Proceedings of the 11th International Conference on Environmental Science and Technology
Chania, Crete, Greece, 3 – 5 September 2009
INDOOR EXPOSURE TO ASBESTOS-LIKE FIBERS RELEASED FROM
CONTAMINATED GROUNDWATER
P. ROCCARO and F. G. A. VAGLIASINDI*
Department of Civil and Environmental Engineering, University of Catania, Italy
*e-mail: fvaglias@dica.unict.it
EXTENDED ABSTRACT
Fluoro-edenite (NaCa2Mg5(Si7Al)O22F2), a new asbestos-like fiber, was found in the rock
of the Etna Volcano at Biancavilla (Catania, Italy). Fluoro-edenite fibers are under
investigation to evaluate their toxicity and carcinogenicity due to its similarity with
asbestos. Overall, epidemiological studies have shown that asbestos fibers cause
bronchial carcinoma and pleural mesothelioma by inhalation, while more studies are
needed to asses their effect by ingestion. Even thought the ingestion is the main route of
exposure associated to asbestos-like fibers in water in terms of potential risk for human
health, other scenarios can occur such as the release of fibers in the air by evaporation or
humidification, and the deposition on textiles during washing and rinsing processes and
subsequent release of fibers during wearing/use of cloth. Thus, the objective of this study
is to explore the indoor occurrence of asbestos-like fibers associated with the use of
fluoro-edenite contaminated tap water.
Experiments were conducted in the bathroom of a residential house in Biancavilla, where
the airborne asbestos-like fibers released by the use of the shower were collected using a
digital constant sampler (mod. ZB1, Zambelli, Italy) equipped with an esters mixed
cellulose membrane (25 mm diameter and 0.8 μm porosity) at the end of each tests.
Experiments were carried out at varying the time of shower and the exposure time.
Temperature and relative humidity in the bathroom were periodically monitored. The
collected filters were first treated by acetone-triacetyne method and then analyzed for
asbestos-like fibers by using a phase contrast microscopy.
Obtained results have shown that the release of asbestos-like fibers during the shower
occurs if contaminated waters are supplied. The concentration of the airborne asbestoslike fibers in the bathroom during and following the shower is much higher than the limit
values set by the European and National regulations. Strong correlations were found
between the concentration of the airborne asbestos-like fibers and, on the other hand, the
relative humidity or the water consumed obtained at fixed exposure time. These
correlations can be used to control and monitor the asbestos-like fibers exposure during
the shower. These results highlight that the risk for the human health related to the
exposure to asbestos-like fibers present in tap water may be relevant and therefore the
removal of these fibers may be pursued at water treatment plant. Further investigations
concerning the exposure scenarios and the removal of asbestos-like fibers from
contaminated water will be conducted in future work.
KEYWORDS: Air, Airborne asbestos-like fibers, Fluoroedenite, Shower, Water.
1.
INTRODUCTION
Subsequent to an epidemiological survey (carried out from 1988 to 1992) on the mortality
due to malignant pleural neoplasm in Italy, a cluster of cases was found in Biancavilla, a
town located in the Etnean Volcanic Complex (Catania, Italy) of eastern Sicily. Several
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epidemiological studies and environmental monitoring were carried out and a new
asbestiform fibre, named fluoro-edenite (NaCa2Mg5(Si7Al)O22F2), was discovered in a
stone quarry (Gianfagna et al., 2001; Bruno et al., 2006). The residents of Biancavilla, for
whom a diagnosis of pleural mesothelioma had been made, never had any relevant
exposure to asbestos during their professional life. The possible cause of such unusual
distribution of the pathology was proposed to be the exposure of the population to stone
quarries located in ‘‘Monte Calvario’’ that contains the fluoro-edenite fibres and was
largely used in the local building industry (Paoletti et al., 2000; Bruno et al., 2006; Bruni et
al., 2006).
