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Risk and Regulatory Issues Associated with the Disposal of Nanomaterials

phone 919-541-7425 • mobile 919-475-9474 • e-mail steveb@rti.org

Stephen M. Beaulieu

Nanomedicine and Molecular Imaging Summit, January 31-February 1, 2010

SNM Midwinter Meeting – Albuquerque, NM

Will regulations designed to deal with disposal issues work for nanotechnology?

In US, EPA has primary responsibility for safe and effective disposal of materials and products at the end of the life cycle

Two key EPA-administered laws that provide the regulatory framework for end-of-life management strategies 1. Resource Conservation and Recovery Act (RCRA)2. Comprehensive Environmental Response, Compensation and

Liability Act (CERCLA)

Other laws such as the Clean Water Act (CWA) and Toxic Substances Control Act (TSCA) also regulate the disposition of chemicals

In terms of “disposal,” however, RCRA is unquestionably the most important regulatory authority that determines how residuals are managed at the end of the life cycle

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Why focus on RCRA?

RCRA regulates the handling, reuse, recycling, storage, treatment, and disposal of solid and hazardous wastes, including medical wastes and mixed wastes

Relatively little research on the environmental, health, and safety issues associated with how NMs are managed as waste residuals or spent products

Recent studies suggest that the risk of release of NMs will be highest during disposal, destruction, or recycling (Breggin & Pendergass, 2007)

RCRA requires EPA to characterize the risks to human health and the environment associated with the management of potentially hazardous wastes

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How are management options determined for a “new” chemical, waste, or material under RCRA?

A risk assessment is conducted to determine whether potential management options pose unacceptable risks to human health and the environment

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Problem Formulation

Compare total conc data to health/eco

Potential risk?

Potential risk?

Interpretation

yes

yes

no

no

Analysis

Risk CharacterizationDevelop

Conceptual Models

Review studies, reports, etc.

Initial Data Collection

Compare leach data to TC limits

Evaluate completeness of data vis a vis conceptual

models and life cycle

Develop exposure scenarios and conduct

screening-level modeling

Tier I – Hazard Characterization

Tier II – Screening Assessment

Secondary Data

Collection

Decision

Tier III – 3MRA Model Simulation

Develop exposure scenarios and conduct

screening-level modeling

Tertiary Data

Collection

What types of approaches are used in the initial tiers of a risk assessment?

A simple Risk Assessment Matrix (RAM) approach is often used in the initial tier 1 hazard characterization to focus on the agents (e.g., chemical, biological) that are most likely to be of concern.

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LikelihoodSeverity

Rare (1)

Negligible (2)

Marginal(3)

Critical (4)

Catastrophic (5)

Improbable(1) 1 2 3 4 5

Remote(2) 2 4 6 8 10

Occasional (3) 3 6 9 12 15

Probable (4) 4 8 12 16 20

Frequent( 5) 5 10 15 20 25

Why are modeling approaches often used in higher level risk assessment tiers?

Modeling allows us to develop quantitative insight into different types of risk questions, to predict potential health and environmental outcomes What are future risks likely to be? What are the most significant risks? What are the critical risk factors? What are the most effective risk reduction options?

Importantly, modeling allows us to deal with data limitations, uncertainties, and variability in exposure and toxicological response

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What are the basic data needs for predictive quantitative risk assessments under RCRA?

Partition coefficients Biodegradation rates Solubility Particle sizes Bioaccumulation factors Biotransfer factors Food ingestion rates Water consumption rates Meteorological data Soil characteristics Hydrogeologic regions Human health toxicity Ecological toxicity

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Can existing risk assessment modeling tools be used for NMs if data are available? (hint: no)

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Are sufficient data available for any NM to support quantitative risk assessment? (hint: no)

In The known unknowns for nanomaterials: describing and characterizing uncertainty within environmental, health, and safety risks, Grieger, Hansen, and Baun (2009) make a compelling case regarding NM data deficiencies

Authors reviewed 31 recent reports and articles describing the state-of-the-science with regard to NMs and risk assessment

Methodology divided the uncertainties into four “locations” including (1) Testing, (2) Characteristics of NM, (3) Exposure Assessment, and (4) Effects Assessment

Authors concluded that “Given these data, it is unclear if quantitative risk estimates including most quantitative uncertainty analyses are able to provide meaningful results.”

