Atmospheric Nanoparticles - Environmental and Human Health Impacts of Nanotechnology - page 160

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Atmospheric Nanoparticles

Aur é lie Charron 1 and Roy M. Harrison 2

1 INRETS Transport and Environment Laboratory, Bron, France
2 Division of Environmental Health and Risk Management, School of Geography, Earth
and Environmental Sciences, University of Birmingham, United Kingdom

5.1 Introduction

Nanoparticles (NPs) are very numerous in the atmosphere, particularly in urban
areas and close to combustion sources. They dominate the number concentration
of particles in the atmosphere but represent a very small proportion of the atmo-
spheric particle mass. The examination of particle number size distributions at
various European sites showed that 70-80% of atmospheric particles have a size
diameter below 100 nm (Van Dingenen et al. , 2004). The knowledge of physical and
chemical properties of atmospheric NPs is both health and climate relevant. There
is increasing evidence that NPs may be deleterious to human health (Oberdö rster,
2000; Harrison and Yin, 2000; Donaldson and Stone, 2003; Stone (Chapter 9), 2009).
NPs may grow to several hundreds of nanometers in diameter and then act as cloud
condensation nuclei or infl uence the global radiation balance by scattering or
absorbing solar radiation (Yu et al. , 2006 ; Penner et al. , 2006). On the other hand,
increasing particle number concentrations infl uences cloud cover and cloud refl ec-
tivity and reduces precipitation effi ciency (AQEG, 2006).
Sources, transformations and concentrations of atmospheric NPs are discussed
in this chapter. NPs are generally defi ned as particles with one dimension ranging
from 1 to 100 nm; even though, there is no widely used defi nition of atmospheric
NPs. Particles smaller than 100 nm diameter are often called ultrafi ne particles and
they are currently widely measured as particle number concentrations. Here, NPs
are also called ultrafi ne particles or are discussed as particle number counts.