text: "The odor exposures that have received the greatest research attention are those that involve irritation. Physiological responses to irritation in the upper respiratory trace (nose, larynx) and/or lower respiratory tract (trachea, bronchi, deep lung sites) have been documented in both humans and animals." http://www.pmac.net/AM/sludge_excerpts.html\nI hope I haven't taken this out of context, but I'm sure it can't be good nonetheless. I lived in a rental that had this problem, and had to remove the carpeting and pad, spray the exposed floor with a water/bleach mixture, and allow it to dry before recovering with new carpet.\nBest of luck!