Radiation Safety Aspects of Nanotechnology Celebrating the 100th Anniversary of Radioactivity at NPL Airborne Radioactivity Monitoring Users Group 3 June 2013
Mark D. Hoover, PhD, CHP, CIH 304-285-6374
[email protected] National Institute for Occupational Safety and Health Morgantown, West Virginia
The findings and conclusions in this presentation are those of the author and do not necessarily represent the views of the National Institute for Occupational Safety and Health. Mention of company names or products does not constitute endorsement by NIOSH.
Nano-enhanced materials and processes are raising issues in radiation-related operations.
What are the sources of radiation-related nanomaterials? How can exposure be assessed over life-cycle processes?
How should radiation dosimetry be conducted for nanomaterials?
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About the National Council on Radiation Protection and Measurements (NCRP) • Created in 1929 as the U.S. Advisory Committee on X-ray and Radium Protection. • Congressionally chartered in 1964 as a not-for-profit service organization by U.S. Public Law 88-376 to serve in the Nation’s public interest for collecting, analyzing, and disseminating the latest scientific information about radiation protection and measurement. • Cooperates with national and international governmental and private organizations to facilitate the effective use of combined resources to further develop the basic concepts of radiation protection and measurement. 3
NCRP is developing a commentary on radiation safety aspects of nanotechnology.
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Commentary Objective • Provide practical operational information for – radiation safety officers, – operational health physicists, – dosimetrists, – workers, – management, and – regulators.
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Commentary Scope • Radiation health and safety issues related to – Use of radiation to characterize or alter materials at the nanoscale level, – Radiolabelling of nanomaterials for tracking or evaluation of physicochemical and biological behavior, and – Use of nano-formulated materials in situations involving radiation or radioactivity. 6
Nanotechnology: A spectrum of activities
Many similarities to nuclear industries
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We can partner to develop a comprehensive risk management scheme to:
• • • • •
Anticipate, Recognize, Evaluate, Control, and Confirm
Training
Hoover et al., Synergist 22(1): 10, 2011.
success in our management of the radiation safety aspects of nanotechnology
by applying a science-based approach to understanding and managing the critical elements over which we have control.
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It makes sense to manage nanoparticles as a component of a traditional Radiation or Chemical Hygiene Program. • • • • • • • • • • •
Basic Rules and Procedures Chemical Procurement, Distribution, and Storage Environmental Monitoring Housekeeping, Maintenance, and Inspections Medical Program Personal Protective Apparel and Equipment Records Signs and Labels Spills and Accidents Training and Information Waste Disposal 9
Particle size-dependent deposition in the human respiratory tract is a critical factor. Deposition Fraction
1 0.9 0.8 0.7 0.6 0.5 0.4 Total
0.3
Head Airways Tracheo-Bronchial
0.2
Alveolar
0.1 0 0.001
0.01
0.1
1
10
100
Particle Diameter (µm) Calculated from the ICRP 66 model for an adult male, light exercise, nose breathing. 10
Radioactive nanoparticles need to be studied in more detail.
Committed effective dose Preliminary data analyses suggest higher urinary excretion per unit measured activity of nano-Pu-239 in urine is higher for larger particles. compared to the default Thus, bioassay interpretation based on the 5-µm particle size. default particle size should be protective. Better sizing of particles will lead to better dosimetry.
Courtesy of L. J. Cash
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Current Challenges: • The traditional assessment and management strategy requires an occupational exposure limit (OEL).
Hierarchy of Exposure Control Practices
Elimination
• OELs for radioactive materials are based on a unified concept of dose.
Substitution
• Such a unifying concept is not available for nanoparticles.
Modification Containment
• How can an effective chemical hygiene program for nanotechnology be developed and implemented in the absence of comprehensive OELs? • What control approaches are feasible and effective?
Ventilation Work Practices Personal Protection 12
A Hierarchical Vision of Hazard and Exposure Control for Comprehensive Health Protection, Health Promotion, and Well-being
Sustainability
Safety, Health, and Well-being
We have retrospective, contemporaneous, and prospective opportunities.
Elimination Substitution Modification
Work Practices
Safety, Health, and Well-being by Design
Containment and other engineered controls
Multiple hazards may be relevant. Personal Protective Equipment
Safety, Health, and Well-being by Procedure
Potential Hazard x Potential Exposure = Potential Risk
Draft for discussion
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A Hierarchical Vision of Hazard and Exposure Control for Comprehensive Health Protection, Health Promotion, and Well-being Safety, Health, and Well-being
Elimination Substitution
Sustainability
Modification
Work Practices
Safety, Health, and Well-being by Design
Containment and other engineered controls PPE Potential Risk
Safety, Health, and Well-being by Procedure
Potential Hazard x Potential Exposure = Potential Risk
Draft for discussion
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A Hierarchical Vision of Hazard and Exposure Control for Comprehensive Health Protection, Health Promotion, and Well-being Safety, Health, and Well-being
Elimination
Sustainability
Substitution Modification
Work Practices
Safety, Health, and Well-being by Design
Containment and other engineered controls Potential Risk
PPE
Safety, Health, and Well-being by Procedure
Potential Hazard x Potential Exposure = Potential Risk
Draft for discussion
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A Hierarchical Vision of Hazard and Exposure Control for Comprehensive Health Protection, Health Promotion, and Well-being
Sustainability
Safety, Health, and Well-being
Elimination Substitution Modification
Safety, Health, and Well-being by Design
Potential Risk
Work Practices
Containment and other engineered controls
Personal Protective Equipment
Safety, Health, and Well-being by Procedure
Potential Hazard x Potential Exposure = Potential Risk
Draft for discussion
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A Hierarchical Vision of Hazard and Exposure Control for Comprehensive Health Protection, Health Promotion, and Well-being
Sustainability
Safety, Health, and Well-being
Elimination Substitution Modification
Work Practices
Safety, Health, and Well-being by Design
Containment and other engineered controls Personal Protective Equipment
Safety, Health, and Well-being by Procedure
Potential Hazard x Potential Exposure = Potential Risk
Draft for discussion
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A Hierarchical Vision of Hazard and Exposure Control for Comprehensive Health Protection, Health Promotion, and Well-being
Sustainability
Safety, Health, and Well-being
We have retrospective, contemporaneous, and prospective opportunities.
