Page 50 - PR 2014 2016 07 Nuclear Science and Technology

192 Nuclear Science and Technology | Progress Report

increase the availability of 238 U and 232 Th to producer of tobacco worldwide, according to
the leaching water. the crop production of 2013/2014. The tobacco
plant (Nicotiana tabacum L.) is used to manu-
Dosimetry of Rn in the air in environments facture all derivatives and the chemical compo-
222
located above and below ground level sition of the resulting tobacco products varies
with the type of tobacco leaves, how they are
Exposure of the general population to ionizing grown, the region where they are cultivated,
radiation comes mainly from natural sources. the characteristics of preparation (compres-
The main contribution is due to inhalation sion, filter and paper) and the temperature
of radon ( Rn), a gas that occurs naturally. variations resulting from the incomplete com-
222
222
The Rn concentration in the environment is bustion of tobacco. Tobacco products are exten-
controlled by factors such as soil permeability sively used throughout the world, and the most
and water content, the weather variability, consumed are cigarettes, cigars and narghile.
materials used in the foundation and the usual The damaging effects that these products cause
positive pressure differential between the soil to human health are discussed globally, and
and the internal environment. Studies indicate many surveys are performed with the aim of
that the concentration of radon shows a wide relating the use of these products with various
variation in the basement, ground floor and illnesses. There is a lack of information about
upper floors of buildings. Radon levels in base- the radiological characterization of the tobacco
ments, ground floor and floors above ground plant both in international and Brazilian liter-
level, at a university in the city of São Paulo ature. The concentration of radionuclides U,
238
and in one residential building in the city of 234 U, Th, Ra, Pb and Po, members of the
226
230
210
210
Peruíbe, were determined. Measurements of 238 U decay series, and the radionuclides 232 Th
222 Rn were performed using the method with and 228 Ra, members of the 232 Th decay series
nuclear track of solid state detectors (CR39). The in the varieties Burley and Virginia, which are
222
studied environments present Rn concentra- the most cultivated in Brazil, was determined.
tion well below the values recommended by Plants from these varieties were cultivated in
the International Commission on Radiological pots with organic substrate and fertilizer and
Protection, published in the 2009 document, also acquired from the producers and analyzed
of 300 Bq · m for homes and 1000 Bq · m by alpha spectrometry for U and Th isotopes
-3
-3
210
for the workplace. In the residential building, and Po determination, and gross alpha and
the concentration of Ra, Th and K in the beta counting, Ra, Ra, and Pb determi-
228
232
40
226
210
226
materials used in the building construction nation. The whole plant, from both places, was
was also analyzed, by gamma spectrometry. analyzed; root, stem, leaves, as well as the or-
The effective total dose for the resident due to ganic substrate, the fertilizers, and the soil. The
external exposure was 0.8 mSv · y , lower than results for U and Th isotopes presented values
-1
the annual dose limit for the general public of below the detection limits of the methods to
-1
1 mSv · y . the leaves and stems of all plants analyzed,
with measurable results only in roots, soil, and
Assessment of natural radionuclides concentration substrate. The radionuclides Ra, Ra, Pb,
210
226
228
from U and Th series in Virginia and and Po were determined in most parts of the
238
232
210
Burley varieties of Nicotiana tabacum L. plants, with the highest values obtained for
228 Ra, which also had the highest value of the
Brazil is the largest exporter and second largest transfer factor. Plants grown at IPEN showed

Instituto de Pesquisas Energéticas e Nucleares