Ph.D. Theses

Peculiarities of the formation of the radon field and its possible pathogenic influence (the territory of Azerbaijan as the case study)

Applicant: Farah Fuad Mahmudova

Speciality: 2508.01 – Geoecology

Field of science: Earth sciences

Relevance of the work.
The radiation safety of the population is a global and important problem of our time. The main radiation background of the Earth is formed due to natural radiation sources. Numerous exploration conducted abroad convincingly proved that radon and its short-lived daughter decay products that create about 40-75% of summary doze that human gets from all natural sources ionizing radiation. Currently, the protection of the population from radon, the natural radioactive gas, is an important problem, necessitating a number of research works to identify the sources of this gas, to determine its amount in residential areas. With an indoor increase of volumetric activity of radon, there is an increase of patients’ number with malignant lung neoplasms. In 1987, experts of the International Agency of Cancer Study classified radon and its daughter decay products as a group of elements definitely carcinogenic to humans. In many developed countries of the world, national and regional programs are working to estimate and map the radon situation. The results of radiometric exploration, taken in Azerbaijan since 1970, showed that the natural radiation background on the territory of Azerbaijan is located within places typical for rocks and soil and accounts for about 4-12 mR/h. At the same time, it was determined a link between natural radiation field and the geological structure of the territory.

However, certain works in our country on radon problem had been done since 2000, the problem demanded a comprehensive and complex study with consideration of specialty of the geological structure of the explored territory, allocation of radon volumetric activity and factors, that affect its changes, the role of radon radiation in the incidence degree of malignant lung neoplasms among population.

The work was carried out as part of a project of the Swiss National Science Foundation “Creation of cadaster and radon spread map in Azerbaijan using Swiss methodology and experience” and with the financial support of the Foundation for the Development of Science under the President of the Azerbaijan Republic within the framework of the grant project №EİF-2013-9 (15) - 46/24/2-M-33 and the State program "Study of radon hazard in Azerbaijan and measures to reduce it" for 2014-2018.

Object and subject of research.
The object of the study is the territory of Azerbaijan, the ubject - the study of radon status in the territory of Azerbaijan and the detection of the degree of pathogenicity of radon radiation for the population of the republic.

Purpose of the work.
The purpose of the dissertation work is a comprehensive assessment of the radon situation in Azerbaijan, the determination of critical areas of radon hazard and the identification of the degree of pathogenicity of radon radiation for the population of various regions.

The next tasks were solved in order to achieve set of goals:
  • Identification of zones with relatively high concentrations of volumetric activity of radon;
  • Identification of the main sources of radon indoor permeability in certain regions;
  • Analysis of statistical data on the incidence of malignant respiratory neoplasms among population for the period of 2005-2015;
  • Identification of link between average radon volumetric activity and index of incidence of patients’ with lung malignances.

Research methods.
For measuring and monitoring of the volumetric activity of radon were used express (with the help of radometer radon RAD7, RadonScout and RadonScoutPlus) and integrated methods (with the help of track detectors Radtrak2 radiative activity of the Swedish firm Radtrak2).

When considering the biological effects of radon exposure, a model approach was used based on the correlation method.

Main defending statements:
  1. Pathogenic zones with high intensity of radon radiation exceeding the level of maximum permissible norms in Azerbaijan;
  2. The link between the volumetric activity of radon and the incidence of the population of malignant lung neoplasms living in pathogenic zones of Azerbaijan.

Scientific novelty of the work:
  • Zones with relatively high radon concentrations were identified and the territory of Azerbaijan was divided into districts according to the degree of radon hazard;
  • Main sources of radon radiation have been identified;
  • High incidence of malignant lung neoplasms were identified within the mountain-fold zone of the Greater and Lesser Caucasus and Talysh, where increased values of the volumetric activity of radon had been recorded;
  • A high level of malignant lung neoplasms patients’ incidence number dependency of the level of radon volumetric activity for certain regions was determined based on correlation analysis.

Practical relevance of the results:
  • Zoned indicators of volumetric activity of radon for the territory of Azerbaijan were determined;
  • Persons, living in conditions of increased radon concentration, were given appropriate recommendations on ensuring radiation safety, there was determined a set of additional researches and measures necessary to reduce the danger of radon exposure to the population.