Wipe sampling as a tool for monitoring aerosol deposition in workplaces

Abstract

As a complement to traditional exposure assessment, monitoring deposition of aerosols can be a simple and quick screening method for identifying deposited aerosols. In this presentation examples of screening studies, based on wipe sampling in combination with adequate analytical techniques, are described. These screening methods are rapid, simple and easy to carry out. The examples given in this presentation show a broad applicability and the methods are proven useful for assessing aerosol distribution in the workplace as well as to identify target spots for more extensive assessment of a worker’s exposure situation.

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Olle Nygren

Olle Nygren was born in Sweden, in 1954. He received his PhD in Chemistry from the Chemical Institution at Umeå University, Sweden, in 1987, and became Associate Professor in Analytical Chemistry at the Chemical Institution, Umeå University, Sweden in 1996. In 1988 he joined National Institute for Occupational Safety and Health as research scientist. Currently, since 1996, he has been Associate Professor at the National Institute for Working Life. His current research interests are focused on development of on-site and user-friendly monitoring methods for assessment of exposure to aerosols and metals in the work environment and on development of methods to monitor spill and leakage drugs during preparation and administration in pharmacies, hospitals and medical care environments.

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Introduction

Emission of aerosols to the work environment occurs in many workplaces and is a common health hazards. Many aerosols contain metallic constituents of various origins. The metals may increase the hazardous health effects of the aerosol. The adverse health effects of emitted aerosols normally occur through inhalation. Sampling the aerosol on a filter using a pump is usually carried out for assessment of occupational exposure to aerosols. The amount of sampled aerosol is then determined gravimetrically and metallic constituents by suitable analytical method, e.g., atomic absorptions spectrometry (AAS), inductively coupled plasma atomic emission spectrometry (ICP-AES) or X-ray fluorescence (XRF).¹

As a complement to traditional exposure assessment, monitoring spatial distribution and deposition of aerosols can be a simple and quick screening method for identifying aerosols, their distribution routes as well as how and where they are deposited. Wipe sampling, in combination with adequate analytical techniques, are examples of procedures that can be used to assess deposition of aerosols in the workplace. Such methods are usually quick and simple and therefore suitable for screening studies. In this presentation, some screening studies based on wipe sampling are described. The studies were carried out for assessment of the distribution and deposition of airborne dust and aerosols in various workplaces. Validated methods, based on wipe sampling and determination of relevant chemical compounds in the samples, have been employed in these studies.^2–5

Materials and methods

Materials for wipe sampling

For collecting wipe samples of welding fumes, abrasive sand dust and Cisplatin drug common household wet tissues (Apoteket AB, Sweden) were used.² A non-woven swab, 5 × 5 cm (Hartmann-ScandiCare, Anderstorp, Sweden), wetted with 1 ml volume of 0.03 M sodium hydroxide solution, was used for collecting wipe samples of cyclophosphamide.³ A sampling template, 4 cm wide plastic frame, surrounding 10 × 10 cm (wipe area = 100 cm²), was used to collect reproducible samples.² Unused tissues were used as blank samples. Spiked wipe samples, made from unused wipe tissues, were prepared for validation of the instrument analytical performance.

Instrumentation

A portable XRF (Niton Spectrum Analyzer, Model 722S, NITON Corp., Bedford, MA, USA) was used for all element determinations. The instrument was equipped with a Cd-109 excitation source with 3 mCi source strength and an Am-241 excitation source. Only the Cd-109 source was used in these investigations. The detector resolution was 400 eV. The instrument was operated in wipe sample mode and each sample was measured 4 times according to the software for wipe samples. A more detailed description can be found in ref. 2.

Determinations of cyclophosphamide were made using liquid chromatography tandem mass spectrometry (HPLC-MS/MS) according to Hedmer et al.³ A Perkin-Elmer Series 200 liquid chromatography system with a Series 200 autosampler (Applied Biosystems, Norfolk, CT, USA) was used. The column was a Genesis C₁₈ (50 × 2.1 mm) with a particle size of 4 µm (Jones Chromatography, Lakewood, CO, USA). The column outlet was coupled to an API 3000 triple quadropole mass spectrometer (Applied Biosystems/MDS-SCIEX, Toronto, Canada) equipped with an electrospray ionisation (ESI) source. The activity of ^m99Tc in the wipe samples using the Tc-test was measured according to Nygren et al.⁵ using a gamma detector [3 × 2 inch NaI(Tl)-crystal detector (Canberra 2007P) with an integrated pre-amplifier]. The samples were placed in a lead-shielded compartment at a well-defined distance from the detector.

