1000-Year Flood Events – Commonplace Occurrences?
This year’s storm experience in South Carolina is the sixth 1000-year flood in the past five years according to a USA Today report. What had seemed extraordinary is becoming common. These seemingly perpetual storms across the U.S. cause a multitude of problems. One significant result is the presence of biological pathogens (such as bacteria, fungi, viruses, and protozoa) found in structures damaged by floodwaters. Structural pasteurization to dry and sanitize may be the best restoration process available.
Structural Pasteurization of Flooded Buildings
A process for a safe and effective sanitization of structures impacted by floodwaters is needed. Pasteurization, a process used successfully for 150 years in food products, can be applied similarly to structures for disinfection. IICRC documents recognize “Structural Pasteurization”, but do not fully express the benefits. By reaching temperatures lethal to many of the pathogens associated with floodwater contamination, ThermaPureHeat® “pasteurizes” structures. ThermaPureHeat® is the most effective application of structural pasteurization.
Buildings impacted by floodwater are Category 3 water losses. Category 3 is defined by the IICRC as “grossly unsanitary”. Structural pasteurization as a part of the drying process can return the structure to pre-loss conditions. Structural pasteurization with ThermaPureHeat® is one of the most thorough restoration processes because of both efficacy toward the target pathogens and the ability to penetrate inaccessible areas. This process does not use chemicals or biocides and therefore no additional hazards are added to the space. It is unique as a restoration process because it thoroughly dries the structure and kills the unwanted pathogens and their insect vectors.
Floodwaters Present a Severe Hazard
In the current aftermath conditions from these most recent storms, the extensive flooding will create a significant environmental health concern. The potential contaminants in floodwaters include a variety of biological pathogens. These pathogens present the opportunity for a number of water and excreta-related health problems and diseases for a significant period of time. Many of these pathogens can remain viable in a structure for up to a year. Some can remain longer in a moist environment. As structures dry, many become aerosolized and migrate throughout the building. Rodents and insects also act as vectors transporting these pathogens throughout a structure. Disinfection of flooded structures is a complex and demanding problem.
Floodwaters present non-biological contamination problems as well. Gasoline, pesticides and other chemicals may be carried by water into structures. The volatile organic compounds (VOCs) associated with many of these chemicals present a potential hazard to occupants as they slowly off-gas over the next several months. Structural pasteurization can speed up the process of off-gassing by increasing the vapor pressure of the impacted material. Chemical vapors are typically exhausted, but under certain conditions must be captured through carbon filtration.
Pathogens Found in Floodwater
Typical assessment of pathogens found in floodwater focuses on the measurement of coliform bacteria. The presence of coliform bacteria is used as a yardstick for the assumption of biological contaminants in structures impacted by floods or other sewage contaminated water. Although this assessment is generally adequate to determine the presence of sewage related biological pathogens, it may not be adequate to determine the appropriate remedial response for the structure. Some floodwater pathogens may be more difficult to kill or reduce to safe levels.
Recent studies of E. coli contaminations indicate that there is a possibility of human infection up to ten months after the original contamination.[i] Other species may have even greater durability. Salmonella, for example, has a longer life outside of the host and therefore has the potential of infecting a larger number of species, including flies, cockroaches and other vectors. This may be true of other microbes as well. It is important to understand that floodwater contaminated structures can remain a health concern for a long period of time. This is particularly true if the building is not properly dried and remains moist or wet. In fact, the conditions will worsen for a period of time. In addition, most buildings are a catalyst for insect infestation.
The bulk of data used in this paper regarding pathogens in floodwater is found in studies provided to assist in the management or design of water supply and sanitation systems.[ii] Because of the size and magnitude of some of the hurricane floodplains the contaminated water and attendant pathogens are most likely comparable to sewage contamination. Efficacy studies regarding the thermal death rate of floodwater pathogens are derived from these sources.
Pathogens found in buildings affected by sewage-impacted floodwaters include bacteria, viruses, protozoa, and helminthes. According to the World Health Organization (WHO) these pathogens impact human health. Although it is not the purpose of this paper to understand specific health concerns associated with these pathogens, it is the intent to understand the resolution – structural disinfection of floodwater contaminated buildings. Included in these categories are a few of the assumed water and excreta-related pathogens.
|Nematodes – roundworms,
Cestodes – tapeworms
The potential for infection of occupants in a structure comes from various vectors. The vectors found to transport or transmit these pathogens in buildings include[iii]: feco-oral, water-washed, water-based, excreta-based insect and rodent vectors, and aerosol.
The importance of this is to demonstrate the dynamic nature of a floodwater-contaminated building. Occupants can be affected by a wide variety of routes and vectors making the resolution more complex. ThermaPureHeat® is the only process that effectively treats all of the pathogens present as well as impacting the vectors and routes, while drying the structure.
