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Distribution of indoor radon levels in Mexico

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Abstract

Our laboratory has carried out a systematic monitoring and evaluation of indoor radon concentration levels in Mexico for ten years. The results of the distribution of indoor radon levels for practically the entire country are presented, together with information on geological characteristics, population density, socioeconomic levels of the population, and architectural styles of housing.The measurements of the radon levels were made using the passive method of nuclear tracks in solids with the end-cup system. CR-39 was used as the detector material in combination with a one-step chemical etching procedure and an automatic digital-image counting system. Wherever a high level was measured, a confirming measurement was made using a dynamic method. The results are important for future health studies, including the eventual establishment of patterns for indoor radon concentration, as it has been done in the USA and Europe.
Radiation Measuremenls
PERGAMON
Radiation Measurements 31 (1999) 355-358
DISTRIBUTION OF INDOOR RADON LEVELS IN MEXICO
G. ESPINOSA*, J.I. GOLZARRI*, J. R/CKARDS*,AND R.B. GAMMAGE.'*
* Instituto de Fisica, UNAM. Apdo. Postal 20-364, 01000 M6xico, D.F.
** Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831, USA.
ABSTRACT
Our laboratory has carried out a systematic monitoring and evaluation of indoor radon
concentration levels in Mexico for ten years. The results of the distribution of indoor
radon levels for practically the entire country are presented, together with information on
geological characteristics, population density, socioeconomic levels of the population, and
architectural styles of housing.
The measurements of the radon levels were made using the passive method of nuclear
tracks in solids with the end-cup system. CR-39 was used as the detector material in
combination with a one-step chenfical etching procedure and an automatic digital- image
counting system. Wherever a high level was measured, a confirming measurement was
made using a dynamic method. The results are important for future health studies,
including the eventual establishment of patterns for indoor radon concentration, as it has
been done in the USA and Europe.
KEYWORDS
Indoor radon; nuclear track methodology; global information.
~TRODUCTION
Radon is the highest contributor to the effective dose equivalent in man (IAEA, 1989) from the
natural sources and has been studied by multiple countries and organizations (Bochicchio
et aL,
1996; Marcionwsky, 1992; Miles, 1998; Starnd, 1992).
Several countries have conducted national programs of indoor radon concentration measurements in
buildings and houses. These programs were motivated by the need to confirm the relationship
between the exposure to radon of the public in general and the lung cancer risk (Chudhry
et al.,
1996;
Cohen, 1998a,b; Lubin, 1998; Nausen and Cohen, 1987; Nazaroff and Nero, 1988; Stidley and
Samet, 1993).
For many nations, the country wide distribution of indoor radon has been established. This
knowledge is important for determining the risk of lung cancer associated with indoor radon.
For about 10 years, the National Autonomous University of Mexico, with the help of international
organizations, has undertaken the task of developing a cost-effective radon measurement method and
then using this methodology to measure indoor radon levels in many parts of Mexico.
In this paper we present the data of indoor radon concentration collected from the measurements of
some locations with more than 100,000 inhabitants in the national territory, excluding the tropical
zones.
1350-4487/99/$ - see front matter © 1999 Elsevier Science Ltd. All rights reserved.
PII:
S 1350-4487(99)00171-7
356
G. Espinosa et aL / Radiation Measurements 31 (1999) 355-358
METHODOLOGY
For this large scale radon measuring program, the passive close-end cup system was selected, using
CR-39, 600 Inn thick polycarbonate (Landauer ®) as the detection material. The CR-39 was cut
automatically by a laser beam into chips of size 9 nun x 18 nun.
To develop the alpha track we used a one-step chemical etching in KOH, 6.25M at 60°C + I°C for 16
hours. (Espinosa and Gammage, 1993). The etched tracks were counted by a Digital Image
Automatic System (DIAS) (Gammage and Espinosa, 1997). All the procedures were optimized step-
by-step, and the calibration was carried out at the Oak Ridge National Laboratory facilities.
The characteristics of Dwellings: The dwellings under study were built in general with volcanic rock
and clay bricks, limestone bricks or soil adobe, with a concrete and iron structure. The walls of the
dwellings can be often covered with gypsum, and several of these materials are expected to contribute
significantly to sources of indoor radon. But on the other hand, the architectural style is communly a
central patio with high ventilation characteristics or open windows and sometimes without a frame or
glass.
RESULTS
In Fig. 1, the locations under study are shown. In Table 1 the names of the towns under study, their
population (INEGI, 1995), the number of surveyed houses, and the indoor radon activity in each
location are given.
Figure 1. Towns under study.
