Advancing Risk Analysis for Nanomaterials and Nanotechnologies

Transcription

1 Advancing Risk Analysis for Nanomaterials and Nanotechnologies Jo Anne Shatkin, Ph.D. Managing Director CLF Ventures, Inc. Boston, Massachusetts November 19, 2008 Society for Risk Analysis New England Harvard School of Public Health

2 Overview Framing the issues Nano challenges to risk assessment Society for Risk Analysis Expert Workshop Findings Risk Analysis:Advancing the Science for Nanomaterial Risk Management Sept , Wash.DC Adopting a life cycle approach in risk assessment 2

3 What Is Nanotechnology? Nanotechnology is the understanding and control of matter at dimensions of roughly 1 to 100 nanometers, where unique phenomena enable novel applications 3

4 What Is Nanotechnology? Current technology, novel engineered nanoscale raw materials (Feynmann, There s plenty of room at the bottom ) In the future, active applications, molecular manufacturing (Drexler) Attributes: Manufactured Surface area to size/mass Unique behavior 4

5 How small is a nanometer? Head of a pin = 20,000,000 nanometers Particulate Matter (PM10) = 10,000 nanometers Bacteria = nanometers Viruses = nanometers DNA = 1-2 nanometers wide 5

6 Categories of Nanoparticles Natural Man-Made Engineered 6

7 Categories of Nanomaterials Metals and metal oxides Titanium dioxide Quantum dots Metal nanotubes Carbon-based Fullerenes Carbon nanotubes Quantum dots Dendrimers Composites 7

8 Carbon at the Nanoscale FULLERENE DIAMOND CARBON NANOTUBE GRAPHITE 8

9 Nanoscale Materials have More Particles and Surface Area per Unit Mass Table 1 Estimates of particle number and surface area per 10 μg/m 3 of airborne particles Particle diameter (μm) Particle concentration (#/cm 3 ) 153,000,000,000,000, ,000,000, ,000, Particle surface area (μm 2 /cm 3 ) 12,000, ,000 12, Adapted from Oberdörster et al. 2005a 9

10 Current Applications Using Nanotechnology 10 SOURCE: Woodrow Wilson International Center for Scholars Project on Emerging Technologies- Consume Product Inventory nanotechproject.org

11 Environmental APPLICATIONS of Nanotechnology Reducing Vehicle Emissions Cerium Oxide in diesel fuel reduces CO 2, particulates, hydrocarbon emissions (Oxonica) Reducing Electric Consumption Flexible solar batteries for personal digital devices (Konarka) Making Solar Cells Affordable Carbon nanotubes could help make nanoparticle-based solar cells more efficient and practical using thinner coatings with improved transfer of energy. 11

12 Risk Analysis: Advancing the Science for Nanomaterial Risk Management Issues for Risk Assessment Insufficient scientific information Physico-chemical changes of nanoparticles Translocation of nanoparticles Interactions with living matter Fate, distribution, and persistence Extrapolation of data from non-nano 12

13 Framing the Issues for Health/ Environmental Risk Assessment Hazard Characterization Toxicity Assessment Exposure Assessment Risk Characterization 13 (NRC 1983)

14 Framing the Issues: Hazard characterization for nanotechnology How to define nanomaterials Distinguish engineered from other nanoparticles? Are agglomerated or aggregated particles nano? Is a composite material containing nanoparticles nano? Do we characterize the particle, or the product? What are the appropriate measurement units? How to characterize variability, uncertainty? 14

15 Framing the Issues: Exposure Assessment for Nanotechnology Need new ways to characterize exposure Mass may not be most useful measure Can mass be a surrogate? When? When does size trigger new measures? Limitations of available analytical techniques Methods require low detection limits Also need to characterize background exposures Limited data on transport and fate 15

16 Framing the Issues: Dose Response for Nanotechnology Uncertainty in defining dose Different behavior of nanoparticles Difficulty in measuring responses- equivocal Absorption, distribution, metabolism, excretion Diversity of materials and characteristics When are particle distributions different? What are the tolerances? 16

17 Framing the Issues: Characterizing Risks of Nanomaterials Current frameworks adequate and appropriate, but significant model and parameter uncertainty Still much research to be done to quantify risks Need to address uncertainty and variability Available studies are comparative, e.g. Brunner et al. (2006) (comparative in vitro toxicity) Sayes et al. (2004) (cytotoxicity of variously substituted C60 fullerenes) Robichaud et al. (2005) (comparative risks of nanomanufacturing Warheit et al. (2007) (characterization of Nano-TiO2 toxicity) Do we need nano-safety factors? New Metrics and Endpoints for Risk? 17

