On the feasibility of polymer fibers with mineral filler as emergency dosimeters

Radiation Measurements 153 (2022) 106718

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Radiation Measurements
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On the feasibility of polymer fibers with mineral filler as emergency
dosimeters
Oskari Ville Pakari a , Eduardo Gardenali Yukihara a , Dariusz Jakub Gawryluk b , Lily Bossin a ,∗
a
b

Department of Radiation Safety and Security, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
Laboratory for Multiscale Materials Experiments, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland

ARTICLE

INFO

ABSTRACT

Keywords:
Emergency dosimeter
Polymer fiber
Mineral filler
Calcite
Thermoluminescence

The objective of this study is to examine the possibility of using the thermoluminescence (TL) of polymer
fibers containing ground calcium carbonate (CaCO3 ) mineral fillers as emergency dosimeters. Calcite, consisting

mostly of CaCO3 , is a TL material that exhibits two distinct TL peaks that can be exploited for dosimetry and
is a naturally occurring mineral that is ubiquitously in use in everyday materials. Polymer fiber materials
with CaCO3 are already produced at scale e.g. for common surgical face masks or surgical gowns, opening the
possibility of using such materials as fortuitous dosimeter in emergency situations. To assess the feasibility of
such materials as dosimeters, we examined the TL properties of two CaCO3 powders as well as commercially
available surgical face mask samples. The results indicate that the TL emissions across all samples stem from
calcite and are in principle usable for dosimetry. We discuss limitations that arise from the fading properties
and the potentially complex TL background. As a case example for emergency dosimetry, we examined samples
from a commercially available surgical face mask. The face mask was found to exhibit a minimum detectable
dose to the order of ∼2 Gy, under laboratory conditions. We provide an outlook on how the materials and
methods can be improved for radiological dose assessment.

1. Introduction

A fortuitous detector (Bailiff et al., 2016), in the form of an item
or material that the average person is likely to have on them during
the exposure, could aid in determining such doses. The material hereby
has to fulfill a range of properties, such as stable proportionality to
received dose, a minimum detectable dose (MDD) well below the
aforementioned 2 Gy, ubiquity among the population, as well as simplicity and speed of the dose information retrieval. For emergency and
fortuitous dosimetry is it thus of interest to investigate a wide range
of materials for their suitability as radiation dosimeters. Previously
examined possibilities for this purpose include mobile phones (Inrig
et al., 2008; Eakins and Kouroukla, 2015), ibuprofen (Mrozik and
Bilski, 2021), or mineral filler containing faux-leather bags (Bossin,
2019; Bossin et al., 2020) using both thermoluminescence (TL) or
optically stimulated luminescence (OSL) methods.
Calcite is an abundantly occurring TL mineral that has found numerous applications e.g. as construction materials, fertilizer, and, particularly of interest for this work, as fillers in polymer plastics to
improve features such as water resistance, cost, ergonomy and breathability (Katz et al., 1987; Brunner et al., 2019). A typical filler consists
of ground CaCO3 processed from calcite.

Large-scale radiological events can potentially result in the exposure
of large numbers of individuals to doses of ionizing radiation that
warrant acute medical care to maximize the odds of survival (Coleman
et al., 2011). Following events such as an urban nuclear detonation,
the number of casualties would quickly exceed local hospital capacities (Knebel et al., 2011) leading to crisis standards of care (Institute of
Medicine, 2009) and triage procedures to be implemented (Caro et al.,
2011).
In such a triage scenario the decision making ought to be guided
by objective information to separate the worried-well from those who
require immediate care. The speed, sensitivity, or specificity of white
blood cell counts or other acute radiation syndrome symptoms is estimated to be well below and often insufficient compared to that of
direct information on the dose (Jaworska et al., 2014). Based on data
of victims of the Chernobyl power plant accident (Guskova et al., 1988)
it is estimated that below a received dose of around 2 Gy no immediate
care is required (Jaworska et al., 2014). Useful dose information must
therefore meet a given sensitivity and specificity around this decision
threshold.

∗ Corresponding author.
E-mail addresses: (O.V. Pakari), (L. Bossin).

/>Received 27 November 2021; Received in revised form 19 January 2022; Accepted 30 January 2022
Available online 12 February 2022
1350-4487/© 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license ( />

Radiation Measurements 153 (2022) 106718

O.V. Pakari et al.

