Radiation Protection Dosimetry (2011), Vol. 145, No. 2–3, pp. 202 –205
doi:10.1093/rpd/ncr040
RADON IN WORKPLACES: FIRST RESULTS OF AN
EXTENSIVE SURVEY AND COMPARISON WITH RADON
IN HOMES
Silvia Bucci1,*, Gabriele Pratesi1, Maria Letizia Viti1, Marta Pantani1, Francesco Bochicchio2 and
Gennaro Venoso2
1
ARPAT (Regional Agency for Environmental Protection in Tuscany), Florence Section, via Ponte alle
Mosse 211, 50144 Firenze, Italy
2
ISS (Italian National Institute of Health), Viale Regina Elena 299, 00161 Rome, Italy
*Corresponding author: [email protected]
Extensive radon surveys have been carried out in many countries only in dwellings, whereas surveys in workplaces are rather
sparse and generally restricted to specific workplaces/activities, e.g. schools, spas and caves. Moreover, radon-prone areas are
generally defined on the basis of radon surveys in dwellings, while radon regulations use this concept to introduce specific
requirements in workplaces in such areas. This approach does not take into account that work activities and workplace
characteristics can significantly affect radon concentration. Therefore, an extensive survey on radon in different workplaces
have been carried out in a large region of Italy (Tuscany), in order to evaluate radon distribution in workplaces over the
whole territory and to identify activities and workplace characteristics affecting radon concentration. The results of this extensive survey are compared with the results of the survey carried out in dwellings in the same period. The workplaces monitored
were randomly selected among the main work activities in the region, including both public and industrial buildings. The
survey monitored over 3500 rooms in more than 1200 buildings for two consecutive periods of ∼6 months. Radon concentration was measured by means of passive nuclear track detectors.
INTRODUCTION
Extensive radon surveys have been carried out in
many countries only in dwellings, whereas surveys
in workplaces are rather sparse and generally
restricted to specific workplaces/activities, e.g.
schools, spas and caves. Few of the surveys in workplaces(1) are representative of all work activities and
still fewer radon concentration distribution in workplaces compared with that in dwellings of the same
area. In Finland(2), about 500 participants randomly
sampled from the entire population accepted to
measure radon concentration in their dwellings and
workplaces. Radon concentration was about three
times higher in dwellings than in workplaces: the geometric mean (GM) was 68 and 20 Bq m – 3, respectively. Similar results were found in a US state(3),
where they monitored a sample of 65 workplaces and
39 dwellings in the same area: median radon concentrations were 55 and 18, for dwellings and offices,
respectively. Also, in Mexico(4) where 288 workplaces
in 26 cities were monitored, radon levels were significantly lower than those in dwellings in some locations.
In all these studies, the authors reported that these
differences may be attributed to the presence of efficient mechanical ventilation systems in most of the
sampled workplaces. In Japan(5) they monitored 705
sites in four categories of workplaces (school, office,
hospital and factory). For all four categories, the
average radon concentration was 21 Bq m23, slightly
higher than for dwellings (16 Bq m23).
It is fundamental—for radon policy purposes as
well—to conduct radon surveys in the workplaces.
As a point of fact, ‘radon-prone’ areas are generally
defined on the basis of radon surveys in dwellings,
while radon regulations use this concept to introduce
specific requirements in the workplaces in such
areas. This approach does not take into account that
work activities and workplace characteristics can significantly affect radon concentration. Therefore, an
extensive survey on radon in different workplaces
was carried out from 2007 to 2009 in Tuscany, a
large region in Central Italy. The aim was to estimate radon distribution in workplaces over the
whole territory, and identify activities and workplace
characteristics affecting radon concentration. The
results of this extensive survey have been compared
with the results of a survey carried out in dwellings
in the same period.
MATERIALS AND METHODS
Sampling
A total of 1541 dwellings and 1159 workplaces were
randomly sampled in the region, with about 7500
rooms monitored. The sample of dwellings covers all
287 municipalities of the region, with at least five
# The Author 2011. Published by Oxford University Press. All rights reserved. For Permissions, please email: [email protected]
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/
licenses/by-nc/2.5/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is
properly cited.
RADON IN WORKPLACES
dwellings measured in 156 of them. The sample of
workplaces is distributed over 75 % of municipalities, with at least five workplaces measured in 64
municipalities. Both samples were concentrated in
areas where high radon levels were expected on the
basis of geology and other surveys(6 – 9). In this way,
it was possible to study the difference between the
workplaces and homes in the presence of a wide
variability of radon concentrations.
The monitored dwellings were randomly selected
from the registry offices of each municipality. More
measurements (about 20) were done in municipalities
where higher radon levels were expected, whereas
fewer dwellings (2 –7) were sampled in the other
municipalities. In any case, at least 10 dwellings were
sampled in each province of the region. Radon was
measured in two different rooms (living room and
bedroom whenever possible) to estimate radon variability in the same building. If dwellings had more
than one floor, radon was measured in each floor.
