The comment above is indicating issues with the pigment, rather than the solvent used to disperse it. You can have very toxic water-based paint, see watercolors

The comment above is indicating issues with the pigment, rather than the solvent used to disperse it. You can have very toxic water-based paint, see watercolors with cadmium etc. That being said, it's completely plausible to mix eg chalk with something non-toxic that also doesn't wash off so quickly.