Polymer fiber materials with CaCO3 filler are already produced
at commercial scale e.g. for common surgical face masks or surgical
gowns, opening the possibility of using such materials as fortuitous TL
dosimeter in emergency situations. Due to the ongoing SARS-COV-2
pandemic, many countries mandate the regular use of common surgical
face masks (Chua et al., 2020), fulfilling the ubiquity requirement.
Finally, a polymer plastic may cover a larger area of the body and could
be sampled in different locations to also give information on the dose
distribution. We therefore identified beneficial characteristics ranging from cost, availability, spatial information, as well as widespread
fortuitous use.
Calcite is already a well studied TL material (Medlin, 1959; Calderon
et al., 1984; Sunta, 1984; Medlin, 1964). The typical TL glow peak
structure contains two prominent peaks at around 110 ◦ C (Peak 1) and
270 ◦ C (Peak 2), see e.g. Down et al. (1985). The luminescence mechanism is believed to stem from Mg impurities acting as recombination
centers. Calcite exhibits a native signal in the thermally stable TL peak
2 region that can be used for dating (Debenham, 1983; Ninagawa et al.,
1992). With no appreciable OSL response, calcite may thus also prove
less light sensitive than other TL materials.
The objective of this study is to examine the potential of using the
TL of polymer fibers containing calcite mineral fillers as emergency
dosimeters. To achieve this, we compare X-Ray Diffraction and TL
characteristics of two different commercial calcite powders and a commercially available face mask. We then discuss the minimum detectable
dose and the limitations of the case example of the face mask used for
emergency dosimetry.

Fig. 1. (a) Scanning electron micrograph of polypropylene fibers that contain 10%
Omyafiber 800. b) Scanning electron micrograph of cross section of a single polypropylene fiber containing 10% Omyafiber 800. Both pictures are courtesy of Omya
International AG (Brunner et al., 2019).

2. Materials and methods

2.3.1. Coarse calcite powder

the literature (Falini et al., 1998; Effenberger et al., 1983; BouletRoblin et al., 2017). Refined parameters were: scale factor, atomic
positions, and isotropic thermal factors. Due to the powdered crystals’
nature, a preferred orientation correction as a March–Dollase multiaxial phenomenological model (Dollase, 1986) was implemented into
the analysis of some patterns.

2.3. Samples

As a reference for the behavior of natural calcite, the commercial
product Nekafill 15 by Kalkfabrik Netstal Switzerland was acquired. It
is ground calcite powder used e.g. as additive for concrete or mortar.
Sieving analysis showed 0.0% remainder at a mesh size of 0.5 mm,
and 18.7% at 0.063 mm. The powder furthermore has a manufacturerreported MgCO3 content of about 1.5%. Filling the bottom surface of
the measurement cups uniformly lead to a use of about 15 mg of powder
per sample. Hereafter we refer to this powder as coarse calcite powder.

2.1. TL measurements
TL measurements were performed using the Risø reader (TL/OSLDA-20, DTU Nutech, Denmark). The samples were placed in stainlesssteel cups. With a built-in 90 Sr/90 Y source for beta irradiations, the
system allows for convenient subsequent TL readout. The source’s dose
rate was calibrated in air kerma using the OSL response of thin Al2 O3 :C
films to a Cs-137 irradiation performed at the Paul Scherrer Institut (PSI) Calibration Laboratory, giving 35 mGy s−1 using the method
described in (Yukihara et al., 2005).
The TL curves were acquired with a photomultiplier tube (PMT;
type ET Enterprises PMD9107Q-AP-TTL; quantum efficiency less than
10% at 600 nm) with no additional filters aside from the built-in silica
windows. TL spectra were measured using an Andor iXon Ultra 888
EMCCD attached to Andor’s Kymera 193i spectrometer (grating 150
lines/mm with a center wavelength at 500 nm, CCD pre-cooled to

−60 ◦ C). A spectral correction obtained with a calibration lamp was applied (See Supplementary Figure A.11). For phototransfer experiments
shown in this work we used a UV light emitting diode (385−410 nm
primary wavelength, 12 nm full width at half maximum (Lapp et al.,
2015), irradiance of 520 mW cm−2 at the sample position (model LZ400UB00, LED Engin, Inc.).

