Beryllium Concentrations at European Workplaces: Comparison of ‘Total’ and Inhalable Particulate Measurements
Ann. Occup. Hyg.
Ber yllium Concentrations at European Workplaces: Comparison of 'Total' and Inhalable Particulate Measurements
A B S T R A C T A field study was carried out in order to derive a factor for the conversion of historic worker exposure data on airborne beryllium (Be) obtained by sampling according to the 37-mm closed faced filter cassette (CFC) 'total' particulate method into exposure concentration values to be expected when sampling using the 'Gesamtstaubprobenahmesystem' (GSP) inhalable sampling convention. Workplaces selected to represent the different copper Be work processing operations that typically occur in Germany and the EU were monitored revealing a broad spectrum of prevailing Be size distributions. In total, 39 personal samples were taken using a 37-mm CFC and a GSP worn side by side for simultaneous collection of the 'total' dust and the inhalable particulates, respectively. In addition, 20 static general area measurements were carried out using GSP, CFC, and Respicon samplers in parallel, the latter one providing information on the extra-thoracic fraction of the workplace aerosol. The study showed that there is a linear relationship between the concentrations measured with the CFC and those measured with the GSP sampler. The geometric mean value of the ratios of time-weighted average concentrations determined from GSP and CFC samples of all personal samples was 2.88. The individual values covered a range between 1 and 17 related to differences in size distributions of the Be-containing particulates. This was supported by the area measurements showing that the conversion factor increases with increasing values of the extra-thoracic fraction covering a range between 0 and 79%. K E Y W O R D S : aerosols; dust sampling conventions; exposure assessment methodology I N T R O D U C T I O N Beryllium (Be) is a lightweight metal element used in the metal industry in high-tech applications. The vast majority of Be used today is in solid, massive forms of metals containing Be, such as pure Be metal, copper-beryllium alloys (CuBe), aluminium-beryllium alloys, and nickel-beryllium alloys. Most Be is used in CuBe alloys containing <2% Be by weight. Overall, usage in the alloy form comprises over 85% of the Be in commerce. Be metal is generally imported into the EU in article form as finished parts. Similarly, alloys containing Be are also imported as finished parts, but is also imported in a semi-finished form. The operations performed downstream from the metal production facilities in the USA mirror the operations performed in the EU. The inhalation of Be particulate
can cause chronic Be disease, a serious lung condition,
in some individuals. The degree of risk varies
depending on the genetic disposition of the individual, degree
of exposure, form of the product, and the nature of the
Personal occupational exposure limits (OELs) have
been developed over time for exposure to airborne
Be. The OELs that are used in most countries range
from 2000 to 1000 ng m−3, 8-h time-weighted average
(TWA) value. For the past several years, the Be
industry has been publicly advocating a 10-fold lowering of
the 8-h TWA OEL to 200 ng m−3 [closed face filter
cassette (CFC)] based primarily on the scientific evidence
generated as part of a 15-year joint research program
with the National Institutes for Occupational Safety
and Health (NIOSH) in the USA (Deubner and Kent,
2007). Ireland, Poland, and Spain in the EU and the
State of California in the USA have adopted the 200 ng
m−3 OEL. In the USA, exposure assessment is
generally carried out following the Occupational Health and
Safety Administration (OSHA) and NIOSH guideline
prescribing the closed face 37-mm filter cassette (CFC)
‘total dust’ sampling method. In Europe, the ‘inhalable’
fraction sampling method following the CEN 481
convention (CEN, 1993) is prescribed in many countries
such as for example the UK and Germany. The
sampling characteristic of the CFC method is different
from the one of the Gesamtstaubprobenahmesystem
(GSP) ‘inhalable’ sampler. In the past, OELs for Be
were summarily adopted without regard to sampling
methodology. As all the human epidemiology
studies used to establish the current OELs are based on
the CFC method, there is a need to properly account
for the difference in results between the CFC and the
inhalable fraction sampling methods when sampling in
the same atmosphere. This difference should also be
considered when setting an OEL that requires the GSP
inhalable method to assess compliance.