We find that out of 39 locations under study, there are only 8 locations with more than 150 Bq m -3,
but less than 179 Bq m -3, 5 locations with values between 100 to 150 Bq m 3, 23 locations between 50
to 100 Bq m -3, and 3 locations under 50 Bq m "3. It is observed that the larger indoor radon
concentrations are fundamentally related with architectonic styles and type of constructions. This
study did not include rustic and semirustic dwellings.
G. Espinosa et al. /Radiation Measurements 31 (1999) 355-358
Table 1. Towns under study with their population and the indoor radon activity m each location
357
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
2O
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
Towns Under Study
clt~
A~uasealientes
Tijuana
Chihuahua
State
Aguasealientes
Baja California
Chihuahua
Population
582,827
991,592
627,662
Number of
Surveyed
Houses
200
250
200
Lower
Activity
(nq .c)
39
62
69
mgher
Act~ff
Ohm-)
154
119
Mean
A~vity
~Bq m-5
79
78
273 169
Ciudad Juarez Chihuahua 1,011,786 280 63 252 159
Saltiilo Coahuila 527,979 200 35 127 79
Torreon Coahuila 508,076 200 61 160 87
Monclova Coahuila 189,738 150 47 110 60
Mexico City
Durango
Tohea
Distrito Federal
Durallgo
Estado de Mexico
Ciudad Netzahualcoyoti "
Ecatepec Estado de M6xico
Estado de Mexico
Nauealpan
Tlalnepantla
Guanajuato
Leon
Estado de M6xico
Estado de M6xico
Guanajuato
Guanajuato
Guanajuato
Ouanajuato
Hidalgo
Hidalgo
Hidalgo
Jalisco
Jalisco
Jalisco
Irapuato
Cela~a
Pachuca
Tulancingo
Tula
Ouadalajara
Zapopan
Tlaquepaque
Morelia Michoacan
Uruapan Michoacan
NuevoLe6n
NuevoLe6n
8,362,670
464,566
564,476
1,457,124
1,233,868
839,723
713,143
128,171
900
200
200
280
Monterrey
Guadalupe
S. Nicolas de los Garza Nuevo Le6n
Oaxaca Oaxaca
Puebla Puebla
Tehuacan Puebla
Queretaro
Queretaro
260
220
200
100
83
33
23
37
15
90
San Luis Potosi
CiudadObregon
Hermosillo
35
57
275
159
215
115
113
200
117
153
San Luis Potosi
Sonora
73
93
59
61
131
55
263 153
1,042,132 280 34 130 85
412,639 150 60 117 73
354,473 150 58 112 60
220,488 120 47 187 137
110,140 100 32 100 48
82,333 100 15 98 63
214 280
Sonora
Tlaxcala Tlaxcala
Zacatecas Zacatecas
Fresnilio Zacatecas
75 1,633,216 179
925,113 250 47 112 73
449,238 180 49 117 75
578,061 200 40 165 80
250,794 150 31 139 73
1,088,143 280 48 295 170
618,933 200 37 120 55
487,924 200 32 97 43
244,827 180 21 93 37
1,222,569 280 62 201 163
190,468 100 73 260 160
559,222 200 39 193 110
625,466 200 33 148 73
345,222 150 30 132 87
559,154 200 27 157 91
63,423 100 15 169 87
118,742 100 70 263 130
71 100 176,885 175 125
CONCLUSIONS
a) Having this National Atlas, with the indoor radon concentration, the radiological risks and lung
cancer cases associated to radon can be analyzed.
b) With this information, the actions to reduce the indoor radon levels in houses and buildings can be
taken.
c) The radiological conditions could be considered for future constructions, houses or apartments.
d) It could be possible to realize multifactorial epidemiology studies of lung cancer if the influence of
the indoor radon is known.
Acknowledgements -- The authors wish to thank to Dr. E. Ley Koo for his usefully comments. This work was
partially supported by Oak Ridge National Laboratory, managed by Lockheed Martin Energy Research Corp. lbr
the U.S. Department of Energy under contract number DE-AC05-96OR22464.
358
G. Espinosa et al. /Radiation Measurements 31 (1999) 355-358
REFERENCES
Bochicchio, F., Carnpos Venuti, G., Nuccetelli, C., Piermatter, S., Risica, S., Tommasino, L. and
Tom, G. (1996). Results of the representative italian national survey on radon indoors.
Health
Phys.
71, 741-748.
Chudhry, M.A., Jiang, Q., Ricanati, M., Horng, M.F., and Evans, H.H. (1996). Characterization of
multilocus lesions in human cells exposed to X-Ray and Radon.
Radiat. Research.