As a consequence, the Biancavilla site was defined “site of national interest” for
environmental reclamation and on site characterization and remedial investigation were
conducted as well as monitoring programs, still ongoing. Despite epidemiological studies
have shown that asbestos-like fibres cause bronchial carcinoma and pleural
mesothelioma by inhalation, there is no unequivocal evidence of the carcinogenicity of
these fibres by ingestion (Kjærheim et al., 2005; Bruni et al., 2006). Recently, it was
observed that, in lung epithelial cells, fibrous fluoro-edenite behaved similarly to the
unrelated asbestos type crocidolite, whose connection with severe inflammation and
cancer of the lung is well known (Travaglione et al., 2006).
The human exposure to fluoro-edenite fibres may be related to the presence of those
fibres in different natural matrices. Indeed, even thought the ingestion is the main route of
exposure associated to asbestos-like fibres in water, other scenarios can occur such as
the release of fibres in the air by evaporation or humidification, and the deposition on
textiles during washing and rinsing processes and subsequent release of fibres during
wearing/use of cloth (Webber et al., 1988; Hardy et al., 1992; Highsmith et al., 1992).
Therefore, more research is needed to asses the toxicity and carcinogenicity of fluoroedenite fibres by different rote of exposure (inhalation and ingestion).
This study, which is part of an ongoing research aiming at evaluating the occurrence, fate
and control of asbestos-like fibres at Biancavilla site, is devoted to investigate the indoor
human exposure to asbestos-like fibres associated with the use of fluoro-edenite
contaminated tap water. In particular, the objective of this paper is to explore the release
of asbestos-like fibres in the air during the shower.
2.
MATERIALS AND METHODS
2.1. Experimental methods
Experiments were conducted in the bathroom of a residential house located at Biancavilla
town (Catania, Italy), where the airborne asbestos-like fibres released from the shower
were collected by a digital constant air sampler (mod. ZB1, Zambelli, Italy) equipped with
an esters mixed cellulose membrane (25 mm diameter and 0.8 μm porosity). The air
sampler was used at a flow rate of 1 L/min during the experiments and the flow rate of the
shower was 9 litre per minute.
In order to have similar initial ambient conditions inside the bathroom, prior to start each
test, the room was ventilated opening the window for some minutes. Experiments were
carried out at varying operating conditions (Table 1) to asses the effect of the time of
shower and exposure time on the presence of airborne asbestos-like fibres. In particular,
the time of shower varied from 4 to 15 minutes, while the exposure time ranged from 6 to
20 minutes. Temperature and relative humidity in the bathroom were monitored every
minute by using an electronic thermo-hygrometer (Delta OHM HD 8901).
2.2. Analytical methods
The collected filters were dried for 12 hours in a desiccator containing blue silica gel as
desiccant and then treated by acetone-triacetyne method and analysed by using a phasecontrast optical microscopy (Axioskop 40 Pol, Zeiss) with a x40 objective and a x500
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magnification. The fibres were counted in accord to (WHO, 1997) employing 200 counting
fields per filter.
The concentration of the fibres were calculated with the following relationship (WHO,
1997):
C(ff/L) = (106 N D2)/(V n d2)
with:
N = total number of fibres counted;
n = number of counting fields;
D = filter diameter (mm);
d = diameter of the Walton Beckett graticule (100 μm);
V = volume of air or water passed through the filter (litres).
All the analyses were carried out at the Laboratory of Environmental and Sanitary
Engineering of the University of Catania.
3.
RESULTS AND DISCUSSION
3.1. Occurrence of airborne asbestos-like fibers released during the shower under
different conditions
Asbestos-like fibres were found in aquifers at Biancavilla site at relatively high
concentration compared to the average Sicilian water quality. The concentration of fibres
found in the tap water of the house investigated was 8229 ff/L. Picardo 1 and Picardo 2
that are the major water sources (wells) used for water supply in Biancavilla had a
concentration of fibres of 8073 ff/L and 8958 ff/L, respectively. The groundwater
contamination may be related to the percolation of rainwater throughout the volcanic
rocks containing the fluoro-edenite. The concentration of these fibres may vary during the
season and may cause heath effects by ingestion or inhalation.