Historically, most of the data available for Be
concentrations and the corresponding health risk studies
at workplaces have been based on samples taken with
the CFC method. One study has also evaluated Be
health risks based on respirable particulate sampling.
Schuler et al. (2012) compared ‘total’ CFC particulate
sampling exposure data to respirable sampling data.
The health risks were found to correlate with both,
the respirable and the ‘total’ sampling methods;
however, the underlying data for the respirable sampling
were 198 samples versus 4022 samples for the CFC
method. No studies have been conducted to
correlate inhalable particulate method exposure data with
chronic Be disease, which is the critical health effect
associated with exposure to Be.
Many laboratory and field studies carried out in
various industrial environments have shown that
measurements of inhalable concentrations are
generally higher than those made when using the ‘total’
particulate (CFC) method. In the papers of Werner
et al. (1996), Davies et al. (1999), and Skaugset et al.
(2013), where the IOM sampler was used for
inhalable sampling, mean conversion factors from 1.2 up
to 4.2 were reported depending on the coarseness
of the workplace aerosol monitored. There are also
field studies dedicated specifically to Be comparing
different sampling methods. Dufresne et al. (2009)
compared Be concentrations as measured with the
IOM, the 37-mm CFC, a respirable cyclone and two
cascade impactors: a low flow (Sierra impactor) and
a high flow (Moudi impactor). The assumed upper
cut-off for their inlets is 50 and 100 µm, respectively.
The measurements were carried out in a magnesium
foundry and in an aluminium smelter. The results
are in qualitative agreement with those of the
intercomparison studies cited previously revealing that the
IOM sampling results, when compared with the CFC
sampling results, yield about a 3-fold higher ratio.
In another study on Be, Virji et al. (2011) used a
Marple personal cascade impactor and a CFC for
characterization of the exposure to airborne Be in a
production facility. They found, that at many workplaces,
the non-respirable fraction of the dust can be
substantial. The median of the mass median diameter values
measured at sites of specific Be processing ranged
from 5 to 14 µm showing that different processes do
generate quite different size distributions. Due to lack
of size resolution of the Marple impactor in the size
range >10 µm, the upper value of 14 µm of the mass
median aerodynamic diameter (MMAD) is probably
underestimated. Measurements of Be concentrations
in the aluminium industry were reported by Skaugset
et al. (2012). From the analysis of Respicon samples,
it was found that on average, ~50% of the Be was
associated with particles in the extra-thoracic size regime.
An overview on Be exposure concentrations
averaged over all industries in 26 European countries is
given by Cherrie et al. (2011). The geometric mean
concentrations ranged from 70 to 170 ng m−3, the 90th
percentile not >2000 ng m−3. Cherrie assumed that
these exposures ‘were measured as inhalable dust’.
The purpose of this study was to conduct personal
sampling for Be using the German GSP as an inhalable
sampler and the 37-mm CFC as a sampler for ‘total’
particulate to compare employee exposure values for
Be obtained by the two methods. Data on this specific
comparison are not available in the literature. Sampling
sites covered widely used metallurgical processing of
alloys containing Be. The aim was to determine a
conversion factor from ‘total’ particulate sampling (CFC)
to inhalable sampling (GSP) specific to Be for use in
the development of an OEL in Europe based
specifically on Be research studies that utilized the CFC
sampling method. The second objective was to conduct
personal exposure monitoring of the inhalable Be
concentration on workers for a full work shift to get
an impression on employee’s exposure in those
operations where specifically Be-containing alloys are used.
The study was not intended to provide a complete
exposure survey for Be at all workplaces in Europe, but
does comprise a good representative example of
exposures at work operations most commonly conducted
in Europe. Be exposures have also been measured in
manufacturing sectors not associated with usage of
Be metal or Be-containing alloys, e.g. construction,
cement, glass, steel production, furniture making, and
shipbuilding (Vincent et al., 2009). As the Be
industry does not serve these sectors, these exposures are
generally associated with naturally occurring Be that is
present in many earthen products.
