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Nanoparticles Hazards, Risks, Filtration and Respiratory Protection

© 3M 2011. All Rights Reserved.

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Nanoparticles

Hazards

Size

Types

Sources

Risks

Effects upon the human body

Filtration

Can standard filter materials

capture nanoparticles?

Respiratory Protection

Considerations and criteria for

selection and use of RPE

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What are nanoparticles?

Source:

Nandiyanto, A.B.D.; Kim, S.G.; Iskandar, F.; Okuyama, K. ” Synthesis of spherical mesoporous silica nanoparticles with nanometer-

size controllable pores and outer diameters” Microporous and Mesoporous Materials, Volume 120, Issue 3, April 2009, Pages 447-453

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What are you breathing right now?

Source:

(adapted from) D. Wake, D. Mark, and C. Northage, “Ultrafine Aerosols in the Workplace”,

Ann Occup Hyg (2002) 46(suppl 1): 235-238

HSL =

Control Lab

Ambient Air -

Health & Safety

Laboratory,

Buxton, UK

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Definition

European Commission adopted a recommendation

on the definition of nanomaterials (18 October 2011)

"Nanomaterial" means a natural, incidental or

manufactured material containing particles, in an unbound

state or as an aggregate or as an agglomerate and

where, for 50 % or more of the particles in the number

size distribution, one or more external dimensions is in the

size range 1 nm - 100 nm.

2011/696/EU - Commission Recommendation of

18 October 2011 on the definition of nanomaterial

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Other terms and definitions used

Nanoparticles (NPs)

Ultrafine particles (UFPs)

Often used to refer to particles caused by nucleation, gas

to particle reactions or evaporation

[Fine] Particle Matter (PM)

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What are nanoparticles?

One of the emerging topics in industrial hygiene today is

nanotechnology and engineered nanoparticles.

Engineered nanoparticles

novel properties and functions because of their nanometer scale

dimensions

Nanoparticles also unintentionally produced by industrial

processes (e.g. welding) or combustion (e.g. diesel fumes)

and occur naturally in the atmosphere.

Viruses and other bioaerosols fall into the nanoparticle size

range

Strictly 3M Confidential.

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Relative sizes of common airborne particles

Bacteria Industrial mists

Pollen Human

hair

Tobacco smoke Welding fume Viruses

Fog Mists &

drizzle Rain

Visible by human eye Visible by

microscope

Visible by electron

microscope

10000 1000 100 10 1.0 0.1 0.01

Inhalable

Thoracic

Particle diameter (microns)

Dust

Respirable CEN/ISO/ACGIH criteria’ / Vincent 2008

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Environmental and Engineered Nanoparticles

Source:

David Y.H. Pui, Center for Filtration Research Meeting, April, 2006

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Examples of Impact of Nanotechnology

Carbon nanotubes -- 10 times as strong as steel at

1/6 the weight

Nanopowder drugs -- 10 times bioavailability and 8

times faster response time as conventional drugs

Nanostructured silicates/polymers as contaminant

scavengers for a clean environment

Nanoporous textures for tissue integration with

medical devices

Computer storage -- 1 million times storage capacity

using nanoscale switching devices

Source: David Y.H. Pui, Center for Filtration Research Meeting, April, 2006

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Nanoparticle Diffusion and Behaviour

Nanoparticles have high diffusion coefficients,

therefore high mobility – they will mix rapidly when

released and disperse.

As particle size decreases, into the nanoparticle

scale diffusion forces start to dominate and

nanoparticles behaviour more like a gas or a vapour.

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Nanoparticle Agglomeration

As a result of diffusion, collisions

between particles occur

coagulation and agglomeration

will occur

Very small nanoparticles

coagulate rapidly to form larger

particles – but still nanoparticles

As size increases, coagulation

half-life is longer

Larger nanoparticles will persist

Particle

Diamm.

(nm)

Half-life at varying particulate concentrations

1 g/m3 1mg/m3 1g/m3 1ng/m3

1 2.2s 2.20ms 2.2s 36.67min

2 12s 12ms 12s 3.34hrs

5 0.12ms 0.12s 2min 33.34hrs

10 0.7ms 0.7s 11.67min 8.1days

20 3.8ms 3.8s 63.34min 43.98days

Source:

Preining, O. (1998) The physical nature of very, very small

particles and its impact on their removal from the air. Journal of

Aerosol Science; 29: 481-495

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Nanoparticle Deposition

Particles will generally fall naturally from the air over time.

Gravitational settling velocity is proportional to diameter

Nanoparticles will remain in the air for extended periods /

indefinitely

This can result in greater exposure to workers

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Nanoparticles: Airports & Aircraft

Limited studies & guidance are available:

ACRP Report 9, “Summarizing and Interpreting

Aircraft Gaseous and Particulate Emissions Data”,

2008

EPA, “Characterization of Emissions from Commercial

Aircraft Engines during the Aircraft Particle Emissions

eXperiment (APEX) 1 to 3”, 2009

Cheng, MD “A Comprehensive Program for

Measurements of Military Aircraft Emissions” –

SERDP Project WP-1401, 2009

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Sources of Particulates

Aircraft engines;

Aircraft auxiliary power units (APU);

Ground support equipment (GSE);

Passenger vehicles;

Tire and brake wear;

Stationary power turbines;

Training fires;

Sand and salt piles;

Construction grading and earth moving; and

Some food preparation ovens (e.g., charbroilers).