2.3.2. Fine calcite powder
As an example of a more finely ground calcite powder that corresponds to a filler product, we used Omyafiber 800 by Omya International AG, Switzerland, a global producer of industrial minerals derived
mostly from calcium carbonate, dolomite, and perlite. The powder is
manufactured from natural calcite that is ground and then surfacetreated with a proprietary chemical agent that improves the properties
of the subsequent dispersion into the polymer. A scanning electron
micrograph (SEM) image of the powder in a polymer fiber is shown in
Fig. 1. Similarly to the calcite powder, we used about 15 mg of powder
per sample. Hereafter we refer to this powder as fine calcite powder.

2.2. Powder X-Ray Diffraction

2.3.3. Surgical face mask

Powder X-Ray Diffraction (XRD) measurements were conducted at
room temperature in the Bragg–Brentano geometry using a Bruker AXS
D8 Advance diffractometer (Bruker AXS GmbH, Karlsruhe, Germany)
equipped with a Ni-filtered Cu K𝛼 radiation and a 1D LynxEye PSD
detector. Data analysis (Rietveld, 1969) of the diffraction patterns was
performed with the package FULLPROF SUITE (Rodríguez-Carvajal,
1993; Roisnel and Rodríguez-carvajal, 2001) (version July-21) using
a previously determined instrument resolution function (Gozzo et al.,
2006; Courbion and Ferey, 1988).
The final Rietveld refinements were then conducted with restrained
zero shift, cell, and peak shapes (Thompson–Cox–Hastings pseudoVoigt function) parameters. The structural models were taken from

As an example for a polymer fiber product we used Zoey Medical
disposable face masks (Zoey medical, 2021). Samples with diameter
of (6.0 ± 0.5) mm were cut out using a standard paper hole-puncher.
We note that the product description does not indicate clearly a polymer that necessarily includes CaCO3 filler. The mask consists of three
layers, an outer blue colored layer and two inner white/transparent
layers. For the TL measurements the cut-outs were pressed together
and the inner-most layer placed facing towards the PMT. The minimum
detectable dose (MDD) for an emergency situation was estimated in a
first approximation as the mean plus three times the standard deviation
of the integral signal calculated from 10 unirradiated samples’ TL
curves (Currie, 1968).
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Fig. 3. Typical TL response of a coarse calcite powder sample to the sequence I) TL
readout to erase the native signal II) TL readout to observe the background signal III)
TL readout after irradiation (50 Gy in this case) to observe the response. The heating
rate was 1 ◦ C/s and the maximum TL readout temperature 400 ◦ C.

Fig. 2. Comparison of the laboratory powder X-Ray diffraction patterns of the two
calcite powder samples (normalized intensities). The strongest lines associated with
calcite-like (CaCO3 ) and dolomite-like (CaMg(CO3 )2 ) phases are indicated with black
lines.

3. Results and discussion
3.1. Sample characterization

3.1.1. XRD
Fig. 2 shows the raw XRD signal for both calcite powders for a
chosen subset of angles. In the observed region we qualitatively indicate the known most dominant peaks that are associated with calcite
(CaCO3 , ∼29.5◦ ) as well as dolomite (CaMg(CO3 )2 , ∼31◦ ) (Al-Jaroudi
et al., 2007). The detailed fitting using the full diffraction pattern’s
angular range as described above was used to estimate the volume
ratios of calcite, dolomite, and any other potentially present phases (see
Supplementary Figure A.12).
The determined volume ratio for the coarse calcite powder was:
Calcite (SG R3c H; No. 167): 79.8(6)%, Dolomite (SG R3H; No. 148):
19.1(4)%, and Graphite-like phase (SG P63/mmc; No. 194): 1.1(2)%.
The lattice distribution of CaCO3 polymorphs suggest the presence of
small Mg doping into the Ca site. The determined volume ratio for the
fine calcite powder was: Calcite (SG R3c H; No. 167): 91.8(7)%, and
Dolomite (SG R3 H; No. 148): 8.2(6)%. The presence of a third phase,
given the experimental resolution, was not found.
Given the used procedure, we indeed find a higher CaCO3 and lower
dolomite volume fraction in the fine powder, lending evidence to our
hypothesis of lower luminescence from such samples due to the lower
Mg content.
A set of face mask samples was also measured using XRD, but the
results are less conclusive due to the habit of the specimen resulting
in diffraction patterns with high background and broad reflections.
Additionally, the likely low content of calcite in the mask may well
be below the detection limit of our laboratory diffractometer (see
supplementary Figure A.13).

