Sewage Contamination

Nothing disrupts your life like sewage backup or overflow. It Stinks! In the next couple of blog posts we will explore why a sewage loss is so-so bad. (Yes, besides the obvious) We often times have clients that have a simple sewage back up contained to the bathroom and are reluctant to have us follow proper sanitization and cleaning processes. That is code for: I really don’t want to replace drywall and flooring just because “a little doo-doo has been sitting in my bathroom for several hours or days.” Yes! Really clients do say this… read on… and you’ll never thinking twice about incorporating proper sanitization and cleaning protocols.


When a building is contaminated with sewage backing up from the septic lines, or flooding of a building occurs that involves sewage, a serious threat to human health exists. Extensive damage to contents and structural materials will occur immediately or in time without appropriate action. If time passes extensive contamination and permeation of absorbent materials such as concrete, paper, gypsum and wood will occur. This penetration with organic matter (sewage) and water leads to the growth of potentially ailment-causing (or opportunistic) microorganisms. These kinds of bacterial organisms may pose a serious health risk to occupants of the building. Organic matter and water-saturated materials can be used as platform for growth of microorganisms that are lethal to humans and are hazardous to materials.

Some of the questions to be answered in this situation include the following: What are the effects of the initial contamination of the building, its contents, and the health and welfare of its occupants? To thoroughly clean up the contamination and repair the damage, what is needed? Should the whole building or just a part of the building be evacuated and for how long should this last? Can semi-porous materials be sanitized and freed from contamination, or should they be replaced? What is the trade-offs of using insufficient measures to remediate the damage? What are the indicators that help show when the building is safe or not safe for people to move it? What procedures should be used to test for these indicators? What is the effect of the sewage damage on other systems, especially the air changing systems (ACS) and the heating, ventilating, and air conditioning (HVAC) systems in the build environment?

There are several factors that are related to the remediation of the problem. Among these are the nature of the contamination, the types of water-damaged materials (organic or synthetic; porous, semi porous, or nonporous), the sewage micro flora (pathogens and allergens), organic matter load, water volume, and impact of ambient outdoor temperature and humidity on the indoor environment. Of major concern is the survival of sewage-borne micro flora (viral, bacterial, fungal, parasitic, and their potential transmission to
humans. The potential exists for some fungal and bacterial contaminants to establish an ecological niche and present a health risk from chronic exposure for some time after the event.



Now What?

The factors that determine the extent of contamination within the building include the volume and the solids content of the sewage backflow, whether flooding is isolated or involves other areas as well, and how long the contamination has been in place. The assumption must be that potential pathogens are present in the contamination. Such microbial contamination includes bacteria, fungi, viruses, and parasites. This lists the micro flora that may be found in raw, untreated sewage and the diseases that these organisms have the potential to cause. Also, hypersensitivity lung disease has been shown to be caused by repeated flooding of homes with sewer water.

The routes of exposure of the building occupants to these pathogens are contact, ingestion, and inhalation. An incomplete or inadequate job of cleaning and disinfection may leave residue that can be a substrate for disease-causing microorganisms. Occupants may be infected by contacting contaminated surfaces, with inadvertent transmission from hands to mouth, or aerosolization of contamination may result in the inhalation of microorganisms or their products (e.g., endotoxins). Residue and microbial contaminants also can be tracked by occupants’ feet to other parts of the building.


Another aspect of health impact is that the conditions caused by sewage backflow are conductive to the growth of nonsewage microorganisms. These conditions include wetness, humidity, and organic matter. Microorganisms, which exist in various life stages in both indoor and outdoor environments, would then have the opportunity for exponential population growth. These species can produce bioaerosols, which are potential sources for disease. For example, mold allergy is a common source of indoor air symptoms and complaints.

In regard to the susceptibility of building occupants, those individuals whose immune systems are in some way compromised (i.e., immune and compromised), or who are otherwise susceptible due to age, medication, or underlying illness, are considered to be at greater risk of contracting potentially fatal infections than those individuals who are healthy.

Next time we will explore the General Precautions for Sewage Contamination on Residential Property.