Source:

ACRP report 19, 2008

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Particulate evolution

Source:

ACRP report 19, 2008

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C130H - T56 Turboprop particulate emissions

C130H Hercules - Rolls Royce

T56 Turbo-prop engines, JP-8

fuel.

Engine run at different power

settings and particulates in

exhaust sampled and analysed

Distribution mostly in nanoparticle

range

Geometric mean diameter

increased with increased engine

power

Source: Cheng, MD “A Comprehensive Program for Measurements of Military Aircraft Emissions” – SERDP Project WP-1401, 2009

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B-52 - TF-33 Turbofans particulate emissions

B-52 - Pratt & Whitney TF-

33 Turbofan engines, JP-8

fuel.

Distribution of size similar to

C130H / T56

Geometric mean diameter

increased with increased

engine power

Idle: 55nm

80%: 63nm

90%: 80nm

95%: 85nm

Source: Cheng, MD “A Comprehensive Program for Measurements of Military Aircraft Emissions” – SERDP Project WP-1401, 2009

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Comparison of particle number emissions for different civilian aircraft engines (at idle)

Source: EPA Characterization of Emissions from Commercial Aircraft Engines during the Aircraft Particle Emissions eXperiment (APEX) 1 to 3

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CFM56-2C1 engine

Average PSD measured by the Nano-SMPS during APEX-1, Test EPA-3, with line loss correction

Source: EPA Characterization of Emissions from Commercial Aircraft Engines during the Aircraft Particle Emissions eXperiment (APEX) 1

to 3

Idle

30% power

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HEALTH RISKS FROM NANOPARTICLES

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Health Effects

Nanoparticles may or may not exhibit size-related

properties that differ significantly from larger, but still

respirable particles with respect to deposition and

alveolar clearance.

The health risks from nanoscale particles compared

to macroscale particles of the same material may be

considerably different.

Strictly 3M Confidential.

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Particle deposition in adult human respiratory system

Source:

ICRP 66 (1994); MPPDep (2000): based upon experimental data

Reproduced from: Hofmann, H. “Nanoparticles Risk and Regulation - Behaviour of Nanoparticles in contact with cells”

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Biological effects

Nanoparticles may translocate to other organs –

penetrate through the alveoli membranes, enter the

circulatory system

Some nanoparticles have the potential to cause cell /

tissue / systemic toxicity.

Some nanoparticles may cross cell membranes and

interfere with cellular reproduction

Source:

ISO/TR 12885:2008

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Toxicity, surface area, surface chemistry and particle number

Studies on rodents have shown that poorly soluble

agglomerated and aggregated nanoparticles have a

greater detrimental effect on the pulmonary system

than larger particles of similar chemical composition

and surface properties

Nanoparticles were observed to have higher levels of

toxicity (pulmonary inflammation, oxidative stress

and tissue injury).

Source:

ISO/TR 12885:2008

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Health Effects Summary

Size selective TLVs that identify an acceptable

concentration in mass terms for specific size

fractions; inhalable, thoracic, and respirable, exist

today.

The nanosize particle fraction may be an additional

fraction to separate from the inhalable dust exposure

if it is shown that the specific health effects are

related to this size fraction.

The health effects of nanoparticles have not been

definitively resolved and is a subject of ongoing

research.

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RESPIRATORY PROTECTION AND GUIDANCE

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What are the respiratory concerns?

No published exposure limits for engineered nanoparticles.

More research is required into specific health effects may

result, if any, from exposure.

According to industrial hygiene principles, a hierarchy of

control measures may be used to help reduce worker

exposure to hazardous levels of contaminants to safe levels.

Enclosing the process

Local exhaust ventilation,

Personal protective equipment (PPE) such as particulate respirators.

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Exposure Metrics

Most of the current occupational exposure limits for particles are based on

mass.

Nanoparticles: the concentration might be small in terms of mass, it might

be quite large based on surface area, and even greater in terms of particle

numbers.

Convenient methods do not currently exist by which exposures to

nanoparticles in the workplace can be accurately measured and

assessed.

Until these issues are resolved, the establishment and justification for

appropriate regulatory occupational exposure limits may be delayed.

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FILTRATION OF PARTICLES (AND NANOPARTICLES)

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Particle Filters

A filters in respirators are NOT screens or sieves.

