Annals of Work Exposures and Health, 2018, Vol. 62, No. 6, 721–732
doi: 10.1093/annweh/wxy029
Advance Access publication 4 May 2018
Original Article
Original Article
Benjamin Sutter1,*, Eric Pelletier1, Morten Blaskowitz2, Christel Ravera1,
Christopher Stolze3, Christian Reim4, Eddy Langlois1 and Dietmar Breuer2
1
French National Research and Safety Institute for the Prevention of Occupational Accidents and Diseases
(INRS), Vandoeuvre les Nancy Cedex, 54519 France; 2Institute for Occupational Safety and Health of the
German Social Accident Insurance (IFA), 53757 Sankt Augustin, Germany; 3BG BAU - Berufsgenossenschaft
der Bauwirtschaft, Gebersdorfer Straße 67, 90449 Nürnberg, Germany; 4BG BAU - Berufsgenossenschaft
der Bauwirtschaft, Landsberger Straße 309, 80687 München, Germany
*Author to whom correspondence should be addressed. E-mail: benjamin.sutter@inrs.fr
Submitted 2 May 2017; revised 20 March 2018; editorial decision 20 March, 2018; revised version accepted 13 April 2018.
Abstract
Bitumen is classed as possibly carcinogenic to humans according to the International Agency for
Research on Cancer. Data on individual exposure to bitumen fumes is therefore required to highlight
the exposing situations and develop methods to prevent them. The Institute for Occupational Safety
and Health of the German Social Accident Insurance (IFA) and the French National Research and
Safety Institute for the Prevention of Occupational Accidents and Diseases (INRS) have both developed methods to measure individual exposure. The objective of this study was to determine a conversion factor to allow interconversion of data acquired by the two methods. To develop this conversion
factor, comparative laboratory and workplace tests were performed according to both the IFA method
(No. 6305) and the INRS method (MetroPol M-2). The amounts of organic material collected on the filters and XAD-2 beds were compared. The results revealed differences between the sampling and analytical methods that could be linked to sampler design, extraction solvent, and the detection method
used. The total quantification returned by the two methods—the sum of the masses quantified on
filter and XAD-2 bed for each sampler—were correlated in both controlled and real-life tests. A conversion equation was therefore determined, based on field tests: CIFA = 1.76 CINRS ± 0.39 (R2 = 0.99)
that is applicable to total quantification data. This formula can be applied to data acquired by the two
institutes to increase the number of data points available on exposure to bitumen fumes in various
conditions, and thus increase the statistical power of studies into occupational prevention.
Keywords: analysing method; bitumen; fumes; method comparison; sampling method; semi-volatile aerosol
© The Author(s) 2018. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.
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Sampling and Analysis of Bitumen Fumes:
Comparison of German and French Methods to
Determine a Conversion Formula
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Introduction
fumes between the IFA method and the TOM method
was weak (R2 ≤ 0.78) due to the differences of treatment in collection and analyse of the vapour fraction.
The vapour content in bitumen fumes was since found
to be non-negligible (Breuer et al., 2011; Sutter et al.,
2016) and to vary as a function of the composition of
the fumes or sampling conditions (Sutter et al., 2010;
Dragan et al., 2015). These results mean that the BSF,
TPM, and NIOSH 5042 methods are no longer considered relevant methods to assess exposure to bitumen
fumes due to the fact that they not consider the vapour
fraction of the fume. The omission of the vapour fraction
explains why results obtained with these methods correlated poorly with IFA results. Thus, only results obtained
with the TOM method were related to those obtained
with the IFA method. The TOM method uses a similar
sampling system to the INRS method, but the extraction
solvents, the chromatographic method using a gas chromatography and flame ionization detector (GC-FID),
and calibration, all differ. Thus, results from TOM and
INRS methods are expected to be non-identical.
In this paper, we describe a study performed by the
IFA and INRS comparing their bitumen fume sampling
and analysis methods. The aim of this study was to determine a conversion factor that could be applied to results
to harmonize German or French quantification data.
To compare the methods, the study was performed
in two parts. The first part was a laboratory comparison, where fumes were generated in perfectly controlled
conditions from representative bitumen samples. This
facet of the study allowed comparison of the methods in
terms of sampler design and solvent extraction effect, as
well as relative detector response/sensitivity. In the second part, the methods were subsequently tested in situ
on German and French road construction sites, to determine the impact of uncontrolled environmental conditions and unknown bitumen products on the results
returned by each method.
