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Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar
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Page 1: Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar.

Exposure Assessment of Engineered Nanoparticles:

Challenges, Progress, Opportunities

Christopher Long, Sc.D.November 19, 2008SRA-NE Seminar

Page 2: Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar.

Overview

• Key Questions:– How, What or Who, When, Where, How Much?

– What data are currently available to evaluate NP exposure potential?

– Are existing Best Management Practices for dusts, fumes, and mists effective for engineered NPs?

– What are some key challenges and data gaps for understanding potential exposures to nanoparticles?

Page 3: Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar.

Motivation

Risk = function (Hazard, Exposure)

Meaning that:

With little or no exposure, there can be no significant health risks.

Page 4: Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar.

Nanotechnology is “Now”

Over 800 consumer products worldwide …Photo by David Hawxhurst, Woodrow Wilson Center

Page 5: Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar.

Not Everything “Nano” is Actually Nano

Page 6: Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar.

Nano-sized Particles Are Not NovelNatural NPs•Ambient air chemistry (e.g., gas-to-particle conversions)

•Forest fires•Volcanoes•Viruses•Biogenic magnetite•Proteins

Anthropogenic Incidental NPs• Internal combustion engines•Fossil fuel power plants• Incinerators•Jet engines•Metal fumes (smelting, welding)•Polymer and other fumes•Cooking (frying, broiling, grilling, baking, toasting)

•Heated surfaces•Electric motors (vacuum cleaners)

•Office equipment•Candles

Page 7: Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar.

Nano-sized Particles Are Ubiquitous!

Hour of Day (EST)

6 8 10 12 14 16 18 20 22 0 2 4

Pa

rtic

le D

iam

ete

r (n

m)

20

30

40

50

60

70

80

90

200

300

400

500

100

1e+2 5e+2 1e+3 3e+3 5e+3 8e+3 1e+4 3e+4 5e+4 8e+4 1e+5 3e+5

Number Conc.dN/dlog(dp)

(#/cm3)

7/10/98 7/11/98

Frying egg;toasting bagel

Mopping withPine Sol

Popping popcornwith air popper

Page 8: Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar.

Year

2000 2001 2002 2003 2004 2005 2006 2007 2008

# of

Pub

licat

ions

0

200

400

600

800

1000

Toxicology Subset of Nano Studies in PubMedHandcount of Exposure Studies in PubMed/ICON Virtual Journal- Only Studies of Engineered NPsExposure Studies per ICON Nano-EHS Database Analysis Tool

What’s Published About NP Exposure Potential?

Page 9: Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar.

How NP Exposure May Occur

Page 10: Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar.

Potential Human Exposure Routes and Pathways

• Potential for inhalation, dermal contact, and ingestion exposures

• Workplace settings recognized to have greatest exposure potential • But general population exposures

cannot be overlooked– Direct exposures from use of consumer products– Indirect exposures to NPs in the environment from

releases resulting from production, use, and end-of-life (e.g., landfilling, incineration, recycling)

Page 11: Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar.

NP Sources and Potential Routes to the Environment

Sector/Application 

Nanomaterial 

Probable Exposure Routes

AirSurface Water

Ground Water

Wastewater Soil

Cosmetics and personal-care products

TiO2, ZnO, fullerene

(C60), Fe2O3, Ag

Catalysts, lubricants and fuel additives

CeO2, Pt, MoS3    

Paints and coatingsTiO2, SiO2, Ag,

quantum dots

Water treatment and site remediation

Fe, Fe-Pd, polyurethane

 

AgrochemicalsSiO2 (porous) as a

carrier

Food packaging Ag, nanoclay, TiO2        

Pharmaceuticals and medicines

Nanomedicines and carriers

(Adapted from Boxall et al., 2007)

Page 12: Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar.

Quantifying NP Exposure: What’s the Relevant Exposure Metric?

“Each One MayBe Right”

Schwartz et al. (2002)

Monteiller et al. (2006)

Stolzel et al. (2007)

Page 13: Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar.

Many Different Shapes, Chemistries, etc.

N. Walker, National Toxicology Program

Page 14: Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar.

Expanded List of Possible Measures of NP Exposure

• Mass concentration• Surface area• Number concentration• Surface reactivity• State of

Agglomeration

• Weighted size distribution

• Morphology (Shape)• Surface charge• Chemical composition

Page 15: Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar.

Measuring Exposure• Mass, Number, Surface Area?

MSP Corp.NanoMOUDI-II

TSI 3007 Portable CPC

TSI 3550 NanoparticleSurface Area Monitor

EcoChem DC2000 CEDiffusion Charger

TEM/SEM

Page 16: Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar.

Particle Size Measurement

TSI 3034SMPS

MSP Corp.Wide-Range ParticleSpectrometer

Dekati Electrical Low Pressure Impactor (ELPI)

Met One HHPC-6Optical Particle Counter

MSP Corp.NanoMOUDI-II

Page 17: Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar.

Lack of Specificity• Process-related or other nanoparticles?

– Need for careful data interpretation and/or more specific detection methods (e.g., shape recognition, elemental analysis)

From Kuhlbusch et al. (2001)

Page 18: Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar.

