Air Krete's makeup is unique, and it doesn't contain harmful materials. It's made from air, water and magnesium oxide (MgO) cement. When seawater reacts with limestone, it creates magnesium hydroxide, or Mg(OH)2. This is milk of magnesia, and while it might be great for your upset stomach, it's not so good for the R-value of your walls.
However, the process of electrolysis splits off a water molecule, creating H2O and MgO, which is, in fact, good for the R-value of your walls when it's blown in, allowing the paste to trap bubbles of air. And because MgO is used in many vitamin supplements, it's safe for you to breathe in.