Fig. 4. Typical TL response of a fine calcite powder sample to the sequence I) TL
readout to erase the native signal II) TL readout to observe the background signal III)
TL readout after irradiation (50 Gy in this case) to observe the response. The heating

rate was 1 ◦ C/s and the maximum TL readout temperature 400 ◦ C.

A.14, we find that a dose response, e.g. using a test dose normalization (Yukihara et al., 2005), shows a linear response for TL peak 1 in
the range from 35 mGy to 14 Gy, and a linear response for Peak 2 above
0.3 Gy. A 0.7 Gy dose repeatability test showed a TL integral variability
of repeated irradiations and readouts below 1% (Supplementary Figure
A.14b).
In Fig. 4 we show the same TL sequence for the fine calcite powder.
We observe a similar behavior but with an important difference: the
background readout shows a significant remaining TL signal in the
region above 150 ◦ C. The corrected TL curve exhibits a negative signal
above 360 ◦ C.
The background signal changes over repeated heating of the sample
as well. When repeatedly heating a native erased fine calcite powder
sample to 400 ◦ C (i.e reading out a TL), as shown in Fig. 5, we observe a
non-linear behavior of a decreasing background in the region between
100 ◦ C and 400 ◦ C, and eventually an increase in the region above
350 ◦ C. We hypothesize this behavior to stem from the coating agent
used in the fine powder that is not stable at the temperatures used to
access TL peak 2. Over successive readouts it thus begins to burn out.
The fact that the coating agent changes the luminescence signal may
affect background subtraction reproducibility, which can impact dose
recovery protocols.
This highlights some of the limitations of using TL of the fine calcite
powder for dosimetry: the samples are likely to contain a native signal
that limits the usability of the TL peak 2 region, as well as a potential
non-linear background behavior.

3.1.2. TL response
Fig. 3 illustrates the successive TL readout signal to 400 ◦ C with a

heating rate of 1 ◦ C/s of the coarse calcite powder. The first readout
shows the native signal dominant in the thermally stable region above
200 ◦ C and no detectable signal below. By native signal we refer to the
signal from accumulated dose in the material due to natural sources of
radiation and/or energy causing electron trapping. The second readout
then shows the background signal (i.e. native signal erased). A third TL
readout after a 50 Gy dose then shows the dose response, showing both
peaks. Note that the native signal well exceeds the equivalent signal
of TL peak 2 at 50 Gy. By subtracting the background signal (readout
2) from the dose response (readout 3) we determine the background
reduced signal used for dosimetry. As shown in Supplementary Figure
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Fig. 5. Repeated TL readout of the unirradiated fine calcite powder. In the region
relevant for dosimetry (room temperature to 400 ◦ C), we find that the background
signal changes in a non-linear, overall decreasing manner. This ‘‘burn-out’’ of the
background indicates that the finer powder has a thermally unstable component that
contributes to the TL signal in a potentially interfering manner.

3.1.3. TL emission spectra
TL spectrum measurements were conducted on all samples to confirm the emission bands, in particular of the face mask samples, to be
that of calcite - around 630 nm (Medlin, 1959). We focused on the
native and general dose responses of the used materials. The samples
were heated to 400 ◦ C with a heating rate of 1 ◦ C/s. Fig. 6 shows the
native TL spectra of the coarse calcite powder, fine calcite powder,

