[en] One of the most massive ⁹⁰Sr releases in mankind's history was produced by the first Soviet nuclear weapon plant Mayak near the Techa River, Urals, Russia. In 1949-1956 about 7.6·10⁷m³ liquid radioactive wastes with a total activity of 10¹⁷ Bq(2.7·10⁶ Ci) was released into the Techa river, with an 11.6% contribution of ⁹⁰Sr to the total activity. As a result of Mayak's radioactive discharges, the population of the Techa riverside (about 28,000 people) was exposed to high levels of ionizing radiation. An EPR dose reconstruction study with 29 teeth of Middle and Lower Techa riverside population was carried out. In total 67 samples from tooth enamel (27), crown (20) and root (20) were prepared and studied with EPR from these 29 teeth. It revealed ultrahigh doses (up to 15 Gy) absorbed in tooth enamel of the individuals born in 1945-1949. The ultrahigh reconstructed doses in tooth enamel for individuals born in 1945-1949 were explained by ultrahigh local ⁹⁰ Sr concentration in tooth enamel of this particular age group of population. The introduction of corrections based on the effective time of the onset of dose accumulation and dose attenuation coefficients has eliminated serious contradictions of the original reconstructed doses. The methodology developed here enabled the dose regime of irradiation of Middle and Lower Techa riverside population to be reconstructed on the basis of ERP dosimetry. The fact that some age groups of Techa riverside population have absorbed doses in tooth enamel a factor of 50 higher than the rest of population can be used for future investigations. This group of the population is a much more sensitive indicator of the previous ⁹⁰Sr releases than others. The other important factor is tooth position. The tooth most sensitive to ⁹⁰Sr internal exposure is the first molar (both tooth enamel and dentin). A tooth from this position can give an additional enhancement factor of 4-6. Thus, selection by age group and tooth position at sample collection can improve the detection and measurement of former ⁹⁰Sr releases by a factor of 200. (author)