Pergamon
Am ocntp. Hyg . Vol 42. No 7. pp 477-488, 1998
Crown Copyright £ 1998 Published by Elscvier Science Ltd on behalf of British Occupational Hygiene Society
All nghu reserved
PII: S0003—4878(98)00057—X
ooo3-4878/98si9oo+ooo
Comparison! <oif Methods for Momintoiriinig Sold Pantkaiatte
Surface Comtfainnininiaitnonii im ttlhe Workplace
J. P. WHEELER* and J . D . STANCLIFFE
_
Health and Safety Laboratory/ Broad Lane {Sheffield} SI 1HQ[\J.KJ
.
J/
/ This paper reports an assessment of various methods for sampling particulate surface contami^ nation for use in the field. The results from the study will be used to develop guidance for monitoring
particulate surface contamination in the workplace. Three types of adhesive tape, two manual and
two 'semi-automatic' wipe methods, and one Smair method were assessed. A field assessment of
selected methods was carried out in two stages. In stage one, the manual wipes, semi-automatic
wipes and adhesive tape (Scotch Tape*) were compared. In stage two, the adhesive tape (Scotch
Tape 4 ), black forensic tape, clear forensic tape and Smair were compared. Visits were made to
ten metal processing facilities and particulate contamination was sampled from six locations at
each site. Sampling locations were chosen for their potential as points of worker dermal contact
and also to represent a range of surface characteristics. The metal content of the samples were
analysed using Atomic Absorption Spectrophotometry (AAS) and X-ray Fluorescence Specrrometry (XRF). It was found that the Smair method proved to be inefficient in removing surface
contamination, particularly where the surface was damp or greasy. Tape methods were found to
be the most satisfactory and have considerably greater efficiency than wipe sampling. The black
forensic tape is the preferred sampling medium as it is highly efficient, reproducible and easy to
use. Crown CopyrighjC) 1998 Published by Elsevier Science Ltd on behalf of British Occupational
Hygiene Society.
INTRODUCTION
Recently there has been considerable interest in contaminated workplace surfaces and in the contribution
that these make to a worker's total exposure to harmful substances (Fenske and Van Hemmem, 1994;
Dost, 1995; McArthur, 1992; Schneider el ai, 1989).
It has been suggested by Chavalitnitikul and Levin
(1984) that in some cases dermal contact with contaminated surfaces may be the most significant pathway for hazardous substances entering the body.
These surface contaminants may enter the body
directly by percutaneous absorption and/or by ingestion (KJinger and McCorkle, 1994; Caplan, 1993).
Workers exposed to hazardous surface may also
develop skin conditions such as dermatitis, an increasingly common occupational disease (Fenske, 1993).
If a comprehensive risk assessment for exposure to
contaminants in the workplace is to be developed it
is essential that the methods employed to assess the
exposure from surfaces be evaluated and standardised. There are various techniques used for measuring
Received 12 September 1997; in final form 11 May 1998
*Author to whom correspondence should be addressed.
Tel.: + 44 (0) 114 2892700; Fax + 44 (0) 114 2892732, E-mail.
VXWheelerCa.dust.demon.co uk/
477
surface contamination such as micro vacuuming (Que
Hee et ai, 1985; EPA, 1993), disposable paper towels
(Vostal el at., 1974) and manual wipe (also called
smear and swipe) (Robbins, 1980). The manual wipe
is the most commonly used method, but while there is
an established protocol for wipe sampling in the USA
no established protocol exists in the UFC.
The USA protocol for manual wipe sampling
involves a medium, such as filter paper, being drawn
across a known area of contaminated surface and then
being analysed to produce an assessment of the level
and nature of the deposit. In laboratory assessments
(Ness, 1994; Millson el ai, 1994; Royster and Fish,
1967) the efficiency and variability of manual wipe
sampling was found to be affected by a number of
factors:
o concentration and particle size distribution of the
surface contaminant
o surface roughness and porosity
o area of surface sampled and wiping pressure applied
o the operator
The purpose of the work reported here was to assess
the relative efficiency of various surface sampling
methods for particulate and to develop a standardised
procedure for sampling particulate from surfaces
commonly found in workplaces.