18 Framing the Issues: Uncertainty Analysis Haven t we been here before? Cellular phones and non-ionizing radiation Foodborne vs. Nosocomial antimicrobial resistance Chemical mixtures Climate change impacts Fish consumption advisories Nano is not new, but does raise some novel challenges Risk Analysis is a robust approach for assessing and managing uncertain hazards and risks 18

19 Risk Analysis: Advancing the Science for Nanomaterial Risk Management Sept 2008, Washington DC Public expert workshop organized by the Society for Risk Analysis Emerging Nanoscale Materials Specialty Group Brought together risk analysts with nano-experts in to advance our understanding and build new networks A deliberative workshop to address: What is nano about risk assessment for nanoscale materials? What tools in the field of risk analysis can be used for managing nanomaterials? What are the needs for communicating about risks? How to consider the benefits of nanotechnology for risk reduction? 19

20 Risk Analysis:Advancing the Science for Nanomaterial Risk Management Workshop Co-Sponsors 20

21 Risk Analysis: Advancing the Science for Nanomaterial Risk Management Main Topics for Workshop Papers Uncertainty Analysis Model and parameter uncertainty pervades material characterization and hazard assessment Exposure Assessment When and how best to get beyond mass-based assessments, can other dimensions be simplified? Dose-response Assessment Dosing regimes must be tied to real world exposure Risk Characterization Not ready for quantitative assessments adopt life cycle approach, can we also consider benefits? Risk Communication Difficult to communicate about uncertain topics. Nano as an enabling technology complicates this message 21

22 Risk Analysis: Advancing the Science for Nanomaterial Risk Management Repeated themes Considerable uncertainty in understanding of nano-specific attributes and relevance to biological and environmental effects Size matters, but its not clear there is a bright line, e.g. at 100 nm Regulatory approaches are likely to be case-by-case in the near term Perceptions outside of industry and the government are critical, and proactive measures to communicate with the public are critical to ensuring the development of nanoproducts 22

23 Risk Analysis:Advancing the Science for Nanomaterial Risk Management Key Issues Identified Many previously identified concerns are not specific to nanomaterials or nanotechnologies Can address some concerns by design Engage risk analysts to work with product designers Need for a long term plan/framework to answer questions with pending data Conduct case-by-case evaluations to elicit key concerns Also conduct expert workshops more broadly to raise overarching issues Test/compare adaptive approaches to risk analysis that incorporate the product life cycle 23

24 Risk Analysis: Advancing the Science for Nanomaterial Risk Management Units of Material Characterization It s possible that once we get the units right, there will be no nano-specific issues in risk assessment However nanoparticles are dynamic this drives decisions about units for a breadth of contexts May need more than one set of units, but it may also be possible to build relationships across units to unify them There may be a role for applying a nanospecific uncertainty factor in some situations. 24

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26 Size tolerances and purity size size size 100% within range 50% within range 50% impurity? What does 99% pure mean for a nanomaterial? 26 10% within range 90% impurity?

27 When are populations different for extrapolation purposes? 27 impurities impurities

28 Risk Analysis: Advancing the Science for Nanomaterial Risk Management Risk Characterization must be Context-specific It is important to consider the context for the material application different applications and decision context might be best served by different levels of uncertainty evaluation or sensitivity analysis. In the case-by-case approach, consider models and data from other substances to inform data gaps 28

29 Risk Analysis: Advancing the Science for Nanomaterial Risk Management Is nano risk communication different? Overall, no. It is similar to that for emerging technologies But, definitional problems exist: Have not defined what we are communicating about Are agglomerates (>100 nm) considered nano? As in other areas, diagram needed to demonstrate parties: who is involved and how 29

30 Risk Analysis: Advancing the Science for Nanomaterial Risk Management Take aways Using expert judgment There is a lot of expertise, and this could be tapped for understanding some of the uncertainties Almost don t need to state, must be informed by data Qualitative approaches are more appropriate in the short term. Strive to be in a position to make quantitative assessments of uncertainty By developing models and frameworks now Build structures and test uncertainty 30

31 Risk Analysis: Advancing the Science for Nanomaterial Risk Management Work toward a 10 year plan To have an overarching frame for the data that are developed To investigate the relationships between the mode of action and properties to allow extrapolation Encourage interaction between risk analysts and product developers to bring about riskinformed product design Build adaptive approaches 31

32 Risk Analysis:Advancing the Science for Nanomaterial Risk Management Workshop Outcomes Publication of white papers Presentations on Symposium at SRA Annual Meeting December 8-10 Identified next steps Follow on conference to discuss role and development of top down/bottom up frameworks Built new networks of experts networks across continents Potential collaboration with Organization for Economic Cooperation and Development (OECD) Research agendas to address key uncertainties about size, nano-specific outcomes Test and compare risk frameworks that incorporate product life cycle 32

