Post-flood health risks

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Record rainfall, heavy snows, and severe storms have made floods a reality for millions of Americans in recent years.  Inspiring examples of communities united in their efforts to stem the rising waters, and heartbreaking footage of people returning to their devastated homes, are familiar to all. Yet, once the waters recede, and people begin to reassemble their homes and their lives, they are not "home free.  " Dangers to health – some of them invisible – still lurk in water-damaged buildings.

Although the water damage induced by violent acts of nature are dramatic, they are not the only source of water damage indoors.  Leaky pipes, inadequate ventilation, and condensation can lead to mold and fungal growth that is hazardous to human health.

Molds and fungi permeate the natural environment, including homes.  When moisture from any source exceeds a certain level, molds that generally occur at extremely low levels proliferate to dramatic – sometimes naked-eye – visible levels.  This can create a real health hazard: Depending on the variety, molds and fungi can be directly allergenic (and thus hazardous to allergic and asthmatic people), can produce many toxic and allergenic chemicals, can infect humans with fungal diseases, and can induce illnesses (including cancer) through the toxins they produce.

[For more information on the health effects of molds and fungi, see The Human Ecologist, Spring 1997 #73 – see HEAL’s Back Issue Guide for ordering information.]

When it comes to natural disasters, the hazards that are most obvious – fouled drinking water, downed electrical lines, broken gas pipes, and teetering structures – are well recognized and well managed in affected communities.  Similarly, buildings that have survived fire-fighting efforts are inspected before occupants are allowed to return.  But after the water supply and utilities have been restored, and buildings have been declared structurally sound, people may return to homes that are anything but livable.  If contaminants related to the water damage are not adequately controlled, severe illness, and even death, may result.

An example of just how moldy wet buildings can become: After the 1993 flood, researchers at Washington University School of Medicine in St. Louis Missouri surveyed homes in the region, some of which had been damaged in the floods, and some of which had not.  They found mold levels in undamaged buildings at fewer than 750 spores per cubic meter (pcm).  Flooded buildings that had not been decontaminated contained from 13,600 to 453,750 spores pcm.  Decontamination did not reduce mold spore counts to pre-flood levels: the researchers found from 23,400 to 77,574 spores pcm in partially decontaminated buildings, and even buildings that had been extensively renovated and decontaminated had much higher levels than unflooded buildings – at least 7700 mold spores pcm (over 10 times the levels in unflooded buildings).

The researchers said that boarding up water-damaged buildings creates the dark, dank conditions that are perfect for mold growth.  They think that once microscopic mold spores permeate the building, complete decontamination is extremely difficult.  They also noted the following: CLEANUP EFFORTS CAN ALSO BE UNDONE BY BUILDING-OCCUPANT REINTRODUCTION OF WATER-DAMAGED MATERIALS INTO THE CLEANED UP BUILDING.

Obviously it’s important to know how to minimize water-related damage in buildings.  But where to begin?


Help for people returning to water-devastated homes

Excellent information about post-flood repair and rehabilitation has been posted on the Internet by the American Red Cross ("Repairing your flooded home").  We recommend that the Red Cross document be supplemented by a fact sheet available (also on-line) from the EPA on flood clean-up.  Contact both the American Red Cross and the EPA for availability and ordering information for these documents through the U.S. mail.

NOTE: Where the Red Cross and the EPA differ in their recommendations, it is usually on the issue of what kinds of materials can be safely decontaminated and turned to use in the home.  In general, EPA's recommendations are more conservative, recommending more materials for discard than for restoration and re-use.  Following EPA’s guidance in these matters may provide an extra margin of safety in deciding what to discard and what to keep from a flood-damaged building.

The guidance given in the Red Cross and EPA documents is considerably reinforced by the information that follows.  In some cases, our recommendations are even more conservative than EPA’S.  We believe that these recommendations offer good, but not necessarily fail-safe, strategies for preventing mold overgrowth in water-damaged buildings.  Regardless of which advice you follow, it is essential that you come to grips with the idea that making your home livable isn't just a matter of drying it out, cleaning it up, and moving back in.  You also must take steps to avoid water-related health problems that can occur long after you resume living a normal life in your home.


It's essential to clean and protect your home's ventilation system.

In order to understand why the ventilation system is so important, it may be helpful to think of flood-related molds as being infectious agents.  Like the germs breathed by a person with a cold, the air that moves through the home ventilation system distributes contaminants from "inside” – within the ventilation ducts and fans.  Even worse, the ventilation system also stirs up whatever contaminants are already in the living spaces.  Contaminants from within the ventilation system and from affected parts of the building can then spread throughout the building, contaminating parts of the building that were unaffected by the flood itself – and contaminating the ventilation system. This sets up a vicious circle of contamination.