The monitored workplaces were randomly selected
among the main work activities in the Region, including both public and industrial buildings. In general,
two measurements were carried out for each floor. The
rooms chosen were representative of the various work
activities, taking care to avoid anomalous situations.
Measurements were not carried out in underground
workplaces, where they are already mandatory according to European and national legislation(10, 11).
exposure levels (20 000 kBq h m23), and quality
control of equipment and personnel. Detectors were
calibrated in the radon chamber of the Italian
National Institute of Ionizing Radiation Metrology;
method accuracy was also checked in European intercomparison exercises. The detection limit of the CR39 used for this experimental work was in the range
30 –40 kBq h m – 3, depending on the detector batch.
Data analysis
For each dwelling and workplace, the mean annual
radon concentration was calculated as the arithmetic
mean (AM) of the radon concentration in all the monitored rooms, also if they were located in different floors.
For dwellings, seldom-used rooms were excluded from
the calculation. The distribution of radon measurements was log–normal in most of the municipalities
with a sufficient number of data; it was therefore
assumed that radon concentration is log–normally distributed in all of them. Then, for each municipality
main distribution parameters (i.e. AM, GM and geometric standard deviation (GSD)) were calculated from
the data; for GSD also the unbiased estimate was calculated(12). Radon variability within rooms of the same
building was estimated by the coefficient of variation
(CV¼standard deviation/AM), expressed as percentage, for both dwellings and workplaces.
RESULTS
Radon measurements
Radon concentration was measured for two consecutive 6-month periods (in few cases for one single
period of 1 y), using passive nuclear track detectors
(CR-39) in small diffusion chambers. The mean
annual radon concentration was calculated as the
time-weighted average radon concentration of the two
periods, using dosemeter exposure time as weights.
More than 20 000 detectors were used for the whole
survey, 20 % of which were for quality assurance.
About 1200 detectors were used as duplicates, i.e.
placed with another detector in the same location, in
order to estimate in-field measurement repeatability.
Description of the measurement technique
Detectors were etched in a 6.25 N NaOH solution
at 908C for 60 min; track counting was performed
with a fully automated image analysis system
(TASLIMAGE). The measurement method has been
accredited since 2007 on the basis of ISO/IEC 17025
‘General Requirements for the Competence of
Testing and Calibration Laboratories’. The quality
assurance program consists of: validation of the
method; estimation of uncertainty of measurements,
including laboratory and in-field repeatability; calibration and linearity response testing up to high
Summary
The overall radon concentration distribution (for
both dwellings and workplaces) is not log–normal, as
a result of the sampling strategy. Therefore, only raw
statistical parameters are reported here (Table 1).
Radon variability within the same site
Radon concentration variability within the same
building is very important to evaluate population and
occupational exposure. The knowledge of the main
variation patterns may determine measurement strategies. For instance, in the presence of wide ranges, it is
Table 1. Gross data distribution results for dwellings and
workplaces.
Summary parameters
N
Min (Bq m23)
First quartile (Bq m23)
Median (Bq m23)
Third quartile (Bq m23)
90th percentile (Bq m23)
Max (Bq m23)
203
Dwellings
Workplaces
1541
4
19
32
65
137
4828
1159
4
21
43
102
260
9417
S. BUCCI ET AL.
Figure 1. Distributions of CV (%) of measurements carried
out in different rooms of the same dwelling and workplace.
Figure 2. GM in workplaces vs GM in dwellings for 28
municipalities of the region.
preferable to increase the number of rooms to be monitored. CV distribution (%) of the measurements
carried out in different rooms of the same dwelling
and workplace are compared in Figure 1.
Radon concentration variability within workplace
was generally higher than the variability within
dwellings: the median CV is 13 % in dwellings and
20 % in workplaces, and the third quartile is 27 %
and 48 %, respectively. This can be explained with
the differences in building dimension and structure,
and with the higher degree of separation of the
rooms in workplaces.
Radon protection policies for workers should take
account for radon concentration variability within
workplaces, and provide an appropriate strategy of
measurements in the workplace in order to better
evaluate worker exposure.
Comparison between radon in homes and workplace
A preliminary comparison was carried out between
radon concentration distribution in dwellings and
Figure 3. GSD in workplaces vs GSD in dwellings for 28
municipalities of the region.
workplaces for 28 municipalities, in which more
than 10 radon measurements were performed in
dwellings or workplaces. These municipalities
include the main towns of the Tuscany Region,
characterised by low radon levels, and those towns
where high radon concentrations were expected from
previous surveys and confirmed by this survey, not
only in dwellings, but also in workplaces.
Figure 2 shows, as expected, a good correlation
between mean radon levels in homes, and workplaces in the same area in a range of one order of
magnitude for GM (from about 20 up to about 200
Bq m23). The mean radon concentration within the
same municipality (GM) tended to be slightly higher
in workplaces than in dwellings, on average 14 %; a
similar finding was reported in a survey(5) having
lower radon levels (mean radon level were 21 and 16
Bq m23 for workplaces and dwellings, respectively).
Conversely, several cases in the literature(3, 4) report
the opposite trend. Our result can be explained with
the lower occupancy time of rooms and with the
limited use of air conditioning and mechanical ventilation in workplaces in Italy.
