note: I was writing this as an e-mail, but then thought more people might be interested.
You might think we're paranoid, but Stephen and I just finished a book called In the Name of Science which discusses human experimentation over the past 100 years. In the book the author discusses in detail the accidental or intended exposure to chemicals either by cooperate or government officials and their results. So as long as this book is fresh in my memory, I don't intend to simply trust a product because it is on the market.
Stephen and I have consolidated our pans so that we don't need to use teflon pans, though we still use our wok that is non-stick which has the same effect when heated to certain temperatures. My parents have gotten rid of all of their teflon pans and only use stainless steel.
anti teflon article:
pro teflon article:
It's still debated as to the actual affect of Methylisothiazolinone (MIT), but still it seems worth avoiding anyway just in case, especially when pregnant. (besides, shampoos that are cheaper usually don't have this chemical)
http://www.naturalnews.com/005342.html (this is quiet anti, but in less technical terms)
As far as tuna, it seems that children and women who are pregnant/nursing/planning on getting pregant in the near future should avoid too much (my dad said not more than once a month before I was even pregnant).
MSG is less of a conern, but its controversial, though most studies I've seen now and in the past have suggested that it is safe, even in large quantities. Though in reality, food with MSG is simply unhealthy and should probably be avoided for that reason alone. But hey, I love my oriental ramen noodles.
I know these articles aren't all that scientific or the best sources, but I was making a quick search. Feel free to delve deeper into the issues and inform me what you find.