Surface Sampling, Consensus Standards, and Laboratory Analysis
What's on YOUR Workplace Surfaces?
The conduct of modern occupational health and safety sampling can be divided into three broad categories: sampling for contents of or contaminants in ambient or workplace air (air sampling); sampling of solids, liquids, or solutions for content or contamination (bulk sampling); and sampling for materials or contaminants that have precipitated out of the air or were purposefully or accidently distributed on surfaces (surface sampling).  Air sampling has been the field industrial hygienist’s bread and butter when it comes to both collecting samples for exposure assessment and for compliance with limit values or action levels. But some programs—EPA and U.S. Department of Housing and Urban Development programs focused on lead from lead-containing paint, for example—require the collection of surface samples. In many workplaces, samples from surfaces, when collected at all, have often been for ancillary purposes such as characterization of legacy facilities for cleanup. Surface samples, particularly wipe samples, are also useful for assessing the presence of surface contamination in areas where workers may not be adequately protected by personal protective equipment (see the OSHA Technical Manual on OSHA's website).
Recent developments have put greater emphasis on the need for surface sampling and standard protocols for such sampling. For example, ACGIH in 2019 established the Threshold Limit Value – Surface Limit (TLV-SL) as a supplement to the airborne TLV, particularly for substances that are dermal or respiratory sensitizers or can be absorbed through the skin. And this year, the COVID-19 pandemic has created another need for surface sampling as OHS practitioners and others study how long the SARS-CoV-2 virus is viable on various surfaces—especially in high-touch areas.  Surface sampling can be a key component in OHS assessments of risk or exposure. This article briefly describes available surface sampling methods, with a focus on consensus standards, as well as caveats to consider when sending these samples to a laboratory for analysis. GENERAL GUIDANCE Subcategories in surface sampling are defined by the sampling media used: swab sampling (for small or confined areas); vacuum sampling (using a personal sampling pump or other such suction-producing machine); tape lift sampling (using tape); and wipe sampling (typically using a dry or premoistened towelette). Any effective sampling campaign begins with a proper sampling strategy. Guidance on this topic can be found in A Strategy for Assessing and Managing Occupational Exposures from AIHA, Surface and Dermal Sampling from ASTM International, and the OSHA Technical Manual. OHS practitioners should consider the purpose for sampling; any similar studies that have been published; the selection of sampling locations; and data evaluation, including outliers or results below reporting limits. An article published in the October 2019 Synergist on consensus standards and technology discusses the benefits of using standard sampling methods. OHS professionals can use these methods to bolster consistency and reproducibility, establish appropriate data quality objectives, enhance data comparability, and build defensibility. Consensus standards, including ASTM, ANSI, and ISO standards, are developed by a cross-section of OHS practitioners and subject matter experts rather than by a single agency or organization. As with any sampling program, taking time up front to develop a good surface sampling strategy can help OHS practitioners anticipate potential issues. With vacuum sampling, for example, it may be quite difficult (though not impossible) to collect surface contaminants through a filter to obtain a representative sample. Surfaces to be sampled may not be readily accessible countertops, floors, and tables and might include ductwork, ceilings, walls,  or other hard-to-reach locations. Thinking about where the sample may have deposited and how to collect representative samples may be a three-dimensional exercise. A free software tool that can help is the Pacific Northwest National Laboratory’s Visual Sample Plan.
Selection of wipe material is important, particularly when it comes to the type of surface.