478
J P Wheeler and J D. Stancliffe
SAMPLING METHODS ASSESSED
Following a laboratory-based assessment of a large
number of different techniques, a sub-set of methods
was chosen for assessment during field use. The field
assessment of the chosen methods was earned out in
two stages. The first stage assessed both automatic
and manual wipe techniques together with one sticky
tape. The second stage assessed a variety of sticky
tapes. In both, the operator was the same, to reduce
operator variability. The affect of the operator on the
measured surface contaminant was not assessed as we
were interested in the efficiency of the methods relative
to the standard OSHA method.
Stage 1 field assessment
Manual wipes. In this stage an assessment of two
manual wipe protocols was made. The first was the
USA standard wipe sampling procedure described by
the U.S. Occupational Safety and Health Administration (OSHA) (Robbins, 1980). This uses Whatman 41, 7 cm diameter, filter papers which are moistened with distilled water to enhance their collection
performance (Klein el al., 1992). The second manual
wipe technique used Clean Cycle™ Wet VDU wipes
(Inmac), pre-packed and measuring 12.5cm by
11.2 cm. Clean Cycle™ Wet VDU wipes are more
resilient than Whatman 41 paper wipes and are premoistened with a solution containing 70% water and
30% isopropyl alcohol. No further solvent was added
to this wipe material before it was tested in the field.
Prior to wiping the VDU wipes were folded twice
along orthogonal symmetrical axes. The wipe pattern
was decided on from a combination of methods (Ness.
1994), and consisted of wiping once round the inside
of a 10 cm by 10 cm template in an anti-clockwise
direction and then wiping across it five times in parallel passes. The wipe matenal was then folded symmetrically, with the collected deposit held inside the
fold, and the region wiped again using a motion consisting of nine consecutive circles (see Fig. 1). Repeat
wipe samples (i.e. two wipes in total) were taken from
each sample region in order to reduce overall contaminant recovery vanability.
While wiping, the operator used their finger to press
down onto the surface with maximum pressure. The
pressure exerted during the wiping technique was estimated by pressing the finger onto a balance and dividing the measured weight by the surface area of the
finger used The average pressure for the parallel wiping action was estimated as 100±10kPa (2sd) and
50 ± lOkPa (2sd), for the circular wiping action
Semi-automatic wipe sampling. The operator variability that effects the recovery efficiency and reproducibility of the manual wipe sampling methods can
be reduced by automating the wipe action, wipe area
and wiping pressure (Dost, 1993). Two prototype
semi-automatic wipe samplers were used as part of
the field assessment.
Slide action wipe sampler. The slide action semiautomatic wipe sampler consists of a wipe pad 5 cm
by 5 cm, on which the wipe medium is placed. The
pad travels on two rods within a template of 50 cm2
area, thereby keeping constant the wipe area as well
as the ratio of the area of wipe sampling medium
used to the surface area sampled. Constant pressure
is maintained on the wipe material by the use of the
slide action semi-automatic wipe sampler and can be
adjusted to vary the applied pressure. The sampler
uses Whatman 41, 7 cm diameter filter papers which
were moistened with distilled water to enhance their
collection performance. These are then placed on the
wipe pad of the semi automatic sampler.
In the field assessment, flat and level surfaces were
selected for sampling. A wipe sample region of 10 cm
by 10cm was marked using a template and pencil.
Prior to wiping, the slide sampler was carefully placed
in the centre of the marked square with the outer edge
of the wipe pad on the inside of the marked line. By
holding the grip handle firmly and pressing down
hard, a constant pressure was applied across the wipe
pad. The wipe pattern consisted of pushing the pad
Fig. 1 Wipe sampling pattern.
Companson of methods for monitonng solid paniculate surface contamination in the workplace
5 cm once across the wipe surface and then pulling it
back again thus sampling from a total area of 50 cm2.
The slide sampler was then lifted from the surface and
the filter paper carefully removed from the pad and
stored in a glass vial with a screw-top, neoprene lined
hd.
