Peccant: Unhealthy. Causing illness or disease.
"...the subtile parts of the tobacco in inspiration are carried into the trachea and lungs, where they loosen the peccant humours adhering thereto, and promote expectoration." (From the entry to tobacco in the First Edition of the Encyclopædia Britannica, 1771)
The word peccant comes from the Latin peccans, from peccare (to sin, to commit a fault, to stumble). Peccant involves stumbling of a sort -- falling into unhealthy behavior.