M AT E R I A L S A N D M E T H O D S
In total, six sites were visited in the time period
between December 2013 and July 2014. All
companies were processing CuBe alloys. At most of the
workplaces, the alloys were processed mechanically such
as drilling, milling, stamping, turning, and sawing.
The others involved high temperatures such as
welding and annealing. No melting or casting processes
were among the metallurgical processes monitored.
The sites, operations, and the personnel and the areas
monitored were selected by an industrial hygienist
certified by the American Board of Industrial Hygiene
and experienced in CuBe processing operations. Each
person having a potential for exposure to airborne Be
was monitored and static samples were collected in
areas where there was a likelihood of measuring
process generated particles. According to the industrial
hygienist, the processes monitored and the controls
utilized were representative of operations processing
CuBe alloys in the EU and in the USA. In brief, the
sites are described as follows:
The company processes CuBe alloy raw materials
(0.5% and 2.0% Be) and cuts bars and plates into
smaller units as requested by their customers. Band
and circular saws are used in one single hall. The
machines have individual local exhaust ventilation
(LEV). Filtered air is redirected into the hall. The hall
has no forced room ventilation system. In addition,
there is some physical testing of work pieces involving
grinding, which was equipped with LEV. This takes
place in a separate room adjacent to the production
Electric contacts containing CuBe alloys (0.15–0.5%
Be) are stamped and welded in automatic systems. All
units are enclosed and have LEV. Workers perform
surveillance and cleaning tasks. The machine hall has
a displacement ventilation system. Clean cool air is
supplied in ~1 m height through many inlets evenly
distributed over the production hall. This
ventilation scheme ensures sufficient make-up air near the
CuBe (1.6–2.0% Be) is treated by various mechanical
processes: lathe turning, drilling, grinding, sanding,
and polishing. In addition, there are welding and
electrical discharge machining operations. Some of the
processes had LEV, e.g. welding or used coolants for
finishing operations, e.g. milling and grinding.
Milling, turning, and lathe turning are the main
operations carried out on CuBe alloys (0.4–0.7% Be; 1.8–
2.0% Be; 0.2–0.6% Be). Most of the processes are not
enclosed. There is no LEV system. Coolants are used
in computerized Numerical Control (CNC) milling
and sawing operations, which act as dust suppressants.
Processing of rods of CuBe alloys (1.9–2.0% Be) into
small pieces, which are subsequently surface treated
by deburring, plating, and pickling. All processes
monitored have local ventilation and are enclosed.
Large pieces of CuBe alloys (1.8–2.0% Be) are heated,
forged, and pierced. In addition, rings are formed in
a ring roller. No ventilation system exists in the
preforming hall. Pre-formed and ring rolled parts are
further processed in a turning machine, equipped
At all sites, the different metal processing machines
were inside large machinery halls with building areas
larger than 1000 m2. Emissions from different work
areas could mix. Depending on their tasks, workers
were partly moving around inside the halls.
Personal and static general area samples were taken.
Workers were told to carry out their tasks in the
normal way. The area measurements were always within
2 m proximity to the emission source. The number of
samples and their allocation to categories of working
processes are shown in Supplementary Table S1,
available at Annals of Occupational Hygiene online.
Samples were generally taken over a complete shift.
In a few cases, shorter sampling periods were chosen
when the workflow of Be-containing material did
not cover a full shift. At all sites, background samples
were taken using the GSP and CFC placed in a remote
room not in direct contact to the production hall. The
sampling volume was accumulated on the filters
during several shifts.
Personal and static sampling of ‘total’ dust and
inhalable dust was carried out using the 37-mm closed
faced filter two-piece cassette (CFC) with 4-mm inlet
diameter (Analyt-MTC GmbH, Mullheim, Germany)
and the GSP (GSA, Neuss, Germany). Static dust
monitoring was complemented with a Respicon TM
(Helmut Hund GmbH, Wetzlar, Germany). This
instrument was used to get some rough information
on the size distribution and the temporal pattern of
the aerosol concentration (Koch et al., 1999).