Material and methods
Sampling and analysis methods
The IFA and INRS methods are based on the same sampling principle: particles are collected on a filter and
vapours passing through the filter are adsorbed on a bed
of XAD-2 resin. However, the nature of the filter, the
extraction, and analytical methods differ.
IFA method n°6305
IFA method No. 6305 ‘Bitumen (Dämpfe und Aerosole,
Mineralölstandard)’ (Breuer, 2008) has been used
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In 2013, the International Agency for Research on
Cancer re-classified straight-run bitumens and their
emissions as class 2B, possibly carcinogenic to humans
(IARC, 2013). It has therefore become even more important to assess individual exposure to bitumen fumes in
road construction workers. In addition, recommendations must be made on practices, products, or design of
the material used on sites to limit worker exposure.
To assess exposure to bitumen fumes, the Institute
for Occupational Safety and Health of the German
Social Accident Insurance (IFA) and the French Research
and Safety Institute for the Prevention of Occupational
Accidents and Diseases (INRS) developed independent
sampling and analysis methods for their own use. The
methods consist of non-specific measurement of the
fumes amount in the sampled air. As bitumen fumes are
a complex mixture of hundreds of compounds, results
act as indicators of exposure which are compared to
respective limit values or recommendations. Both methods were developed and fully validated in line with the
requirements of the standards EN 482 (CEN, 2012) and
EN 13936 (CEN, 2014) in terms of performance, reproducibility, sensitivity, and sample storage.
IFA and INRS collect their individual exposure
assessment data in databases. The German database is
called ‘Measurement data relating to workplace exposure to hazardous substances’ (Messdaten zur Exposition
gegenüber Gefahrstoffen am Arbeitsplatz in German)
(MEGA) and the French one named ‘System for collecting exposure data from regional health insurance
funds’ (Système de COLlecte des données d’exposition
CHImique des Caisses régionales d’assurance maladie).
Today, these databases are exploited individually and
therefore offer a low statistical power when attempting to correlate hygiene recommendations (reducing
bitumen temperature, setting up engineering control
systems, installing windshields on finishers, etc.) with
effective bitumen fume exposure concentrations for different classes of workers. The statistical power of observations could be significantly increased by merging the
databases, thus leading to a better understanding of the
effect of various hygiene recommendations for bitumen
producers and users.
In a previous study (Kriech et al., 2010), the IFA
method was compared to a number of alternative
methods, including benzene soluble fraction (BSF),
total particulate matter (TPM), total organic matter (TOM), and the method 5042 from the National
Institute for Occupational Safety and Health (NIOSH)
(NIOSH, 1998). But the correlation for paving bitumen
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INRS method MetroPol M-2
MetroPol method M-2 (INRS, 2015) is the current
French method for sampling and analysis of bitumen
fumes in workplaces; it was published by INRS in 2015.
The sampling system includes a 37-mm polystyrene cassette (Millipore) containing a Polytetrafluoroethylene
(PTFE) membrane (ZefluorTM 1.0 µm, 37 mm, Pall Life
Science), and an XAD-2 amberlite sorbent tube (OrboTM
– 609, 400/200 mg, Supelco Analytical). The sampling
flow rate was 1 l/min. Due to the pressure drop of about
12,400 Pa, a Sensidyne Gilian 5000 personal pump was
used to manage the high-pressure drop induced by the
sampler in all sampling situations.
In MetroPol method M-2, it is recommended that the
extraction step be performed simultaneously on the PTFE
membrane and the first bed of the XAD-2 sorbent tube,
by placing them in the same extraction vial. However,
to allow comparison with the IFA method No. 6305
in this study, material was extracted from the collection substrates separately. Each substrate was extracted
in n-heptane (n-C7H16) and the extract analysed by gas
chromatography and flame ionization detector (GC-FID).
N-hexadecane (C16H34) was used as a standard for the
calibration of the GC-FID. More details on the analytical
method are provided in Sutter et al. (2016).
Flow rate control pumps and sample storage
conditions
GSA SG5100 personal pumps were used in tests performed in German workplaces. Sensidyne Gilian 5000
personal pumps were used to ensure the sampling flow
rate for laboratory tests of both systems, and in French
workplaces. Laboratory samples were stored at 4°C and
field samples were stored at ambient temperature until
analysis with a maximum storage time of 21 days.
Bitumen fume generation for laboratory
test series
The bitumen fume-generation system was the one developed and validated by Sutter et al. (2016) in which the
fume-generation conditions (temperature, concentration,
and hygrometry of the fumes) and the temperature of
the bitumens were fully controlled to ensure homogeneous exposure of the samplers (coefficient of variation
[C.V.] = 3% for 12 samplers).
