Monitor for detecting and assessing exposure to airborne - - PowerPoint PPT Presentation

4 November, 2008

Monitor for detecting and assessing exposure to airborne nanoparticles

Johan Marra1, Matthias Voetz2, Heinz-Jürgen Kiesling2

1 Philips Research Laboratories; Eindhoven 2 Bayer Technology Services; Leverkusen

CONFIDENTIAL

Philips Research Laboratories, Author, August 21, 2008

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Current situation

• Increasing societal significance of the nanomaterials industry;
• Increasing reliance on processes / products comprising nanoparticles (NPs);
• Hazards associated with many engineered NPs still unknown;
• Increasing awareness about potential NP exposure risks;

Proposed safety measures in the workplace are pragmatic:

• Exposure minimization;
• Continuous monitoring of the workplace environment;
• Monitoring of the worker’s cumulative exposure;

Portable NP monitors needed for quantifying the NP exposure and the associated relative health risk

CONFIDENTIAL

Philips Research Laboratories, Author, August 21, 2008

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1 10 100 1 103 1 104 0.2 0.4 0.6 0.8 1 DFAL( ) dp DFTB( ) dp DFHA( ) dp . dp 103

HA AL TB

Fractional deposition efficiency dp (nm)

1000 10.000

Exposure risk NP deposition in respiratory tract

Particle number concentration N Average particle size dp,av Deposited particle surface area S in the lungs

NPs / UFPs

Chemical particle composition, size, and shape (Hazard)

CONFIDENTIAL

Philips Research Laboratories, Author, August 21, 2008

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The Aerasense nanoparticle sensor

Key finding:- particle charge Q(dp) ∝ dp

Air in Current meter attached to Faraday cage for measuring Isensor Fan Air out

Vscr

Vcor

Needle-tip electrode surrounded by a screen electrode

Vpl

Isensor = I1 Isensor = I2 Isensor = 0 time Vpl = V1 Vpl = 0

Precipitation section Charging section Sensing section

CONFIDENTIAL

Philips Research Laboratories, Author, August 21, 2008

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Inferring from sensor signals I1 and I2

• UFP number concentration N (particles/cm3)
• Average UFP diameter dp,av (nm)
• Particle surface area concentrations S that deposit in
• the head airways (SHA)
• the tracheo-bronchial region (STB)
• the alveolar region (SAL)
• Air pollution index P (relative exposure-induced health risk)

CONFIDENTIAL

Philips Research Laboratories, Author, August 21, 2008

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R2 = 0.9992 4 8 12 16 20 200 400 600 800 1000

I1 (fA) Ndp,av*10

• 6 (part.nm/cm

3)

L Nd I

av p

= ∝

, 1

* ,av p appd

N =

1

I C N

app

N app =

Inferring an apparent number concentration Napp from I1

(for particles sized ≈ 10 – 300 nm)

CONFIDENTIAL

Philips Research Laboratories, Author, August 21, 2008

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R2 = 0.996 2 4 6 8 100 200 300 400 500 600

(I1-I2) (fA) N *10

• 5 (particles/cm

3)

Inferring the real number concentration N from I1 and I2

(for particles sized ≈ 10 – 300 nm)

( )

2 1

I I N − ∝

( )

2 1

I I C N

N

− =

CONFIDENTIAL

Philips Research Laboratories, Author, August 21, 2008

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Inferring the average particle diameter dp,av from I1 and I2

(for particles sized ≈ 10 – 300 nm)

R2 = 0.9751 20 40 60 80 100 120 140 2 4 6 8

I1/(I1-I2) dp,av (nm)

N L d

av p

=

, 2 1 1 ,

I I I C d

dp av p

− =

CONFIDENTIAL

Philips Research Laboratories, Author, August 21, 2008

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Inferring the deposited surfaces areas SHA, STB and SAL from I1

(ICRP model for reference worker)

20 40 60 80 100 50 100 150 200 250 Sappha ( ) dp1av Sapptb( ) dp1av Sappal ( ) dp1av . dp1av109

Alveolar region Tracheo-brochial region Head airways dp,av (nm) S (µm2/cm3)

N = 100.000 part/cm3

1 ,

I Nd S

av p HA

∝ ∝

1 ,

I Nd S

av p TB

∝ ∝

1 ,

I Nd S

av p AL

∝ ∝

1

I C S S S S

S total AL TB HA

= = + +

CONFIDENTIAL

Philips Research Laboratories, Author, August 21, 2008

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Inferring air pollution index number P from I1

( )

( )

        =         =

ref ref av p av p

I I Nd Nd P

1 1 , ,

log 2 log 2

• Safe threshold concentration (Ndp,av)ref, ∝ (I1)ref

depending on particle toxicity Assumption:

• Exposure risk ∝ Stotal ∝ Ndp,av ∝ I1

( )ref

I I

1 1 ≥

for

= P

for Relative health risk incurred through exposure can be indicated via P through either a number or a color

( )ref

I I

1 1 <

CONFIDENTIAL

Philips Research Laboratories, Author, August 21, 2008

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Ultrafine particle measurements in outdoor air

P(t)

Outdoor air

P(t) P time (hours) N (part/cm3)

P(t)

Outdoor air

P(t) P time (hours) N (part/cm3)

CONFIDENTIAL

Philips Research Laboratories, Author, August 21, 2008

Comparison Aerasense NP monitor vs. SMPS

Particle number concentration

■ SMPS NP monitor

20 40 60 80 100 19:45 21:45 23:45 1:45 3:45 5:45

time (hh:mm) N*10-3 (particles/cm3)

■

SMPS NP monitor

CONFIDENTIAL

Philips Research Laboratories, Author, August 21, 2008

Average particle diameter

20 40 60 80 100 19:45 21:45 23:45 1:45 3:45 5:45 7:45 9:45

time (hh:mm) dp,av (nm)

NP monitor ■

SMPS

CONFIDENTIAL

Philips Research Laboratories, Author, August 21, 2008

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Conclusions

Proposition of a (portable) NP monitor capable of

• exposure monitoring, both indoors and outdoors;
• relative exposure-induced health risk assessment via Stotal;
• characterizing the NP pollution in terms of N and dp,av;
• assessing the cumulative NP exposure;
• tracing emission sources of NP pollution;
• monitoring effectiveness of exposure minimization measures;
• awareness creation about extent / hazards of the NP pollution

Note: Aerasense monitor on display at the Aerasense booth Wednesday: Additional presentation about equipment