Average wiping pressure applied by the semi-automatic slide action wipe sampler was measured to be
24.0 ±0.5 kPa using the balance technique previously
described.
Roll action wipe sampler. The roll action semi-automatic wipe sampler consists of a roll mechanism held
in a chassis by adjustable load springs. Constant pressure is maintained on the wipe surface by pressing
down firmly on the chassis handle until the four
height-adjustable feet of the chassis contact with the
wipe surface. Whatman 41 filter papers, measuring
12.5cm by 10cm and moistened with distilled water
were used as the wipe material. With the chassis held
firmly in place, the loaded roller is pulled and then
pushed back across a total wipe area of 106 cm2.
In the field assessment flat and level surfaces were
selected for sampling Prior to wiping, the roll sampler
was carefully placed in the centre of a marked square
with the wipe roller push/pull rod fully extended and
the outer edge of the wipe roller on the inside of the
marked line. After use the wipe sampler was carefully
lifted from the test area and the filter paper taken
off the roller. This was then stored under the same
conditions as the slide action samples. Average wiping
pressure applied by the semi-automatic roll action
wipe sampler was measured to be 84 + 2kPa.
Scotch" tape. A standard adhesive Scotch Tape"
which was 2.54 cm wide was used in the stage one field
visits. A 10 cm length of tape was cut for use and
placed across the centre of a 10 cm by 10 cm template
prior to application onto the contaminated surface.
The surface area sampled was therefore 25.4 cm2.
The tape was applied by removing one end of the
tape from the template and then pressing both the
template and the tape firmly onto the contaminated
surface. This ensured that no air bubbles were trapped
between the tape and the contaminated surface. Once
removed, the tape was folded onto itself along its
sticky side. The adhesive tape sample was then stored
in a sealed glass vial with a screw-top. Average pressure applied to the tape during sampling was
100±10kPa.
Two samples were taken from each sample site in
order to reduce overall contaminant recovery variability. Reproducibihty of sampling position was
ensured by use of the drawn pencil template.
Stage 2 field assessment
Scotch" tape. In stage two of the field assessment,
the same type of Scotch" tape used in stage one was
cut into pieces measured 2.5x2.5 cm before being
applied to the surface. The outline of the first Scotch"
479
tape sample was used as a template for the second
sample by drawing round it. On removal from the
surface the tape was covered with Mylar XRF film
(Graseby Spectrace Ltd) along its sticky side in order
to prevent further contamination and to render the
sample ready for X-ray fluorescence analysis. The tape
samples were then stored in individual labelled Millipore Petri slide containers.
Forensic tape. The black forensic tape (BVDA International Ltd) and clear forensic tape (BDVA International Ltd) are supplied in 13 cm by 18 cm sheets.
Both types of tape consist of three layers, a clear
plastic top coat which covers the sticky surface of the
middle layer and a base layer. In the case of the black
forensic tape the middle layer is black and the base
layer is white, while for clear forensic tape both these
layers are transparent.
When used in the field pieces of tape measuring
2.5 x 2.5 cm were cut from the sheets. The clear plastic
top coat was removed prior to application onto the
contaminated surface. The tape was applied to the
surface by pressing onto it with a finger before it was
removed and stored in the same manner as the stage
two Scotch * tape samples. Two samples were taken
from each location with reproducibility of sampling
position ensured by drawing around the first sample.
Smair sampling The Smair sampling procedure
employs air impingement to redisperse loose contamination from the surface and the resulting airborne
material is then collected on a filter (Royster, 1967).
The Smair sampler (Fig. 2) is similar to a conventional
air sampler with the open end placed against a surface.
The air intake is then restricted to a series of small
holes drilled at angles so as to direct jets of air onto
the surface to be sampled. Particles dispersed by air
impingement are collected on a filter.
In the field assessment Smair samples were collected
by holding the sample head against the surface for 60
seconds at each location with a volumetric flow rate
of 10 litre/minute The Smair sample filters were then
stored in individually labelled Millipore Petri slide
containers. Repeat Smair samples (i e. two in total)
were taken from each sample location in order to
reduce overall contaminant recovery variability.