IFA samplers (n = 6) and INRS samplers (n = 6)
were placed inside the exposure chamber for simultaneous exposure to the same humidified fumes. The system
generated bitumen fumes at 170°C with a concentration
ranging from 0.01 to 9.36 mg/m3 and a relative humidity
ranging from 22 to 80%. The particle size of the fumes
was consistent with values measured in workplaces.
Details of the comparison between laboratory and workplace fumes can be found in Sutter et al. (2016).
Bitumen samples
The composition of bitumen fumes can differ depending on multiple parameters such as temperature, grade,
fluxing additives, refinery, origins, etc. Therefore, the
sampling and analysis methods must be tested on many
different bitumens currently used in Germany and
France.
For this study, four 35/50 grade hot road-paving bitumens, numbered 1 to 4, were provided by the
French trade union of bitumen producers [Groupement
Professionnel des Bitumes (GPB)]. Two other 25/55 and
70/100 grade hot road-paving bitumens, numbered 5
and 6, were provided by German producers. Since these
bitumens were produced in the refineries that supply
French and German road-paving companies, they were
considered to be representative of the bitumen used on
road construction sites in the two countries.
Equivalence of samplers
The aerosol sampling efficiencies of the two different
samplers had previously been evaluated with non-volatile particles (Kenny et al., 1997; Kenny et al., 1999).
Results of these studies demonstrated that the closedface 37 mm cassette is less efficient than the GPP sampler for sampling of airborne particles measuring over
10 µm in calm air. Below this diameter threshold, the
two samplers display close performances. Since bitumen fume particles, mainly fall below 10 µm (Brandt
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in Germany to sample bitumen fumes since 2008.
The inhalable dust-gas-sampling ‘Gesamtsstaub-GasProbenahme’ (GGP) system used by IFA to sample bitumen fumes is composed of an inhalable particle sampler,
that includes a glass-fibre depth filter (1 µm liquid nominal pore size) for particle collection, and a 10-g XAD-2
amberlite resin cartridge (0.5–0.9 mm) to adsorb organic
vapours. The method indicates a sampling flow rate of
3.5 l/min associated with a pressure drop of 2500 Pa.
As recommended in the method, material collected
on the filter and XAD-2 cartridge were extracted separately in 10 ml of tétrachloroéthylène (C2Cl4) for a minimum of 16 h. Extracts were stored at 4°C until analysis.
Elements contained in bitumen fumes were detected by
infrared absorption at the C-H aliphatic stretch frequencies (from 2800 cm−1 to 3000 cm−1). Predominantly aliphatic compounds or aliphatic chemical functions are
detected at these frequencies by the infrared detector.
A pool of four bitumen fume condensates was used for
signal calibration.
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Method comparison
The first part of this study also aimed to compare the
two analytical methods in a laboratory generation system. The second part of this study was a field comparison where the samplers were exposed to real bitumen
fumes on road construction sites.
Laboratory comparison
During each sampling session, six IFA samplers and six
INRS samplers were placed inside the exposure chamber.
Target fumes concentrations were 0.5, 2, and 5 mg/m3 for
all bitumens and bitumen 4 was used for two supplementary concentration targeted at 0.1 and 20 mg/m3. Sampling
times were adapted to keep the mass collected in the samplers above the quantification limit. A total of 20 different
generation conditions were developed to determine effects
on results due to the identity of bitumens, fume concentrations, and analytical methods. Initial results indicated
that bitumens 1, 2, and 6 produced no quantifiable material on the filters for either sampler. This observation was
confirmed in additional experiments. Thus, a total of 34
sampling sessions were performed.
Workplaces comparison
In field tests, six IFA and six INRS samplers were systematically placed as static samplers on the finisher used
at the road construction site. Each sampler was identified and placed as close to the others as technically possible. Figure 1 shows where the samplers were placed
during field samplings. Samplers were placed close to an
emission source to collect a maximum of fumes over a
minimum of 2 h. Thus, sampling could be repeated up to
three times during a working day.
Due to design differences between German and
French finishers, samplers could not be placed in identical positions on the finishers. On German finishers, the
samplers were fixed to the outer wheel-covering of the
finisher, whereas on French finishers they were fixed on
the engine-cover.
Two additional samplers were used as the environmental blanks for each sampling session; they were
placed at least 50 m from the construction site.
