is it Organic? or is it regular soil? you really need to find out what the natural fertilizer source is----then you can determine if it is safe or not...
Potting soil labeled as "organic" contains pulverized poultry droppings as fertilizer. Some of the "non-organic" potting soils contain other sources of fertilizer, some chemical based, but not all of them. There are actually some that contain natural fertilizers but aren't marketed as "organic".
Fertilizers aside, potting soil basically consists of compost material (leaves, sticks) & sphagnum (peat) moss. Many also contain some sand. Many contain perlite, which is a type of volcanically formed glass that is porous. It traps and holds moisture within the potting soil. The perlite are the little white beads that you see in the mix.
If fertilizer is a concern than bagged top soil is a good alternative to potting soil, organic or inorganic. Prepared top soil usually consists of soil (dirt), finely ground leaf and wood compost and lime.
Or you can make your own substrate if you have a source of chemical free soil by adding your own mixture of coconut coir, ground leaves and/or sphagnum or peat moss.