Joint Effect Of Radiation And Nitrate Content In Groundwater ñ Major Factors Affecting Incidence Of Childhood Thyroid Cancer In Belarus After The Chernobyl Accident

Valentina DROZD, Project Chernobyl, Brooklyn, NY 11235 USA, United States
SAENKO V. 3 , BRENNER A. 4 , DROZDOVITCH V. 4 , PASHKEVICH V. 5 , KUDELSKY A. 5 , DEMIDCHIK Y. 6 , BRANOVAN I. 1 , SHIGLIK N. 1 , ROGOUNOVITCH T. 3 , YAMASHITA S. 3 , BIKO J. 7,2 , REINERS C. 7,2

1 Project Chernobyl, Brooklyn, NY 11235 USA
2 The International fund “Help for patients with radiation-induced thyroid cancer “Arnica”, Minsk, Belarus
3 Department of Molecular Epidemiology, Atomic Bomb Disease Institute, Nagasaki University, Nagasaki, Japan
4 Division of Cancer Epidemiology and Genetics, National Cancer Institute, NIH, US DHHS, Bethesda, USA
5 Laboratory of Hydrogeology and Hydroecology, Institute for Nature Management of the National Academy of Sciences, Minsk, Belarus
6 Department of Oncology, Belarusian Medical Academy for Postgraduate Education, Minsk, Belarus
7 Clinic and Polyclinic of Nuclear Medicine, University of Wuerzburg, 6 Oberdurrbacher str., Wuerzburg D-97080, Germany

          One of the most serious  health consequences of the Chernobyl Nuclear Power Plant accident in 1986 was a dramatic increase in the incidence of thyroid cancer among those who were aged less than 18 years at the time of accident.
            Among the factors that may increase the incidence of thyroid cancer, the following have been identified: radiation dose, young age at exposure, thyroid screening, iodine deficiency, and genetic predisposition.
            Various screening programs conducted in 1990-2008 in Belarus have shown the prevalence of thyroid carcinoma among children of 0.19%-0.62% in different regions. The highest thyroid dose (320 mGy) was  in children of Gomel Oblast. The doses in Mogilev and Brest Oblasts were 65 and 51 mGy, respectively. However, the results of ultrasound screening programs suggested that given comparable screening and thyroid radiation doses, the prevalence of pediatric thyroid cancer in Brest Oblast was substantially higher than in Mogilev Oblast (5.5 vs 1.5 per 100,000 PY).
            Concentration of nitrate in groundwater in the early 1990’s was 112 mg/L in Gomel, 40 mg/L in Mogilev, and 185 mg/L in Brest Oblast exceeding the MCL 2.5- and 4.0-fold in Gomel and Brest, respectively. Groundwater from open wells is the main source of drinking water in rural areas in Belarus.
Study of the relationship between childhood thyroid cancer incidence, radiation thyroid dose and nitrate in groundwater in Belarus have shown that radiation dose was significantly associated with thyroid cancer incidence (P=0.029). Effect of radiation significantly varied according to nitrate concentration (P=0.004). (Drozd V et al., 2015).
            Analytic epidemiological studies aimed at quantification of the joint effect of nitrate content in groundwater and radiation present a promising approach to understanding the impact and control of environmental factors on the growing incidence of thyroid cancer all over the world.