and a face mask sample. The subsequent response (i.e. with native
signal erased) to 80 Gy of 𝛽 irradiation was recorded as well and is
also shown in Fig. 6. The shapes of the TL curves in the direction
of temperature follow the already introduced pattern: at temperatures
below 200 ◦ C no significant emissions are visible. This is consistent with
the aforementioned thermal fading characteristics of TL peak 1. Above
this temperature all samples exhibit a bright native signal (TL peak 2),
with the fine powder and face mask showing a much lower brightness.
The face mask sample TL response to 80 Gy shows a differing peak
structure to the calcite powders, notably by a strong emission at 160 ◦ C.
This coincides with the melting temperature of the polymer (polymerdatabase.com, 2021); we therefore hypothesize that the mineral filler
in the fiber is not heated efficiently until the melting point is reached.
Once the fiber begins to melt, the filler then quickly reaches a higher
temperature and the signal increases as observed. Another effect could
be the change in opacity of the fiber when molten, leading to a higher
effective light output.
We confirm the dominant emission to be indeed in the expected
range around 630 nm for all the examined samples. We note that the
signal at wavelengths shorter than 400 nm suffer from a large efficiency
correction (see Appendix, Figure A.11) and are thus likely not a true
signal in the case of the low signal recorded from the face mask sample.

Fig. 6. Native and dose response TL spectra of coarse calcite powder (a, d), fine calcite
powder (b, e), and the face mask sample (c, f). Note that the calcite native signal was
bright enough to cause saturation and the thus incurring plateau shape of the signal.

with a stretched exponential decay, indicating that the TL peak 1 region
consists of a distribution of traps in terms of activation energy (Chen
and McKeever, 1997).
This implies that, for practical purposes, TL peak 1 could be used

for same day dosimetry and emergency situations, with the possibility of using cold storage of samples to mitigate fading and enable
retrospective dose assessment.
3.1.5. PTTL response
Phototransfer (PT) effects could potentially allow for dose recovery
or signal enhancement (e.g. by accessing deeper traps without heating
to the required temperature) by light stimulation of the samples prior
to TL readout — or indicate that a sample is light sensitive and
thus be subject to optical bleaching. We therefore conducted a PTTL
quantification experiment to assess the impact of PT in calcite.
The procedure was as follows: after irradiation, the sample was
heated to a temperature 𝑇𝑝ℎ in the range 50-400 ◦ C and held at that
temperature for 60 s. Thereafter, the sample was illuminated for 5 s using the UV LED of the reader to elicit a PT response. The subsequent TL
readout should then show signal below 𝑇𝑝ℎ if significant PT occurred.
As we display in Fig. 8, we find no evidence of PTTL to an extent
that could aid the dose recovery, as the supposed PTTL signal at 100 ◦ C
constitutes less than 1% compared to the reference TL after irradiation.
The observed signal is nonetheless not trivial compared to a normal TL
readout (compare to Fig. 3) and indicates a PT or UV induced trapping.
As no coincident loss of signal in TL peak 2 with appearance of signal in

3.1.4. Fading
Fig. 7a presents the results of a qualitative fading study conducted
by irradiating a calcite samples with 16 Gy and then waiting a time
period (sample remained in the reader, i.e. in the dark at room temperature) before reading the TL. The procedure was then repeated for
four other time points with an annealing of the sample performed at
450 ◦ C in-between two measurements. Fig. 7b shows the average peak
1 integral (60 ◦ C to 190 ◦ C) of four different samples subject to the same
experiment, normalized to the respective value at 0 h waiting time.
Consistent with literature (Singh and Ingotombi, 1995; Bossin et al.,
2020), we find that the integral TL signal between 60 ◦ C and 140 ◦ C of

TL peak 1 fades more than 50% within 2 h, whilst for TL peak 2 we
observe no significant fading. The fading in TL peak 1 was best fitted
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Fig. 7. (a) TL curves of the calcite sample for various intervals after irradiation. (b) Integral of Peak 1 (60 ◦ C to 190 ◦ C) of four samples (mean shown as dot with an errorbar to
reflect the standard deviation) over time, normalized to the respective value at 0 h.

Fig. 8. (a) Step annealing TL signals in calcite powder acquired after a dose of 16 Gy. After irradiation, the sample was heated to temperature T𝑝ℎ and subsequently illuminated
using a UV LED to stimulate a PTTL response. (b) The same TL curves in logarithmic scale to display that a PTTL effect, if at all present, affects less than 1% of the signal at
100 ◦ C. (c) TL peak intensities for TL peak 1 and TL peak 2 over preheat temperature.

