Synthetic marijuana is a relatively new phenomenon and there haven’t been long term studies on its effect on the user and virtually none on second hand effects. The Center for Disease Control reports based on information from Poison Control Centers, those symptoms can include rapid heart rate, vomiting, agitation, confusion, and hallucinations. Spice can also raise blood pressure and cause reduced blood supply to the heart (myocardial ischemia), and in a few cases it has been associated with heart attacks.
A lot is still not known about all the ways Spice may affect human health or how toxic it is. One public health concern is that there may be harmful heavy metal residues in Spice mixtures. Without further analyses, it is difficult to determine whether this concern is justified.
You have to ask yourself; do you really want to take a chance being exposed to these artificial chemicals. Just look at all the years of research that it took before we learned the significant risks from second hand cigarette smoke.