Human exposure to conventional and nanoparticle--containing sprays-a critical review.

The release of pesticides from conventional spray products has been investigated in depth, and suitable analytical techniques detecting the mass of the released substances are available. In contrast, nanoparticle-containing sprays are less studied, although they are perceived as critical for consumers because inhalation exposure can occur to potentially toxic nanoparticles. A few recent studies presented analytical concepts for exposure experiments and generated data for exposure assessment. This study attempts to review and compare the current approaches to characterize nanosprays and to identify challenges for future research. Furthermore, experimental setups used for exposure assessment from conventional sprays are reviewed and compared to setups used for nanoparticle-containing sprays. National and international norms dealing with nanoparticle characterization, spray characterization and exposure are inspected with regard to their usefulness for standardizing exposure assessment. Different approaches in the field of exposure modeling are reviewed and compared. The conclusion is that due to largely varying experimental setups to date exposure values for nanosprays are difficult to compare. All studies are only conducted with a limited set of sprays, and no systematic evaluation of the study conditions is available. A suitable set of experimental setups as well as minimum reporting requirements should be agreed upon to enable the systematic evaluation of consumer sprays in the future. Indispensable features of such experimental setups are developed in this review.