Description of workplaces and applied procedures

Distribution of welding fumes in a mechanical workshop. In a mechanical workshop, welding was performed in a separate room. Although the door to the welding room normally was kept closed during welding and an exhaust was used, there was concern that the welding fumes were distributed outside of the welding room. Wipe samples were collected on top of fluorescent strip light armatures under the ceiling and welding fume target elements (Fe and Mn) were determined on-site using X-ray fluorescence spectrometry (XRF).²

Distribution of welding fumes into office areas. In a welding workshop there was concern among the office staff that welding fumes were distributed into the office area. Wipe sampling and on-site XRF analysis² of the collected samples, using Mn as target substance for the welding fumes, were used to screen the distribution and deposition of welding fumes. Wipe samples were collected in all kinds of rooms, e.g., the welding room, locker rooms, lunchroom, office rooms, and rest rooms.

Distribution of sand dust from abrasive water jet cutting. In three abrasive water jet cutting workshops, there was concern that metal containing dust was distributed into other parts of the premises. The workshops had different cleaning routines and there was of interest to evaluate the efficiency of the cleaning routines. Wipe samples were collected in all parts of the premises and a target element (Fe) in the samples were determined on-site using XRF.²

Distribution of drug spill in hospitals. There was concern that exposure to anti-cancer drugs could occur at the hospital pharmacy and the oncology department in a local hospital in Sweden. Wipe samples were collected in the drug preparation rooms in the hospital pharmacy and in three oncology wards according to previously described procedures.^2,3 At the time of sampling, cyclophosphamide (CP) was handled in the pharmacy and ward 1, while Cisplatin was handled in ward 2 and ward 3. In the samples from the hospital pharmacy and ward 1, determinations of CP, using liquid chromatography tandem mass spectrometry (HPLC-MS/MS)³ was carried out. Platinum (Pt), as a tracer for Cisplatin or related drugs, was determined using on-site XRF,⁴ in the samples from ward 2 and ward 3.

Test of drug preparation systems. A traditional open drug preparation system was compared with a new closed system regarding spill and leakage during drug handling. A test system, based Technetium m-99 (^m-99Tc) and collection of wipe samples, was employed for the comparison.⁵ CP drug vials (Sendoxan, Asta Medica, Germany), prepared with ^m-99Tc,⁵ was used for this test. Four test subjects made 5 preparations with each preparation systems. Wipe samples were collected inside of the biological safety cabinet (BSC), where the test was performed, and in the vicinity of the BSC as well as in other parts of the preparation room. The sampling was carried out immediately after the twenty preparations with each system had been completed. Spot urine samples were also collected from two of the subjects performing each test. ^m-99Tc was determined in the wipe samples⁵ and CP in the spot urine samples.⁶

Results and discussion

Distribution of welding fumes in a mechanical workshop

In a mechanical workshop where high quality products were manufactured, welding was performed in a separate room. Normally the door to the welding room was closed during welding and an exhausted was used to trap the welding fumes. There was, however, concern that welding fumes would be distributed to the other rooms in the workshop and possibly cause contamination problems of some products. To evaluate possible distribution of welding fumes from the welding room to the other rooms, a screening was carried out using wipe sampling. Wipe samples were collected on top of light strip armatures in the ceiling. Table 1 shows the results of the screening. A concentration gradient of the target elements (Fe, Mn) from the welding workstation through the welding room and out to the adjacent room was found.

Table 1 Distribution gradient of welding fumes in a mechanical workshop^a

Location	Before new cleaning regime		After new cleaning regime
	Fe	Mn	Fe	Mn
a Wipe samples collected on strip light armatures in the ceiling at A above the welder; B in the middle of the welding room; C by the door at the other end of the welding room; D in the room outside close to the door to the welding room; E in the middle of the room outside of the welding room; F in the room outside at the opposite side of the welding room; G in the far end of the room outside the welding room. Target elements analysed on-site using portable XRF and expressed in μg dm^−2. Nd, not detected.
A	2808	221	1563	163
B	3182	207	965	86
C	780	63	354	42
D	135	27	87	12
E	87	25	Nd	Nd
F	77	Nd	Nd	Nd
G	98	Nd	Nd	Nd

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The results of this simple screening made the management aware of a possible contamination problem from the distribution of welding fumes outside of the welding room. A more rigorous cleaning procedure was introduced and the level of deposited welding fumes outside the welding room has now been decreased (see Table 1).

