Let me go ahead and ease your mind friend. For any microorganism to grow certain conditions must be met: Temperature and humidity must be high, typically over 85% but ideally over 90%; food must also be present; this food should be in the form of simple sugars. This is one major reason plants store the food for their seeds in the form of starches! And finally, access to water is needed to fuel the fermentation process of breaking down the sugars for food.
Propylene glycol has a magical effect of preventing mold growth. It is used in humidifiers for this very purpose. Along with its emulsifing properties and very low toxicity, PG, even when mixed with water, keeps humidity levels at 70%. It also prevents water uptake by these microorganisms therefore preventing germination of the spore itself. Indeed, PG is a truely magical substance!
Also, if the carto is made of inorganic material as opposed to, say, cotton, that will inhibit mold growth as well.
Hope that makes you feel better!
* Maybe this thread should be moved to the "concerns" forum?
