SPATIAL-DISTRIBUTION OF NATURALLY-OCCURRING PO-210 AND RA-226 IN CHILDRENS TEETH

Deciduous and permanent teeth extracted from juveniles for orthodontic purposes have been analysed using alpha-sensitive plastic track detec tors for the spatial distribution of total alpha-activity and naturall y occurring Pb-210-supported Po-210 and Ra-226. The distribution of th ese radionuclides is nonuniform, with Po-210 being primarily associate d with outer enamel and Ra-226 With the pulp. The observations suggest that Pb-210/Po-210 concentrates at the interface of enamel with saliv a or blood, by means of unidirectional ionic exchange with calcium. In contrast, Ra-226 concentrates in the predentine band at the interface with pulp and with systemic blood circulation, where its uptake is pe rmitted by the incomplete calcification in this band. Activity concent ration was measured in 900 teeth. Total concentration on the outer ena mel surface of deciduous teeth, permanent teeth from children less tha n or equal to 10 years and permanent teeth from children >10 years giv e respective mean values of 8.63+/-0.26, 5.76+/-0.48 and 7.00+/-0.15 B q kg(-1). Ra-226 concentration on the corresponding longitudinal secti ons comprising pulp, dentine and annular enamel give respective mean v alues of 0.7I5+/-0.055, 0.418+/-0.083 and 0.514 +/-0.029 Bq kg(-1). Me an activity concentration in 32 foetal teeth was 2.05+/-0.31 Bq kg(-1) . The results form the basis of more detailed studies of (1) age-depen dent uptake of alpha-radionuclides in teeth and their microdistributio n, and (2) the geographical variation in activity concentration with r espect to environmental factors such as domestic radon exposure.