exposure assessments and risk management guidance update … · 2013-07-15 · exposure assessments...
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Exposure Assessments and Risk Management Guidance – Update on Strategic Approaches Kenneth Martinez, CIH, MSEE Field Studies Team Leader
Nanotechnology Research Center
Education and Information Division
National Institute for Occupational Safety and Health
The findings and conclusions in this presentation have not been formally reviewed by the National Institute for Occupational Safety and Health and should not be construed to represent any agency determination or policy.
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NNI EHS Risk Management Research Framework
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Key Elements of Risk Management
Hazard Identification
“Is there reason to believe this could be harmful”
Exposure Assessment
“Will there be exposure in real-world conditions?”
Risk Characterization
“Is substance hazardous and will there be exposure?”
Risk Management
“Develop procedures to minimize exposures.”
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Research Strategy Correlation
Hazard Identification
Exposure Assessment
Risk Characterization
Risk Management
Measurement
Human Exposure
Human Health
Environment
NIOSH NNI Risk Management Research
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Key Elements of Risk Management
Hazard Identification
“Is there reason to believe this could be harmful”
Exposure Assessment
“Will there be exposure in real-world conditions?”
Risk Characterization
“Is substance hazardous and will there be exposure?”
Risk Management
“Develop procedures to minimize exposures.”
Focus for today
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NTRC Field Studies Team Background
Formally organized in 2006 as a component of the NIOSH Nanotechnology Research Center
Conducted 20 site visits in a variety of work places
Tasked with “learning nanomaterial processes”…
Attempting to fill an important knowledge gap regarding nanomaterial creation and use:
Is there a release?
To what extent?
Is there potential worker exposure?
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NFST – 2011 to Present Goals
Evaluates the entire material flow of a process and identifies points of potential material emission that can result in worker exposure
Uses an array of instruments and conventional air sampling methods to characterize exposures
Available to the practicing industrial hygienist
Evaluates engineering controls and their effectiveness in reducing emissions and exposures
Evaluates work practices used during the production or use of nanomaterials
Evaluates the use of Personal Protective Equipment in use, if any, including respiratory protection
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NFST – 2011 to Present Methods
Preassessment
Occupational exposure limits and health effects
- Review pertinent literature
Toxicology
Epidemiology
- Provides context of interpretation of data
Develop sampling strategy
- Integrated samples
- Real-time instrumentation (RTI)
- Wipe sampling
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NFST – 2011 to Present Methods
Sampling Strategy
Integrated samples
- Core component of exposure assessment
- Filter-cassette based
- Elements
- Electron Microscopy
- Area and personal breathing zone
- Full-shift and task-based
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Integrated Sampling
Elemental mass
Sampling and analytical methods not designed for nanomaterials
- Specificity
NMAM 5040 (elemental carbon) versus NMAM 7300 (cadmium)
- Sensitivity
10 µm particle weighs the same as 109 (1 billion) 10 nm particles
Electron microscopy
TEM versus SEM
Morphology
EDS for chemical composition
Particle count
No counting convention exists
Respirable fraction
• 100 µm diameter Inhalable
• 10 µm diameter Thoracic
• 4 µm diameter Respirable
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Integrated Sampling
Personal breathing zone
“True” indicator of worker’s exposure
Determines levels of exposure throughout workday
Can be compared to OELs
Area
Survey sources of contaminant
Evaluate engineering controls
Background
Other contributions not related to the process
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Integrated Sampling
Full-Shift versus Task-Based
Most OELs are based on TWA
+ Full-shift
- No OELs exist for nanoparticles
Except NIOSH (CNT and TiO2)
Identify level of source contribution
+ Task-based
- Activities may be of short duration
Analytical sensitivity ↓
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Direct Reading Instruments
TSI CPC 3007 (TSI Inc., Shoreview, MN)
ARTI HHPC-6 (Hach Company, Grants Pass, OR)
TSI DustTrak DRX (TSI Inc., Shoreview, MN)
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Appropriate Use of DRIs
Assess efficacy of engineering controls
Assess potential for emission of specific processes/tasks
Identify general increases or decreases in total particle concentration
Provide supporting evidence for integrated samples
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Limitations of DRIs
No material identification
Condensation Particle Counter
Engineered to measure ‘particle’ concentrations – not fibers
Upper dynamic range in the order of 105 pt/cc
• Small inlet can become clogged with larger particles
• Optical Particle Counter (DustTrak)
• Unable to accurately assign ‘size bin’ to fibrous materials
Optical Particle Counter (ARTI)
Unable to accurately assign ‘size bin’ to fibrous materials
• Only total count is useful data
• Only 50% collection efficiency for the smallest size bin (0.3-0.5 µm)
• Unable to correct accurately due to inaccurate size designations
• Clean room instrument
• Inlet easily clogged in dusty
environment
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Wipe Sampling
Surface contamination
No correlation with worker inhalation exposures
Assess worker hygiene practice
NMAM 9102
Elements
Wash ‘n Dry or ASTM equivalent
Pre-packaged moist disposable towelette
Analysis by inductively coupled argon plasma atomic emission spectroscopy
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Vacuum Sampling
Surface contamination
Filter sock
- More mass
- Less time
- Use of a template
- Analysis requires resuspension
37-mm filter cassette
- Good for hard to reach areas
- Less mass
- Labor intensive
- Amenable to standard sample analysis and EM
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NFST – 2010 to present 12 Field Studies
Types of facilities Number of sites
Primary producer of nanomaterials 9
Secondary user of nanomaterials (manufacturer) 1
Agents
Carbon nanotubes, aluminum oxide, amorphous silica, cerium oxide, quantum dots, silver nanowires, zirconium oxide, hafnium oxide, catalytic nanoparticles (iron, nickel, silver-palladium, and magnesium) and nickel-titanium alloy
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[Adapted from Schulte et al. 2010, J Nanopart Res]
Possible Strategy for Developing Exposure Control Limits & Bands
Available
Toxicity &
PC Data
Suggestive
Qualitative Risk
Assessment
Reason by
Analogy
Quantitative
Risk
Assessment
Adequate Minimal
Determination of
Occupational
Exposure Limit
Hazard Banding
Structure-Activity
Relationship
Control Banding PC: physical-chemical
19
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Output to Participating Companies
Report
Introduction
Background
Evaluation Criteria
Methods
Results
Discussion
Conclusions and Recommendations