Environmental parameters, such as temperature,
humidity, and atmospheric pressure were recorded
for both German and French workplaces; wind speed
was also recorded for German sites. All these data
were acquired at 1 Hz throughout sampling sessions.
A GRIMM aerosol spectrometer (model 11-A) was also
used to measure the mass median diameter (MMD) and
the geometric standard deviation (SD) (σg) of the airborne particles in the air close to samplers; samples were
taken every 6 s.
A first group of sampling sessions was scheduled for
the 1st, 2nd and 3rd of December 2015 around the city
of Arras in northern France; a total of 24 samples each
were produced for the IFA and INRS methods over four
sampling sessions. Bitumens having a 20/30 and 35/50
grade were applied at hot temperatures from 140 up to
190°C. A second group of sampling sessions was scheduled from the 2nd to the 4th August 2016, producing 42
samples for each method over seven sessions. Bitumens
having a 50/70 grade were used at hot temperature
from 180 up to 210°C). The environmental conditions
recorded for these two groups of samplings were different, thus, any effect due to environmental conditions
should be observable in the results.
Statistical analysis
All statistical analyses were performed using Statgraphics
Centurion software.
Method comparison
Each of the 34 sampling sessions was composed by six
IFA samplers and six INRS samplers producing two
analyses by sampler for filters and adsorbents. Once the
collection substrates were analysed by the corresponding IFA and INRS methods, the concentrations of fumes
were statistically tested for normality using the ShapiroWilk test (n = 6). For all sampling sessions, P-values were
above 0.05 demonstrating the normality of the experimental data. Moreover, since the samples were generated
inside a homogenized exposure chamber leading to less
than 3% variability of the concentration on 12 samplers,
the homoscedasticity of the data is assumed. Finally,
the six concentrations are averaged for each sampling
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and de Groot, 1999; Calzavara et al., 2003; Herrick
et al., 2007), the total amounts (particles + vapours)
collected in both type of samplers in this study is
expected to be similar.
The first part of this study was to confirm this hypothesis and verify that the German and French sampling methods displayed equivalent sampling efficiencies for bitumen
fumes. To do this, four IFA and two INRS samplers were
exposed to the same fumes produced in the fume-generation setup described above, and in which bitumen type 4
was used as the source of fumes. The collection substrates
from two of the IFA samplers and both INRS samplers
were analysed using the INRS analytical method, with
n-heptane as extraction solvent; collection substrates from
the other two IFA samplers were extracted with tetrachloroethylene. The masses of organic compounds extracted
were then determined by the INRS method and compared
as a function of sampler type and extraction solvent.
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725
session: the studied data is composed of 34 averages for
IFA and 34 for INRS.
For comparing IFA and INRS data, linear regressions
were used as employed by Kriech et al. (2010). First,
the possibility of removing the intercept so the slope of
the linear regression would be a conversion factor was
assessed. For this, regressions with intercept were computed and the 95% confidence intervals (CI) of the intercepts were compared to zero. All intercept values were
included within the 95% CI except for the bitumen n°2
where the zero intercept value was included in the 97%
CI of the intercept. Consequently, all regressions used for
the later comparisons of the methods were performed
without constant.
Since several linear regressions were computed,
the assessment of the statistical differences between
the slopes is performed by the analysis of covariance
(ANCOVA). This procedure used the protocol described
by Andrade and Estevez-Perez (2014), implemented in
the Statgraphics software.
Field comparison
Regarding the field comparison, the variability of all
collected data was assessed separately for France and
Germany. The variables were tested for similarity using a
t-test and F-test for averages and SD with the H0 hypothesis that the parameters measured in Germany and
France were similar (P > 0.05). The tested variables are
temperature and humidity, aerosol characteristics measured by the Grimm spectrometer on field (MMD, σg),
and concentrations in bitumen fumes analysed by both
the methods.
Linear regressions on field data were done with the
same procedure than for laboratory data, including the
ANCOVA.
Results and discussion
Laboratory tests
Equivalence of samplers and extraction solvents
The data produced in laboratory on the amounts collected on the different sampler substrates are shown
in Fig. 2. As n = 2 for each conditions, averages were
directly compared taking into account a CI defined
as ± 3% of the average, corresponding to the variability of the concentration determined on 12 samplers
exposed simultaneously to a fume generated inside the
generation system.
The comparison of the averages indicated that INRS
samplers extracted with n-C7H16, GGP extracted with
n-C 7H 16, and GGP extracted with C2Cl 4 all gave significantly different total concentrations as no interval
is overlapping others. The mean total concentrations
were determined at 7.39 ± 0.22, 8.04 ± 0.24, and
9.15 ± 0.27 mg/m3, respectively.
