1. Occupational Exposure Assessments of Nanomaterials in the USA
Laura Hodson, MSPH, CIH
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.

2. Considerations Realm of possible measurements
Nanomaterials with an exposure limit
Nanomaterials without an exposure limit
“Newer” sampling devices
In-depth assessments
Challenges
Practical approach to all the options

3. Realm of possible measurements

4. What metric to use? Metric Qualification Mass
Standard (NIOSH CNT and TiO2 CIB)
Surface Area
Advantage for low solubility particles
Surface Chemistry
Toxicological studies
Particle Number
Relevance
Particle Size
Translocation
Particle Shape
HAR versus spheres

5. Nanomaterials with an exposure limit

6. Assessing Worker Exposure: Nanomaterials with exposure limits
NIOSH Current Intelligence Bulletins
Recommended Exposure Limits (RELs) are mass based:
300 µg/m3 for nano TiO2
1 µg/m3 for CNT and CNF
How and where to measure 6 6

7. Sampling for Titanium Dioxide
NIOSH Method 0600 for Respirable Dust (pre-weighed PVC filter and cyclone)
This is weighed
If > 0.3 mg/m3 analyze same filter by NIOSH Method 7300, Metals for Titanium by ICP
Collect a duplicate open-face sample using MCE filter (for electron micrograph)

8. Sampling for CNT/CNF
NIOSH Method 5040 for elemental carbon (EC). Collect the respirable fraction (25mm quartz fiber filters with a cyclone inlet)
Collect a second open face MCE filter sample to be analyzed by electron microscopy
Personal breathing zone, source and background samples

9. Sampling for CNT/CNF Particle counters have limitations
Verify elemental carbon using electron microscopy
SEM or TEM with energy dispersive X-ray spectrometry (EDS)
Helpful for identification ( composite matrix bound vs. free unbound elemental carbon)
No counting convention exists
Particle counters have limitations
with fiber structures

10. Sampling for nanomaterials without an exposure limit

11. History of the initial Nanoparticle Emission Assessment Technique (NEAT)
NEAT was developed as an initial step to semi-quantitatively evaluate emissions in nanomaterial workplaces and consists of a combination of field portable, direct-reading instrumentation (DRI) and filter-based air sampling with subsequent laboratory analysis.
No-cost field evaluations have been available from NIOSH since We have completed over 100 site visits!

12. NEAT – Lessons Learned Direct-reading Instrumentation
Background concentrations fluctuate significantly
Averaging pre- and post-task does not adequately address background influences
Data logging would better capture and account for background variations
Documentation of critical events is essential
Direct-Reading Instruments alone are insufficient to adequately evaluate a worksite
Filter-Based Sampling
Need both task-based and full-shift sampling
Need both open-face cassettes and respirable cyclone inlets

13. Highlights of the new Nanomaterial Exposure Assessment Technique NEAT 2.0

14. Key Elements of NEAT 2.0 Pre-assessment prioritization
Field measurements
Risk management
Routine monitoring (confirmation)

15. Comparison of US Risk Management Approach and ISO (EU) Tiered Approach
NEAT 2.0
Tiered Approach
Pre-assessment prioritization
Exposure sampling (particle counters, EM samples, mass samples in personal breathing zone and area. Sometimes expanded into additional aerosol samples
Risk management summary
Confirmation
Tier 1- Pre-assessment information gathering
Tier 2- Basic exposure assessment (area particle counters and EM samples)
Tier 3- Personal breathing zone samples, mass samples, additional aerosol samples

16. Pre-assessment Prioritization (Similar to Tier 1)
Process description and flow
Number of employees and job description
Safety Data Sheets or other information
Walk about to look at process, identify possible exposure potentials
Review occupational exposure limits and health effects.
Identify and review pertinent literature.
Photo courtesy Adrienne Eastlake, NIOSH

17. Field Measurements Filter-cassette based Data logging with DRI’s
Elements and Electron Microscopy (EM)
PBZ, Source/ Area, Background
Full shift and task specific
With and without cyclones
Various filter media
Data logging with DRI’s
Source/Area and Background
Note that red font corresponds to Tier 2
Photos courtesy Adrienne Eastlake, NIOSH

18. Filter Media and Methods
NMAM 7402 (Transmission Electron Microscopy) open-face cassette with Mixed Cellulose Ester filter. Scanning Electron Microscopy collection on Polycarbonate or Teflon filter
NMAM 5040 (Elemental Carbon) respirable fraction collection with Quartz Fiber filter
NMAM 7300 (Elements by ICP) both open-face cassette and respirable with Mixed Cellulose Ester filter

19. Total dust, inhalable or respirable filter samples?
Total dust: open-face cassettes. Tells the “whole story”. Good for electron microscopy and elemental analysis.
Inhalable: collected with a 100 µm cut size cyclone
Respirable- collected with a 4 µm cut size cyclone. Tells what is reaching the lungs. Corresponds to NIOSH RELs for Ti02 and CNT/CNF.
GK 2.69 BGI, Inc.
Mention of a trade name does not constitute endorsement

20. Direct Reading Instruments (DRIs)
TSI CPC 3007 (TSI Inc., Shoreview, MN)
Condensation Particle Counter
Measures particles between 10 nm and ~ 1 µm
TSI OPS 3330 (TSI Inc., Shoreview, MN)
Optical Particle Counter with collection filter
16 user defined bins
Measures particles between 300 nm -10 µm
TSI DustTrak DRX (TSI Inc., Shoreview, MN)
4 pre-determined size bins (1, 2.5, 4.0, and 10 µm)
Mention of a trade name does not constitute endorsement

21. Interpretation of real-time data

22. In- depth assessments (Corresponds to Tier 3)
Wipe sampling
Concentration mapping
Use of advanced aerosol sampling equipment (SMPS, FMPS, ELPI, MOUDI, Surface Area)
Complete industrial hygiene sampling
(VOCs, acids, IAQ, etc.)

23. “Newer” sampling devices and analyses being explored in US

24. Taping of EM grids to filters in cassettes
Collection directly onto a EM grid (thermophoretic or electrostatic sampling)
Taping of EM grids to filters in cassettes
Analysis of filters by dark field hyperspectral imaging microscopy
Zefon Personal NRD (Nanoparticle Respiratory Deposition) sampler
300 nm cut size, elemental analysis
PENS: Personal nanoparticle sampler

25. Challenges to nanomaterial exposure assessments

26. Challenges Need for portability & cost effective evaluations
Variability of incidental background nanoparticles
There is no prescribed counting convention for microscopy (though many are offering suggestions)

27. We need to be practical
“of or concerned with the actual doing or use of something rather than with theory and ideas.”

28. Particle Counters and Size Analyzers
NEAT 2.0 includes a set of filter based samples and data-logging real time particle counters
Elemental Analysis
Electron microscopy
Particle Counters and Size Analyzers 28

29. To assess workers’ exposures to nanomaterials, personal breathing zone, source and background samples are all necessary
Photo credits, Laura Hodson, Chris Sparks and Adrienne Eastlake, NIOSH

30. Photos courtesy A Eastlake and L Hodson, NIOSH

31. Thanks to the NIOSH Field Team
Photos courtesy Chris Sparks, Doug Evans, NIOSH

32. Thank you!