33 Consider Adaptive Life Cycle Approaches to Risk Assessment and Risk Management Provide a framework for assessing biological and environmental exposure- a significant advance How to implement these approaches not part of the current risk management paradigm A variety of frameworks exist/proposed Nano LCRA (Shatkin Nanotechnology Health and Environmental Risks CRC Press) Comprehensive Environmental Assessment (Davis 2007) Nano Risk Framework (EDF/DuPont 2007) 33

34 NANO LCRA Adaptive Streamlined Life Cycle/ Risk Assessment Framework for NM (Shatkin 2008) IDENTIFY AND CHARACTERIZE HAZARDS ASSESS EXPOSURE EVALUATE TOXICITY RAW MATERIALS Process PRODUCT Packaging USE/ REUSE/ DISPOSAL CHARACTERIZE RISK ASSESS CONFIDENCE ITERATE 34

35 Key Attributes of NANO LCRA Adaptive Risk Framework Initially, a streamlined analysis appropriate for early stage decisions Proactive approach for evaluating safety of novel materials Steps sequentially across processes through product lifecycle Applies to health and safety and environmental concerns Transparent decision framework 35

36 Key Attributes of NANO LCRA Adaptive Risk Framework Identifies Potential for Hazard and Exposure at each step Focuses on exposure potential to streamline analysis Only evaluates toxicity and risk when exposure may occur Allows comparison of different NM products and processes Adaptive: easy to update when new information is available Focuses and prioritizes risk management on key concerns 36

37 NANO LCRA framework Adaptive approach applies broadly to array of situations not nano-specific Use as a screening tool to identify and prioritize health and environmental/ process issues Identifies key uncertainties Revisits early decisions with new information 37

38 NANO LCRA Case Example Nano Silver as Coating in Consumer Product SILVER RAW MATERIALS ID and CHARACTERIZE HAZARDS Process PRODUCT PACKAGING PRODUCT USE EVALUATE EXPOSURE RECYCLE/ DISPOSAL Analysis Hazard Identification Release of silver during manufacturing Improper disposal practices for NM wastes Packaging step allows release of particles Product contains unbound silver particles Disposal may release silver to environment Exposure Assessment Worker exposure during production process Packaging into final product poorly controlled Final product includes human dermal contact exposure Recycling creates inadvertent exposure Environmental pathways unknown Toxicity Assessment Potential dermal toxicity during use Unknown ecological fate and toxicity 38 Recommendations Occupational hazards Install secondary containment in production area Develop disposal practices for NM wastes Contain packaging releases Exposure Assessment Test dermal uptake in bioassays Conduct ecological fate evaluation Toxicity Assessment Material characterization Assess toxicity of product?? Conduct ecological tox studies??

39 Comprehensive Environmental Assessment (CEA) CEA LC + RA LC = Product Life Cycle framework RA = Risk Assessment paradigm See: Davis, J. M. How to assess the risks of nanotechnology: learning from past experience J. Nanosci. Nanotechnol. 7(2): ,

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41 Comprehensive Environmental Assessment (CEA) Life Cycle Stages Environmental Pathways Fate & Transport Exposure Effects Feedstocks Manufacture Distribution Air Water Primary contaminant s Biota Eco-systems Storage Use Soil Food chain Secondary contaminant s Human populations Human Health Disposal 41 Source: adapted from Davis, J. M. and Thomas, V.M. Annals N.Y. Academy of Science 1076: , 2006

42 Process Focus on specific case studies Include diverse technical & stakeholder perspectives Use expert judgment methods Identify strategic priorities Repeat periodically / adaptive management 42

43 EPA s Nanomaterial Case Studies Goals: Identify & prioritize research needed for comprehensive assessment of nanomaterials Refine long-term research strategy for nanomaterials risk assessment Rationale: Focus on specific examples & scenarios Selected applications of nano-titanium dioxide (TiO 2 ): Case study 1: Water treatment (e.g., arsenic removal) Case study 2: Sunscreen Organized around CEA approach (see next slide) Note: Case studies are not completed assessments 43

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46 Summary Risk assessment continues as a valid approach to managing emerging substances Broad agreement to adopt a life cycle approach in risk assessment NANO LCRA Screening Level Risk Assessment is a useful tool for identifying and managing amidst uncertainty Comprehensive Environmental Assessment also an adaptive approach SRA Workshop concluded risk analysis can inform management of NM and NT Top Down (frameworks) and Bottom Up (case by case) approaches Risk Perceptions must be addressed by transparent and proactive communication 46

47 Thank You Very Much! Jo Anne Shatkin, Ph.D. CLF Ventures