All filters used in this study were special metal
sampling filters with low background
contamination [mixed cellulose ester (MCE) filters, 5-µm pore
size; Analyt-MTC GmbH]. They were either already
integrated in the sampling devices (CFC) or were
transported in special capsules that were inserted in
the sampling instruments before the measurements
started. Loaded filters were put back into the transport
capsules. Filter samples were always transported with
the loaded side facing up.
All personal samplers were operated using sampling
pumps of the same type: SKC-PCXR8 purchased
from Analyt-MTC GmbH. They provide a constant
air flow rate that can be adjusted between 1000 and
5000 ml min−1. The pump allowed for 8-h continuous
operation. For the static samples, the airflow through
the samplers was established via critical orifices
operated by an oil-free vacuum pump.
Prior to each sampling action, the flows through
the sampling devices were checked using a flow
calibration device. For this purpose, a primary calibration
standard based on volume displacement was used
(Defender 520; Mesa Labs, Inc., Butler, NJ). The
accuracy is 1% of reading. The intended flow rates were 2 l
min−1 for the CFC, 3.5 l min−1 for the GSP, and 3.1 l
min−1 for the Respicon.
The two personal instruments were attached to the
person on one side of the lapel using their
corresponding holders. The opening of the GSP was situated in a
horizontal direction; the inlet of the CFC essentially
faced downward along the lapel. The identical
orientation of the instruments was also maintained for
the static samples. The Respicon is not orientation
dependent as it has a circular slit inlet. The
instruments were mounted next to each other at a lab stand
with their inlets at the same height.
For all sampling instruments, only the MCE filters
were used for analysis. The MCE filters were digested
using the following procedure: (i) Microwave
digestion with 1-ml sulfuric acid (98%, suprapure; Merck)
and 1-ml nitric acid (65%, suprapure; Merck). The
digestion is carried out according to the work flow as
given in Supplementary Table S2, available at Annals
of Occupational Hygiene online. (ii) Addition of water
(Milli-Q system, conductivity < 0.05 µS). A final
sample volume of 50 ml was selected to be used for the
analysis of Be.
The Be content in the solution was measured
by inductively coupled plasma mass spectrometry
(X-series II; Thermo Fisher Scientific GmbH, Dreieich,
Germany) using the prepared samples after
recommended dilution with water. For all solvent ratios and
final sample volumes, blank solutions including acids
and filter material are prepared too. Every sample was
analyzed at least twice using two different dilutions
to avoid or detect possible matrix interference. The
Be concentration in the solution was determined by
standard addition. Quality control was facilitated using
certified reference materials (SRM, TMRAIN-04, Lot
# 0913, Environment Canada) of 0.378 ng ml−1,
arithmetic standard deviation (2-sigma limit for an
individual measurement) of 0.0688 ng ml−1.
The limit of quantification was evaluated by
spiking a filter with 0.5 ng of Be and following the
digestion and analysis procedure as described previously.
The intended concentration of the 50-ml sample was
therefore 10 pg ml−1. The evaluation, according to
DIN 32645 (DIN, 2008), included the filter blank
solution and three standard additions of 25 pg. The
limit of quantification (3.3 × limit of detection) was
found to be 5 pg ml−1 corresponding to 0.25
ng/filter and 0.25 ng m−3 for an air sample volume of 1 m3,
the typical shift value sampled by the CFC during a
Two tests were carried out in order to determine
the recovery of Be on spiked filters. First, seven
37-mm MCE filters were spiked with known amounts
of Be between 5 and 50 ng from a reference solution,
digested, and analyzed according to the above
procedure. The results revealed an average recovery of
99.5%. In a second test, spiked filters with Be content
that was unknown to the analytical laboratory were
provided by Materion Corporation. Analysis
according to the procedure described above revealed Be
masses between 0 and 2000 ng, matching the spiked
masses with an average recovery 100.06%.
In order to quantify correlations between pairs of
concentration data for sampler #1 and sampler #2, the data
were log transformed. Linear regression was applied to
the transformed data:
log (c1 ) = a + b⋅ log (c2 ).