Elimination Substitution Modification
Work Practices
Safety, Health, and Well-being by Design
Containment and other engineered controls
Multiple hazards may be relevant. Personal Protective Equipment
Safety, Health, and Well-being by Procedure
Potential Hazard x Potential Exposure = Potential Risk
Draft for discussion
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Conventional Controls Should Work Exhaust Ventilation Capture Diffusion Dominates
About 1 nm 200 to 300 nm Most Fine Dusts
Inertia Dominants
No Capture
Micro Scale
Air Stream
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Particle penetration through personal protective equipment: N95 respirators • Use of respiratory protection for nanomaterials professional judgment and hazard assessment 3.0 % Penetration
2.5 2.0 1.5 1.0 0.5 0.0 1
10
100
1000
Particle Size (nm)
Maximum penetration is in the region of minimal Brownian motion and minimal inertial effects
Silver
Sodium chloride
n = 5; error bars represent standard deviations Flow rate 85 L/min; NIOSH Approved N95 (NPPTL)
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Developing an Effective Control Strategy mild / reversible
Occupational Health Hazard
severe / irreversible 8 hours
Closed Systems
Engineered Local Exhaust Ventilation
Laboratory Hoods
milligrams
General Ventilation agglomerated
Glovebox Enclosures
highly dispersible Physical Form powder Adapted from Heidel, in NIOSH Approaches to Safe Nanotechnology 2009 slurry or suspension
Task Duration
Quantity
kilograms
15 minutes
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Key guidance is available from NIOSH. 3-15-2010 DRAFT
NIOSH Current Intelligence Bulletin Occupational Exposure to Carbon Nanotubes
English Spanish Portuguese Italian Japanese
www.cdc.gov/niosh/topics/nanotech
DEPARTMENT OF HEALTH AND HUMAN SERVICES Centers for Disease Control and Prevention National Institute for Occupational Safety and Health
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A technical report is also being developed on measurement and characterization. • International Electrotechnical Commission – Technical Committee 45 (Nuclear Instrumentation) – Scientific Committee 45B (Radiation Protection Instrumentation) • Technical Report on Radiation Protection Instrumentation Issues for Particles including Nanomaterials – Clarifying current practice – Identifying critical gaps – Attention to issues for workplace and offsite dispersion • Input is welcome – The writing group will meet in Moscow in June 2013.
International collaboration on consensus standards
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Characterization Methods
• Particle number • Mass concentration • Size distribution (by count or mass) • Surface area • Qualitative – Morphology – Extent of agglomeration – Complexity
• Confirmation – e.g. TEM with elemental analysis
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Graded Approach to exposure assessment and control Level 1
Level 2
Level 3
Initial Screening and Detection
Comprehensive Characterization and Assessment
Routine Monitoring and Control
• Process knowledge • Gross mass or activity counting • Optical particle counting • Condensation particle counting • Microscopy
• Composition - Elemental and chemical
• Particle size - Physical - Aerodynamic - Thermodynamic - Electrical mobility
• A necessary and sufficient subset of Level 1 and 2 methods for the material and situation of interest
• Exposure Concentrations - Peaks, averages, variability
• Biophysical properties - Shape, surface area, solubility
• Other factors relevant to the assessment
Adapted from Hoover 2011
Essential for cost and feasibility 25
Characterization Methods Overview Periodic Performance Testing
Mission Evaluation
Research and Development Prototype Testing
Maintenance and Recalibration
Operational Experience
A Life-Cycle Approach for Instrumentation and Methods
Type Testing
Production Control Testing
Functional Checks Initial Calibration
Acceptance Testing
Training
Successful approaches address all issues Hoover and Cox, 2004 and 2011 http://www.aiha.org/insideaiha/Documents/DREAM%20Radiation.pdf http://www.nano.gov/node/848
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Questions ? Mark D. Hoover, PhD, CHP, CIH NIOSH Nanotechnology Research Center and Division of Respiratory Disease Studies National Institute for Occupational Safety and Health Centers for Disease Control and Prevention 1095 Willowdale Road Morgantown, West Virginia 26505-2888 Phone: 304-285-6374 Email:
[email protected]
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