Abstract From 1949 onwards, radioactive waste was re- leased into the Techa River in the southern Urals and the population living along the river was exposed to ionising radiation. Relocation of these people did not start until several years later, causing many individuals to be ex- posed to substantial doses from internal and external ra- diation. The identification and follow-up of the exposed individuals started more than 40 years ago and is still continuing. The Techa River offspring cohort (TROC) that has recently been established, comprises 10,459 children born to at least one parent living along the Techa River during the period 1950–1992. Of these chil- dren, 3,897 were born during the period of highest re- lease, i.e. between 1950 and 1956 and might thus have been exposed in utero. A total of 1,103 individuals have since died mainly due to infectious and respiratory dis- eases, injury and poisoning. Only 25 cases were identi- fied as having died of a malignant condition. The radio- active contamination of the Techa River in the southern Urals gives a unique possibility to study the adverse effects of protracted exposure to ionising radiation in a large well-described cohort. The Techa River offspring cohort will make it possible to study the effects on those exposed in utero or early in life and the follow-up of the cohort in the future is, therefore, of great importance. Comparisons with other cohorts of humans exposed ear- ly in life, will increase our knowledge in this field of re- search. Introduction It is a well-established fact that ionising radiation induc- es cancer and leukaemia in humans, as has been shown after medical exposure as well as among the Japanese A-bomb survivors [1]. Several factors influence the risk of a subsequently occurring cancer, of which the most prominent factors are radiation quality, dose rate, tissue exposed, time since exposure and, probably most impor- tant, attained age [1]. For certain cancers, age at expo- sure has a profound impact on risk; for example, the risk of thyroid cancer among the survivors of the bombings in Hiroshima and Nagasaki decreased from a 10-fold in- creased risk in those exposed before the age of 10 years to a risk not different from unity among those exposed at the age of more than 20 years [2]. Exposure to ionising radiation during various phases of the oogenesis and spermatogenesis can result in germ- cell depletion, manifested as sterility or reduced fertility. Chromosome and DNA abnormalities causing malforma- tions, hereditary diseases and cancer [3] could be the result of ionising radiation. Little is known, however, about cancer in offspring after exposure of parental gonads. Childhood leukaemia in the vicinity of the Sellafield nuclear facility has been correlated to paternal gonadal exposure [4], and the so-called Gardner effect [5] has been under discussion, since such observations have not been made elsewhere. An increased risk of childhood leukaemia was actually found in areas where nuclear facilities had been planned but not yet built [6], and there is some possibility that risk factors other than ionising radiation, such as socio-economic status and infectious agents, influence the risk of childhood leukae- mia as previously suggested [7, 8]. In utero exposure to ionising radiation is known to re- sult in abortion, stillbirth, congenital malformations, foe- tal growth retardation, neurobehavioural abnormalities and cancer [3]. Studies of the carcinogenic effect on the foetus after x-ray examinations of pregnant mothers yield conflicting results [9]. As early as 1956, Stewart et al. [10] reported that prenatal radiation was associated M.M. Kossenko · Y. Ostroumova · A. Akleyev · N. Startsev M. Degteva Urals Research Center for Radiation Medicine, Chelyabinsk, Russia F. Granath · P. Hall ( ✉ ) Department of Medical Epidemiology, Karolinska Institute, P.O. Box 281, 171 77 Stockholm, Sweden e-mail: per.hall@mep.ki.se Tel.:+46-87286152, Fax: +46-8314975 Radiat Environ Biophys (2000) 39:219–225 © Springer-Verlag 2000 ORIGINAL PAPER M.M. Kossenko · Y. Ostroumova · A. Akleyev N. Startsev · M. Degteva · F. Granath · P. Hall Mortality in the offspring of individuals living along the radioactively contaminated Techa River: a descriptive analysis Received: 18 August 2000 / Accepted: 22 September 2000