The amount of settled dust on the surface is another factor to consider. For large amounts of settled dust, a bulk sampling technique may be more effective than other surface sampling methods. While a pre-wetted wipe substrate is usually preferred, a dry wipe or swab may be more appropriate if the surface is oily. For metals and metalloids, ASTM D7659 provides guidance for the development of sampling plans and data quality objectives, selection of methods for sampling and laboratory analysis, and evaluation of the data. A similar ASTM guidance document for selected organic contaminants is under development. WIPE SAMPLING What do we mean by a wipe sample? EPA’s regulation on lead-based paint poisoning prevention in certain residential structures (40 Code of Federal Regulations 745.63) defines lead sampling as “a sample collected by wiping a representative surface of known area, as determined by ASTM E1728 [now E1728/E1728M]…or equivalent method, with an acceptable wipe material as defined in ASTM E1792.” This definition encompasses some key aspects that define the sampling area, the sampling substrate, and the sampling technique. For beryllium, lead, and several other substances, the sampling area is defined by regulation, but in any event the sampling area should be predetermined and consistent. Checking for regulation is always a worthwhile search. The sampling area may also depend on the amount of settled dust on the surface. ASTM E1728/E1728M, Standard Practice for Collection of Settled Dust Samples Using Wipe Sampling Methods for Subsequent Lead Determination, suggests a range of 100 cm2 (10 cm by 10 cm) to 1 ft2 (12 inches by 12 inches), but adjustments may be needed based on the amount of visible dust on the surface. The OSHA Technical Manual also suggests 100 cm2 since it is about the size of a worker’s palm. Selection of wipe material is important, particularly when it comes to the type of surface. For example, sampling a rough surface might require a different material than a smooth or oily surface. The wipe material should not have measurable amounts of the contaminant being measured. Specifications such as ASTM E1792 for lead and D7707 for beryllium address this in more detail. Sampling technique is addressed in ASTM E1728/E1728M; ASTM D6966, Standard Practice for Collection of Settled Dust Samples Using Wipe Sampling Methods for Subsequent Determination of Metals; and NIOSH Method 9102, “Elements on Wipes,” among others. These describe the use of an “S” or “Z” pattern to ensure wiping of the entire area being sampled, as well as the importance of folding the wipe to prevent sample loss. A variety of standard wipe sampling methods is available. A partial list is provided in Table 1.
Table 1. Standard Wipe Sampling Methods
Tap on the table to open a larger version in your browser.
SWAB AND TAPE LIFT SAMPLING Sterile swabs are most often used to collect biological materials such as powders or fungal material from surfaces. ASTM International has two standard methods. ASTM D7789 was developed for swab sampling for fungal materials and can be used for analysis by direct microscopy, culture, or biochemical analysis. ASTM E2458 addresses swab sampling of nonporous surfaces for “residual suspicious powders that are suspected biological agents and toxins from solid nonporous surfaces.” In addition, NIOSH has posted a swab sampling procedure for use in collecting culturable samples for Bacillus anthracis spores on its website.  Prepared swabs, as test kits, can be useful when collecting a sample of or for testing for contaminants in small or hard-to-reach places. Swab testing kits for lead and other metals and drugs are commercially available, and a web search for the analyte of interest as a test kit could produce an appropriate product. For example, when dealing with lead-based paint and lead-based paint hazards, see the EPA website for the list of EPA-recognized test kits. Tape lift sampling is typically used for microscopic examination rather than instrumental analysis. Standard methods include ASTM E1216, which focuses on sampling for particulate contamination by tape lift, and ASTM D7910. ASTM E1216 can be used for microscopic examination of metal, metalloid, or organic particulates, while ASTM D7910 is used for fungal materials. VACUUM SAMPLING Vacuum sampling is often a good choice for obtaining samples from carpeted floors and similar surfaces, and for collecting bulk samples. Standardized vacuum sampling protocols include ASTM D7144, which uses a personal sampling pump for micro-vacuum sampling on soft surfaces including carpets, and ASTM D5438, which uses a modified stand-up “high-volume sampler” (HVS) vacuum cleaner to perform carpet sampling. Collection efficiencies of both methods have been investigated and performance data published in peer-reviewed literature (see two articles from the Journal of Occupational and Environmental Hygiene in the resources section on page 28 for more information).  