The effect of sampler design on the concentration
measured was assessed by analysing the differences
between IFA_n-C 7H 16 series and INRS_n-C 7H 16. The
effect of extraction solvent on the concentration measured was assessed by comparing IFA_n-C 7 H 16 and
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Figure 1. Systems used to place the 12 samplers on the finisher in Germany (a) and France (b).
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IFA_C2Cl4 series. The quantitative differences, expressed
as percentages are reported in Table 1.
Focusing on filters, the design differences between
the samplers (GGP versus 37 mm cassette), in terms of
geometry and sampling flow rate, resulted in 4.5% higher
quantification values with GGP than with the cassette.
This result is consistent with the data from Görner et al.
(2010), where differences in sampler design and sampling
flow rate were reported to alter the particulate fraction
sampled compared to the conventional inhalable particulate fraction.
The different extraction solvents also produced differences in the concentrations measured, with C2Cl4 extraction
resulting in 8.6% higher values than n-C7H16. This result
contrasted with the data reported by Sutter et al. (2015),
where no significant differences were found between extraction solvents used to extract particles collected on filters.
Combining the effects of sampler design and extraction solvent, quantification of particles collected on filters by the IFA method returned values 13.1% higher
than those determined with the INRS method.
With regard to the XAD-2 collection substrates, the
sampler design and extraction solvent also affected quantification results. Thus, the IFA method produced results
that were, respectively, 18.2 and 24.3% (42.5% overall)
greater than results obtained with the INRS method. As
already demonstrated by Dragan et al. (2015), the flow
rate of the GGP, which is 3.5 times higher than that for
the 37 mm cassette, causes the transfer of more semi-volatile material from the filter to the XAD-2. Differences
Table 1. Mean percentage differences in concentrations ±
max absolute differences, measured by the IFA method
compared to the INRS method. Results are classed
according to sampler type and extraction solvent.
Sampler
Solvant
Total
Filter gap
XAD-2 gap
Total gap
4.5 ± 1.1%
8.6 ± 1.9%
13.5 ± 0.9%
18.2 ± 8.4%
24.3 ± 8.3%
46.9 ± 2.3%
8.7 ± 1.8%
13.9 ± 2.3%
23.8 ± 1.2%
in extraction efficiency for these solvents were also
observed on XAD-2 beds (Sutter et al., 2015), but with
a lower difference between n-C7H16 and C2Cl4 in comparison of the previous study (+ 24.3% against + 38%).
The values for total difference indicated in Table 1 are
closely linked to the conditions in which fumes were generated (source bitumen, temperature, concentration, etc.).
Therefore, they are not transferable to a general case.
Laboratory comparison of methods
All data produced by the laboratory assays can be found
in the Table 1 of the Supplementary Material.
Total quantification of bitumen fumes
Total quantifications for all bitumen types, relative
humidities, and bitumen temperatures are presented in
Fig. 3.
A linear regression without constant could be fitted
to the 34 observations (Fig. 3a). The slope of this curve
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Figure 2. Mean concentrations quantified on filters and XAD-2 and total mean concentrations, determined with three sampling/
extraction setups tested. Error bars account for a 3% variation coefficient systematically observed inside the exposition chamber
of the generation system with 12 samplers.
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was 1.69 with R2 = 0.93 demonstrating a correlation
between the methods. The maximum dispersion was
observed for values greater than 10 mg/m3 according to
the IFA method or 5 mg/m3 as measured by the INRS
method. In workplaces, values such as these would be
encountered only exceptionally; therefore, the graph was
redrawn excluding the highest concentrations (Fig. 3b).
The slope of the low values’ linear regression was equal
to 1.82 with a R2 = 0.97. Both regressions were not
determined as significantly different (ANCOVA with
F-test, P = 0.74).
Representing data points in Fig. 3b as a function of the different bitumen identities (Fig. 4) gives
regression lines with R2 of 0.94 or greater. The dispersion of x, y values observed for total bitumen fumes
in Fig. 3b was statistically explained by the bitumens’
identity (ANCOVA with F-test on the six regressions,
P = 0.0382). Consequently, the different bitumen identities, in other word the individual compositions of the
bitumens with different origins, lead to different methods performances. A maximum difference of 20.3% was
calculated between the extreme slopes and the average
slope of 1.82. Thus, in workplaces, the two methods
are expected to return different quantification results
if the bitumens used are identical to the ones tested in
laboratory.
