What are nanoparticles or ultrafine particles?
There are different sizes of liquid and solid particles in the air.
Particles are divided into different fractions according to their size.
A distinction is made between particles with a maximum diameter of 10 micrometres (µm) and so-called ultrafine particles with a diameter of less than 0.1 µm (100 nm nanometres).
In contrast to ultrafine particles, nanoparticles are usually man-made particles with special material properties. Nanomaterials are therefore primarily a potentially hazardous substance in the industrial workplace.
What are the origins of ultrafine particles?
The main sources of ultrafine particles are emissions from motor vehicles, power and heating plants, airports, domestic furnaces and heating systems, and metal and steel production.
In urban areas, road traffic is the dominant source of ultrafine particles. They are emitted into the air not only from engines, especially diesel engines, but also from brake and tyre wear. Indoor sources include cooking and heating with stoves.
There are also isolated natural sources, such as evaporating salt water droplets near the sea, from which a small salt particle remains in the air.
Increasing attention is also being paid to gaseous precursors that transform into ultrafine particles in the atmosphere with a delay, known as secondary aerosols.
Why are ultrafine particles dangerous?
Because of their very small size, ultrafine particles can penetrate deeper into the respiratory tract than larger dust particles.
This allows them to reach areas where they cannot be exhaled and to enter the bloodstream via the alveoli.
Initial toxicological studies suggest adverse effects on the respiratory and cardiovascular systems.
Why is particle matter PM a bad measurement unit for ultrafine particles?
Several laboratory studies have shown that, on a mass basis, smaller particles appear to be more toxic than larger particles. This is due to the greater surface area of smaller particles:
The particle surface is where our body interacts with the particles. Particles can transport toxins adsorbed on their surface, or their surface can act as a catalyst inside a cell, generating reactive oxygen species (ROS). If you have a lot of small particles, their total mass is very small, but their surface area is huge. So you are greatly underestimating the toxicity. It is better to measure their surface area or at least count the number of particles, which gives the particle number concentration.
In addition, mass-based instruments often use optical principles. Because optical particle detection is limited to the wavelength of light, which is limited to ~300nm, smaller particles cannot be seen. They simply cannot be detected.
The partector 2 on the other hand, usese an electrical principle to detect ultrafine particles and can detect particles down to 10nm.