A Chicago-based indoor air quality consultant told Indoor Air Review (a trade publication for air quality professionals) in June 1993 that if patches of mold growth are visible on indoor surfaces, immediate steps should be taken to protect the ventilation system from further contamination.  If the duct work itself has been flooded, it should be cleaned of mud and debris, the ducts flushed out, and the coils and fans pressure-washed.  Once the ventilation system has been cleaned, it must be protected from contamination while the rest of the building is rehabilitated.

NOTE: Environmental consultants note that porous insulation material inside ductwork is extremely difficult to clean under the best of circumstances.  If ductwork containing this type of insulation has been flooded, it may be wise to remove the insulation, as well as the debris and dirt inside the ducts.  If the building has visible mold growth indoors but the ductwork itself was not flooded, it may still be wise to strip the porous insulation out of the ductwork as part of the overall cleanup effort: Any condensation that later forms inside the ducts will provide the moisture necessary for proliferation of the mold spores trapped in the insulation.

If the ductwork and ventilation appliances must be cleaned, you should be aware that this is work for qualified professionals who know both what they are doing, and the materials they are doing it with.  Indoor Air Review reported that, while contractors may want to treat affected surfaces with an antimicrobial agent or a fungicide, consumers should proceed with caution.  "A lot of these chemicals have not been tested for long-term effects on [building] occupants," according to the consultant they interviewed.

There are three government-regulated categories for antimicrobials: sterilants (kill all life forms)-, disinfectants (kill agents that can infect humans); and sanitizers (must reduce – but not necessarily eliminate – microbes). [Note: Antiseptics are not used on things, but on people.  A product that claims to be an antiseptic for use on surfaces is making a false claim.] Before you decide to have your contractor use an antimicrobial product in your ventilation system, you should find out what kind of product will be used.  Your decision whether or not to go ahead with the treatment should take into account both the limitations of what the product can accomplish, and the (unknown ?) long-term effects of exposure to their residues in indoor air.  If you decide to have antimicrobials applied to your ventilation system, it would be prudent to have it done when the building is empty, and to allow the residues to be purged from the ventilation system before returning to the building.

Therefore use common sense about your ventilation system during post-flood cleanup.  Do not run the ventilation system while cleanup work is ongoing.  It is tempting to use the furnace to dry out the building, or the air conditioning to dehumidify it.  But running the ventilation system when the building still contains much water-damaged material is likely to spread contaminants from affected parts of the building to those that are not even damaged.


Prioritizing cleanup tasks

Putting a flooded house back in order is an overwhelming job, both physically and emotionally: It's hard to even know where to begin.  The Red Cross document contains invaluable information about how to prioritize clean-up tasks.

Indoor Air Review's consultant interview noted above contained the following tips to add to the Red Cross's advice: If a surface (any surface) in the building is black with mold growth, rip it out and throw it away.  If a surface is non-porous (glass or ceramic, stone, some plastics, some paint finishes, metals), clean it mechanically (hose it off, scrub it down, wipe it off), and disinfect it with chlorine bleach.  We think the Red Cross's formula should work fine.

If the surface is porous (wood, some plastics, some paint finishes, brick, some tile, all textiles and upholstered furniture), the consultant recommended cleaning it as best you can, and monitoring it over time for musty odors, mildewed patches and other evidence of mold.  We think that this course of action may be risky, since molds may be active, releasing spores and contaminating surfaces and objects throughout the building, long before odors or visible evidence are apparent.

We realize, however, that many people will be unable or unwilling to dispose of all porous materials affected by flooding. The following suggestions may help you decide which things to dispose of immediately, which things to attempt to rehabilitate, and which things to deal with on a delayed basis.

