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Airborne Monitoring to Distinguish Engineered Nanomaterials from Incidental Particles Thomas M. Peters, PhD Department of Occupational and Environmental Health The College of Public Health The University of Iowa My Background BS MS in

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Airborne Monitoring to Distinguish Engineered Nanomaterials from Incidental Particles

Thomas M. Peters, PhD Department of Occupational and Environmental Health The College of Public Health The University of Iowa

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My Background

  • BS MS in Environmental Engineering

– Ambient air quality standard for PM2.5

  • PhD in School of Public Health

– Particle transport in ventilation ducts

  • Assistant Professor of Industrial Hygiene

– Teach “Aerosol Technology” and “Occupational and Environmental Epidemiology” – Research in aerosol measurement methods – Collaborate with Chemists, Geographers, Toxicologists, and even MDs

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Acknowledgements

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  • Funding through NIOSH career award
  • Support from companies who have welcomed us to sample in their facilities
  • Collaboration with RJ Lee Group
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Industrial Hygiene Paradigm

Generation and Dispersal Exposure

Epidemiology / Toxicology Health-Based Exposure Limit

Working Exposure Limit Measurement

Dose Respons e

Control

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Engineered Nanomaterials

Active Nanostructures Agglomeration Size

Shape

Surface Composition Toxicity (dose/response) Adapted from Tinke, Govoreanu, Vanhoutte (2006) Amer. Pharm. Rev. 9(6) Sept/Oct 1.

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Generation / Dispersal

  • Hot processes

– Vapor particle – Dp < 1 µm – Welding, combusting

  • Mechanical processes

– Dp > 1 µm – Grinding, sanding

Particle Diameter

Number Surface Mass

0.001 0.01 0.1 1 10 µm 1 10 100 1000 104 nm

Nucleate Condense C

  • a

g Vapor Mechanical Generation

Dust Mist Spray Fume Smoke Smog

Nano Ultrafine Fine Coarse 6

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Generation / Dispersal Engineered Nanomaterials

  • Generation

– Mechanical (ex: handling nanomaterials) favors agglomerate / large particle release (>100 nm) – Vapor condensation (ex: leak during nanomaterial production) favors sub-100 nm particles

  • Particles disperse into background

– Complicates measurement – Demands specificity in measurement methods

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Where Are We?

Generation and Dispersal Exposure

Epidemiology / Toxicology Health-Based Exposure Limit

Working Exposure Limit Measurement

Dose Respons e

Control

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Control

  • Airborne behavior well-known (<100 nm:

diffusion; > 500 nm: intertial / gravitational)

  • Capture

– Local exhaust ventilation effective

Methner (2008) JOEH 5(6): D63-D69.

– Hoods work but have variable effectiveness

Tsai et al. (2008) J Nano Res 11(1) 147-161

  • Collection

– Filters work for nanoparticles

Kim et al. (2006) J Nano Res 117-125

– PPE performance

Rengasamy (2009) Ann Occ Hyg 53(2):117-128

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Enclosure Effectiveness Varies Sanding CNT-Epoxy Composite

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Respirable Mass Concentration (µg/m3)

Fume Hood Work Table Biosafety Cabinet Cena and Peters (in prep) J. Occup. Envir. Hyg.

Kim and Flynn (1991) AIHAJ 52:287-296

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Where Are We?

Generation and Dispersal Exposure

Epidemiology / Toxicology Health-Based Exposure Limit

Working Exposure Limit Measurement

Dose Respons e

Control

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Adverse Health Effects

  • Toxicity evidence of adverse health effects

from nanomaterials

– Available for several of 1000’s currently in use – Highly dependent on size, morphology, surface chemistry, etc.

  • Very limited epidemiology
  • Each change to tune a nanomaterial

represents a new hazard

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Health-Based Exposure Limits

  • Primarily based on mass concentration

measured with size-selective samplers

– Respirable or Inhalable (Occupational) – PM10 or PM2.5 (Environmental)

  • Nanoparticle mass is often negligible

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Bad Stuff = f(Surface Area) ≠ f(Mass)

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Oberdörster, G., E. Oberdörster and J. Oberdörster (2005). Environ Health Perspect 113(7): 823-39.

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Sampling Criteria

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Sampling Criteria

“There’s plenty of room at the bottom” Richard Feynman, 1959

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Titanium Dioxide NIOSH Intelligence Bulletin

  • Current exposure limit (TLV)

– 10 mg/m3 for total TiO2

  • Recommendations

– 1.5 mg/m3 for fine TiO2 – 0.1 mg/m3 for ultrafine TiO2

  • General sampling and analysis specified but

need detailed methods

17 http://www.cdc.gov/niosh/review/public/TIo2/pdfs/TIO2Draft.pdf New version under internal review

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Where Are We?