As shown in Table 1 the release of asbestos-like fibres in the bathroom ambient occurs
due to the shower if contaminated water is supplied. Indeed, in this study airborne
asbestos-like fibres were detected at concentration ranging from 350 to 850 fibres per
litre (Table 1). The observed concentrations of airborne asbestos-like fibres are much
higher than the limit values set by the European Directive 2003/18/EC and the Italian
regulation (D.Lgs. 257/2006) concerning the protection of workers from the risks related
to exposure to asbestos at work (100 ff/L) and by the Italian regulation (DM 6/9/94) on the
extraction, manufacture, processing and removal of asbestos from contaminated
buildings (20 ff/L as threshold indicator of the presence of pollution by asbestos and 2 ff/L
for the restitution of buildings after the remediation). It is noteworthy that the limit value of
2 ff/L was suggested by the local authorities as warning threshold during outdoor
environmental monitoring at Biancavilla site. Obtained results highlight that a relevant risk
for human health may be related to the supply of contaminated water by asbestos-like
fibres.
As reported in Table 1, the concentration of airborne asbestos-like fibres released from
the shower is strongly affected by the water consumed (i.e. the time of shower) and the
exposure time that can vary because of the behaviour of the users. As expected, at fixed
exposure time, higher shower time results in higher airborne fibres concentration. On the
other hand, at fixed shower time, higher exposure time results in lower concentration of
airborne fibres. This observation highlights that the transfer of the asbestos-like fibres
from the shower in the air inside the bathroom is a complex mechanism that is related to
the simultaneous release of a significant amount of fibres in the air during the shower and
to the dispersion of these fibres inside the bathroom.
It can be concluded that the fibres concentration reported in Table 1 can not be intended
as concentration value homogeneously distributed inside the chamber, but are point
values that change during the release and dispersion mechanism. These values
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Table 1. Concentration of airborne asbestos-like fibres detected inside the bathroom
during or following the shower and related operating parameters.
Time of
shower
(min)
Test
1
2
3
4
5
6
7
8
9
10
11
12
13
Water
consumed
(L)
6
8
4
8
15
2
6
10
12
9
4
10
15
Final relative
humidity
inside the
bathroom (%)
Exposure time
(shower +
after shower)
(min)
54
72
36
72
135
18
54
90
108
81
36
90
135
6
8
15
15
15
15
15
15
15
10
20
20
20
Concentration of
airborne fibres
(ff/L)
65
86
76
90
100
78
93
99
100
100
92
93
100
794
775
385
552
688
354
453
625
682
859
379
449
574
correspond to the concentrations that can be inhaled by a user that is in the same
position of the air sampler (i.e. close to the shower box). Therefore, obtained results
demonstrated that the portable air sampler working at a flow rate of 1 L/min can be used
to simulate the real human exposure to fibres released during specific activities that
involve multiple parameters.
The release mechanism can also vary with the initial temperature and relative humidity
inside the bathroom. Figure 1 shows the variation of ambient temperature inside the
bathroom during the experiment for selected tests, while in Figure 2 is reported the
changes of the relative humidity in the bathroom for the same experimental tests.
