sondra, there are many different types of plastics and other synthetic materials that are quite safe to cook with nowadays. my wife just bought me 2 pot holders that appear to be rubber, but are made of a high temp synthetic, so they won't melt. it took me a while to get used to grabbing something hot with a rubbery little mat, thinking it would melt to the handle.
i'm sure the plastic in the steamer is suited for cooking temperatures.
in nomine patri, et fili, et spiritus sancti.
beidh ar la linn.
wisdom is often in short supply within ones' ego.