Fecal sterols: the next-generation sewage indicator. (Technical Briefs).

Assessment and investigation of indoor air quality issues, water damage claims, occupant health complaints, and remediation efforts associated with water incursions all begin with identification of the water source. Proper identification and confirmation of water damage is imperative to the health and safety of occupants as well as to that of the remediation team that restores a structure.

The Institute of Inspection, Cleaning and Restoration Certification (IICRC) * has classified water damage into three categories that take into consideration the source, contents, history, and characteristics of the water:

* Category I--clean water--refers to water that does not pose health risks. The source is water that does not contain contaminants. Examples of clean water sources are broken water lines, malfunctioning appliances, toilet tanks, snow, rainwater, and melting ice. Upon contact with structures, surfaces, and building materials, clean water can progress to Category 2 water.

* Category 2--gray water--refers to water that can pose health risks and contain significant levels of chemical and biological contamination. Discharges from dishwashers, washing machines, sinks, showers, aquariums, and waterbeds are examples of gray water. Extensive gray-water contamination (flooding) or gray water exposed to environmental stresses (time and temperature changes) can progress to Category 3 water in as little as 48 hours.

* Category 3--black water--refers to water containing sewage and other contaminants that can include pesticides, heavy metals, and toxic organic and inorganic chemicals. More than 120 different viruses; parasitic agents such as Giardia, Cryptosporidium, and Entamoeba histolytica; and bacterial organisms such as Klebsiella, Salmonella, Esclierichia coli, and Enterobacter may be found in Category 3 water. Black water originates from domestic and industrial wastes, and nonpoint sources (groundwater, surface water, sea, river, and atmosphere).

Health effects from exposure to gray and black water range from allergic reactions to infectious diseases including gastroenteritis, respiratory infection, eye infections, and inflammation of the liver.

Testing for E. coli, Enterococcus, and total coliforms has been the industry standard for the indication of sewage, black-water and gray-water contamination in environmental samples. Positive results for any one of the three indicators imply the potential presence of disease-causing organisms, sewage contamination, or water pollution. Alternatively, negative results indicate that the microbiological quality of the sample is acceptable.

False negatives can result, however, from exposure to everyday environmental conditions such as elevated temperatures or desiccation, and time sensitivities create analytical limitations. In addition, all three bacterial indicators are highly susceptible to any type of chlorine disinfection.

Research performed by the Environmental Monitoring Division (EMD) of the Broward County, Florida, Department of Natural Resource Protection proposed that Coprostenol, a fecal sterol specific to human sanitary waste, might be a far more reliable indicator of sewage contamination in environmental samples than the traditional microbiological methods. ** EMD focused on the sewage contamination of surface water and waterways in Florida, and the research proved to be instrumental in developing analytical protocols and guidelines for the determination of Coprostenol and other sterols present in human and animal waste. Aerotech has applied the same analytical protocols to the indoor environmental setting. Results from Aerotech's indoor air quality (IAQ) investigation are consistent with those found by EMD.

The study initiated at Aerotech Laboratories involved the contamination of six replicate carpet samples with influent wastewater from a local wastewater treatment facility (Category 3, black water). A negative control with no fecal contamination was also analyzed to show that the carpet was free of contamination prior to the study. The individual contaminated carpet samples were analyzed over an eight-day period to evaluate the presence and survival of fecal contamination as well as Coprostenol.

At Day Zero, immediately after application, the bacterial indicators on the carpet samples were all positive. Once the carpet samples had been exposed to normal environmental conditions, however, the microbial indicators after Day Zero fell below detectable limits. The negative results incorrectly implied that the microbiological quality of the carpet samples was acceptable.

Unlike the results given by microbial indicators, the Coprostenol results remained positive throughout the study, consistently revealing the presence of fecal contamination. The resistance of Coprostenol to typical environmental conditions provided more reliable data.

* Institute of Inspection Cleaning and Restoration Certification. http://www.iicrc.org.

** Department of Natural Resource Protection (1998).

Implementation of a chemical method for differentiating human and animal fecal impacts in surface waters and sediments (Technical Report 98-01). http://www.co.broward.fl.us/moi00708.pdf (9 Dec. 2002).