ALL materials are toxic, it just depends on the dose received.
From what I can tell, acrylics should be relatively safer than enamels, considering the kinds, types and characteristics (e.g.,volatility, concentrations, etc.) of the base solvents. Regardless of the type of paints used, precautions such as respirators, opening windows, turning on fans, and using a spray booth should be employed during painting sessions.
Based on what little I know about particle dynamics, I don't think that there should be any concern about acrylics coating the lungs over time. Solvent vapor inhalation is the primary concern, IMHO.
I think there are some "non-toxic" acrylic craft paints, but that is based upon the primary intent of use (i.e. brushing, where the primary hazard would be skin contact and ingestion--important considerations for childrens' paints). In addition, the removal of heavy metals like cadmium, chromium and lead also lend a hand toward a reduced toxicity paint, but I think any time you start spraying, you increase the risk of potential toxicity through solvent vapor inhalation by a couple orders of magnitude.
Gip Winecoff