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How Long Do Bacteria Live After an Indoor Sewage Backup?
Jason Yost • December 9, 2022
How Long Do Bacteria Live After an Indoor Sewage Backup?
When you’ve worked in the indoor environmental industry as long as I have, you hear all kinds of opinions. One large mold assessment company in Florida contends that Category 3 water (i.e., grossly contaminated water) doesn’t require the removal of any building materials because bacteria die once the building has dried. Their theory is that a structural drying company should be able to dry out a building without removing any building materials exposed to such water. Another Florida-based company believes that the bacteria remain indefinitely until removed from the indoor environment. What’s the truth?
Well, the truth is there isn’t a clear answer when it comes to the bacterial decay (i.e., death) rates of these bacteria in water damaged environments. Virtually all research related to the survival of these bacteria has focused on water, manure, sewage sludge, and soil. And all of this research focuses on estimates of survival time for some important bacteria: (All of the following references to this research literature indicates “greater than” (>), meaning the residual organisms were present at the end of each of these experiments.)
Escherichia coli (E. coli) in water > 100 days, in lettuce > 9 – 11 days, and in soil > 60 days.
Enterococcus in dry surfaces > 24 hours
Staphylococcus aureus in dry hospital surfaces > 9 – 11 days
This research indicates that without some form of remediation to reduce the population, the bacteria will remain for a long time. But does that mean building materials should be removed because of high concentrations of these organisms? There are several factors to consider when making that decision, including but not limited to:
- The type and concentration of bacteria in the water and the accessibility to that water for safe and effective removal.
- The bacteria’s ability to negatively impact the indoor environment when building materials are left in place. (Once a contaminated water incident has occurred, the bacteria are not confined to the wet places. They could be on other, higher surfaces, making it important that all surfaces be addressed on such water damages.)
- Occupants’ biological disposition in relation to the environmental stressors and the risk potential. (It should be noted that risk potential can’t be determined by a simple hazard assessment. Testing alone doesn’t indicate risk. It’s a component of risk assessments, but not the single variable in determining risk. In a later blog I’ll touch on the differences between hazard and risk assessments.)
- Public health and environmental and occupational safety and health laws and/or their use of industry-based knowledge.
- The goals of remediation (e.g., the acceptable bacterial load upon completion of remediation).
A collaboration of indoor environmental professionals and the laboratories that they use for analysis, has shown that artificial activities to reduce the population have a quick and impressionable impact on the indoor environmental quality of a water damaged building. For example, a sewage damaged indoor environment where the restorers didn’t remove building materials – just dried the building out – showed a decay rate of 1 log/day. This would indicate that it would take nearly two weeks of consistent drying or atmospheric manipulations (e.g., temperature and humidity controls) to get the bacterial load to generally acceptable levels. (Some showed a slow increase after 24 hours to 2 logs/day, which would put the necessary atmospheric manipulation time to 3 – 5 days, but these drying formulas relied on high temperatures, containment, air exfiltration (to the outside atmosphere) and/or other unique and less common drying practices.) When solids and water were accessed and removed (e.g., through removing obstructing and sensitive (to cleaning) building materials) a 99% reduction in the bacterial load was achieved on day one. When a biocide was used to clean the remaining surfaces, after the removal of solids and water, the bacterial load was at generally accepted loads by the end of the first day.
Based on this collaboration, the removal of some building materials in conjunction with thorough cleaning and structural drying can have an immediate impact on the indoor environmental quality and provide for the safety and health of building occupants. The determination of which building materials are removed, what cleaning products are utilized, the structural drying system utilized, and other administrative and engineering controls requires the one(s) engaged in making these determinations be competent in the hazard and risk assessment processes, the administrative and engineering controls being questioned, laws and standards related to the assessment and remediation processes, and other pertinent variables. Resources like the Institute of Inspection, Cleaning and Restoration Certification’s S500, Standard for Water Damage Restoration, and R500, Reference Guide for Water Damage Restoration and the American Conference of Governmental Industrial Hygienists Bioaerosols: Assessment & Control are available, as well as college courses in industrial hygiene and occupational safety and health. These resources help prepare people for a profession in remediation and assessment.
Gulf Coast Center for Indoor Air Quality Services’ employees are college education, peer-reviewed, Council-certified, and board-awarded in assessment, testing, remediation supervision, and emergency operations and response, so, if you’re faced with the question of whether contaminated water is present in your home or office, or if a conflict, limitation, complexity, or complication arises during the water damage restoration project, contact us and let’s discuss how we can serve you.
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