Distribution of welding fumes into office areas

In a welding workshop there was concern among the office staff that the welding fumes were distributed into auxiliary areas of the workshop. Wipe sampling followed by on-site XRF determinations with manganese (Mn) as target element of welding fume, were applied to investigate possible distribution of welding fumes to office rooms, the locker room, the washroom, and other rooms. Table 2 shows the results of the investigation. Welding fumes had been distributed into almost all rooms in the workshop. The amount of dust in the washroom was about 30%, in the lunchroom and offices about 15% of the amount in the workshop room, respectively. Only in the dressing room, no Mn was detected.

Table 2 Distribution gradient of welding fumes^a

Location	Mn
a Wipe samples were collected for screening and analysed on-site using portable XRF. Mn was used as target element and values are expressed in μg dm^−2.
Workshop room	200
Corridor	118
Canteen	41
Office room	34
Washroom	73
Dressing room	<20

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This screening has shown both the staff and management that the welding fumes are distributed also into auxiliary areas such as the offices. It has not yet, however, resulted in any action from the management.

Distribution of sand dust from abrasive water jet cutting

In three workshops, utilizing abrasive water jet cutting, different cleaning routines were used. There was concern that the metal containing dust from the cutting was distributed into the offices and other areas and the efficiency of the different cleaning routines was evaluated.

In company A, an external firm cleaned the workshop twice every year during holiday periods when there was no production. The floor in offices and other areas was cleaned once every week. A full cleaning in those areas was made twice every year. In company B, the workshop was vacuum cleaned by the regular staff once every month. The floor in offices and other areas was cleaned twice every week. A full cleaning in those areas was made every third month. In company C, the workshop was vacuum cleaned continuously by one in the regular staff, following a standardized procedure so all areas in the workshop was cleaned at least once each week. The floor in offices and other areas was cleaned every second day. A full cleaning in those areas was carried out every month.

Wipe samples were collected on top of cupboards or on high-located shelves with settled and undisturbed dust. The samples were collected from various rooms in the workshops at the end of a working day. Iron (Fe), as target element, was analysed on-site using XRF. The result of this screening is shown in Fig. 1. There was a clear difference in the distribution of the dust between the workshops. The difference in the level of deposited dust in the workshop room was low between the three workshops. The dust level in the workshop with good cleaning routine was about 10% lower than in the workshop with the least rigorous cleaning. There was, however, a significantly less distribution of dust from the workshop room to other rooms in the workshop with a good cleaning routine as compared with workshops with less rigorous cleaning. In the well-cleaned workshop, the level of dust in the auxiliary areas was only 15–20% of the workshop room level, as compared with the worse cleaned workshop, where the level in auxiliary areas was almost 50% of the workshop room level.

Fig. 1 Wipe samples from various locations in three companies using abrasive waterjet cutting with different cleaning routines (A–C). Iron is used as target substance. See the text for details on cleaning routines.

This screening took less that 30 min at each workshop and resulted in awareness among the staff that made them change the cleaning routines. Today, the dust level has been decreased in two of the workshops and the work environment has been improved.

Distribution of drug spill in hospitals

At a local hospital in Sweden, there was concern that the staff was exposed to anti-cancer drugs during preparation and administration, although these drugs were prepared in BSCs according to the regulations.⁷ Wipe sampling was used in a screening study to assess possible spill and leakage of anti-cancer drugs and to monitor how drugs had been distributed. Wipe samples were collected in the hospital pharmacy and in three different wards at the drug preparation place and at various distances from that place in order to show the distribution. Different types of cancer were treated in the various wards and to properly assess possible spill and leakage of anti-cancer drugs the most frequently used drugs at each place were determined as target substances. In the hospital pharmacy and ward 1, CP was frequently handled and was used as target substance. In ward 2 and ward 3, Cisplatin was the most frequently handled drug. Cisplatin contains Pt that, consequently, was determined as a tracer for Cisplatin. The result of this screening is shown in Table 3. There was a significant spill and leakage on the preparation spot inside the BSC and on adjacent areas inside the BSC. The spill and leakage of the drugs had also been distributed from inside the BSC out into the preparation room. A clear gradient into the preparation room could be found. In case of a large spill, the gradient could be followed across the room to the opposite side. In this screening, no drugs were detected in the room or corridor outside of the preparation room.

