Barkeeper's Friend: Is it Safe?

A few weeks ago, commenters on The Best Way to Clean Your Bathtub were giving rave reviews about a product I'd never heard of—Bar Keepers Friend . I researched it a little, and found that its active ingredient is Oxalic Acid – which is naturally derived and found in lots of green leafy things. Intriguing. . .

I had to try it out. I picked up a can of the powdered variety, and Holy Clean Pots, Batman!

Yep, it definitely works.

My favorite stainless steel pot was all brown on the bottom and now. . .well, it's not "as good as new," but it's pretty darn good all the same. BKF also took a rust ring out of my stainless steel kitchen sink. (Who's the wiseacre that left the cast iron skillet in there overnight??)

You know, we eat oxalic acid all the time in spinach, carrots, and a bunch of other things. But it's the reason that rhubarb leaves are considered poisonous—too much can cause nausea, kidney stones/failure, and even be fatal.

So the question remains, just how safe is Bar Keepers Friend ? 

Here's what I've read about it:

• The MSDS is rather dire about oxalic acid, citing it not only as toxic when taken internally, but a dangerous skin, eye, and respiratory irritant.
• Oxalic Acid can be absorbed through the skin.
• Commenters on a number of blog posts about BKF have cited peeling skin after use.
• Of course, being in crystal form in a cleaning powder, the oxalic acid is probably much more concentrated than what you would find in plants.
• The MSDS on Barkeeper's Friend seems to indicate that oxalic acid constitutes just 5-10% of their powder by weight. (Am I reading that right?? I wonder what the other 90% is, then.)

These are my thoughts on it:

• Barkeeper's Friend is definitely a poison. But then again, you wouldn't drink your bleach or dishsoap either, would you?
• It seems like it isn't bio-accumulative, since it's flushed out through the kidneys.
• I used BKF before I read anything about it being a skin irritant. So I didn't use gloves. . .But I didn't notice any unusual reactions to it.
  
•  It also seems pretty negligible as a respiratory irritant. The stuff dissolves in water so readily that you'd almost have to be deliberately snorting it to inhale it.
• It does concern me that it can be absorbed through the skin. I think I wouldn't use it for a large job—like cleaning the shower—where there would be prolonged exposure.
• I also think I wouldn't use it for surfaces that come in direct contact with food. (Dishes, cutting boards, whatnot.)

Overall, it seems to me that Bar Keepers Friend does have the potential to be very toxic, so I will probably reserve it for just the toughest jobs—badly stained stainless steel, for instance. It's highly effective, and I think in small doses it shouldn't pose any health hazards.

What do you think of Barkeeper's Friend? 
Does it belong in the Green Cleaner's repertoire?

Note:  I'm not a licensed anything! So definitely use your own judgment about Barkeeper's Friend, and you use it at your own risk!
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