Refinement of Sampling and Analysis Techniques for Asbestos in Soil

JULIE WROBLE* U.S. Environmental Protection Agency, Region 10, 1200 6th Avenue, Seattle, WA 98101

TIM FREDERICK U.S. Environmental Protection Agency, Region 4, 61 Forsyth Street SW, Atlanta, GA 30303

DANIEL VALLERO U.S. Environmental Protection Agency, Office of Research and Development, National Exposure Research Laboratory, 109 T.W. Alexander Drive, Research Triangle Park, NC 27709

Key Terms: NOA, Asbestos, Soil Sampling, Incremental Sampling, Fluidized Bed

ABSTRACT

Measuring the concentrations of asbestos in contaminated soils is challenging. Data are often highly variable. Variability in soil measurements has led to limitations in comparing results from sites nationally and difficulties in reproducing results, even from the same sites over time. The difficulties in collecting reproducible soil data limit the ability to extrapolate from concentrations in soil and compare to concentrations in air. This extrapolation is necessary if soil data are to be used in human health risk assessments. To address this substantial limitation of asbestos soil data, researchers from Environmental Protection Agency (EPA) regions and the National Exposure Research Laboratory are conducting a series of efforts to advance the use of data that are collected, processed, and analyzed using the most reproducible methods. These soil data, collected from a variety of sites across the country, will be compared to air data from activity-based sampling in an attempt to establish a quantitative relationship between asbestos soil concentrations and airborne fiber concentrations. This research plan summary provides an update on the EPA efforts under way and the challenges that lie ahead.

INTRODUCTION

The Framework for Investigating AsbestosContaminated Superfund Sites of the Environmental Protection Agency (EPA) establishes activity-based sampling (ABS) as the preferred method for estimat-

*Corresponding author email: Wroble.Julie@epa.gov

Figure 1. Sampling team collecting incremental samples in area contaminated with asbestos-containing material (ACM). (Inset) ACM debris on the ground in sample area.

ing potential risks from asbestos in soil at Superfund sites (U.S. Environmental Protection Agency, 2008). ABS usually follows a site determination that asbestos is present or may be present based on soil sampling data and/or the visual identification of asbestos debris in soil. Using this approach, the air concentrations measured using ABS can be used to quantify the potential risks to current or future site users. Implementing ABS at potentially contaminated sites can be costly and time consuming. It can also be difficult to implement when members of the general public are located nearby. Devising methods that would allow for using soil samples in risk-based decision making at Superfund sites would lead to a more efficient process. In a previous study, EPA researchers compared three soil analytical methods and two soil sampling

methods to determine whether one method or a combination of methods would yield more reliable soil asbestos data than other methods (Wroble et al., 2017). Samples were collected using both traditional discrete (“grab”) sampling and incremental sampling methodology (ISM) (Interstate Technology and Regulatory Council, 2012). Analyses were conducted using methods established by the California Air Resources Board (California Environmental Protection Agency, 1991, 2017), the American Society of Testing and Materials (2013), and the Environmental Protection Agency (Januch et al., 2013; U.S. Environmental Protection Agency, 2011, 2018). Our data show that the fluidized bed asbestos segregator (FBAS), a process developed by EPA scientists, followed by analysis using transmission electron microscopy, was the most sensitive analytical method (Wroble et al. 2017).

It was anticipated that ISM would provide less variable data than discrete sampling. While this was true for metals data collected to provide an additional measure of variability, the asbestos data remained highly variable.

The next phase of this work is intended to address some of the issues identified in the earlier study. Soil will be collected from a variety of asbestoscontaminated sites (naturally occurring asbestos as well as soils contaminated with asbestos-containing materials) and contaminated with a variety of fiber types. Increasing the number of increments collected for each sample from 30 to 100 may help to overcome the problems of representativeness when asbestos in soil is not homogeneously distributed in soil. The number of replicate samples collected at each site will be increased from three to five to allow for better statistical comparisons. To be more rigorous, soil processing will be conducted in a laboratory rather than the field. Laboratory preparation of samples is expected to be more consistent across samples than field preparation because preparation conditions can be more controlled. Finally, activity-based air samples will be compared to FBAS data. The collected data may provide a scientific basis for using FBAS data directly for risk-based decision making at asbestos-contaminated Superfund sites.