TL peak 1 was observed, we infer that the signal is UV induced trapping
rather than PT.
This result still presents as an advantage with regards to fortuitous
dosimetry: a weak PTTL signal indicates little optical mobility of the
trapped charges and a resistance to bleaching due to UV light. 5 s under
the UV LED corresponds in a first approximation to 36 h of UV-index
8 sunlight (neglecting that sunlight reaching the earth’s surface may
have significant contributions of UV down to 300 nm Fioletov et al.,
2010). We show an explicit experiment for the TL response as a function
of UV bleaching time after irradiation in Supplementary Figure A.15
confirming the weak bleachability of calcite.
The PTTL experiment further shows relevant features of calcite TL:
the preheat clearly moves the peak location to higher temperatures in
both peaks, lending evidence to the aforementioned hypothesis of a

distribution of trap levels rather than a single trap. Furthermore, as the
higher temperature end of TL peak 1 is more thermally stable, we may
thus explain why the fading does not follow an exponential behavior.

3.2. Emergency dosimeter case example: Polymer fiber face mask
We next display the results of an applied case example for dose
assessment using the face mask samples. Due to the melting of the
polymer fibers above 160 ◦ C a TL measurement up to 400 ◦ C can be
considered destructive. Therefore, we undertook two experiments: I)
the dose response of 23 face mask samples with TL readout to 400 ◦ C to
test a destructive readout scenario with doses up to 30 Gy. II) the dose
response of 23 face mask samples with TL readout to only 150◦ C to test
a non-destructive readout with doses up to 42 Gy. For both experiments
we therefore may encounter inter-sample variability, but the procedure
mimics the actual application case of an irradiated mask and allows for
more realistic conclusions as to the operational dosimetric usability.
The results are displayed in Fig. 9.
The mask samples show proportional response for TL peak 1 above
the MDD of about 1.8 Gy. TL peak 2, due to the native signal, was
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Fig. 9. TL dose response of face mask samples using either (a) a destructive readout to 400 ◦ C and (c) a non-destructive readout to 150 ◦ C. The resulting integral TL responses
over dose with estimated MDD for TL peak 1 are plotted for the destructive case (b) and non-destructive case (d).

4. Discussion

Calcite mineral fillers in polymers showed a TL response proportional to dose that could allow for such materials, e.g. a face mask, to
be used in emergency dosimetry.
We demonstrated that commercially available calcite powders show
the expected TL response. The fine powder was shown to display an
important background behavior that may lead to reproducibility issues
in dose recovery protocols. The dominant source of luminescence in the
examined samples is indeed centered at around 630 nm, confirming our
hypothesis of Mg sites in calcite being the source of luminescence.
The native signal in the herein examined samples consistently exceed an equivalent dose of >10 Gy. Dose assessment using the TL peak 2
region thus requires the material to be annealed at temperatures above
450 ◦ C. The favorable thermal stability makes TL peak 2 very relevant
for potential retrospective dose assessment applications. Currently, the
calcite is not exposed to sufficient heat during the manufacturing chain
down to the polymer fiber incorporation. Whether this change can be
easily achieved in the industrial manufacturing process prior to the
incorporation into the polymers in the prospect of enabling dosimetry
remains an open question.
The main limitation for TL peak 1 dosimetry is hereby thermal
fading, constraining practical applications to acute dosimetry when
timing and environmental parameters were well known. A procedure
of freezing samples after a suspected exposure could improve this, but
requires a careful characterization of the reduced fading (Bossin et al.,
2020).
Phototransfer properties of calcite have previously been shown to be
weak (Bruce et al., 1999) and our experiments using the Risø reader’s
UV LED showed no significant PTTL signal in the examined samples. We
conclude that PT cannot be used in calcite to improve dose recovery.
Looking at the results of an emergency dosimeter case example
using a commercially available face mask, we confirm a dosimetric
application of TL peak 1 (up too 200 ◦ C). The face mask furthermore

fulfills several desired emergency dosimeter characteristics, such as

Fig. 10. TL curves of nine samples taken from the same surgical face mask (dashed
lines), with the tenth sample being irradiated with ∼16 Gy before readout. The native
signal in this commercially available product is strong enough to completely mask the
radiation induced response in the TL peak 2 region. TL peak 1 is well discernible as a
radiation-induced peak, but fades thermally within days.