Filter and XAD-2 quantifications
Quantification data for samples collected on filters
are shown in Fig. 5a. Quantifiable organic material was recovered from filters after sampling for only
three of the six bitumens tested. The slope of the linear
regression fitted to this data (1.12; R2 = 0.97) was less
than the slopes determined for total quantification data.
Conversion of the slope to a percent difference would
give + 12.0% for the IFA method, which is very close
to the difference between the two methods determined
during the sampler equivalence test (+ 13.1% for the
IFA method). Thus, the detection techniques (FT-IR and
FID) had the same response for the material collected on
filters.
Quantifications of the material collected on XAD2
beds (excluding high concentrations above 10 and 5 mg/
m3 for IFA and INRS, respectively) are shown in Fig. 5b.
For all bitumens tested, organic matter was collected in
quantifiable amounts on XAD-2 beds. The same quality
of data fitting (R2 ≥ 0.94) was obtained for data from
XAD-2 and for total quantifications (Fig. 4). The average slope calculated from the XAD-2 quantifications
represented in Fig. 5b is 1.95, which is equivalent to a
percent difference of + 94.8% between the two methods.
As differences in sampler design and extraction solvent
resulted in 42.5% higher values determined by the IFA
method compared to the INRS method, the remaining +
52.3% must be linked to differences in detector sensitivity for the material collected on XAD-2.
To understand this difference in detector sensitivity,
the chromatographic method used in the INRS method
was calibrated with a mixture of n-alkanes from C 8
to C40. Based on this calibration, the chromatographic
retention times for compounds collected on filters and
XAD-2 could be converted to an equivalent carbon number (ECN). This conversion is a rough estimate of the
molecular weight of the different compounds detected.
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Figure 3. Total bitumen fumes quantified by the IFA and INRS methods: (a) all data, (b) excluding values greater than 5 mg/m3
for INRS and 10 mg/m3 for IFA.
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Each chromatogram was then integrated point-by-point
to determine an area that was compared to the total area
for each ECN and bitumen number (Fig. 6).
These data for material collected on filters indicate
that 80% of the total matter corresponds to compounds
with equivalent carbon numbers (ECN80) ranging from
C25 to C28. In contrast, the ECN80 of the material collected on XAD-2 differed widely (C13 to C19). ECN80 and
the slopes determined in Fig. 5b were correlated by a linear model (ECN80 = −11.56 slope + 36.82; R2 = 0.89).
Based on these results, it appears that the difference
in response between the IFA and INRS methods can
mainly be explained by differences in detector response.
These differences increase in magnitude for low ECN80
values. In other words, the FT-IR detector quantifies
much more material than FID when the material analysed has a low ECN80.
To conclude on the comparison of laboratory results,
sampler design, extraction solvent, and detector all significantly influence the amount of material quantified on
filters or XAD-2. As the quantities of material collected
on each collection substrate are expected to change as a
function of the concentration of particles and vapours,
the semi-volatile character of the fumes and thus, the
nature of the bitumen, it was not possible to determine a
correction factor for interconversion of results obtained
by the different methods for each collection substrate.
Thus, only the total quantification (filter + XAD-2) can
be converted.
Field tests: comparing methods using data
collected in workplaces
Environmental conditions
All data acquired in workplaces, including the atmospheric temperature, humidity, wind speed and pressure,
particle count, the MMD, and the geometric SD calculated from the GRIMM spectrometer data can be found
in the Table 2 of the Supplementary Material. To resume,
the environmental condition of the German and French
sessions were significantly different (all P-values < 0.05).
The averaged environmental temperature was 29.8°C
Figure 5. IFA and INRS methods in good agreement for quantification of material collected on filters (a). Quantities of material
collected on XAD-2 (b) reveal strong differences between IFA and INRS methods. The legend indicates the identity of bitumen
number, the slope and R2 of the linear regression fitted to data points.
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Figure 4. Total bitumen fumes quantified by the IFA and INRS
methods in function of the bitumens identity. The legend indicates the identity of bitumen number, the slope and R2 of the
linear regression fit to data points.
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for German sampling sessions and 13.4°C for the French
ones. The granulometry of the fumes and the concentration in particles were also significantly different.
The atmospheric temperature and humidity were significantly different between German and French workplaces, mainly due to normal variations between summer
and winter. These differences could affect concentrations
of particles and vapours, increasing the vapour quantity
and reducing the airborne particle number at higher air
temperatures.