Moreover, also radon concentration variability in
workplaces within the same municipality, which is
estimated by means of unbiased GSD, tends to be
generally higher (10 %) than radon concentration
variability in dwellings (Figure 3).
This outcome depends on several factors affecting
radon concentration, such as building characteristics
and its use, which are much less uniform in workplaces than in dwellings.
CONCLUSIONS
An extensive survey on radon in dwellings and workplaces of a large region of Italy (Tuscany) was
carried out. Aims of the study were: (i) to identify
radon-prone areas that—according to national legislation—have to be defined in order to limit radon
204
RADON IN WORKPLACES
exposure only in workplaces, and (ii) to assess
whether radon levels are different in homes and
workplaces. The results of the survey showed, as
expected, that radon levels in workplaces and homes
are well correlated in the same area and therefore
mapping can be based on both sets of data.
Nevertheless, radon variability in homes appear to
be smaller than in workplaces, probably because
building characteristics and their use are more
homogeneous if compared with workplaces.
Therefore, radon data from dwellings are more suitable for mapping radon potential from soil.
Nonetheless, strategies for radon-prone areas identification should consider that radon levels and their
variability appears to be higher in workplace than in
dwellings within the same area. If these results had a
general validity, the use of radon-prone area criteria
stemming from surveys in dwellings to rate workplaces should account for this difference.
3.
4.
5.
6.
7.
ACKNOWLEDGEMENTS
The authors thank local administrations and participants who contributed to the survey and the ARPAT
working group who performed the measurements:
S. Gambi, R. Magnanelli, I. Peroni, D. Piccini,
E. Bafaro, P. Vaselli and D. Ceseri. The authors also
thank Ms M. Brocco for linguistic revision of the
manuscript.
8.
9.
FUNDING
This survey was funded by the Health and
Environment Department of Toscana Region.
10.
REFERENCES
1. International, and Atomic Energy Agency (IAEA).
Radiation protection against radon in workplaces other
than mines. Safety Reports Series No. 33. IAEA
(2003).
2. Makelainen, I., Moisio, S., Reisbacka, S. and
Turtiainen, H. Indoor occupancy and radon exposure in
Finland. In: Radioactivity in the Environment, Volume
7. Seventh International Symposium on the Natural
11.
12.
205
Radiation Environment, Rhodes, Greece, 20–24 May
2002, pp. 687– 693 (2005).
Whicker, J. J. and McNaughton, M. W. Work to save
dose: contrasting effective dose rates from radon
exposure in workplaces and residences against the backdrop of public and occupational regulatory limits.
Health Phys. 97(3), 248–256 (2009).
Espinosa, G., Golzarri, J. I., Angeles, A. and Griffith, R.V.
Nationwide survey of radon levels in indoor workplaces in
Mexico using nuclear track methodology. Radiat. Meas. 44,
1051–1054 (2009).
Oikawa, S., Kanno, N., Sanada, T., Abukawa, J. and
Higuchi, H. A survey of indoor workplace radon concentration in Japan. J. Environ. Radioact. 87, 239– 245
(2006).
Bucci, S., Gambi, S., Giannardi, C. and Giovannini, F.
Identification of high exposure areas in Toscana. In:
Proceedings of Fifth International Conference on High
Levels on Natural Radiation and Radon Areas:
Radiation Dose and Health Effects, Munich,
Germany, 4–7 September (2000).
Gaidolfi, L., Malisan, M. R., Bucci, S., Cappai, M.,
Bonomi, M., Verdi, L. and Bochicchio, F. Radon
measurements in kindergartens and schools of six Italian
regions. Radiat. Prot. Dosim. 78, 73–76 (1998).
Giannardi, C., Giovannini, F., Bucci, S., Gambi, S.,
Trotti, F., Caldognetto, E. and Fusato, G. In progress
identification of radon prone areas: Toscana and Veneto.
Radiat. Prot. Dosim. 97(4), 349– 354 (2001).
Bochicchio, F., Bucci, S., Bonomi, M., Cherubini, G.,
Giovani, C., Magnoni, M., Minach, L. and Sabatini, P.
Areas with high radon levels in Italy. In: Proceedings of
a Workshop on ‘Radon in the Living Environment’,
Athens, 19– 23 April 1999, pp. 985–996 (1999).
European Commission (EC), 1996. Council Directive
96/29/Euratom of 13 May 1996, laying down basic
safety standards for the protection of health of workers
and the general public against the danger arising from
ionizing radiation. Off. J. Eur. Communities No. L 159,
29/6/1996.
D. Lgs. 241/2000. Decreto Legislativo 26 maggio
2000, n. 241, Gazzetta Ufficiale n. 203 Suppl.
Ordinario, August 31, 2000 (in Italian).
Andersen, C. E., Ulbak, K., Damkjær, A.,
Kirkegaard, P. and Gravesen, P. Mapping indoor radon222 in Denmark: design and test of the statistical model
used in the second nationwide survey. Sci. Total
Environ. 272, 231– 241 (2001).