SAMPLE ANALYSIS
All wipe samples were either analysed by Atomic
Absorption Spectrophotometry (AAS), following
acid treatment to dissolve the metal and release the
particles from the wipe materials or by X-ray fluorescence spectrometry. The choice of analysis was
related to sample type. Analysis of eight metals per
wipe sample was performed following examination of
the XRF data and by consideration of the nature of
the site activities.
In order to establish relative efficiency of each wipe
method, the total mass of all metals measured by
480
J. P Wheeler and J. D. Stancliffe
FtHer poper
Holes parallel
to radial line
Holes 30° to
radial line
12 ta2" dio. holes drilled
parallel to radial
line ana 30° to
axis
30*
12 V32"dio holes
drilled 30° to radiol
line and 45° to
axis
Fig. 2. The SMAIR sampler (Royster and Fish. 1967).
each wipe method is used in preference to results for
individual metals. To enable a direct comparison
between the various methods examined it was necessary to scale the results for the differing sampling areas
measured.
Field assessment
The field assessment of the methods was performed
during visits made to ten metal processing facilities.
At each facility the particulate contamination was
sampled from six locations. At each location the
methods being assessed were used to sample as close
to each other as possible. This was done to reduce
sampling variability arising from the inhomogeneity
of surface deposits.
When selecting a sampling area, any visible nonuniformities in the contaminant distribution were avoided. However, when sampling in the field it is highly
probable that there will be significant variations in
the quantity of surface contamination even between
parallel sampling areas. This variation is further
increased as a result of the different sampling areas
employed by each method.
Sampling locations were chosen for their potential
as points of worker dermal contact and also to rep-
resent a range of surface characteristics and exposure
ranges. Ten industrial sites were chosen for the field
assessments using the following criteria:
o site activities generate sufficient metal particulate
o there exists a range of contamination levels across
the facility
o appropriate contaminated surfaces can be identified
and wiped
o the selected surfaces should possess a range of
characteristics, i.e. roughness and composition
o the individual wipe locations should be sufficiently
large, numerous and similar to accommodate five
parallel samples of 100 cm2
o the sampling locations should be possible areas of
potential dermal contact
Tables I and 2 give the description of the sites and
sample locations used in the two field assessments.
The locations also represented a contamination gradient for each site visited.
RESULTS
Stage I field assessment.
Sample data (total of metals analysed) are presented
in Fig. 3 using the following abbreviations:
Comparison of methods for momtonng solid participate surface contamination in the workplace
481
Table 1 Description of stage 1 field assessment sites and sample locations
Site
Activity
Wipe location
Surface type
Welding
1. MIG welding room
2. large welding bay
3. oven room
4. TIG welding room
5. TIG welding room
6. machine room (office)
vinyl floor tiles
painted metal oven
sealed wooded work top
Formica work bench
aluminium work bench
Formica desk top
Lead Processing (1)
1. canteen
2. canteen
3. shop floor office
4 rolling mill
5. shop floor
Formica table top
painted steel mill panel
vinyl floor
painted steel mill panel
painted metal balance
Lead Processing (2)
1. canteen
2 shower room
3 shop floor
4. shop floor
5 storage area
6 shop floor
Formica table top
sealed wooden bench
painted metal table
painted concrete floor
painted metal shelving
PVC work bench
Steel Mill (1)
1 canteen
2. canteen
3 canteen
4 canteen
5. control pulpit
6 control pulpit
Formica table top
painted tiles, window sill
painted wooden shelf
vinyl floor tiles
Formica table top
painted metal shelf
Steel Mill (2)
1 canteen
2 canteen
3 cloak room
4 control room
5 control room
6. control room
Formica table top
glazed ceramic tiles
painted metal cupboard
Formica table top
sealed wooden drawer unit
vinyl floor tiles
PW1 and PW2
first and second manual filter
(Whatman 41) wipes, recommended by OSHA for wipe sampling
VWI and VW2 first and second manual VDU
wipes
ATI and AT2 first and second adhesive tape
samples
RS
semi-automatic roll action wipe
sampler
SS
semi-automatic slide action wipe
sampler
The wipe sample data are sorted according to the
wipe method used and to the type of surface from
which the wipe samples were taken. Comparisons of
the data are made relative to the wipe sampling
method prescribed by OSHA (i.e. the first 'paper'
wipe, PW1). They are presented in Fig. 3 as a percentage of the contaminants recovered using method
PWI. Second sample efficiency and total cumulative
sample efficiency relative to the OSHA (PWI) method
are also shown. Standard deviations are not shown
on the graphs due to the highly diverse origin of the
results i.e. they provide little information on the variability of each wipe method and serve only to highlight
the range of conditions in which the field measurements were made
The surface found to produce the most consistent
comparative results for each wipe method was
Formica. Wipe samples were taken from eight Formica surfaces with a wide range of surface contamination levels during the field visits (see Fig. 4).
