3. How can exposure to nanomaterials be measured?
The most reliable currently available methods are for measuring the intake of nanoparticles via iar (lung) exposure by inhalation. These are based on established techniques for assessing exposure to other kinds of very small particles (also known as ultrafines), such as those produced by fires or diesel engines. This gives some basis for understanding how nanoparticles travel in the atmosphere. However, such methods do not distinguish between natural and man-made particles, so it is hard to separate exposure to manufactured nanomaterials from other kinds.
Exposures to nanoparticles may also occur through contact with liquids and solids, as in some food and consumer products. Exposure assessments normally focus on workers, consumers, or the general public. Workers are generally at risk of breathing in man-made nanoparticles. Consumers and the public may also be exposed by swallowing them or through skin absorption.
These routes are not completely distinct because some of any particles which are inhaled will pass into the stomach after removal from the lungs in mucus which is then swallowed.
Techniques exist to assess nanoparticle exposure, and they are suitable for personal or area-based monitoring, continuous or discontinuous use, and basic characterisation of samples. However, the literature on measurement strategies for assessing exposure to manufactured nanomaterials is currently very limited. Data on airborne exposures are scarce, and there have been few if any studies outside the workplace.
Exposure estimates from food and consumer products also remain difficult. Information on the presence of manufactured nanomaterials comes from manufacturers. There is also limited information about product use, and multiple products may contain similar nanoparticles.