22
21
Temperature (°C)
20
19
18
17
16
15
Test 3
Test 4
Test 5
Test 6
Test 7
Test 9
Test 10
Test 11
Test 12
Test 13
Test 8
14
0
2
4
6
8
10
12
14
16
18
20
Time (minutes)
Figure 1. Temperature variation inside the bathroom in different experimental tests
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22
105
Relative Humidity (%)
95
85
75
65
55
45
35
Test 3
Test 4
Test 5
Test 6
Test 7
25
Test 9
Test 10
Test 11
Test 12
Test 13
10
12
Test 8
15
0
2
4
6
8
14
16
18
20
22
Time (minutes)
Figure 2. Relative humidity variation inside the bathroom in different experimental tests
As shown in Figure 1 and 2, both the temperature and relative humidity increased during
the experiment reaching asymptotically the maximum value. However, the increasing rate
is much prominent for the relative humidity, whose values first increase linearly until 7-8
minutes of exposure time and then reach their maxima asymptotically. Furthermore, the
data of relative humidity have the same behaviour regardless of the different operating
conditions (dissimilar experimental tests), with the exception of data carried out at the
shorter shower times (tests 3 and 6) that have shown a different pattern. Indeed, for
these two dataset the maxima values are lower than those obtained from the other tests
and these maxima values are reached at shorter time.
Overall, it can be concluded that when water consumed is about 54 litres or higher,
corresponding to a shower time at least of 6 minutes, and the exposure time is higher
than 8 minutes the relative humidity will reach its maximum value. In these conditions the
risk of exposure to asbestos-like fibres may be higher. However due to the complexity of
the mechanism of fibres release, the use of alternative parameters to predict the human
exposure to airborne fibres released during the shower may be useful. This aspect is
addressed in the following section.
3.2. Relationships between the concentration of airborne fibres and alternative
parameters
Strong correlations were found between the concentrations of airborne asbestos-like
fibres released by the shower and alternative surrogate parameters at fixed exposure
time. For instance, Figure 3 and 4 show the correlations between the concentration of
asbestos-like fibres and, on the other hand, the relative humidity or the water consumed
obtained at 15 minutes of exposure time. These surrogate parameters can be used to
control or monitor the exposure to the airborne asbestos-like fibres during the shower and
therefore to predict the relative risk of mesothelioma or lung cancer.
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Concentration of fibres (ff/L)
800
700
R2 = 0.85
600
500
400
300
200
100
0
60
70
80
90
100
110
Relative humidity (%)
Figure 3. Relationship between the concentration of asbestos-like fibres and the relative
humidity at fixed exposure time of 15 minutes
Concentration of fibres (ff/L)
800
R2 = 0.94
700
600
500
400
300
200
100
0
0
20
40
60
80
100
120
140
Water consumed (L)
Figure 4. Relationship between the concentration of asbestos-like fibres and the water
consumption at fixed exposure time of 15 minutes
4.
CONCLUSIONS
In this study it was observed that the shower is a relevant source of airborne asbestoslike fibres even when the supplied water contains trivial concentrations (at least
compared with the current limit values for drinking water) of these fibres. The
concentration of airborne asbestos-like fibres released by the shower at realistic time of
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shower and exposure (after shower) was very high compared to the limit values set by
the National and European regulations.
The concentration of these airborne asbestos-like fibres can be predicted by the use of
the relative humidity or the water consumed obtained at given exposure time. Although
the risk for human health related to the ingestion of asbestos-like fibres is not well known,
a relevant risk may result from the inhalation of these fibres released from the shower
when contaminated water is supplied. The surrogate parameters found in this study may
be also used to predict the risk for human health.
Based on the results obtained in this study, the addition of specific limit values for
asbestos in drinking water regulations is strongly recommended. In particular, a limit
value more stringent than of that set by the EPA (7 million of fibres per litre) should be
fixed. Furthermore the removal of the asbestos-like fibres must be pursued by treating
drinking water sources used in Biancavilla.
Further investigations concerning the exposure scenarios and the removal of asbestoslike fibres from contaminated water will be conducted in future work.
ACKNOWLEDGEMENT
This study was partially supported by the Italian Ministry of Instruction, University, and
Research (MIUR), through the program Research Projects of National Interest “Criteria
and tools for environmental remediation and functional regeneration of contaminated
sites”. Authors are very thankful to Drs. Mario Finocchiaro, Gianfranco Caruso and Letizia
Della Fortuna, graduate students of University of Catania, for their help in experimental
work.
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