Estimates as well as upper and lower 95%
confidence intervals of the regression parameters, a and b,
as well as the regression coefficient, R2, were calculated
using the regression function in Excel. Furthermore,
geometric mean values of the concentration ratios
were calculated. An extreme studentized deviate
outlier test was used to identify outliers of the
R E S U LT S
In total, 39 personal samples and 21 static samples were
taken. During a shift, two workers were monitored in
parallel. The available instrumentation allowed only
1 set of instruments for a static shift sampling. In most
cases, the sample volume was ~1 m3 for the CFC, 1.75
m3 for the GSP, and 1.55 m3 for the Respicon. The
corresponding concentration data, arranged by process
categories, are shown in Supplementary Table S3,
available at Annals of Occupational Hygiene online, for the
personal samples and Supplementary Table S4, available
at Annals of Occupational Hygiene online, for the static
samples. Concentration values of less than the limit of
quantification (0.25 ng m−3) are replaced by this value
for further statistical analysis of the data sets. The outlier
test was applied to the logarithms of the conversion
factors. The largest value (ln(85.6)) is identified as outlier
(P = 0.05). The corresponding data pairs were omitted
in the regression analysis. The data are arranged
according to the work process monitored. However, in many
cases, it was not possible to isolate one single process as
the workers were moving around and were exposed to
atmospheres from different sources. Table 1 represents a
summary of the data of the personal and static samples.
For the personal samples taken by the inhalable
sampler (GSP), the TWA values of the Be
concentrations vary by four orders of magnitude from <1 to
>10 000 ng m−3. The majority of the TWA values of the
inhalable particulates (36 out of 39 personal samples)
are <2000 ng m−3. The concentrations determined
from the CFC samples cover the range between 0.5
and 1000 ng m−3. For the static samples, the variation
of the concentration values is about three orders of
magnitude. Background concentrations ranging from
0.2 to 1.5 ng m−3 for the GSP and 0.25 to 4.35 ng m−3
are reported in Supplementary Table S5, available at
Annals of Occupational Hygiene online. They are
different at the various sites but are always lower than the
workplace values measured at that site. Even at Plant
D, the relatively high background concentration is half
of the lowest TWA-value for the personal sample.
Table 1. Summary of the concentration data for the personal and the static samples as measured with
the CFC, the GSP, and the Respicon (static samples only).
CFC (ng m−3)
GSP (ng m−3)
CFC (ng m−3)
GSP (ng m−3)
Respirable (ng m−3)
Thoracic (ng m−3)
Inhalable (ng m−3)
EF denotes the extra-thoracic fraction defined in equation (2) as measured with the Respicon. Outliers are not included.
The ratios of the GSP and CFC values range from
1 to 17 for the personal samples and from 1 to 10 for
the static samples. The geometric mean value of all
conversion factors GSP/CFC is 2.88 for the personal
and 1.99 for the static samples. In the practice of
occupational exposure evaluations, area measurements are
only used for qualitative purposes and generally are
not representative of actual employee exposures. The
Respicon employed in the static samples does,
however, provide some information on particle size
distribution. Since it was operated in parallel with the CFC
and the GSP, the data obtained from the static samples
were used primarily to investigate the influence of
aerosol size distribution on the conversion factors.
Estimates as well as upper and lower 95%
confidence intervals of the regression parameters, a and
b, as well as the regression coefficient, R2, were
calculated using the regression function in Excel. The
analysis of all personal concentration data of the CFC
(sampler #2) and the GSP (sampler #1) based on the
regression of pairwise data according to equation (1)
are shown Fig. 1 for the personal samples and Fig. 2
for the static samples. For the personal samples, the
regression coefficients are a = 2.65 and b = 1.05. The
corresponding values of the static samples are a = 1.99
and b = 1.00. As the values of the regression coefficient
Figure 1 Log-log-plot of all personal concentration
data for ‘total’ and inhalable particulates and the results of
the corresponding regression analysis, u.c.i. (l.c.i.) upper
(lower) limit of 95% confidence interval.
b are statistically indistinguishable from 1.00, the
hypothesis that the magnitude of the CFC
concentration influences the GSP/CFC ratio is not supported.