In ASTM D7144, dust collected is captured in a sample cassette fitted with a collection nozzle. The collection efficiency varies widely with the surface being sampled; also, material gets caught in the collection nozzle. Despite these limitations, micro-vacuum sampling is viewed as a practical design-based method that enables data comparisons if the standard method is used. Collection efficiency of the D5438 method is enhanced due to high sampling flow rate and rigorous agitation of the surface, is demonstrably high (overall mean 88 percent), and supports the ASTM standard.  DERMAL SAMPLING A number of dermal sampling techniques are outlined in ISO Technical Report 14294, Workplace Atmospheres — Measurement of Dermal Exposure — Principles and Methods. The report describes methods such as wiping using a cotton fabric; dermal patches for selected organics; smear tabs for polychlorinated biphenyls, or PCBs; and in situ methods using clothing as the collection medium. Gloves have also been used to collect the sample by intercepting it before it reaches the hand. Most of these methods have not been validated. ASTM D7822, which applies to sampling for metals and metalloids, is based on methodologies developed by NIOSH and utilizes a wipe (either premoistened or moistened in the field) with a wiping pattern starting from the perimeter and moving to the interior of the area being sampled. It includes a protocol for estimating the surface area of a hand when the entire hand is being wiped. SARS-COV-2 CORONAVIRUS Surface sampling for viruses, including the new SARS-CoV-2 virus (cause of COVID-19), has typically been done in the same way as sampling for fungi and bacteria: with a pre-wetted swab. The wetting agent is often phosphate buffered saline. Analysis is by reverse transcription polymerase chain reaction (RT-PCR) in which a specific ribonucleic acid (RNA) sequence is converted to DNA for amplification and detection. RT-PCR can be used to indicate just presence/absence, but it may also be used quantitatively (qRT-PCR) to track the rate of amplification. The swab should be analyzed very quickly as RNA is not as stable as DNA. Some protocols require overnighting refrigerated samples; others require placing the swab in a viral transport medium or chaotropic lysis buffer in the field, the latter being preferred for long-term storage.  While data on the limits of quantitation is available for analytical procedures, no data exists regarding the efficiency or uncertainty in the transfer of virus from different surfaces to swab, or the stability, recovery, or uncertainty of the transfer from swab to analyzer. Hence, the qRT-PCR procedure is semi-quantitative at best, and studies should be performed to improve knowledge in this area. Swabs are currently scarce due to the pandemic and wipes can cover much greater areas, potentially improving the sensitivity. Research into suitable wiping procedures is ongoing. See the U.S. Food and Drug Administration’s frequently asked questions on testing for SARS-CoV-2 for information regarding SARS-CoV-2 test kits. WHAT THE LAB NEEDS TO KNOW Communication with the lab is key to the success of the sampling program. It’s important that the OHS practitioner understands what the lab can and cannot do; the lab knows what it is getting and the desired data quality objectives; and the OHS practitioner understands what the data from the lab mean. Thus, the lab needs to know:
  • What is the target analyte?
  • How well do you need it done? (Here, screening methods may be faster and cheaper than methods with all the “bells and whistles” that come with accreditation.)
  • What else is in the sample that might impact or interfere with handling and the analysis? For example, are there other sample components that may interfere with the target species? Are there any regulatory considerations? Does the sample require special handling? What about the disposal of the residual and waste?
  • What is the sample matrix? (Note that some media are more difficult to dissolve/digest/extract than others.)
Wipe material is especially important for the laboratory. Certain wipe materials may not be compatible with some methods used in the laboratory, so it is important to check in advance to make sure the laboratory can handle what you plan to send. In return, the lab should provide:
  • how much it will and did cost
  • how long it will and did take
  • what method is to be and was used
  • how sensitive the method is given a sample size and was given the sample size as received
  • how much of the target species (reporting limit) can be and was found
  • how the data will be reported
  • the data

Call the lab! They are there to help. (Editor’s note: More tips for improving collaboration between field IHs and laboratory professionals can be found in an article from the August 2016 Synergist.) 

