Albert, Most of stonetech's water based sealers are almost all environmentally friendly and voc complient. But what I would preach to with green people is thus: if you use a weaker sealer, you have a better chance of leaving contamination behind in your grout, while a better sealer will make cleaning easier and more effective, and the easeir it is the more effective green cleaning products will be and the less often you'll have to use said products. Ergo the minimal exposure to a better product will result in a greatly reduced exposure to their cleaning solutions over the life of the sealer..