In other words, there is a linear relationship between
the concentrations measured with the CFC and those
measured with the GSP sampler. This suggests that
the geometric mean values of 2.88 for the personal
Figure 2 Log-log-plot of all static concentration data
for ‘total’ and inhalable particulates and the results of
the corresponding regression analysis, u.c.i. (l.c.i.) upper
(lower) limit of 95% confidence interval.
samples and 1.99 for the static samples are
appropriate conversion factors for the set of Be alloy processing
operations selected in this study.
D I S C U S S I O N
This field study was designed to compare the
concentrations of airborne Be measured at multiple workplaces
using two different types of samplers: the CFC and the
GSP. The GSP’s sampling characteristic has been shown
to comply with the definition of inhalable particulate
sampling (Kenny et al., 1999). The CFC’s sampling
performance regarding the inhalable sampling convention
has been subject to many published studies in the
literature and conversion factors as large as 5 between the CFC
sampling and inhalable sampling have been reported.
For Be, side by side data involving the CFC and the
GSP sampler are not available. Therefore, a sampling
program was initiated to monitor exposure
concentrations for metallurgical processes covering Be aerosols
of different size distributions because it was expected
that the differing size distributions captured by the two
methods influences the conversion factor. Personal as
well as area samples were taken. Besides the CFC and
the GSP sampler, a Respicon was used for the area
samples. This sampler allows for size segregated sampling of
the respirable, the thoracic, and the inhalable fraction.
For all sampling instruments, only the MCE filters
were used for analysis. The internal wall losses of the
Respicon were determined by Li et al. (2000) to be <20%
confined to a narrow size range around the cut-off sizes
of the virtual impaction stages. For the GSP sampler,
no information is available regarding losses on the inner
surfaces. In Germany, the measurement of the inhalable
particulate concentration is based on the evaluation of
the GSP filter only. Inner losses on the sampling cone are
not incorporated. The issue of wall losses in the CFC has
been extensively discussed in the past decade. Ashley and
Harper (2013) give some guidance on how to include
them. For Be, median values for CFC wall losses of 12%
was reported for four samples. The vast majority of the
available historic CFC concentration data for Be that
are used in context with epidemiology were obtained
without taking the wall losses into account. As the main
objective of this study was to establish a conversion factor
between GSP inhalable sampling and CFC ‘total’
particulate sampling that allows for the use of the historic CFC
data in the light of the inhalable convention, wall losses
were not included in the determination of the exposure
concentration. This study suggests the application of a
geometric mean conversion factor of 2.88 for the
conversion between ‘total’ particulate sampling to inhalable
sampling is appropriate due to the linear relationship
between the concentrations measured with the CFC and
those measured with the GSP sampler.
These values are compared with published data
obtained for other metal processing work
environments. Tsai et al. (1996) and Tsai and Vincent (2001)
report on nickel concentrations for nickel alloy
processing and for processes in the primary nickel
industry, respectively. They obtained a geometric mean
conversion factor of 2.0 (range between 1.57 and 2.40)
for Ni processing and 2.15 (1.16–4.01) for Ni
mining and production. Earlier studies of Vinzents et al.
(1995) reveal factors of 1.4 for aluminium in welding
fume and 3.4 for aluminium averaged over a cross
section of all workplaces in Norway. For electroplating
of arsenic, Nield et al. (2014) report on a conversion
factor of 1.4. For manganese, the geometric mean
values of conversion ratios are found to range from 1.4 to
2.6 (IEH, 2004). Overall, the ranges of the individual
values on metal-associated conversion factors found
in published studies were similar to what was found
in this study. A classification of conversion factors
according to tasks carried out by the workers was not
possible in our study due to the small number of
individual measurements carried out for each task. In 8
out of the 39 personal measurements, the conversion
factors were larger than 8. Six of them were measured
at site C, two at site E. They were all obtained at
workplaces where surfaces were treated by sandblasting,
grinding, and polishing, and the worker was close to
these sources of the Be-containing particulates. These
tasks are common to metal finishing operations and it
is to be expected that the aspirated dust has a high
fraction of coarse particles. This reflects the physics of
aerosol sampling suggesting the aerosol size distribution
to be a key factor determining the aspiration efficiency
of the two samplers and, hence, the conversion factors
between the measured concentrations. This becomes
evident from the data from the static samples. The
aerosol size information provided by the Respicon helps
to further elaborate on this. An extra-thoracic
fraction that is the size fraction >10 µm can be obtained
from the thoracic concentration, CRT, measured by the
Respicon and the inhalable concentration, CINH,
measured by the Respicon or by the GSP:
FET = (CINH − CRT ) CINH .