Thermal Inactivity of Specific Floodwater Pathogens
Temperature is a more thorough intervention process in the inactivation of enteric pathogens. According to the WHO, “…heating to pasteurization temperatures (generally 60C) for periods of minutes to tens of minutes will destroy most waterborne pathogens of concern”[iv]. This general statement may be adequate to recommend utilization of heat for the disinfection of floodwater-impacted structures. However, for the purpose of this paper, more specific targets have been identified to further define the efficacy of the process. The following table shows specific pathogens that can be rendered inactive by temperatures within the range of structural pasteurization:
|Escherichia coli||Bacteria||60C/140F||45 minutes||Padhye & Doyle[v]|
|Enterococcus faecium||Bacteria||60C/140F||<45 minutes||Spelina[vi]|
|Giardia lamblia||Protozoa||60C/140F||2-3 minutes||Univ of Utah[ix]|
|Entamoeba hisolytica||Protozoa||60C/140F||1 minute||Feachem[x]|
|Rotovirus||Virus||63C/145F||30 minutes||G.N. Woode[xi]|
|Ascaris lumbricoides||Helminths||55C/131F||1 hour||Feachem[xiii]|
Application of the ThermaPureHeat® Technology
The efficacy of ThermaPureHeat® in its simplest form is a result of the combination of temperature and duration. The complexity of any thermal sanitization is achieving efficacy in all areas of the structure. What differentiates ThermaPureHeat® is the ability to sanitize the entire structure, including inaccessible areas and difficult areas such as crawlspaces.
Buildings are complex and the requirement for uniform temperature throughout a structure is necessary to achieve efficacy. Heat technicians are thoroughly trained in construction materials, thermal dynamics and the intended targets. Buildings have materials that conduct heat, some that create radiant losses, and others that are heat sinks. The heat technician must understand each of these conditions and others. Temperatures are monitored in real-time in all areas including difficult to heat locations. In a wooden structure these places might be under sill plates, between header boards, and in wall cavities. Crawlspaces and sub-areas provide additional difficulties. ThermaPureHeat® can treat all structures. Additionally, this process typically includes laboratory testing to document the reduction of bacteria following treatment.
The process of pasteurization of a structure appears to uniformly impact these pathogens related to floodwaters. Other methods of disinfection are not as uniform in result. For example, Giardia cysts are resistant to chlorination and a wide range of pH.[xiv] Other methods may not be ovacidal, for example with some helminths, such as Ascaris, the eggs are more resistant than the larvae. Other processes are not as safe or not as effective, or both. Heat, as a disinfectant, is uniform and non-discriminatory in application. Pasteurization of a building is an effective process to reduce pathogens to safe levels.
Structural Pasteurization with ThermaPureHeat
All buildings affected by floodwaters should be sanitized. The most thorough method is structural pasteurization with ThermaPureHeat®. It is a patented, non-chemical, engineered process that “pasteurizes” structures. This process is the most effective because it is the only process that kills or inactivates the majority of pathogens present while thoroughly drying the structure. Additionally, it is the only treatment that inactivates pathogens in inaccessible areas. It prevents pathogens from vectoring by other sources. Vector sources include aerosol, rodents, cockroaches, and other insects. Added value for the process is the reduction of VOCs that may have resulted from chemical contamination associated with the floodwaters. Much like the pasteurization of food products, ThermaPureHeat® reduces the biological contaminants in a structure to levels safe for occupants.
Larry D. Chase, Consultant to ThermaPure, Inc.
Original article reviewed by Sean P. Abbott, Ph.D., E-Therm Inc., Scientific Advisory Board
[i] Varma, J.K., et al, (2003). “An outbreak of Escherichia coli infection following exposure to a contaminated building”. Journal of American Medical Association, 290(20), 2709-2712.
[ii] Feachem, R. et al,(1983). Sanitation and Disease Health Aspects of Excreta and Wastewater Management. Wiley, Dorchester, England.
[iii] Mara, D.D., Feachem, R.G.A., (1999) “Waterborne and Excreta-Related Disease: Unitary Environmental Classification”, Journal of Environmental Engineering-ASCE, 125 (4), 334-339.
[iv] Sobsey, M., (2002) “Managing water in the home, accelerated health basis of improved water supply”, World Health Organization.
[v] Padhye, N.V. and Doyle, M.P. 1992. “Escherichia coli 0157:H7: Epidemiology, pathogenesis, and methods for detection in foods”. J. Food Protect. 55(7):555-565.
[vi] Spelina, et al, (2007). “Thermal Inactivation of Enterococcus faecium, National Institute of Public Health, Prague, Czech Republic.
[vii] Feachem, R. et al, (1983) Sanitation and Disease Health Aspects of Excreta and Wastewater Management, Wiley, Dorchester, England, p278.
[viii] Feachem, R. et al, (1983) Sanitation and Disease Health Aspects of Excreta and Wastewater Management, Wiley, Dorchester, England, p294.
[ix] Wilderness Medicine, (2005) University of Utah, School of Medicine.
[x] Feachem, R. et al, (1983) Sanitation and Disease Health Aspects of Excreta and Wastewater Management, Wiley, Dorchester, England, p342.
[xi] Feachem, R. et al, (1983) Sanitation and Disease Health Aspects of Excreta and Wastewater Management, Wiley, Dorchester, England, p188.
[xii] Feachem, et al, (1983)
[xiii] Feachem, et al, (1983).
[xiv] Feachem, et al, (1982) p354.