216,000–326,000 persons/Sv (or even 514,000 persons/Svonly for Belarus; National BelarussianReport, 2006). The worldwide collective dosefrom the Chernobyl catastrophe is estimatedat 600,000–930,000 persons/Sv (Table 1.6).However, it is now clear that these figuresfor collective doses are considerably underestimated.1.8. How Many People Were andWill Be Exposed to Chernobyl’sContamination?The first official forecasts regarding thehealth impact of the Chernobyl catastrophe