The fraction of the inhalable concentration allocated
to the extra-thoracic size range based on the Respicon
samples range from 0 to 79% (see Table 1). When the
inhalable concentration at the static sampling sites is
taken from the GSP samples in conjunction with the
Respicon samples, the extra-thoracic (ET)-fraction
spans a range up to 85%. (It is known that the Respicon
underestimates the extra-thoracic size fraction and a
conversion factor of 1.5 has been proposed to account
for this. See also Supplementary Figure S1, available at
Annals of Occupational Hygiene online.)
Large percentages in the extra-thoracic size range
were measured in Plant C, where the largest GSP/
CFC-conversion factors were obtained for the static
as well as the personal samples. As can be seen from
Fig. 3, there is a trend of increasing ratio of GSP and
CFC concentration as the extra-thoracic fraction
increases, i.e. the larger the particles, the lower the
aspiration efficiency of the CFC sampler. This may
be partly due to the orientation of the CFC sampler
in which its inlet hole faces downward. This finding is
in agreement with results of Görner et al. (2010) and
Buchan et al. (1986) who measured the aspiration
efficiency of the CFC sampler at various angles of
inclination in a laboratory study as well as with results from
Skaugset et al. (2013) obtained in a field study carried
out in the aluminium industry.
Figure 3 GSP/CFC-conversion factor as a function of
the extra-thoracic fraction. Triangles: ET-fraction based on
Respicon samples, circles: ET-faction based on Respicon
samples (thoracic) and GSP samples (inhalable).
This implies that the application of the mean
conversion factor between ‘total’ and inhalable Be particulates
determined in this study can be used for the conversion
of historic concentration values if it is assumed that the
workplaces selected are representative in view of the Be
size distributions. The value of 2.88 is in accord with what
was found in other metal producing work environments.
C O N C L U S I O N S
A field study was carried out in order to derive a
factor for the conversion of historic data on Be
concentrations obtained by sampling according to the CFC ‘total’
particulate method into concentration values to be
expected when sampling following the inhalable
convention. Workplaces, selected to represent the different
CuBe work processing operations that typically occur
in Germany and the EU, as well as the USA, were
monitored revealing a broad spectrum of prevailing Be size
distributions. The data set and the statistical evaluation
from this study reveal a geometric mean value of 2.88
for the factor used to convert Be concentrations from
CFC sample to concentrations obtained from
inhalable samplers. This fact has to be taken into account for
the derivation of an OEL from Be epidemiology
studies that have been based on the CFC ‘total’ particulate
method, where the inhalable fraction sampling method
is to be the basis for assessing compliance. The findings
of this study mirror results found in previous studies
with in other metal processing plants.
S U P P L E M E N TA R Y D ATA
Supplementary data can be found at http://annhyg.
F U N D I N G
Beryllium Science and Technology Association.
A C K N O W L E D G E M E N T
Materion Corporation, a member of Beryllium Science
and Technology Association, provided technical
expertise and expert knowledge relative to industrial
hygiene and beryllium processing operations. T.C. is
an employee of Materion and had no right to
withhold publication and was bound by an agreement that
a paper would be developed and submitted for
publication upon completion of the research. The research
was under the sole direction of the Fraunhofer ITEM
as were the compilation of the data and the reporting
of findings and preparation of the manuscript.
D I S C L A I M E R
The findings and conclusions in this paper are those of the
authors and do not necessarily represent the views of the
National Institute for Occupational Safety and Health.
R E F E R E N C E S
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