“Bioavailability of Contaminants in Soils and Sediments: Overview of SERDP and ESTCP Funded Research and Recommendations” by Dr. Hans Stroo

Bioavailability can be important to consider when assessing or mitigating the risks of contamination because not all contaminants present in a soil (or sediment) pose the same risks. However, incorporating bioavailability into risk assessments has proven to be difficult. Validated and cost-effective methods to measure bioavailability are needed, but the development and adoption of such methods has been challenging. The Strategic Environmental Research and Development Program (SERDP) and the Environmental Security Technology Certification Program (ESTCP) have invested in research on contaminant bioavailability for over a decade and have recently prepared a white paper summarizing the accomplishments to date and remaining data gaps and challenges. This presentation presented key findings from this white paper including recommendations for future research and technology transfer activities.

“PAH Interactions with Soil and Effects on Bioaccessibility and Bioavailability to Humans” by Ms. Yvette Lowney

Polycyclic aromatic hydrocarbons (PAHs) have emerged as one of the most important contaminants driving risk estimates and remedial decisions for soils at Department of Defense (DoD) sites. Substantial research efforts have focused on PAH bioavailability from solid matrices, including investigations into the chemistry of PAH interactions with soil and sediments, the oral and dermal uptake of PAHs into ecological and human receptors, extraction methods that are predictive of bioavailability measures, and in situ methods to reduce the bioavailability of PAHs in soil and sediments. This research yielded an extensive understanding of PAH chemistry and bioavailability. However, the ability to apply these research findings broadly to human exposures at contaminated sites remains elusive due to the narrow focus of prior studies.

The objective of this research was to examine the fundamental physical and chemical interactions between PAHs and soils, and how these interactions control the oral and dermal bioavailability of PAHs in soil to humans. A broad-based understanding was achieved by tying together research on soil/PAH chemistry with in vivo measures of bioavailability across a diversity of soil types and contaminant sources.

“Mechanisms and Permanence of Sequestered Lead and Arsenic in Soils: Impact on Human Bioavailability” by Dr. Nicholas Basta

Lead and arsenic are the most common metals exceeding risk criteria because soil ingestion is the primary human health risk driver at many Department of Defense (DoD) sites contaminated with toxic metals. The objectives of this study were to (1) link the binding mechanism of arsenic in soil (i.e., speciation) with in vitro bioaccessibility (IVBA) and in vivo methods used to predict relative bioavailability (RBA), and (2) to evaluate the permanence of bioavailability of lead in treated (i.e., remediated) soils. Study results show that 5 IVBA methods were predictive of the relative bioavailability of arsenic in 27 contaminated soils and solid wastes indicating that IVBA methods provide reliable data for use by DoD site managers. A firing range at the Oak Ridge National Laboratory and a lead smelter site in Joplin, Missouri were used to evaluate the permanence of bioavailability of lead in treated soils. Results indicated that both biological fungal treatments and chemical acidification did not affect lead bioavailability. In situ remediation using inexpensive and widely available phosphorus soil amendments is a proven technology that has been used to remediate lead contamination on DoD sites. Concern over the long-term permanence of lead relative bioavailability in soils amended with phosphorus is a barrier for implementation of this technology. This study demonstrated that sequestered lead in phosphorus treated soil is stable and can be used as a long term remediation practice at DoD sites.

Dr. Hans Stroo is a Technical Advisor to the Strategic Environmental Research and Development Program (SERDP) and the Environmental Security Technology Certification Program (ESTCP). He has over 30 years of experience in the assessment and remediation of contaminated soil and groundwater, including as a Principal with RETEC and HGL before starting Stroo Consulting LLC. He is co-editor of four SERDP-facilitated books on in situ remediation of contaminants in the subsurface. Dr. Stroo received B.S. degrees in Biology and Soil Science from Oregon State University, an M.S. in Soil Science from West Virginia University and a Ph.D. in Soil Science from Cornell University.

Ms. Yvette Wieder Lowney is an independent environmental consultant focusing on human health risk assessment for clients in the government, industry and non-governmental organizations. She has over 30 years of professional experience conducting research in the assessment of exposure and risks from chemicals in environmental media, workplaces and consumer products. In the context of conducting risk assessments for contaminated sites, Ms. Lowney has designed and coordinated original research regarding the bioavailability of metals and organic chemicals in soils. This research included assessment of the relative oral bioavailability and percutaneous absorption, and generating bench-top extraction models for estimating the relative bioavailability of chemicals from soil, for application in both human health and ecological risk assessments. Results from this original research have been presented at professional-society meetings, as testimony before scientific advisory panels and in peer-reviewed publications. In 2015, Ms. Lowney served as part of an international delegation to provide an advanced risk assessment workshop delivered as part of the Chemical Dialogue at the APEC meetings in Cebu City, Philippines. Currently she is a writing team leader for an ITRC effort to develop bioavailability guidance for use by U.S. state regulators and the regulated community.
 

Dr. Nicholas Basta is Professor of Soil and Environmental Chemistry and Co-Director of the Environmental Science Graduate Program at The Ohio State University in Columbus, Ohio. His research focuses on environmental chemistry and bioavailability of contaminants and nutrients in soil with emphasis on human, agronomic and ecosystem health. His research program is internationally recognized for the development and evaluation of in vitro bioaccessibility methods used to predict relative bioavailability of lead, arsenic and other metals in contaminated soils and solid media, and also the development and evaluation of in situ remediation of metal contaminated soils. Dr. Basta has more than 400 career publications including over 100 peer-reviewed manuscripts. He has delivered over 160 invited presentations including 45 at international scientific meetings. He has served on several Editorial Boards including 12 years as Technical or Associate Editor for the Journal of Environmental Quality. Dr. Basta is an active member of several international and national scientific committees focused on bioavailability and environmental fate of soil contaminants. He is a Fellow of the Soil Science Society of America and the American Society of America.