What kind of plastic is the bucket made out of? If it's not HDPE (High Density Polyethelyne) or PolyEthylene TerEphthalate (PETE / Polyester) it probably shouldn't be used. If it's any color but white or clear it definitely shouldn't be used. If the plastic was made in China, you're probably going to die
Basically, any plastic that is not not Food Grade can leach more than just flavor into your beer.