Breathing sewer fumes can make a person sick, according to the Wisconsin Department of Health Services. Sewer gas is a potent mix of several poisonous gases that can cause dizziness, headache, drowsiness and asphyxiation.
Sewer gas typically contains carbon monoxide, nitrous oxide and sulfur dioxide, states the Wisconsin Department of Health Services. In addition, municipal sewer systems often contain chlorine bleach and other industrial solvents. One of the primary risks associated with prolonged exposure to sewer fumes is hydrogen sulfide poisoning. Not only can exposure to this gas cause dizziness and headache, but high enough concentrations can interfere with a person's sense of smell, making detection unlikely. If hydrogen sulfide levels grow even higher, immediate loss of consciousness and eventually death can occur.