Depending on their size, dusts penetrate more or less deeply into the respiratory system: the largest are retained by the upper airways, while the finest reach the lower airways and can impair respiratory function as a whole. Particles reduce the effectiveness of defence mechanisms against infections and interact with pollens to increase sensitivity to allergens. Some also act as vectors for various toxic or even carcinogenic or mutagenic substances (metals, PAHs, etc.), which are then likely to enter the bloodstream.
The effects on the environment are the most obvious: particles contribute to the physical and chemical degradation of materials, buildings, monuments, etc. Accumulated on plant leaves, they can interfere with photosynthesis.