  • Important papers: Gather them together, pack them as flat as possible in zipper-style freezer bags, and freeze them at 0 degrees Fahrenheit or below for later attention. (See the Red Cross document for detailed how-to instructions.)  Do not delay on this step, as papers deteriorate rapidly once soaked.  Freezing them wet should not add to the harm they have undergone by wetting and handling.  But leaving them at room temperature to dry out is an invitation to increased damage.
  • Food, including the contents of the refrigerator and freezer (unless undisturbed by water or power-outage), all open food packages, and foods not in undamaged vacuum-sealed cans):  Discard outdoors (in covered trash cans) at once.  Even if the packages do not seem wet, they are probably contaminated with mold, will deteriorate rapidly, and will add to contaminants indoors.  Mold-contaminated food is unsafe to eat.
  • Closets and cabinets: Open all doors and drawers, remove contents, and leave open to air dry.  Discard, clean or store contents until cleanup is complete.
  • Loose paper materials (newspapers, magazines, paperback books etc.): Discard at once, away from the building.  Wet paper and paper products are favorite breeding-grounds for molds, including some that are very dangerous to people.
  • Hard-cover books (cloth, leather or other bindings): If you must keep them, try to dry them out as quickly as possible outdoors (follow the Red Cross instructions).  If you have valuable books, you should contact your insurer as soon as possible after the damage occurs, and you should obtain prompt services from a professional book restorer.  Unless attended to promptly and carefully, wet books are difficult to dry thoroughly without warping, spotting and crumpling.
  • Upholstered furniture, mattresses: Remove from the building.  It may be best to simply discard these materials.  Even if they are well-dried and thoroughly cleaned, they may continue to harbor mold spores that will proliferate and contaminate your home later.  However, if you can't bring yourself to discard these items at once, or if you elect to keep them, let them dry completely in the open air, under a roof or in an open garage.  Have them professionally cleaned and sanitized before use, and do not re-introduce them into the building until clean-up is complete.  These materials will continue to be a potential hazard, and should be vigilantly protected from moist conditions, wet spills, and other conditions that will foster mold growth.  Given the difficulty of achieving this (and the nuisance of his ongoing care), outright discarding these items will save time, money, anxiety and grief in the long-run.
  • Wooden furniture: Open all drawers and doors if possible.  If these are warped shut, do not pry them open.  Follow instructions in the Red Cross document mentioned above.  Remove contents, discard or clean them, and store until cleanup is complete.  Clean the furniture according to the Red Cross instructions.  Let the furniture dry completely before returning to use.  Bring it back into the building after building cleanup is complete.
  • Area rugs and wall-to-wall carpets: Remove rugs (and carpets, if possible) from the building and let them air dry until you can have them professionally cleaned, sanitized, and thoroughly dried.  To avoid re-contaminating them, do not bring them back into the building until the entire building clean-up process is complete.  NOTE: Wet carpet that is left in place for any length of time will become severely mold-contaminated.  If it is not possible to have a professional service come immediately to extract the water from the carpet, clean and thoroughly dry it, it may be best to discard it outright, and early.  Mold-contaminated carpet is a health hazard.  A particularly dangerous mold, Stachybotrys, is associated with wet carpet: It can cause (usually) non-fatal but severe illness in adults, and in infants it can cause death.
  • Textiles and furs: Remove them from the building and line-dry them until you can launder or dry-clean them.  Once they are thoroughly dry, you can put them, still soiled, in open containers.  But don’t compound the damage that textiles and furs have sustained by sealing them, wet, in bags or boxes – such conditions will promote mold and mildew growth on textiles that might be simply soiled.

Moving back in: Caring for your water-damaged home

The contractors have gone, everything has been cleaned that can be cleaned, and new materials have replaced those that could not be saved.  You're ready to re-occupy the building.  Can you also return to your former (probably carefree) attitude about mold contamination indoors?
No. Remember the researchers who found mold spore levels more than ten times higher in decontaminated buildings than in those that had never been water damaged?  It's wise to assume that your home contains similar levels of mold spores – each waiting for enough moisture to blossom forth into a full-fledged source of contamination and health hazard.  You need to remain vigilant about moisture indoors once your home has sustained water damage.


Steps you can take

Before you run your ventilation system, have it inspected and balanced by a qualified professional.  Be particularly careful to have an inspection for cold spots in the home where moisture can condense.  Be aware that cold spots can occur in both heating and cooling conditions – not  always in the same spots for
both types of thermal conditioning.  These sometimes tiny "microclimates" can defeat elaborate attempts to control moisture and mold indoors – it’s worth having some detective work done to identify and correct them.
If your home sustained extensive water damage, it may be wise to contact an environmental consultant about monitoring your home after you have moved back into it. (HEAL publishes a national directory of such professionals.)  Monitoring and documenting results may be essential for evaluating the quality of the work that was done to restore your home, and to evaluate health complaints that may occur after you move back in, for not only mold spore levels, but also mold and fungal species identification.  Some molds are more dangerous than others.

Install and use dehumidification devices in areas prone to dampness, like basements and closed-off rooms.  Empty the collection reservoirs often, and wash them in soap and water at least weekly.  Keep the condenser coils clean.

Be careful about using humidifiers (including nebulizers) in a building that has sustained water damage.  These devices not only deposit significant quantities of moisture into indoor environments, but they also can themselves become contaminated by airborne molds.  If such devices must be used, they should be run only in rooms closed off from the rest of the building (including the ventilation system – use only electric space heating and cooling devices in such spaces).  The contents of the room should be as simple as possible, to prevent mold contamination. Install and use exhaust fans (with or without energy recovery units) in all areas where moisture is routinely generated, like the kitchen, baths, and laundry.  Such exhaust fans should be vented to the outdoors, not to an attic or crawl space.  The object is to remove moisture from the building, not to re-distribute it to areas in the building where it will condense and form conditions favorable to mold growth.