practically indiscernible from background. For 10 samples of the same
face mask we exemplify the native signal’s relative strength in Fig. 10.
In the non-destructive TL experiment we find a higher MDD of 2.5 Gy.
We observe an important few outliers in both destructive and nondestructive readouts that exceed the MDD limit despite having received
a much smaller dose. The high variability, in particular for the destructive readout case, seems to arise from the melting peak at 160 ◦ ,
indicating a complex and not necessarily proportional response to dose.
Such outliers may warrant sampling a given mask multiple times to
confirm the signal. The test dose normalization method was shown to
work for calcite samples (Supplementary Figure A.14), which could
potentially be applied to the non-destructive readout. The destructive
readout may require a more complex calibration procedure.
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Acknowledgments

ubiquitous availability, simplicity of readout method, speed of sampling
using a standard hole puncher, speed of readout using TL, as well as

a high likelihood of the item being voluntarily yielded to emergency
responders (unlike e.g. a mobile phone). The main limitation is once
more the thermal fading. We found that the MDD for either nondestructive or destructive read-outs may be low enough to deliver
useful dose information. Nonetheless, assuming a decision threshold of
2 Gy, the sensitivity of this setup may not yet be sufficient for triage
scenarios.
The presented results could therefore be improved in the future:
Firstly, the complex background term in the fine calcite powder and
thus also in the face mask samples could be reduced by introducing a
thermally stable particle coating. Secondly, if annealed at least 450 ◦ C
for 15 min before incorporation into the fiber, the used fine powders
could allow for a dosimetric use of TL peak 2. Thirdly, an optimized
procedure using cold storage of the samples could allow to extend the
time frame of usability of a given sample for TL peak 1 dosimetry.
Finally, the experimental setup could be optimized for detection in
the 500 to 700 nm range by using a red sensitive PMT – e.g. a
Hamamatsu H7421-40 – that could yield a comparative increase of
quantum efficiency of a factor 8 or more at 630 nm. This last change
could improve the MDD, alleviating fading concerns as well as boosting
sensitivity and specificity.

The authors greatly appreciate the help of M. Brunner of Omya
International AG, both for providing the samples as well as technical
details in discussion. This work was supported by a Swiss National Science Foundation SPARK grant (project number CRSK-2_196453). The
Risø TL/OSL-DA-20 reader (DTU Nutech, Denmark) was acquired with
partial support from the Swiss National Science Foundation (R’Equip
project 206021_177028).
Appendix A. Supplementary data
Supplementary material related to this article can be found online
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5. Conclusion
In this work we investigated the feasibility of polymer fibers with
calcite filler as emergency dosimeters. We identified the potential of
this material both based on the known TL characteristics of the underlying mineral, calcite, as well as the favorable characteristics of the
polymer fiber product that is used e.g. in face masks or surgical gowns.
For this purpose, we presented several experiments using commercial
calcite powders, as well as a surgical face mask.
The TL spectral behavior was found to be consistent among the samples and likely stemming from Mg-doped CaCO3 phases. The examined
samples showed a native TL signal in the thermally stable (peak 2)
region, and limits the usability of currently available materials to the
lower temperature (peak 1) region. Due to the known thermal fading,
and the complex TL background in the fine calcite powder, we conclude
that currently available calcite powders as well as polymer fibers such
as face masks are limited to dosimetry using TL peak 1.
In our detection setup, we found that samples taken from a face
mask reach minimum detectable doses of the order of 2 Gy. On top of

the other favorable qualities of the face mask, we conclude that face
masks using calcite based mineral fillers may be suitable to deliver
useful dose information in emergency situation, depending on the
required sensitivity. We outlined improvements to the detection setup
that likely alleviate these limitations.
Given the prevalence e.g. of the common face mask in both professional and currently also the general population, it is clear that
polymer materials with mineral fillers remain an interesting candidate
for fortuitous dosimetry. Important changes in the manufacturing or
dedicated detection equipment may aid in improving the sensitivity and
ease the constraints due to the thermal fading.
CRediT authorship contribution statement
Oskari Ville Pakari: Investigation, Methodology, Software, Writing
– original draft. Eduardo Gardenali Yukihara: Investigation, Conceptualization, Writing – review & editing, Resources. Dariusz Jakub
Gawryluk: Investigation, Software. Lily Bossin: Funding acquisition,
Project administration, Conceptualization, Writing – review & editing.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to
influence the work reported in this paper.
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