Sent by Eternal VoyageurEditor: This is a great question. For starters, we'll say that, yes, non-toxic grout sealers do exist. I know you're not interested in particular brands, but we'll throw this out there anyway: AFM Safecoat makes a non-toxic grout sealer, which is formaldehyde-free and contains zero VOCs.
If a grout sealer is non-toxic, it should be labeled as such, or tout itself is being "formaldehyde-free" or low in VOCs. Regarding specific chemicals to look out for and avoid, we compared the Material Safety Data Sheets for both the non-toxic sealer from AFM Safecoat and a traditional grout sealer from Miracle Sealants for more insight.
What we found for the traditional sealer is that, first of all, it had a "hazardous ingredients" entry (which the AFM Safecoat sealer did not), and underneath that it listed "petroleum distillates" with a VOC output of 762 g/L. (As a point of reference, low-VOC is generally thought to be 100 g/L or less.) So, first of all, products containing petroleum distillates should be one tip-of that you should probably avoid it. Secondly, the health hazards section said the material was "toxic" if ingested, and that a "high vapor concentration may cause central nervous system depression." And finally, excessive safety warnings on the label should be another tip you off that the product is no good. The Miracle Sealants MSDS included a paragraph stating that the "grout sealer contains combustible petroleum distillates. All solvents must be considered toxic and must be used in a well ventilated area... Exposure to high vapor concentration must be avoided. Inhaling the vapors can be harmful. Keep away from heat and open flames. Avoid prolonged contact with skin. Chemical resistant gloves should be worn at all times. Keep small children and pets out of area until product or surface has thoroughly dried." Doesn't sound so great, huh?
In contrast, the ingredients list for the non-toxic sealer from AFM included "Water" and a "Potassium Siliconate Solution," which are non-combustable and have a 0 g/L VOC output. The potential hazards section stated that there could be some gastrointestinal irritation if swallowed, but that there were no known symptoms, effects, or medical problems known that could result from over exposure. And importantly, the AFM Safecoat product, when discarded, is "not classified a "Hazardous" waste under RCRA. This product is not ignitable, corrosive, reactive, or toxic; therefore is not defined as hazardous by the EPA." [Emphasis added]
I hope that gives you some insight!
Anyone else have suggestions?