Table 3 Distribution gradient of anti-cancer drugs in preparation rooms

Distance/m	0	0.5	1.5	3	5	7
a Wipe samples were collected at various distances from the preparation place. The distance 0 m is inside the BSC, and 0.5, 1.5, 3, 5 m are at increasing distance from the BSC in the preparation room, while 7 m is in the room or corridor outside of the preparation room. Nd, not detected.
Pharmacy (CP)/ng cm^−2	22	1.82	0.32	0.12	0.05	Nd
Ward 1 (CP)/ng cm^−2	42	0.66	0.23	Nd	Nd	Nd
Ward 2 (Pt)/μg cm^−2	7.59	1.85	0.65	0.50	0.20	Nd
Ward 3 (Pt)/μg cm^−2	2.56	0.75	0.31	0.28	Nd	Nd

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Table 4 Test of drug leakage with different preparation systems

Sample site	Open system/nL cm^−2	Closed system/nL cm^−2
a Drug vials were prepared with a radiotracer (^m-99Tc). Wipe samples were collected after all preparations with each system and the activity was monitored as a measure of the leak volume.
BSC	12 500	120
Floor	4 450	62
Bench	1 650	25
Bench opposite	450	<10

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This screening, showing both the staff and management that there was a leak of anti-cancer drugs into the preparation room during handling the drugs inside a BSC, resulted in a change of handling routines. The drug preparation rooms were thoroughly cleaned and a closed preparation system was introduced for drug preparation. The daily cleaning procedure was also improved. A new similar screening is also discussed to follow up these measures.

Test of drug preparation systems

The purpose of this screening was to compare the preparation technique traditionally used in Sweden (the pump or “milking” technique) with a new closed preparation system. This screening (see Table 4) showed that a significant spill and leakage occurred with the traditional system, while almost no spill and leakage occurred with the closed system. Spot urine samples were also collected from two individuals that performed each test. The samples were collated two hours after each subject had carried out the test preparations. CP was detected in the urine samples from the selected test subjects that made preparations using the traditional system, while no CP was detected in the urine samples from the selected subjects that made preparations using the closed system.

This screening clearly showed the applicability of wipe sampling for a quick and simple comparison of different drug preparation systems.

Conclusions

Wipe sampling is an efficient sampling method that is rapid, simple and easy to carry out and therefore suitable for screening studies. The examples above show a broad applicability and the methods are proven useful tools for assessing aerosol distribution and deposition in the workplace as well as to identify target spots for more extensive assessment of a worker’s exposure situation. The simplicity and rapidity of the procedure make this technique a useful complement to more traditional monitoring methods.

References

1. NIOSH Manual of Analytical Methods, NIOSH, Cincinnati, OH, USA, 2005, http://www.cdc.gov/niosh.
2. O. Nygren and O. Aspman, Validation and application of wipe sampling and portable XRF analysis as an on-site screening method for assessment of deposited aerosols on workplaces, Aust. J. Chem., 2004, 37, 1021–1028.
3. M. Hedmer, B. A. Jönsson and O. Nygren, Development and validation of methods for environmental monitoring of cyclophosphamide in workplaces, J. Environ. Monit., 2004, 6, 979–984.
4. O. Nygren, New approaches for assessment of occupational exposure to metals using on-site measurements, J. Environ. Monit., 2002, 4, 623–627.
5. O. Nygren, B. Gustavsson and R. Eriksson, A test method for assessment of spill and leakage from drug preparation systems, Ann. Occup. Hyg., 2005, 49, 711–718.
6. R. P. Bos and P. J. M. Sessink, Biomonitoring of occupational exposure to cytostatic anticancer drugs, Rev. Environ. Health, 1997, 12, 43–58.
7. AFS 1999:11, Cytostatika och andra läkemedel med bestående toxisk effekt [Cytostatics and other drugs with permanent toxic effects], the Swedish Work Environment Authority, Solna, Sweden, 1999.

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Footnote

† Presented at the Fifth International Symposium on Modern Principles of Air Monitoring & Biomonitoring, June 12–16 2005, Norway.

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