Do you know where your 3D printer plastic filament came from? Do you know who produced it, and how they did it? Is it possible you purchased 3D printer filament that was made by children, perhaps in dangerous environments?
It seems that some filament is produced in third world countries by having the poor pick through waste dumps looking for recyclable material, which is then melted down and extruded into filament.
If these matters concern you, you might want to check out the Ethical Filament Foundation, which aims to provide a certification of ethical production for 3D printer filament.
Their goal is to develop a "brand" that can be associated with filament manufacturers that tells consumers that the product has been ethically produced. They'll also work with manufacturers to educate them on appropriate methods of production.
We spoke with a representative and asked whether toxicity would be a consideration. Our belief is that some filaments are colored with lead pigments, making them potentially toxic. At this time, the EFF does not consider toxicity, but we hope they will make it part of their program in the future.