A full-day professional development course titled “Surface Sampling – Issues, Methods, and Strategy for Metals, Metalloids, Organics, and Biologicals” was presented at AIHce EXP 2019 and included much of the information contained in this article with more detail and discussion. The PDC was accepted for this year’s conference, but it was not presented online at AIHce EXP 2020 because it does not lend itself to virtual presentation. The same PDC will be proposed for AIHce EXP 2021. In addition, a Sampling Quality Assurance Manual compiled by the AIHA Sampling and Laboratory Analysis Committee is scheduled for release next year.    MICHAEL J. (MIKE) BRISSON, MS, PMP, FASTM, is a fellow technical advisor at Savannah River National Laboratory, Aiken, South Carolina. He is a past chair of the AIHA Sampling and Laboratory Analysis Committee, on the Board of Directors of ASTM International and past chair of Committee D22 (Air Quality), chair of ISO Technical Committee 146, Subcommittee 4, on Air Quality General Aspects, and convener of four ISO working groups. KENNETH T. (KENN) WHITE, MS, MM, CIH, CSP, FAIHA, FASTM, is the principal of Consultive Services in Virginia Beach, Virginia. He is a three-time recipient of the AIHA Edward J. Baier Technical Achievement Award, chair of the ASTM International Subcommittee D22.12 on Sampling and Analysis of Lead for Exposure and Risk Assessment, and a member of the AIHA Sampling and Laboratory Analysis Committee, serving as chair of the Environmental Lead Subcommittee. The following applies to Mike Brisson: This manuscript has been authored by Savannah River Nuclear Solutions (SRNS), LLC under Contract No. DE-AC09-08SR22470 with the U.S. Department of Energy (DOE) Office of Environmental Management (EM). Disclaimer: The United States Government retains and the publisher, by accepting this article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for United States Government purposes. Acknowledgements: The authors gratefully acknowledge Eric Esswein, Lisa Rogers, and Martin Harper for providing their valuable inputs.

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ACGIH: Annual Reports of the Committees on TLVs and BEIs for Year 2018. AIHA: A Strategy for Assessing and Managing Occupational Exposures, 4th edition. ASTM International: ASTM D5438, Standard Practice for Collection of Floor Dust for Chemical Analysis (2017). ASTM International: ASTM D6480, Standard Test Method for Wipe Sampling of Surfaces, Indirect Preparation, and Analysis for Asbestos Structure Number Surface Loading by Transmission Electron Microscopy (2019). ASTM International: ASTM D6661, Standard Practice for Field Collection of Organic Compounds from Surfaces Using Wipe Sampling (2017). ASTM International: ASTM D6966, Standard Practice for Collection of Settled Dust Samples Using Wipe Sampling Methods for Subsequent Determination of Metals (2018). ASTM International: ASTM D7144, Standard Practice for Collection of Surface Dust by Micro-Vacuum Sampling for Subsequent Metals Determination (2016). ASTM International: ASTM D7296, Standard Practice for Collection of Settled Dust Samples Using Dry Wipe Sampling Methods for Subsequent Determination of Beryllium and Compounds (2018). ASTM International: ASTM D7659, Standard Guide for Strategies for Surface Sampling of Metals and Metalloids for Worker Protection (2015). ASTM International: ASTM D7707, Standard Specification for Wipe Sampling Materials for Beryllium in Surface Dust (2016). ASTM International: ASTM D7789, Standard Practice for Collection of Fungal Material from Surfaces by Swab (2012). ASTM International: ASTM D7822, Standard Practice for Dermal Wipe Sampling for the Subsequent Determination of Metals and Metalloids (2018). ASTM International: ASTM D7910, Standard Practice for Collection of Fungal Material from Surfaces by Tape Lift (2014). ASTM International: ASTM E1216, Standard Practice for Sampling for Particulate Contamination by Tape Lift (2011). ASTM International: ASTM E1728/E1728M, Standard Practice for Collection of Settled Dust Samples Using Wipe Sampling Methods for Subsequent Lead Determination (2020). ASTM International: ASTM E1792, Standard Specification for Wipe Sampling Materials for Lead in Surface Dust (2016). ASTM International: ASTM E2458, Standard Practices for Bulk Sample Collection and Swab Sample Collection of Visible Powders Suspected of Being Biological Agents and Toxins from Nonporous Surfaces (2017). ISO: Technical Report 14294, Workplace Atmospheres — Measurement of Dermal Exposure — Principles and Methods (2011). Journal of ASTM International: Selected Technical Papers STP1533, “Surface and Dermal Sampling” (PDF).  Journal of Occupational and Environmental Hygiene: “Evaluation of a Standardized Micro-Vacuum Sampling Method for Collection of Surface Dust” (March 2007). Journal of Occupational and Environmental Hygiene: “House Dust Collection Efficiency of the High Volume Small Surface Sampler on Worn Carpets” (June 2006). NIOSH: Surface Sampling Procedures for Bacillus anthracis Spores from Smooth, Non-Porous Surfaces (April 2012).  NIOSH Manual of Analytical Methods: Method 9102, “Elements on Wipes” (PDF, March 2003).  NIOSH Manual of Analytical Methods: Method 9111, “Methamphetamine on Wipes by Liquid Chromatography/Mass Spectrometry” (PDF, October 2011).  OSHA: Method ID-125G, “Metal and Metalloid Particulates in Workplace Atmospheres (ICP Analysis)” (September 2002).  OSHA: Method ID-206, “ICP Analysis of Metal/Metalloid Particulates from Solder Operations” (May 1991).  OSHA: OSHA Technical Manual, Section II, Chapter 2, “Surface Contaminants, Skin Exposure, Biological Monitoring and Other Analyses (February 2014). Pacific Northwest National Laboratory: Visual Sample Plan, Version 7.13, The Synergist: “First Choice: Consensus Standards, Technology, and the IH Professional” (October 2019). U.S. Department of Housing and Urban Development: Policy Guidance Number 2017-01 Rev 1: “Revised Dust-Lead Action Levels for Risk Assessment and Clearance; Clearance of Porch Floors” (PDF, 2017). 
