Is divided into several subgroups according to particle size. PM₁₀ covers all particulate matter with an aerodynamic diameter of 10 micrometre and less followed by PM_2.5 for all particulate matter with an aerodynamic diameter of 2,5 micrometre and less and ultrafine particles with an aerodynamic diameter of less than 0,1 micrometre. In Europe, binding limit values for particulate matter fractions PM₁₀ (daily limit value 50 μg / m³) and PM_2.5 (daily limit value 25 μg / m³) ensure air quality and protection of human health.

Greek pathos - suffering and genesis - origin, a disease causing. All substances or organisms that can cause a disease are summarised as pathogens.

Short for predicted environmental concentration, is a theoretical value giving an indication of the expected concentration of a material (e.g. nanoparticles) in the environment (exposure assessment). The calculation takes into account the amount initially present (or added to) the environment, its distribution in the different environmental compartments, and the probable rates of environmental degradation and removal, either forced or natural.

Refers to a molecule that is composed of 2 or more amino acids linked by peptide bonds (chemical bond between carboxyl and amino group of two adjacent amino acids).

In biology and environmental chemistry, the term “persistence” denotes the property of substances to persist in the environment over long periods of time while remaining unchanged by physical, chemical or biological processes.

Latin pestis - plague and caedere - kill. Man-made chemical substances used to kill, displace or inhibit reproduction of organisms regarded as annoying or harmful. Generic term for all plant protection products and substances for pest control.

Latin, short for pondus/potentia hydrogenii - weight/power of hydrogen. Dimensionless measure of the acidic or alkaline (basic) reaction of an aqueous solution. The pH of a nanoparticle suspension affects the behaviour of particles in the solution (agglomeration, solubility, suspensibility).

Greek phagein - to eat. Mechanism of uptake from particles to small cells in a single eukaryotic cell. Usually, particles are taken up by the cells as membrane-bound aggregates, i.e. large aggregates in vesicles, vacuoles or lamellar bodies (cell compartments surrounded by membranes) through phagocytosis. In mammals, phagocytosis is performed mainly by special cells of the immune system, including the macrophages, monocytes (precursor cells of macrophages), and neutrophils (or neutrophilic granulocytes, belonging to the white blood cells). This uptake is an active, regulated process.

Ability of some nano materials (e.g. TiO₂) to speed up a certain reaction ("photoreaction") as a catalyst in combination with light (sunlight, ultraviolet light). In the case of TiO₂, for example, influenced by sunlight radicals (see also ROS) are formed, which decompose organic materials. This effect is used for self-cleaning surfaces.

Is the ingestion of liquid into a cell by the budding of small vesicles from the cell membrane.

Short for predicted no effect concentration, predicted concentration of a hazardous substance in the environment, which shows no impact on the environment (effect assessment). If this concentration is thus below the PNEC, it should not have any negative effects. PNECs find application especially with PECs in the risk quotient in environmental risk assessment.

Greek poly - more and méros - part, meaning "build from many parts", describes chemical  compounds that are composed from identical or similar units (so-called monomers). These units can be linked to either chains or branched molecules.

Nanoparticles, which can affiliate to a bigger linked system (agglomerate, aggregate).