Page 197 - 00. Complete Version - Progress Report IPEN 2014-2016

Nuclear Science and Technology | Progress Report 197

crease the availability of U and Th to the est producer of tobacco worldwide, according
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leaching water. to the crop production of 2013/2014. The to-
bacco plant (Nicotiana tabacum L.) is used to
Dosimetry of Rn in the air in environments manufacture all derivatives and the chemical
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located above and below ground level composition of the resulting tobacco products
varies with the type of tobacco leaves, how
Exposure of the general population to ionizing they are grown, the region where they are
radiation comes mainly from natural sources. cultivated, the characteristics of preparation
The main contribution is due to inhalation of (compression, filter and paper) and the tem-
radon (222Rn), a gas that occurs naturally. The perature variations resulting from the incom-
222Rn concentration in the environment is plete combustion of tobacco. Tobacco products
controlled by factors such as soil permeabili- are extensively used throughout the world,
ty and water content, the weather variability, and the most consumed are cigarettes, cigars
materials used in the foundation and the usu- and narghile. The damaging effects that these
al positive pressure differential between the products cause to human health are discussed
soil and the internal environment. Studies in- globally, and many surveys are performed with
dicate that the concentration of radon shows a the aim of relating the use of these products
wide variation in the basement, ground floor with various illnesses. There is a lack of infor-
and upper floors of buildings. Radon levels mation about the radiological characteriza-
in basements, ground floor and floors above tion of the tobacco plant both in internation-
ground level, at a university in the city of São al and Brazilian literature. The concentration
Paulo and in one residential building in the of radionuclides U, U, Th, Ra, Pb and
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city of Peruíbe, were determined. Measure- 210 Po, members of the U decay series, and the
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ments of 222Rn were performed using the radionuclides Th and Ra, members of the
method with nuclear track of solid state de- 232 Th decay series in the varieties Burley and
tectors (CR39). The studied environments pres- Virginia, which are the most cultivated in Bra-
ent 222Rn concentration well below the values zil, was determined. Plants from these variet-
recommended by the International Commis- ies were cultivated in pots with organic sub-
sion on Radiological Protection, published in strate and fertilizer and also acquired from the
the 2009 document, of 300 Bq·m3 for homes producers and analyzed by alpha spectrometry
and 1000 Bq·m3 for the workplace. In the res- for U and Th isotopes and Po determination,
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idential building, the concentration of 226 Ra, and gross alpha and beta counting, Ra, Ra,
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232 Th and 40K in the materials used in the and Pb determination. The whole plant, from
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building construction was also analyzed, by both places, was analyzed; root, stem, leaves,
gamma spectrometry. The effective total dose as well as the organic substrate, the fertilizers,
for the resident due to external exposure was and the soil. The results for U and Th isotopes
0.8 mSv·y1, lower than the annual dose limit presented values below the detection limits
for the general public of 1 mSv·y1. of the methods to the leaves and stems of all
plants analyzed, with measurable results only
Assessment of natural radionuclides concentration in roots, soil, and substrate. The radionuclides
from U and Th series in Virginia and 226 Ra, Ra, Pb, and Po were determined in
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Burley varieties of Nicotiana tabacum L. most parts of the plants, with the highest val-
ues obtained for Ra, which also had the high-
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Brazil is the largest exporter and second larg- est value of the transfer factor. Plants grown at