Environmental exposure refers to exposure of the population outside the occupational context (see Chap. 6.4) and excluding also medical exposure. The kind of exposure discussed in this chapter is due to the presence of nanoparticles in the various environmental compartments, such as the air (indoors or outdoors), water (water for drinking, bathing, etc.), soils, foodstuffs, and so on. These nanoparticles may come from the nanomaterials that contain them and upon which they bestow specific novel properties, or they may be formed unintentionally by human activities such as industry, traffic, domestic fuel combustion, etc., or natural phenomena such as forest fires, for example, or again by physicochemical reactions, e.g., the reaction between gases and particles in the air, spray formation, vapour condensation, and so on. This book is concerned with the former, namely manufactured nanoparticles, but the related questions and acquired knowledge must often be viewed from the perspective of what is already known about the latter, commonly referred to as ultrafine particles.
