5 1/2 months pregnant -is it safe to use trisodium phosphate to clean the walls before painting the nursery? Or should my husband do it solo?

Probably fine. Tsp is actually used as an approved food additive in the us and eu and in low doses has no toxic effects.The dry powder is caustic to the GI tract and fumes may produce superficial irritation or cough. Your body will dispose of any irritant issues before it could ever get to baby. If you use it in a well ventilated space its irritant quality will be minimal.If you want daddy to do it solo, let him.