145, 31-38.
Cohen, B.L., (1998a). Response tu Lubin's proposed explanations of our discrepancy.
Health Phys.
75 18-22.
Cohen, B.L. (1998b). Response to criticisms of Smith
et al. Health Phys.
75, 23-28.
Espinosa, G., and Gammage, R.B. (1993). Measurement methodology for indoor radon using passive
track detectors.
Appl. Radiat. 1sot.
44, 719-723.
Gammage, R.B. and Espinosa, G. (1997). Digital imaging system for track measurements.
Radiat.
Meas.
28, 835-838.
IAEA.
Facts about low-level radiation.
IAEA/PI/A9E 85-00740 (march, 1989). Edited by American
Nuclear Society.
INEGI. (1995). Poblaci6n por entidad federativa. (http://www.inegi.gob.mx/omepara/conteo
/cua2_33.html).
Lubin, J.H. (1998) On the discrepancy between epidemiologic studies in individuals of lung cancer
and residential radon and Cohen's ecologic regression.
Health Phys.
75, 4-10.
Marcionwsky, F., (1992). Nationswide survey of residential radon levels in the United States.
Radiat.
Prot. Dosim.
45, 419-424,
Miles, Jon. (1998). Mapping radon-prone areas by longnormal modeling of house radon data.
Health Phys.
74, 370-378.
Nansen, R. and Cohen, B.L. (1987). Correlation between 226Ra in soil, 222Rn in soil gas, and 222Rn
inside adjacent houses.
Health Phys.
52, 73-77.
Nazaroff, W.W. and Nero, A.V. (1988).
Radon and its decay products in indoor air.
John Wiley,
New York.
Starnd, T., Green, B.M.R. and Lomas, P.R. (1992). Radon in norwegian dwellings.
Radiat. Prot.
Dosim.
45, 503-508.
Stidley, C.A. and Samet, J.M. (1993). A review of ecological studies of lung cancer and indoor
radon.
Health Phys.
65, 234-250.
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The results of a large-scale survey of radon concentrations in Norwegian dwellings are reported. Measurements of radon have been made in a total of 7500 dwellings. The dwellings were randomly selected and the number in each municipality is proportional to its population. The measurements were performed using etched track detectors from the National Radiological Protection Board in the UK. One detector was placed in the main bedroom in each dwelling for 6 months. The annual average of radon concentration in Norwegian bedrooms is calculated to be 51 Bq.m-3. The frequency distribution is approximately log-normal with a geometric mean of 26 Bq.m-3 and about 4% of the bedrooms have concentrations above 200 Bq.m-3. The radon concentrations are found to be about 40% higher for bedrooms in single-family houses than in blocks of flats and other multi-family houses. In a large proportion of single-family houses the living room and the kitchen are located on the ground floor and the bedrooms on the first floor. An additional factor is that the winters of 1987-1988 and 1988-1989 were much warmer than normal. Taking these factors into account, the average radon concentration in Norwegian dwellings is estimated to be between 55 and 65 Bq.m-3.
Article
The US Environmental Protection Agency's (EPA) National Residential Radon Survey (NRRS) is the first comprehensive effort to estimate the frequency distribution of average annual radon concentrations in occupied housing units across the 50 United States. A stratified three-stage area probability sample was used to randomly select approximately 11,000 homes from 125 counties nationwide. Two to four alpha track detectors were placed in approximately 7100 eligible homes for a period of 1 year. A 22 page questionnaire gathered information on occupant living patterns, smoking habits, house construction, weather-proofing, heating, ventilation, and air conditioning (HVAC) characteristics. The results indicate that the arithmetical average annual radon concentration in US housing units is 46 � 2 Bq.m-3 (1.25 � 0.06 pCi.1-1) with a median value of 25 Bq.m-3 (0.67 pCi.1-1). Based on the empirical evidence, 6.01 � 0.68% of housing units exceed the US EPA Action Level of 150 Bq.m-3 (4 pCi.1-1). This translates into approximately 6,000,000 US housing units exceeding the Action Level.
Article
Although radon exposure is an established cause of lung cancer among underground miners, the lung cancer risk to the general population from indoor radon remains controversial. This controversy stems in part from the contradictory results of published studies of indoor radon and lung cancer, including 15 ecologic studies, seven of which found a positive association, six no association, and two a negative association. To address the misunderstanding of the indoor radon risk that has resulted from these ecologic studies, the authors discuss the general methodologic problems and limitations of ecologic studies, and the particular limitations of these 15 studies. The authors conclude that the shortcomings of the ecologic studies render them uninformative on the lung cancer risk associated with indoor radon.