Atmospheric pollution caused by humanity since the industrial revolution is not only gaseous; solid particles are also emitted (atmospheric particulate matter).

The combustion of organic matter creates what is known as a reducing environment, because there is little or no oxygen. This and the high temperatures involved in combustion cause the formation of millimetre- to micrometre-sized balls or fragments composed of strongly magnetic minerals, heavy metals and non-magnetic minerals (see pictures below). Once they are emitted into the environment they represent an acute health risk and also a latent potential source of soil pollution after they have sunk to the ground.

Magnetic minerals formed during combustion have different properties than those caused by soil formation or those that sink to the ground as natural dust, e.g. Sahara dust.