The recovery of the first adhesive 'wipe1 (ATI) from
this surface type was found to be on average seven
times that of the OSHA wipe method (PWI). The first
VDU wipe method (VWI) was on average three times
as efficient and both semi-automatic methods (RS and
SS) were twice as efficient. The most variable surface
from which to take wipe samples by any method was
found to be painted metal. From this surface type, the
recovery of both the first adhesive tape 'wipe' (ATI)
and the first VDU wipe (VWI) was only three times
that of the OSHA wipe method (PWI). When averaged over all of the surfaces encountered during the
field visits the adhesive tape recovery was four times
the OSHA wipe method and the VDU wipe was twice
the OSHA wipe.
The adhesive nature of the tape accounted for the
its increased efficiency compared to the OSHA method
while the stronger fabric of the VDU wipe accounted
for its increased efficiency. Also the material used for
482
J. P. Wheeler and J. D. Stancliffe
Table 2 Description of stage 2 field assessment sites and sample locations
Activity
Wipe location
Surface type
1
Lead Processing
1. canteen
2. canteen
3. canteen
4. shop floor
5 shop floor
6 shop floor office
7. shop floor office
painted wooden bench
Formica table top
painted metal cabinet
painted metal roll mill
painted metal cabinet
vinyl floor
Formica table top
2
Steel Mill (1)
1 control pulpit 1
2. control pulpit 1
3. control pulpit 2
4. control pulpit 2
5. control pulpit 2
6. canteen
painted wooden shelf
painted metal shelf
Formica table top
sealed wooden cabinet
Formica cabinet
painted metal unit
3
Steel Mill (2)
1. canteen
2. canteen
3. canteen
4. control pulpit
5. control pulpit
6 shop floor
vinyl floor tile
painted tiles, window sill
painted wooden shelf
painted metal shelf
painted metal shelf
painted metal shelf
4
Steel Mill (3)
1 cloak room
2. canteen
3. canteen
4. control pulpit
5. control pulpit
6. control pulpit
painted metal shelf
Formica window sill
painted metal shelf
Formica desk top
vinyl floor tile
sealed wooden drawer unit
5
Steel Mill (4)
1. canteen
2. canteen
3. shop floor
4. shop floor
5 warehouse
6. warehouse
painted metal
painted metal
painted metal
painted metal
painted metal
plastic drum
the OSH A wipe method had a tendency to break down
under maximum operator pressure
The repeat wipe recoveries, calculated as a percentage of the first wipe by the same method and
averaged over all surfaces were 50% for the second
adhesive tape wipe (AT2), 30% for the second VDU
wipe (VW2) and 40% for the second OSHA method
wipe (PW2).
The adhesive tape paniculate sampling method
consistently recovered loose surface paniculate more
efficiently in its first and second 'wipes' combined than
any other wipe method tested during the field visits.
The least effective wipe method and material was
found to be the OSHA method. No significant
improvement over the OSHA wipe method was
achieved by using either of the semi-automatic wipe
methods. The VDU wipe material provided a noticeable improvement in recovery efficiency over the wipe
material prescribed by OSHA.
Stage 2 field assessment.
Sample data (total of metals analysed) are presented
in Fig. 5 using the following abbreviations.