SOIL SAMPLING

Soil samples from three asbestos-contaminated sites will be collected using ISM (Fig. 1). Four performance evaluation (PE) samples (two asbestos types at two different concentrations) will also be included in the study in attempt to provide a comparison of known concentrations of asbestos in a consistent medium to uncertain concentrations of asbestos in environmental samples. PE samples are prepared by adding a known mass of asbestos to a known volume of soil, whereas soil measurements often rely on point counts or visual area estimation, which may not relate directly to mass. The PE samples will be prepared according to an approved work plan by a contracted laboratory. Analysis of PE samples will help to provide context to the environmental soil measurements for asbestos in this study. Both PE samples and site samples will be processed at a single location. Processing will include vigorous mixing of each sample using a Turbula mixer. Samples will then be systematically subsampled to provide the necessary soil volume for each analytical method: American Society of Testing and Materials, California Air Resources Board, and FBAS. The remaining soil from each sample will be reserved and combined with other soil from each site for ABS conducted in a laboratory setting.

AIR SAMPLING

A key part of the next phase of this project will be conducting activity-based sampling in a laboratory setting. One combined sample from each location will be used for the ABS activity. ABS will be performed inside of an exposure chamber at the EPA’s Office of Research and Development laboratories in Research Triangle Park, North Carolina or a similar facility. Investigators in personal protective equipment will mimic the activity of a child playing in the dirt while wearing sampling pumps with sample media attached. Investigators will also perform ABS activities with the PE soil samples.

DATA COMPARISONS

When all the data have been collected as described above, a variety of comparisons can be made. The team will compare the relative variability of each soil sample location and the PE samples for each soil analytical method. The purpose of these comparisons will be to determine which of the analytical methods, if any, provides reproducible soil data. The comparisons of site samples to PE samples will determine whether samples collected from contaminated sites are inherently more variable than laboratory-prepared PE samples.

The investigators will also compare the ABS samples to the FBAS sample data. The data may provide a scientific basis for using FBAS data directly for risk-based decision making at asbestos-contaminated Superfund sites.

CONCLUSIONS

When completed, the researchers intend to have established FBAS as the preferred method for detecting

low levels of asbestos in soils based on ability to detect and reproducibility. The researchers also hope to demonstrate that by refining ISM techniques, reproducibility of asbestos sampling/analytical methods for soil is improved. The inclusion of PE samples will provide context to relate real-world concentrations of asbestos in soil to standards.

REFERENCES

ASTM D7521-13, 2013, Standard Test Method for Determination of Asbestos in Soil: ASTM International, West Conshohocken, PA. doi:10.1520/D7521-13. www.astm.org California Environmental Protection Agency, Air Resources Board, 1991, Determination of Asbestos Content of Serpentine Aggregate, Test Method 435: Electronic document, available at https://www.arb.ca.gov/testmeth/vol3/m_435.pdf California Environmental Protection Agency, Air Resources Board, 2017, Implementation Guidance Document, Field Sampling and Laboratory Practices, Test Method 435: Determination of Asbestos Content of Serpentine Aggregate: Electronic document, available at https://www.arb. ca.gov/toxics/asbestos/tm435/guidancedocument.pdf Interstate Technology and Regulatory Council, 2012, Incremental Sampling Methodology: Electronic document, available at http://www.itrcweb.org/ism-1 ISO 10312, 1991, Ambient Air—Determination of Asbestos Fibres— Direct-Transfer Transmission Electron Microscopy Method: International Organization of Standardization, Geneva, Switzerland. Januch, J.; Brattin, W.; Woodbury, L.; and Berry, D., 2013, Evaluation of a fluidized bed asbestos segregator preparation method for the analysis of low-levels of asbestos in soil and other solid media: Analytical Methods, Vol. 5, No. 7, pp. 1658–1668. U.S. Environmental Protection Agency, 2008, Framework for Investigating Asbestos-Contaminated Superfund Sites: Asbestos Committee of the Technical Review Workgroup of the Office of Solid Waste and Emergency Response, U.S. Environmental Protection Agency, Washington, DC. OSWER Directive No. 9200.0-68. U.S. Environmental Protection Agency, 2011, Field Standard Operating Procedure: Sampling, Sample Preparation and Operation of the Fluidized Bed Asbestos Segregator: U.S. Environmental Protection Agency, Seattle, WA. OEAFIELDSOP-102. U.S. Environmental Protection Agency, 2018. Other Test Method—42: Sampling, Sample Preparation and Operation of the Fluidized Bed Asbestos Segregator: Air Emission Measurement Center, U.S. Environmental Protection Agency, Washington, DC. Wroble, J.; Frederick, T.; Frame, A.; and Vallero, D., 2017, Comparison of soil sampling and analytical methods for asbestos at the Sumas Mountain Asbestos Site—Working towards a toolbox for better assessment: PLoS ONE, Vol. 12, No. 7, p. e0180210. https://doi.org/10.1371/journal. pone.0180210