Journal of Nanoparticle Research

, Volume 12, Issue 1, pp 21–37

Monitor for detecting and assessing exposure to airborne nanoparticles

  • Johan Marra
  • Matthias Voetz
  • Heinz-Jürgen Kiesling
Special focus: Safety of Nanoparticles

DOI: 10.1007/s11051-009-9695-x

Cite this article as:
Marra, J., Voetz, M. & Kiesling, HJ. J Nanopart Res (2010) 12: 21. doi:10.1007/s11051-009-9695-x

Abstract

An important safety aspect of the workplace environment concerns the severity of its air pollution with nanoparticles (NP; <100 nm) and ultrafine particles (UFP; <300 nm). Depending on their size and chemical nature, exposure to these particles through inhalation can be hazardous because of their intrinsic ability to deposit in the deep lung regions and the possibility to subsequently pass into the blood stream. Recommended safety measures in the nanomaterials industry are pragmatic, aiming at exposure minimization in general, and advocating continuous control by monitoring both the workplace air pollution level and the personal exposure to airborne NPs. This article describes the design and operation of the Aerasense NP monitor that enables intelligence gathering in particular with respect to airborne particles in the 10–300 nm size range. The NP monitor provides real time information about their number concentration, average size, and surface areas per unit volume of inhaled air that deposit in the various compartments of the respiratory tract. The monitor’s functionality relies on electrical charging of airborne particles and subsequent measurements of the total particle charge concentration under various conditions. Information obtained with the NP monitor in a typical workplace environment has been compared with simultaneously recorded data from a Scanning Mobility Particle Sizer (SMPS) capable of measuring the particle size distribution in the 11–1086 nm size range. When the toxicological properties of the engineered and/or released particles in the workplace are known, personal exposure monitoring allows a risk assessment to be made for a worker during each workday, when the workplace-produced particles can be distinguished from other (ambient) particles.

Keywords

NanoparticlesUltrafine particlesWorkplace monitoringNanoparticle monitorUltrafine particle monitorOccupational healthInstrumentationEHS

List of symbols

A0

A parameter defined in Eq. 13

C1

A proportionality factor defined in Eq. 7

C2,C3

Proportionality factors defined in Eq. 19

CAL

A proportionality factor defined in Eq. 26

Cc(dp)

The Cunningham slip factor defined by \( C_{\text{c}} (d_{\text{p}} ) = 1 + {\frac{\lambda }{{d_{\text{p}} }}}\left( {2.284 + 1.116\exp \left( {{\frac{{ - 0.5d_{\text{p}} }}{\lambda }}} \right)} \right) \) wherein λ = 0.066 × 10−6 m, the mean free path of air molecules at atmospheric pressure (1 atm) and 20 °C

dp

The particle diameter (m)

dp,av

The number-averaged particle diameter (m)

\( d_{\text{p,av}}^{*} \)

The assumed (default) number-averaged particle diameter (m)

d0

The particle diameter at which ξq(dp,Epl) = 1 for dp ≤ d0 and q ≥ 1 at the chosen electrical field strength Epl (m)

dpl

The spacing between the electrode surfaces in the precipitation section (m)

DAL(dp)

The fractional deposition efficiency of an inhaled particle of diameter dp in the alveolar region

DHA(dp)

The fractional deposition efficiency of an inhaled particle of diameter dp in the head airways

DTB(dp)

The fractional deposition efficiency of an inhaled particle of diameter dp in the tracheo-bronchial region

e

The elementary charge (e = 1.6 × 10−19 C)

Epl

The applied electrical field strength between the electrode surfaces in the precipitation section (V/m)

fq(dp)

The fraction of all particles of diameter dp charged with “q” elementary charges

Isensor

The electrical current signal measured by the NP monitor (A)

I1

The measured electrical current signal when Vpl = 0 in the monitor’s precipitation section (A)

I2

The measured electrical current signal when Vpl = V1 in the monitor’s precipitation section (A)

L

The particle length concentration defined by L = Ndp,av (m/m3)

Lpl

The traveling length of the electrode surfaces in the precipitation section

N

The total particle number concentration (particles/m3)

Napp

The inferred apparent particle number concentration when a default average particle diameter \( d_{\text{p,av}}^{*} \) is assumed to exist (see Eq. 8) (particles/m3)

N(dp)

The number concentration of particles of diameter dp (particles/m3)

Nion

The number concentration of airborne ions in the particle charging section (ions/m3)

(Ndp,av)0

The safe threshold particle length concentration (particles m−3 m)

P

The air pollution index number defined in Eq. 29

q

The number of elementary charges on a particle

Q(dp)

The average number of elementary charges on a particle of diameter dp

Sdp

A proportionality factor defined in Eq. 17

SN

A proportionality factor defined in Eq. 15

SNapp

A proportionality factor defined in Eq. 9

SAL

The deposited particle surface area per unit volume of inhaled air in the alveolar region (m2/m3)

SHA

The deposited particle surface area per unit volume of inhaled air in the head airway region (m2/m3)

STB

The deposited particle surface area per unit volume of inhaled air in the tracheo-bronchial region (m2/m3)

tr

The exposure time of airborne particles to airborne ions in the particle charging section (s)

vair

The average air speed between the electrode surfaces in the precipitation section (m/s)

Vpl,V1

The applied voltage difference between the electrode surfaces in the precipitation section (V)

σ

The size distribution parameter

ϕ

The airflow through the NP monitor (m3/s)

ϕ*

The reference airflow through the NP monitor (m3/s)

ξq(dp,Epl)

The fractional degree of precipitation of particles of diameter dp charged with “q” elementary charges under the influence of an applied electrical field strength Epl

ηair

The viscosity of air (ηair = 1.8 × 10−5 Pa.s)

Copyright information

© Springer Science+Business Media B.V. 2009

Authors and Affiliations

  • Johan Marra
    • 1
  • Matthias Voetz
    • 2
  • Heinz-Jürgen Kiesling
    • 2
  1. 1.Philips Research LaboratoriesEindhovenThe Netherlands
  2. 2.Bayer Technology ServicesLeverkusenGermany