Radiation Exposure and Thyroid Disease in Kazakhstan
Condition: Thyroid Cancer; Thyroid Nodules; Other Thyroid Disease
MeSH terms: Thyroid Nodule; Thyroid Diseases
Study type: Observational

Summary: 
      Residents of certain villages in Kazakhstan were exposed during childhood to radioactive
      fallout from nuclear tests conducted at the Semipalatinsk Nuclear Test Site (SNTS) between
      1949 and 1962.

      Radiation doses to the thyroid from external and internal (i.e., ingested) radiation sources
      deposited as fallout are of interest because they may be jointly and differentially
      associated with increased risk of thyroid disease in this population.

      Objectives:

      To collect information about factors influencing radiation dose to the thyroid gland in
      children of two ethnic groups who were exposed to radioactive fallout from nuclear tests at
      the SNTS between 1949 and 1962. The two groups are Kazakhs (historically nomadic herders) and
      Europeans (typically descendants of Russian and German farmers).

      Eligibility:

      Women 70 years of age and older who had children or provided care to children during the
      1950s.

      Men age 70 and older who were engaged in farming and care of dairy animals at the time of the
      nuclear tests.

      Design:

      In focus group format, participants are interviewed to collect information on the following
      at the time of nuclear tests:

        -  Dairy consumption;

        -  Source, storage and availability of milk and milk products;

        -  Time that children of different ages and ethnic groups spent indoors;

        -  Building material of houses and schools;

        -  Herding, grazing and supplemental feed of dairy animals.
    

Detailed description: 
      The proposed work will improve our understanding of historical, fallout-related radiation
      doses received by residents of villages in Kazakhstan immediately downwind from the
      Semipalatinsk Nuclear Test Site (SNTS), where multiple nuclear test explosions were carried
      out between 1949 and 1962. In collaboration with scientists at the Institute for Biophysics
      in Moscow, NCI has developed a combined bi-national dose reconstruction methodology based on
      lessons learned from studying radioactive fallout from tests at the SNTS in Kazakhstan, the
      Nevada Test Site in the United States, and other test sites. Gamma rays from radionuclides
      such as cesium 137 in fallout are highly penetrating and can affect all organs even when the
      radioactive source is outside the body, whereas less-penetrating beta particles from iodine
      131, also plentiful in fallout, mainly affect the thyroid gland when ingested in milk from
      dairy animals grazing on contaminated pasture. We are particularly interested in both kinds
      of radiation doses to children, because their thyroid glands are small and very active, tend
      to concentrate ingested iodine, and are highly sensitive to radiation carcinogenesis. The
      conditions of fallout exposure in Kazakhstan are directly relevant to those following a
      hypothetical nuclear accident or radiation terrorism incident involving high levels of local
      fallout.

      We propose a field study in Kazakhstan to investigate aspects of typical daily village life
      in areas affected by fallout that might influence individual radiation doses to the thyroid
      gland. Using focus group interviews, we will collect retrospective information about factors
      influencing radiation dose to the thyroid gland in children of two distinct ethnic groups
      (Kazakh and European). These factors include milk and milk product consumption, dependence on
      different species of dairy animals known to differ with respect to concentration of iodine in
      milk, seasonal practices of pasturing and supplemental feeding of dairy animals at the time
      of the nuclear tests, time children typically spent outdoors, and radiation shielding
      provided by dwellings and other buildings. We will also ask about protective measures taken
      at the time, such as details of temporary evacuations of villages predicted to be in the
      fallout paths from particular tests. These data will fill key gaps in the current
      dose-reconstruction methodology and should result in improved dose estimates, as well as a
      basis for evaluating and quantifying dosimetric uncertainty and related biases in risk
      estimates.
    

Time perspective: Retrospective
Keywords: Radioactive Fallout; Childhood Exposures; External Radiation Dose; Internal Radiation Dose to Thyroid Gland; Pasture-Dairy Animal- Milk- Thyroid Pathway