The MMD confirmed this trend with a significant
difference between data for the two countries, with an
MMD of 1.31 µm for France associated with the lowest temperatures (13.4°C), compared to 0.44 µm for
Germany, where the hottest temperatures were recorded
(29.8°C). These MMD were similar to values measured
during the laboratory comparison step.
The particle count (PC) was also significantly different between countries, with 34 times greater values measured for German workplaces than for French
ones. The main reason for this difference is the bitumen
temperature used in the workplaces—around 150°C in
French workplaces compared to 190°C in German ones.
A correlation between total particulate matter and bitumen temperature was previously reported (Brandt and
de Groot, 1999; Brandt et al., 2000; Cavallari et al.,
2012; Bolliet et al., 2015), although the PC was not
measured in these previous studies. As demonstrated in
the Quantification Comparison section of this paper, the
total quantifications on the samplers were significantly
higher for German samples than for French ones. As
the MMD was lower for Germany than for France, the
only way to obtain this result is to significantly increase
the PC and the vapour concentration. This was confirmed by the PC determinations and also by the XAD-2
quantifications.
Quantification comparison
All quantification data related to workplace samples are
reported in the Table 3 of the Supplementary Material.
For all sampling sessions, the environmental blanks
showed no quantifiable material, even though road traffic was not stopped in some workplaces. Thus, the values
measured by the two methods correspond to bitumen
fumes only.
The average quantifications for all sampling sessions
were compared keeping data for the different methods
separate (Fig. 7). The average concentrations, as determined using the INRS method, ranged from 0.51 to
4.9 mg/m3. A linear regression without constant gave an
excellent fit with the dispersion of the averages, with a
slope of 1.76 and R2 of 0.99. The laboratory regression
was very similar to the regression determined on workplace data, and is within the 95% CI for variations in
workplace data. Thus, the two regressions are equivalent
and agree well.
Significant differences between the medians and averages of the concentrations determined in Germany and
France were identified. The concentrations measured in
Germany were significantly higher than those measured in
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Figure 6. Relative cumulative mass determined from GC-FID chromatograms for material collected on filters (a) and XAD-2 (b)
as a function of the equivalent carbon number for the different bitumen number.
730
France, with an average of 5.97 versus 2.77 mg/m3 determined by the IFA method (t-test, P = 2.97 × 10−12) and 3.37
versus 1.50 mg/m3 determined by the INRS method (t-test,
P = 1.77 × 10−11). This difference could be explained by the
very different environmental conditions between the two
periods but also by the differences between the bitumens
used during road construction operations and the conditions of use (e.g. temperature, finisher).
The SD of the concentrations determined in Germany
were 1.58 for the IFA method and 1.01 for the INRS
method, while SD were 1.21 and 0.65, respectively
for the French sampling sessions. The greater SD for
German sampling sessions can be explained by the
dispersion between results for the six quantifications
performed during each sampling session with a concentration gradient linked to the position of the samplers on
the fixation system. In French workplaces, in contrast,
the dispersion between samples taken at the same time
was low and homogeneous around the average.
The samplers were placed on the finisher at variable
distances from the bitumen distribution screw, where
fumes are emitted in high quantity. Despite the gradation
of the concentrations measured for the different sampler
positions, all individual quantifications were well fitted
by the workplace regression.
Figure 8a,b compares the average and individual concentrations determined for material collected on filters
and XAD-2 by the two methods.
Unlike during German sampling sessions, no quantifiable material was detected on filters for any of the
French sampling sessions performed in December,
regardless of the method used. Although some types of
bitumen produced particles that could be counted with
the GRIMM spectrometer, these particles evaporated
during the sampling time causing them to no longer be
present on filters.
The workplace concentrations detected on filters
therefore did not fit the laboratory regression (Fig. 8a).
This discrepancy between laboratory and workplace
data can be explained by different responses of the methods due to differences in composition of the material
collected on the filters (Sutter et al., 2016). The material
generated in the laboratory and collected on filters had
higher molecular weights than the material generated in
workplaces, with an equivalent median carbon number
of 23 for laboratory samples compared to 14 for workplace samples. As the laboratory comparison test demonstrated, lighter material produces greater differences
between the detectors used in the different methods,
with a greater response of the FT-IR detector than the
one of the FID detector for this class of particles. This
difference produced steeper slopes in Fig. 5b.
