Unclear. Not enough information available yet, but why take the chance? There is no benefit and plenty of risk associated with putting any smoke in your lungs when you don't have to. Most smoke of any kind contains irritants and potential carcinogens so it becomes a matter of how much for how long to determine risk.
Smoking. Smoking tobacco, marijuana, or any other plant or herb will all have toxins and tars when burned or smoked. Depending on what else has been laced with the herbs, other dangerous drugs may be ingested. Herbal cigarettes have not been studied, but cancers would be likely if smoked like tobacco.
Beware. What is a herbal cigarette? Be careful and skeptical of marketing claims by the tobacco industry. The so-called herbal cigarettes may have tobacco and have the same risks as conventional cigarettes. Even if these do not have tobacco, inhaling products of combustion is not good for your airways and lungs.