How can we think about risk assessment given the uncertainties associated with NMs?

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Perhaps we should focus on developing an answer to the question: “what level of research and data are needed to develop a predictive tool that can reliably be used to support waste management decisions under RCRA?”

Higher CostMore Complex Models

Greater Data RequirementsLower Uncertainty

Lower CostSimpler Models

Limited Data RequirementsHigher Uncertainty

How can we conceptualize NM risk assessment in a meaningful way?

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Perhaps we should draw on our previous RA experience to create a modeling framework that provides useful (not perfect) information to support the decision making process

Environmental Behavior

Simulation

Health and Ecological Endpoints

Chemical-Physical Properties

DECISION

NM Release

NM Effects NM Exposure

NM Fate and Transport

Predictive Risk Model

Risk Estimates

What about other regulatory entities that use RA to support decision making?

Under the CWA, the EPA regulates the management of an enormous volume of sewage sludge (aka biosolids) that are treated and used as a soil amendment for agricultural lands – same problems

Under TSCA, the EPA has broad authority to regulate the manufacture, use, distribution in commerce, and disposal of new and existing chemical substances – same problems

FDA is responsible for product safety and effectiveness, and the Agency is a frequent user of risk assessment to address safety concerns – same problems

The NRC and DOE are responsible for regulating the radioactive aspects of solid wastes, including wastes that contain nanomaterials and radionuclides – same problems

Potential keys to the path forward for assessing end-of-life risks?

Most statutes (certainly RCRA), in their current form, contain sufficient regulatory breadth to cover nanomaterials; however, some changes will likely be needed to define the products and wastes in terms of nanomaterial characteristics

In the absence of reliable tools/data to perform predictive, quantitative risk assessments, alternative approaches such as multi-criteria decision analysis may provide a transparent method to determine the most appropriate management option

Other structured approaches to managing uncertainty in environmental modeling may provide a sound basis for the development of simple models that incorporate new research data as it becomes available (e.g., Koprogge, van der Sluijs, and Peterson, 2009)

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A few references of interest ….

Grieger, K.D., S.F. Hansen, and A. Baun (2009). The known unknowns for nanomaterials: describing and characterizing uncertainty within environmental, health, and safety risks. Nanotoxicology. 3:3.

Kloprogge, P., J.P. van der Sluijs, and A.C. Peterson (2009). A method for the analysis of assumptions in model-based environmental assessments. Environmental Modelling and Software. In press.

Breggin, L.K., and J. Pendergrass (2007). Where Does the Nano Go? End-of-Life Regulation of Nanotechnologies. Project on Emerging Nanotechnologies, PEN 10, Woodrow Wilson International Center for Scholars.

Refsgaard, J.C., J.P. van der Sluijs, A.L. Hojberg, and P.A. Vanrolleghem (2007). Uncertainty in the environmental modelling process – A framework and guidance. Environmental Modelling and Software. Vol. 22, pp 1543-1556.

Thomas, T., K. Thomas, N. Sadrieh, N. Savage, P. Adair, and R. Bronaugh (2006). Research Strategies for Safety Evaluation of Nanomaterials, Part VII: Evaluating Consumer Exposure to Nanoscale Materials. Toxicological Sciences. Vol. 91, No. 1, pp 14-19.

Walker, W.E., P. Harremoes, J. Rotmans, J.P. van der Sluijs, M.B.A. van Asselt, P. Janssen, and M.P.Krayer von Krauss (2003). Defining Uncertainty: A Conceptual Basis for Uncertainty Management in Model-Based Decision Support. Integrated Assessment. Vol. 4, No. 1, pp 5-17.