Plastic bottles have been making headlines for leaching chemicals into products. Synergy products are filled in #2, HDPE (high density polyethylene) bottles that do not leach chemicals.
To determine if any of your bottles are safe, check the recyling symbol on the bottle and the number in the center of the circle. If it is a #2 HDPE (high density polyethylene), or a #4 LDPE (low density polyethylene), or a #5 PP (polypropylene), your bottle is fine. The type of plastic bottle in which water is usually sold is usually a #1, and is only recommended for one time use.