We may have a sense PLA is a environmental friendly material, but fewer people know how it effects our environment and ourself. PLA (Polylactide) a unique polymer that behaves like Polyethylene Terephthalate (PET), and performs like Polypropylene (PP) in many ways. It's a biodegradable materials that derived from renewable resources, mostly corn starch. Therefore, PLA is safe to be used as cups, bags, holders and everyday goods that may have contact with human bodies and skin.
Eventhough some people are allergic to corn, but it will not effect on PLA products. The reason is the heat used in the process of deriving the starch from corn destroys the immunologically reactive profilin, and this profiling is the chemical that causes allergic reaction.
ABS known as Acrylonitrile Butadiene Styrene has been massive production in Asian countries, and it's been used in wide range of industries and commodities. Under the normal temperature, ABS is not hazardous to the human body. However, heating up ABS materials will produce fumes of acrylonitrile and this reaction predisposes to human carcinogen. ABS grants you a relatively high strength of the material's property. Therefore, it's good to use ABS materials to print out crucial components such as open source 3D printer components, or components that required weight bearing function.