Answer: You will get different answers to your question depending on who you talk to. I can't give you a definitive answer. However, I did some research, and came up with the following web sites. Unfortunately, I only had time to scan them. I suggest you look them over, and perhaps inquire as to where they get their facts--what research results their information is based on. Then you'll have to make your own decision about the safety of the material for your use.
Here is the web site for the Polystyrene Packaging Council. Obviously they are pushing the merits of polystyrene,and I didn't see mention of leaching.
Here is a site (compiled by MIT, I believe) on polystyrene:
The following is a site about the negative aspects of polystyrene; It's hard to tell who maintains the site. Here, they do say that polystyrene leaches "toxic chemicals", though I don't know how or where they get their information.
Here's a site called "Polystyrene and Health".
I'll let you read this information and come up with your own conclusions. If you come up with a definitive answer, I would appreciate it if you would let me know.
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