Airborne Monitoring to Distinguish Engineered Nanomaterials from - PowerPoint PPT Presentation

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 Environmental Engineering – Ambient air quality standard for PM 2.5 • 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 2

Acknowledgements • Funding through NIOSH career award • Support from companies who have welcomed us to sample in their facilities • Collaboration with RJ Lee Group 3

Industrial Hygiene Paradigm Generation and Dispersal Exposure Dose Epidemiology Control / Toxicology Measurement Respons e Health-Based Exposure Limit Working Exposure Limit

Engineered Nanomaterials Agglomeration Active Nanostructures Size Shape Surface Composition Toxicity (dose/response) Adapted from Tinke, Govoreanu, Vanhoutte (2006) Amer. Pharm. Rev. 9(6) Sept/Oct 1.

Fume Dust Smoke Mist Generation / Dispersal Smog Spray Mechanical Vapor Generation Nucleate Condense • Hot processes Mass – Vapor � particle – Dp < 1 µm g a o C – Welding, combusting Number Surface • Mechanical processes – Dp > 1 µm – Grinding, sanding Nano Ultrafine Fine Coarse 0.001 0.01 0.1 1 10 µm 1 10 100 1000 10 4 nm 6 Particle Diameter

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 7

Where Are We? Generation and Dispersal Exposure Dose Epidemiology Control / Toxicology Measurement Respons e Health-Based Exposure Limit Working Exposure Limit

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 9

Enclosure Effectiveness Varies Sanding CNT-Epoxy Composite Concentration (µg/m 3 ) Respirable Mass Fume Work Biosafety Hood Table Cabinet Kim and Flynn (1991) AIHAJ 52:287-296 Cena and Peters (in prep) J. Occup. Envir. Hyg. 10

Where Are We? Generation and Dispersal Exposure Dose Epidemiology Control / Toxicology Measurement Respons e Health-Based Exposure Limit Working Exposure Limit

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 12

Health-Based Exposure Limits • Primarily based on mass concentration measured with size-selective samplers – Respirable or Inhalable (Occupational) – PM 10 or PM 2.5 (Environmental) • Nanoparticle mass is often negligible 13

Bad Stuff = f(Surface Area) ≠ f(Mass) Oberdörster, G., E. Oberdörster and J. Oberdörster (2005). Environ 14 Health Perspect 113(7): 823-39.

15 Sampling Criteria

Sampling Criteria “There’s plenty of room at the bottom” Richard Feynman, 1959 16

Titanium Dioxide NIOSH Intelligence Bulletin • Current exposure limit (TLV) – 10 mg/m 3 for total TiO 2 • Recommendations – 1.5 mg/m 3 for fine TiO 2 – 0.1 mg/m 3 for ultrafine TiO 2 • 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

Where Are We? Generation and Dispersal Exposure Dose Epidemiology Control / Toxicology Measurement Respons e Health-Based Exposure Limit Working Exposure Limit

Measurement: Type of Sampling Surface Number Mass Area Conc. Conc. Conc. Area Personal 19

Our Work In Personal Sampling A. Cutaway Back View B. Front View PM2.5 • Real-time monitoring Sampler DC Umbilical DC Charger/ Electrometer DC Pump / Control Box PM2.5 Pump AC/DC Inverter Hip Belt Carries Equipment AC Power Battery Pack Weight At Sleep Fig. C-1. Small backpack that holds sampling equipment. • Filter-based sampling with electron microscopy Tubing Miniature Sampling Pump Conductive 25-mm Cassette 20

General Assessment Strategy Using Area Monitors • Identify hot spots through screening • Detailed characterization • Routine monitoring NIOSH (2009) Approaches to safe nanotechnology. Pub # 2009-125. http://www.cdc.gov/niosh/docs/2009-125/ 21

Screening: Aerosol Mapping Number Concentration Mass Concentration Condensation Particle Counter Photometer 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 22 (2006). Ann Occup Hyg 50(3): 249-57.

Nanoparticle Emission Assessment Technique (NEAT) - NIOSH Production System OFF • Measure background concentration • CPC – very fine particles number concentration • OPC – number concentration by size of large particles fffffffffffffffffffff Production System ON • Repeat measurements No ON > OFF Controls Adequate Yes Collect Open Face Filters For TEM Analysis 23 Methner, Hodson Geraci (under review)

Screening: Task-Based Monitoring Fill Hopper Condensation Counter Particle Mass, not number, related to tasks Thus, not nanoparticle issue But… Photometer Peters et al. (2009) JOEH 6:73 24

Detailed Characterization: Super-micrometer Spheres Have Nano-features 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. 25

Detailed Characterization: Sanding CNT-Epoxy Composites Generates Particles Unlike Bulk Airborne Particle From Sanding Bulk CNT 25 nm 100 nm 1 um 300 nm Cena and Peters (in prep) J Occup Envir Hyg 26

Nanomaterial Application: CNTs With Metal Catalyst Characterize Source Material Courtesy Gary Cassucio RJ Lee Group http://www.lbl.gov/ehs/esg/Reports/assets/Phase%20I%20Final%20Report2009.pdf

Nanomaterial Application: Characterize Source Material BF-STEM Image DF-STEM Image Example of Carbon Nanotubes with nickel and iron nanoparticles from the carbon particulate source material

Nanomaterial Application: Characterize Source Material Fe Si C Ni

Material Source � Workplace Sample �

Material Source X Workplace Sample X

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 32

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 33

Where Are We? Generation and Dispersal Exposure Dose Epidemiology Control / Toxicology Measurement Respons e Health-Based Exposure Limit Working Exposure Limit

The IH Paradigm Is Stuck Generation and Dispersal Exposure Dose Epidemiology Control / Toxicology Measurement Respons e Health-Based Exposure Limit Working Exposure Limit

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 36

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

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 38

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 39