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Filter Media in Respirators

Fibrous filter media

remove particulates

Fibers create a tortuous

flow path

Filter media made of:

Natural fibers

Polymer fibers

Glass fibers

Disposable Respirator

Filter Media

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Filter Performance

%penetration (%pen, or %P) is a measure of the ability of particles to penetrate

Pressure Drop (ΔP) is a measure of the resistance to air flow

P0 P

C0 C

0

%100%C

Cpen

PPP 0

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There are four common mechanisms of filtration

Mechanical Filtration

Interception capture

Inertial impaction

Diffusion capture

Electrostatic Filtration

Electrostatic Attraction

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Filter fibre

Inertial impaction

Impaction - Dominant for large particles (>0.6µm)

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Filter fibre

Interception capture

Interception - Operative for particles greater than 0.1 µm

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Filter fibre

Diffusion Capture

Diffusion - Operative for particles < 0.4 µm, dominant for < 0.1 µm

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Mechanisms of Filtration: Cumulative Effects

Interception Impaction Diffusion

Source:

Air Filtration by R.C. Brown, Pergamon Press

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Electrostatic filtration

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Electrets Enhance Filtration

An electret has a persistent

distribution of electric

charge

Generally, stable electrets

are composed of solids

which are good electrical

insulators

Charged and uncharged

particles are attracted to

electret fibers

Filtration efficiencies are

significantly improved with

the inclusion of Electrets.

+

-

- +

Coulombic Force

Induced Force

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Filter fibre

Electrostatic attraction

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Electrostatic

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Electrostatic

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Electrostatic Forces Play a Significant Role in Filtration

particle diameter (mm)

colle

ctio

n e

ffic

ien

cy

charged media

discharged media

Source:

Baumgartner and Loffler, 3rd International Conference on Electrostatic Precipitation, October 1987

Mechanical

Filtration

Only

Electrostatic

+

Mechanical

Filtration

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The three dimensional filter

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Three Dimension Filters

Filtrete Split Fibre

Polypropylene Blown Microfibre FIlter

Resin & Wool

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MOST PENETRATING PARTICLE SIZE

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Most Penetrating Particle Size

Minimum in efficiency between diffusion and interception/impaction regimes

For air filtration, typical most penetrating size is between 0.1 and 0.5μm

Filtration efficiency depends on particle size and flow rate

Electostatic filtration increases efficiency for particles < 0.1μm

This graph is

an example

from a 1970s

era air filter.

This is not

necessarily

representative

of a NIOSH or

CE approved

respirator /

filter

MPPS region

Graph - Source: Lee , K. W. , and Liu , B. Y. H. ( 1980 ). Air Pollut. Control Assoc. 30 : 377 .

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EN 149:2001+A1:2009 Filter Penetration

EN 149:2001+A1:2009 has challenge particulate aerosols with mean particle diameters of 0.3μm

EN 149 and NIOSH (42 CFR 84) respiratory protective devices are tested under highly demanding conditions

„Standard‟ industrial aerosols typically have mean particle diameters of approx. 3.0μm

This graph is

an example

from a 1970s

era air filter.

This is not

necessarily

representative

of a NIOSH or

CE approved

respirator /

filter

MPPS region

Graph - Source: Lee , K. W. , and Liu , B. Y. H. ( 1980 ). Air Pollut. Control Assoc. 30 : 377 .

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NANOPARTICLE FILTRATION BY EN 149 (& NIOSH N95) RESPIRATORS

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0

1

2

3

4

5

6

7

0.01 0.1 1

Particle Diameter (m)

% P

enet

rati

on

2.84%

1.25%

1.21%

1.22%

0.60%

0.53%

TSI 8130

NIOSH N95 Respirator Penetration (85 lpm) – 6 x different models Penetration Vs. Particle Size (TSI 8160)

Penetration per NIOSH NaCl Light Scattering Photometer (TSI 8130)

Both tests rank respirators

in a similar, predictable manner

TSI 8160

n = 10

3M data – selection of commercially available N95 respirators

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Filtration Performance of N95 Respirator

Filtration efficiency varied between models and within the ten

samples of each model. However, the shape of the filtration

efficiency curve was similar for all tests, with the most

penetrating particle size (MPPS) falling in the range between

40 and 100 nm.

These results show that that “smaller” particles are not

necessarily more difficult to capture due to diffusion and

electrostatic attraction.

Thus, engineered nanoparticles can be filtered by NIOSH /

CE (FFP2 or FFP3) approved particulate respirators.

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Balazy et al. “Manikin-Based Performance of N95 Filtering-Facepiece Respirators Challenged with Nanoparticles” Ann. Occup. Hyg. 50(3), 2006.

Respirators A & B were NIOSH N95 respirators (~ EN149:2001+A1:2009 FFP2 respirator)

Previous testing: Respirator A Fit Factor > Respirator B Fit Factor

Q – inhalation flow rates

Challenge NaCl

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Other Questions / Issues

Conflicting papers have suggested varying performance of particulate respirators at sizes <10nm

In this size range there is limited data

Recent research indicates that nanoparticles that the threshold for thermal rebound is 1.5 to 3.0nm at which they behave like gas molecules

Engineered nanoparticles obey the laws of physics and classical filtration models.

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© 3M 2011. All Rights Reserved.