U.S. Government Publishing Office: 40 CFR Part 745, Lead-Based Paint Poisoning Prevention in Certain Residential Structures
Although the print version of The Synergist indicated The IAQ Investigator's Guide, 3rd edition, was already published, it isn't quite ready yet. We will be sure to let readers know when the Guide is available for purchase in the AIHA Marketplace.
My apologies for the error.
- Ed Rutkowski, Synergist editor
Disadvantages of being unacclimatized:
  • Readily show signs of heat stress when exposed to hot environments.
  • Difficulty replacing all of the water lost in sweat.
  • Failure to replace the water lost will slow or prevent acclimatization.
Benefits of acclimatization:
  • Increased sweating efficiency (earlier onset of sweating, greater sweat production, and reduced electrolyte loss in sweat).
  • Stabilization of the circulation.
  • Work is performed with lower core temperature and heart rate.
  • Increased skin blood flow at a given core temperature.
Acclimatization plan:
  • Gradually increase exposure time in hot environmental conditions over a period of 7 to 14 days.
  • For new workers, the schedule should be no more than 20% of the usual duration of work in the hot environment on day 1 and a no more than 20% increase on each additional day.
  • For workers who have had previous experience with the job, the acclimatization regimen should be no more than 50% of the usual duration of work in the hot environment on day 1, 60% on day 2, 80% on day 3, and 100% on day 4.
  • The time required for non–physically fit individuals to develop acclimatization is about 50% greater than for the physically fit.
Level of acclimatization:
  • Relative to the initial level of physical fitness and the total heat stress experienced by the individual.
Maintaining acclimatization:
  • Can be maintained for a few days of non-heat exposure.
  • Absence from work in the heat for a week or more results in a significant loss in the beneficial adaptations leading to an increase likelihood of acute dehydration, illness, or fatigue.
  • Can be regained in 2 to 3 days upon return to a hot job.
  • Appears to be better maintained by those who are physically fit.
  • Seasonal shifts in temperatures may result in difficulties.
  • Working in hot, humid environments provides adaptive benefits that also apply in hot, desert environments, and vice versa.
  • Air conditioning will not affect acclimatization.
Acclimatization in Workers

Why Is the Prevalence of Asthma Increasing?
It is not clear why the prevalence of asthma has increased, but a 2019 journal article focused on the epidemiology of asthma in children and adults describes several hypotheses that have been considered over the years:
  1. increased exposure to indoor allergens due to tighter insulation in modern housing as well as the increased use of plush furniture and carpets has contributed to an increase in asthma and other allergies
  2. reduced exposure to “unhygienic environments” early in life may lead to the increased prevalence of asthma and similar conditions
  3. the “microbial diversity” hypothesis, which suggests that “microbial diversity in the gut mucosa and respiratory tract are the key factors in priming and regulating the immune system” (therefore a lack of exposure to nonpathogenic microbes might explain the increased prevalence of asthma and other allergic diseases)