Generation and Dispersal Exposure

Epidemiology / Toxicology Health-Based Exposure Limit

Working Exposure Limit Measurement

Dose Respons e

Control

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Measurement: Type of Sampling

Number Conc. Surface Area Conc. Mass Conc. Area Personal

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Our Work In Personal Sampling

  • Real-time monitoring
  • Filter-based sampling

with electron microscopy

  • A. Cutaway Back View
  • B. Front View

PM2.5 Sampler DC Pump / Control Box Hip Belt Carries Equipment Weight AC/DC Inverter DC Umbilical AC Power At Sleep PM2.5 Pump Battery Pack DC Charger/ Electrometer

  • Fig. C-1. Small backpack that holds sampling equipment.

Miniature Sampling Pump Tubing Conductive 25-mm Cassette

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General Assessment Strategy Using Area Monitors

  • Identify hot spots through screening
  • Detailed characterization
  • Routine monitoring

21 NIOSH (2009) Approaches to safe nanotechnology. Pub # 2009-125. http://www.cdc.gov/niosh/docs/2009-125/

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Screening: Aerosol Mapping

Number Concentration

Condensation Particle Counter

Mass Concentration

Photometer

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Look at Block-Head-Rod Line High number concentration with almost no mass concentration indicates presence of ultrafine particles

Peters, T. M., W. A. Heitbrink, D. E. Evans, T. J. Slavin and A. D. Maynard (2006). Ann Occup Hyg 50(3): 249-57.

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Nanoparticle Emission Assessment Technique (NEAT) - NIOSH

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Methner, Hodson Geraci (under review) Production System OFF

  • Measure background concentration
  • CPC – very fine particles number concentration
  • OPC – number concentration by size of large particles

Production System ON

  • Repeat measurements

ON > OFF

No

Controls Adequate

Yes

Collect Open Face Filters For TEM Analysis

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Screening: Task-Based Monitoring

Fill Hopper

Photometer Condensation Particle Counter Mass, not number, related to tasks Thus, not nanoparticle issue But…

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Peters et al. (2009) JOEH 6:73

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Detailed Characterization: Super-micrometer Spheres Have Nano-features

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Peters, T. M., S. Elzey, R. Johnson, H. Park, V. H. Grassian, T. Maher and P. O'Shaughnessy (2009). J Occup Environ Hyg 6(2): 73-81.

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Detailed Characterization: Sanding CNT-Epoxy Composites Generates Particles Unlike Bulk

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Bulk CNT 1 um

300 nm 100 nm 25 nm

Airborne Particle From Sanding Cena and Peters (in prep) J Occup Envir Hyg

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Nanomaterial Application: Characterize Source Material

Courtesy Gary Cassucio RJ Lee Group

http://www.lbl.gov/ehs/esg/Reports/assets/Phase%20I%20Final%20Report2009.pdf

CNTs With Metal Catalyst

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Example of Carbon Nanotubes with nickel and iron nanoparticles from the carbon particulate source material

BF-STEM Image DF-STEM Image

Nanomaterial Application: Characterize Source Material

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C Si Fe Ni

Nanomaterial Application: Characterize Source Material

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Workplace Sample

  • Source

Material

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Workplace Sample

X X

Source Material

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Routine Monitoring

  • After detailed measurements have been

made, recommendations can be made for routine monitoring

  • Last step in general strategy for workplace

monitoring with available equipment

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Measurement Needs

  • Refine tools / strategies for screening
  • Personal measurement methods
  • Define standard methods

– Analogous to NIOSH NMAMs that define how to perform sample analysis – Lab standardization – Ex: detect nanotubes apart from background aerosol

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Where Are We?

Generation and Dispersal Exposure

Epidemiology / Toxicology Health-Based Exposure Limit

Working Exposure Limit Measurement

Dose Respons e

Control

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The IH Paradigm Is Stuck

Generation and Dispersal Exposure

Epidemiology / Toxicology Health-Based Exposure Limit

Working Exposure Limit Measurement

Dose Respons e

Control

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The Path Forward

  • Toxicity tests need to relate to occupationally

relevant exposures

  • Reliance on traditional IH paradigm is not a

good short-term solution

– A priori definition of toxic nanomaterials unrealistic

  • Constructive use of available techniques can

go a long way to eliminating exposures

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Control Banding

37 Example application from RJ Lee Group found at LBL website http://www.lbl.gov/ehs/esg/Reports/assets/Phase%20II%20Final%20Report2009.pdf

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http://GoodNanoGuide.Org

  • Wiki-based collaboration platform designed to

enhance exchange of how to best handle nanomaterials in occupational setting

  • Information sorted by knowledge level

– Novice – Work practices – Expert specific detailed information

  • Beta form now

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Summary

  • Engineered nanomaterials represent new

potential occupational hazards

  • IH paradigm does not fit well
  • Alternative strategies to protect workers are

available and being improved upon

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