Potential Exposures During Simulated CNT Handling Scenarios

• Evidence for agglomeration under realistic handling processes; low respirable CNT concentrations

Adapted from Maynard et al. (2004), Maynard (2005)

Page 19: Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar.

Airborne PM in a Fullerene Factory

• During removal of fullerenes from storage tank for bagging and/or weighing, no elevation in Dp<50 nm, but elevation for Dp>1,000 nm

• SEM confirmed emission of fullerene aggregates/ agglomerates

• Consistent with findings from Maynard et al. (2004), observed increase in particle number conc. at Dp<50 nm during vacuuming

(Fujitani et al., 2008)

Page 20: Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar.

Airborne Metal Oxide NPs at an Industrial Pilot Plant

• Results indicate high temperature gas-phase production unit to be main particle source– Average conc. of 59,100 cm-3

and 188 g/m3

– Direct reactor leaks?• Vacuum cleaner increased

number conc. but not mass conc.

• No substantial rise in submicron particles during particle handling and processing

(Demou et al., 2008)

Page 21: Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar.

Airborne Exposures During NP Handling in Fume Hoods

• Pilot study demonstrates NP exposures when handling dry powders in standard fume hoods

– Potential for NP releases: Conventional>by pass>constant velocity

– Highly dependent on many variables- e.g., hood design, hood operation, work practices, type and quantity of NPs, etc.

• Released NPs remained airborne in laboratory air for up to 2 hours

• Well-designed hoods, operated at a constant face velocity (e.g., constant velocity hoods), shown to be protective under all test conditions

Pouring of 100 g Nanoalumina NPs

(Tsai et al., 2008)

Page 22: Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar.

NIOSH Field Investigations• Since 2006, NIOSH field team has conducted ~20 site

visits– Variety of workplaces- e.g., commercial R&D labs, university labs,

manufacturing facilities– Variety of NP types- e.g., carbon nanofibers, metal oxides, QDs

• Development of Nanoparticle Emission Assessment Technique (NEAT)– Baseline assessment utilizing portable instruments (CPC and

HHPC-6) for particle number measurements• Are particle number concentrations “higher” with production system

on? • ~25% increase above background used as subjective decision point • If Yes, filter-based samples for TEM and chemical analysis collected

– Expanded assessment using less portable, more expensive particle analyzers (e.g., SMPS, surface area analyzers)

Page 23: Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar.

Preliminary NIOSH Results• Available data show measurable particle

releases (but generally not NPs!) – Release of >400 nm particles during weighing/

mixing of carbon nanofibers and wet-sawing of composite materials (Methner et al., 2007)

– Effectiveness of Local Exhaust Ventilation (LEV) during reactor cleanout operations (Methner, 2008)

Page 24: Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar.

Exposure to Free NPs from Consumer Products???

• Few available data for realistic consumer product use scenarios– For sunscreens, studies show

no significant penetration of TiO2 or ZnO NPs.

– For products such as nanocomposite sporting goods, low exposure potential expected due to incorporation into solid, impermeable matrices.

– Limited data suggest releases possible during product modification (e.g., sanding, sawing).

PNNL Sanding Study of CNT Nanocomposites

Page 25: Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar.

Categorization Framework for Consumer Products (Hansen et al., 2008)

• Based on location of nanostructure in product• Three broad exposure categories

– Expected to cause exposure: “nanoparticles suspended in liquids” and “airborne nanoparticles”

– May cause exposure: “surface-bound nanoparticles”– No exposure expected to consumer: “nanoparticles suspended in solids”

• Applied to Woodrow Wilson Consumer Products Inventory– Categorized 45% of products into the “likely exposure” category, 9% into

the category of “no likely exposure,” and 25% as unclassifiable– Highest exposure potential for products in the categories food/

beverages and health/fitness– Highest exposure potential for Ag, TiO2, and ZnO– Several limitations, including lack of information about location of

nanomaterials in many products

Page 26: Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar.

Effectiveness of Traditional Filter Media

(Pui et al., 2008)

Page 27: Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar.

Conclusions

• Measurable NP emissions can be released during typical manufacturing and handling processes– Only moderate increases in NP conc. compared to background

levels- i.e., uncertain relevance to human health

• Critical need for additional data representative of real-world exposure conditions– Need for not only more workplace studies, but also studies to

determine the likelihood and conditions for potential releases of free NPs from consumer products and end-of-life processes

• Growing evidence that traditional exposure controls can effectively reduce NP exposure levels – Research indicates that not all fume hoods may be protective

Page 28: Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar.

Exposure Assessment Needs• Field measurements of actual workplace

conditions– Need to establish the relationship between basic

measurements and research-grade measurements– Need to establish the relevant exposure metric(s)

• Personal universal aerosol monitor that meets criteria for price, ease of use, and size

• Real-time instrumentation that can discriminate nano-sized particles of interest

• Standardized methods and reference materials for assessment of particle size, size distribution, shape, structure, and surface area

Page 29: Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar.
Page 30: Exposure Assessment of Engineered Nanoparticles: Challenges, Progress, Opportunities Christopher Long, Sc.D. November 19, 2008 SRA-NE Seminar.

Any Questions?

[email protected]

(617) 395-5532


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