We, as occupants of this beautiful planet, put up with a lot from our chemical-spewing brethren, but we should never have to put up with it in our homes, even if someone else's name is on the mortgage.
I recommend that you seal again with multiple coats of shellac. Shellac is completely organic and inert once it dries in about 1 hour. This should seal the wall.
Then top the shellac with a good clay plaster. Clay is a great purifier and can also help to regulate indoor humidity.
The shellac is dissolved in alcohol, so this may not be something you can apply yourself, but once that is dry, clay is actually good for you. So grab a trowel and get dirty. When the surface is leathery, use a large wet sponge to rub out the imperfections. If you dig a hole, fill it with more clay.
I don't seal my clay walls -- they are more easily damaged that way, but very easily repaired.