This is the 'short version' of CPSIA for crafters/ small businesses (which is just slightly easier to understand than the long version... ):
http://www.cpsc.gov/ABOUT/Cpsia/smbus/manufacturers.htmlAfter February 2010, if your buttons are UNTREATED wood, they are exempt from testing. However, if they are sealed, they are treated and need testing. If they are untreated, they may end up splintering after washing a few times which really isn't safe...
You can use mother of pearl, shell, stone, or coconut buttons since they are all made out of natural materials. Basically we just need to start getting creative with our material choices to avoid crazy-expensive testing fees.
I am slowly phasing out all non-exempt materials for the February date, but still keeping an eye on the ever-changing legislation. *IF* they pass the 'component testing' then you can use zippers, buttons, etc. as long as the manufacturer has tested the items and you can get the proof of certification...
Hope this helps!