ATI and AT2
BT1 and BT2
CT1 and CT2
SI and S2
shelf
shelf
guard rail
support
support
first and second adhesive tape
samples
black forensic tape samples
clear forensic tape samples
the Smair, 2.5cm Whatman glass
fibre filters
The sample data are sorted according to the method
used and the type of surface from which the samples
were taken. Comparisons of the data are made relative
to the Scotch11 tape sampling method, as used in the
first field assessment (i.e. the first Scotch11 tape wipe,
ATI) and are presented in Fig. 5 as a percentage of the
contaminants recovered using this method. Second
sample efficiency and total cumulative sample
efficiency relative to the Scotch B tape method are also
shown.
All three tape methods, the Scotch" tape, the black
forensic tape and the clear forensic tape consistently
recovered loose surface paniculate more efficiently
than the Smair method except on Formica where the
dust was not compacted. The black forensic tape was
generally equivalent in performance to the Scotch*
tape except in particular circumstances, e.g. painted
Comparison of methods for monitoring solid paniculate surface contamination in the workplace
First Wipe Efficiency Relative to OSHA (PWl)
800
-PWl
(OSHA)
-RS
600
400 -
•a &
EO
200
li
Surface Type
Second Wipe Efficiency Relative to OSHA (PWl)
400 -r
—D-PWl
(OSHA)
—53—PW2
Surface Type
Cumulative Sample Efficiency Relative to OSHA (PWl)
-O-PW1+PW2
- & - V W 1 +VW2
AT1+AT2
PWl (OSHA)
Surface Type
Fig. 3. Comparative wipe efficiencies (c.f.OSHA method)
483
484
J. P. Wheeler and J. D. Stancliffe
Formica : First Wipe Efficiency Relative to OSHA (PWl)
2000 -r
£,1500
8.
1000 •
E
S.
a
500
o
U
site 1 Ioc4
sitel Ioc6
site3 loci
site41ocl
site4 Ioc5
site5 loci
sitcS Ioc4
Average
Wipe Location
Formica : Second Wipe Efficiency Relative to OSHA (PWl)
site 1 Ioc4
sitel Ioc6
sitc3 loci
site4 loci
site4 Ioc5
sitcS loci
siteS Ioc4
Average
Wipe Location
Formica : Cumulative Wipe Efficiency
site 1 loot
sitel Ioc6
site3 loci
site4locl
sitc4 locS
site5 loci
Wipe Location
Fig. 4. Comparative wipe recovery efficiencies (Formica surface)
sitc5 Ioc4
Average
Comparison of methods for monitoring solid paniculate surface contamination in the workplace
First Sample Efficiency Relative to Scotch® Tape (ATI)
1
h
b
6
12
o S
fad
Surface Type
Second Sample Efficiency Relative to Scotch® Tape (ATI)
— O - ATI
—O— AT2
—D—BT2
—A—CT2
-M—S2
Painted
Wood
Formica
Painted
Metal
Vinyl
Floor
Other
Surfaces
All
Surfaces
Surface Type
Cumulative Sample Efficiency Relative to Scotch® Tape
(AT1+AT2)
— 0 — AT1+AT2
—Q-BT1+BT2
—A—CT1+CT2
-M—S1+S2
Painted
Wood
Surface Type
Fig. 5. Comparative wipe recovery efficiencies (c.f Scotch" tape.
485
486
J P. Wheeler and J. D. Stancliffe
Formica: First Wipe Efficiency Relative to Scotch® Tape (ATI)
700
T
600
500
400
300
|
200
100
Site2
Loc3
Site2
Loc5
Average
Sample Location
Formica: Second Wipe Efficiency Relative to Scotch® Tape (ATI)
1
S. .a
Sitel Loc2
Sitel Loc7
Site2 Loc3
Site2 Loc5
She4Loc4
Site4Loc2
Average
Sample Location
Formica: Cumulative Wipe Efficiency Relative to Scotch® Tape
(AT1+AT2)
—O—AT1+AT2
-O-BT1+BT2
A CT1+CT2
^1—S1+S2
E2
She4
Loc4
Sitc4
Loc2
Sample Location
Fig 6 Comparative wipe recovery efficiencies (c f. Scotch Jt tape)
Average
Comparison of methods for monitoring solid paniculate surface contamination in the workplace
wood surfaces where its efficiency was significantly
greater than any other tape. This is probably due the
gel-like nature of the finger print tape being able to
pick up particles more efficiently from rough surfaces.