The min and max slopes of the laboratory data are
shown in Fig. 8b where the quantifications of material
collected on XAD-2 and quantified by the two methods are compared. All the average workplace points
fell between the extreme laboratory slopes. Thus, the
responses of the methods were similar between laboratory and workplace assays. The dispersion of the individual data points indicates differences in the ECN80
between the sampling sessions leading to different
responses of the methods.
As the ECN80 cannot be predicted for the materials
collected on each samples, the responses of the methods
cannot be corrected to account for the material collected
separately on the collection substrates of the samplers.
Furthermore, the INRS method recommends simultaneously quantifying material collected on both filter and
XAD-2 substrates. Consequently, the ECN80 for the different collection substrates will not be available to correct the INRS quantifications based on the nature of the
material collected.
Finally, even if some differences between the IFA
and INRS methods were identified for different bitumen
types/natures, the relationship between total quantification results is strong enough to allow conversion of the
German and French data, making more exposure data
available for statistical studies. This relation is defined
by this unique equation at the 95% CI calculated on the
averaged values as represented in Fig. 7:
CIFA = 1.76 CINRS ± 0.39
where CIFA and CINRS are the total concentrations determined by the IFA and INRS methods, respectively.
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Figure 7. Total bitumen fume quantifications for all workplace sampling sessions performed in Germany and France.
Mean regression line for laboratory data is indicated for reference. Legend refers to the date of the sampling session and
E# the number of the sampling session in the day mentioned.
Error bars represent two standard deviations calculated on
the results from the six samplers of the considered sampling
session.
Annals of Work Exposures and Health, 2018, Vol. 62, No. 6
Annals of Work Exposures and Health, 2018, Vol. 62, No. 6
731
Conclusion
IFA n°6305 and INRS MetroPol M-2 methods are similar in principle but differ in terms of sampler design,
extraction solvent, and analysis method. The IFA
method systematically gave higher quantifications than
the INRS method.
Our results indicated that differences in sampler
design account for 4.5 and 18.2% of the increase in
quantification measured with the IFA method on filters and XAD-2 beds, respectively. This increase can
be explained by differences in the particulate fraction
sampled and by differences in the flow rate that enhance
transfer of the semi-volatile material from filters to the
XAD-2 bed during sampling.
Tetrachloroethylene extracts more material than
n-heptane, leading to an increase of + 8.6% and +
24.3% of values determined by the IFA method on filters
and XAD-2 beds, respectively.
A significant difference was also identified between
the detectors used in the different methods. In laboratory conditions, the FT-IR detector and FID detectors
returned similar results for material collected on filters with a stable difference of + 12%. In contrast, for
material collected on XAD-2 beds, FT-IR systematically
returned higher quantification results, with an average
increase of + 52.3%. This difference can be explained
by the quality of the material analysed by taking the
equivalent carbon number into account. At low ECN,
the FT-IR has a greater response than the FID, a trend
that was confirmed in workplaces where the material
collected on filter was lighter than the material collected during laboratory assays. In these conditions,
FT-IR results were + 44% higher for material collected
on filters in workplace assays compared to laboratory
assays.
As the differences between the methods were well
identified, it was possible to apply corrections to the
results. However, the particle size distribution and concentration of the particles, the semi-volatile nature of the
fumes and the equivalent carbon number for the material
collected on filters and XAD-2 beds remain unknown
during the sampling time. Consequently, it is not possible to specifically correct the results to account for those
different effects. Thus, workplace quantification should
only consider the total concentration, which is the sum
of the material collected on the filter and XAD-2 bed.
In these conditions, a strong relationship was found
between the two methods that can be summarized by
this equation: CIFA = 1.76 CINRS ± 0.39. This relation
was not affected by environmental conditions, even
though they were drastically different in the workplace
comparison step.
Therefore, the total bitumen fume concentrations
measured using the IFA or INRS methods can be interconverted with a high level of confidence. Databases
created in Germany and France should be combined to
allow more extensive analyses by type of work, equipment, engineering control equipment on finisher, and
elaborate new hygiene recommendations.
Supplementary Data
Supplementary data are available at Annals of Work
Exposures and Health online.
Declaration for Publication
The authors are employed by INRS or IFA or BG BAU. The
three institutes provided their own funding for this study. The
authors designed and executed the study and have sole responsibility for the writing and content of the manuscript.
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Figure 8. Average filter (a) and XAD2 (b) concentrations determined by the IFA and INRS methods on workplaces. Average laboratory and workplace linear regressions are indicated for filters. Laboratory (min and max) and average workplace linear regressions are indicated for XAD-2. Legend refers to the date of the sampling session and E# the number of the sampling session in
the day mentioned.
732
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