You probably spotted this article: http://www.ehow.com/about_5343595_dangers-silicone-bakeware.html where it states silicone is inert, naturally occurring, and manufacturing pretty straightforward.** The only caution I read is the use of fillers when making a final [inexpensive] product. The article says, twist and if you see white, then fillers have been used. Folks report an odor with these items. Suspect could be more to THAT story.
Sorry I, too couldn't find anything else. Pundits say "foodsafe". I have seen products with silicone gaskets being sold at lots of "green" web storefronts if that means anything. Who knows what we'll know in ten years, though.
Clearly a downside will be what to do with a product when it's past a usable lifetime. Looks like it would end up at the landfill. The extremely high melt point could prove an issue for future recycling. If folks have heard different, would like to know! I would just be careful and look for OVERALL durability of products, as well as the twist test.
Folks like stainless steel, glass (non Pyrex-type) because even when you're done, the material is recyclable.
**EDIT: Please read Sandra's comments below as this info is not correct!
A very interesting question. I was about to post a comment when I saw Jay's reply. The ehow article provides some helpful info. There's just one mistake, and it's in regard to silicone being a natural occurring element. Silicon is the natural occurring element; silicone is a synthetic (man-made) substance that contains silicon molecules in it. So, there's more to the manufacturing process of silicone than just extracting it from the Earth.
Silicone is actually an umbrella term for a number of different substances that contain silicon. So, the silicone in bakeware is different from silicone found in caulk, machinery, and, um, breast implants. The fact that it's a synthetic means that it is less likely to biodegrade. I've heard that some silicones are recyclable, but I don't remember the details off the top of my head.
Whether silicone is toxic is still a topic of debate. It's used in so many different applications (electronics, medicine, cookware, hair products, etc.) that I’m surprised it hasn’t garnered more attention and research. I remember at one time there was a controversy on the safety of silicone gel breast implants. From what I recall, they were banned by the FDA during the height of the controversy but eventually re-approved for use when no definitive study could link silicone to a specific illness (though it has been widely reported that silicone gel injected into the body can cause an intense, localized inflammatory reaction). Other types of silicone are still widely used in medicine (e.g. implanted in the body as part of joint replacement, silicone patches that you stick on the skin for delivering medicines, not to mention its use in menstrual cups, lubricants, etc.).
I'm really curious to hear more about the manufacturing process of silicone. From an environmental point-of-view, it would be helpful to know if producing it is energy intensive and what sort of by-products are made in the process. Right now, I'm realizing I use silicone regularly in my bakeware, in the form of parchment paper or a silicone mat that's used to prevent cookies from sticking to the baking sheet.
When it comes down to it, I think the small amount of information you’ve been able to find in your search is reflective of the little knowledge that we actually have on silicone’s long-term safety and environmental impact. I'll be eying my silicone cookie mat with more suspicion now.
Thanks to you both for the helpful responses. I did see the eHow article, but as Jay mentioned, it didn't answer my questions. I think you made some good points Sandra. I will plan to contact my local recycling to learn more about what they have to say in regards to silicone (probably will just be not to recycle it).
It sound like it's best just to avoid when possible, until or unless it's clear how recyclable and non-toxic it is or isn't.