A detailed comparison of the results for Formica surfaces is shown in Fig. 6. This shows that there is
considerable variation between sampling locations.
487
greasy. No obvious improvement could be made to
the method to improve its efficiency; however, it may
prove to be useful for sampling particles from carpets
or fabrics.
CONCLUSION
Our main finding were:
DISCUSSION
From the stage I field assessment, adhesive tape
was found to be the most effective method and the
OSHA method the least effective. For all methods
examined in stage 1 and stage 2 it was found that
taking repeat samples from the same area significantly
improved the overall recovery efficiency.
The OSHA wipe method was found to have a low
relative efficiency, and practical disadvantages. For
example the abrasive nature of some surfaces causes
the filter paper to disintegrate. The subsequent loss of
filter material can be significant especially when very
rough surfaces are wiped with 'maximum' pressure.
The recovery efficiency of wipe sampling is significantly improved by using a much stronger wipe
material e.g. pre-moistened VDU wipes. However,
these larger wipes are much harder to digest prior to
analysis.
Neither of the semi-automatic wipe methods provided any practical advantages over the OSHA
method. The slide wipe had a tendency to sweep surface deposits to one side as it was drawn across the
wipe surface. The roll wipe proved difficult to load and
handle. A major disadvantage of both semi-automatic
methods is that a large, flat, stable surface is required
for wiping. Wiping of irregular shaped surfaces is
impossible.
Adhesive tape sampling was found to be a highly
efficient alternative to OSHA sampling method and is
less likely to suffer from operator variables. It significantly out-performs all other manual and semiautomatic methods tested during the first field assessment on both the first and second 'wipe', and across
all surface types used. Adhesive sampling can also be
used on irregular and curved surfaces.
From the second field assessment adhesive tapes
were found to be the most effective methods and the
Smair sampling method the least effective. Of the three
tape methods used in this assessment the black finger
print tape proved to be generally more efficient than
the Scotch* tape and the clear forensic tape proved
to be generally less efficient than the Scotch11 tape.
However, the thicker adhesive layer of the black and
clear forensic tapes and their easier handling qualities
gives them a performance edge over the Scotch11 tape
method, making them the recommended choice for
sampling particles from contaminated surfaces.
The Smair method was found to be consistently
least efficient over all the surface types. The Smair
method was very dependant on the nature of the particles and whether the surface was damp, dry or
o Of the surface contamination sampling methods
tested, the adhesive tape methods were significantly
more effective overall, across all surface types.
o Of the adhesive sampling methods tested the black
forensic tape was significantly more efficient for
some surfaces. This type of tape is simple to use,
versatile and reduces operator variability. The
stickiness and consistency of the material is always
guaranteed.
o Of the manual wipe methods tested the OSHA
method was the least efficient across all surface
types.
o The efficiency of the wipe sampling can be improved
by using pre-moistened VDU wipes, but there is no
clear advantage in using the semi-automatic wipe
methods in the field in favour of the manual options.
o The Smair method proved to be inefficient in removing surface contamination particularly where the
surface was damp or greasy. It may be of more
use in measuring surface contamination from fabric
and carpets.
Our aim has been to assess which method recovers
the most contaminants from typical work surfaces.
Ongoing work will try to assess what might be
removed by normal contact with the hands. The
results from this work will be used to develop guidance
on surface contamination measurement, to be published in the HSE's 'Methods for the determination of
Hazardous Substances' series.
Acknowledgements—Thanks to Dr A A. Dost for developing
the semi-automatic wipe samplers, and for carrying out the
preliminary laboratory assessment of factors affecting wipe
sampling efficiency and reproducibility and to Peter Baldwin
for proof reading the manuscript.
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