Consider using air filtration devices.  Whole-house units are available that can filter a variety of substances – including mold and fungal spores – from the air.  Room-size filters are also available.  Be careful to match the filtration unit to the problem you are attempting to solve: too "coarse" of a filter will let spores through.  High efficiency particulate (HEPA) filters are a good (though expensive) choice.  Electrostatic air filters can precipitate particles out of the air, but they are then deposited on surfaces that must be cleaned frequently.  Whatever type of filtering device is chosen, it must be properly maintained in order to do its job.  It is particularly important to clean the devices and change their cartridges/filtration media as soon as it becomes saturated.  A combination of whole-house and room-size filtering units may be an economical choice for families with especially sensitive family members (infants, small children, the chronically ill, the allergic, the asthmatic, those with pulmonary or other chronic disease).olea


Look before you leap: making choices about maintaining your rehabilitated home

It is common in the US to rely on household disinfectant products for a variety of purposes.  However, once you return to a formerly-flooded home, you should monitor your use of these products.  If it seems that you are using them more often and in greater quantities that previously, you should try to determine if you are simply being more careful than you were before your flood experience, or if you are finding more and more mold contamination.  If the former, you should be aware that using these products in greater quantity and/or more frequently than the product directs can be harmful, and may not add any increase in mold control.  If you are actually finding more mold indoors, you should not rely on these products alone: You need to reassess your home's mold contamination status.

A careful do-it-yourself inspection may reveal problems that you can identify and amend yourself, and you should do so promptly.  You may also find more serious problems that require professional help, including problems arising from faulty rehabilitation of your home by contractors who repaired your flood damage.  If the work is still under warranty, your repairs should be covered.  If not, you may have to come to other arrangements with the contractor, or hire a different contractor.  The work should be as soon as possible after identification of the problem.

We feel that it is also very important to warn occupants of water-damaged buildings that the use of disinfectant/ deodorizing products is not advisable in such buildings.  In buildings undamaged by water, the occasional musty odor is a nuisance and easily controlled.  But in a water-damaged building, such odors, especially if they are persistent, are a symptom of mold contamination.  These odors are a warning sign that something serious may be wrong, and that an inspection – and maybe some professional advice – is needed.  Act on these warnings promptly, and seek the source of the odor, rather than trying to cover it up.


And speaking of covering up odors:

The use of air-freshening products and devices in a flood-damaged building is not recommended.  They are not intended to do anything but cover up unpleasant odors while adding a more pleasant odor to the air.  They do not fix the source of odors, and they may blunt your perception of such problems until they are so severe that they overwhelm the action of the freshener. Your sense of smell gives you useful warnings that molds are present in your home.  Do nothing that will interfere with this valuable warning system!  You should be aware that there are devices that claim to reduce odors by removing odor-causing substances, including mold.  We believe that you should examine all such claims carefully before you purchase and use such devices.
Air filtration devices that generate ozone, and appliances sold as ozone generators, are designed to introduce ozone into the air in order to control odor-causing substances (among other purposes).  You should be aware that outdoors, ozone is considered an air pollutant – a  component of smog, in fact – and millions of dollars are spent each year to control ozone emissions that can harm health.  Indoors, ozone at high levels can also be harmful – and the higher the level, the more harmful it may be.

Mark Boeniger, a researcher at NIOSH, has reported that ozone indoors can interact with other substances in the environment in ways that do not necessarily reduce health risks.  In a letter to Indoor Environment Review, he said, "A better strategy [than use of ozone-generating appliances] for cleaner indoor air is to remove or control the sources of indoor pollutants and ensure that ventilation is adequate, or if necessary, use proven cleaning technology like filtration and Absorbents, rather than adding a known toxic pollutant like ozone to the indoor air."

Richard Shaughnessey, Program Manager for Indoor Air Pollution Research at the University of Tulsa (Oklahoma) has written," Our university has conducted studies demonstrating that these devices can generate indoor zone levels that quickly exceed OSHA [workplace) and EPA outdoor standards.  Without proper monitoring and effective control options (that may not be practical or feasible for a typical application) these devices may generate hazardous concentrations of ozone.  This may be extremely dangerous for immune-compromised individuals (e.g. asthma patients) for which (sic) these devices are often targeted."

Before deciding to use a device that adds ozone to indoor air, it may be prudent to consider what you are attempting to accomplish by using such a device, and how likely it is that the device will enable you to achieve that goal.  The careful use (or avoidance of use) of a method that might create another – perhaps more serious – problem merits consideration.  If you are concerned about potential health effects of ozone generating devices used indoors or if you have allergic, asthmatic or other sensitive family members, you may wish to consult a physician about the use of ozone-generating devices before introducing them into the home environment.

It's not necessary to be constantly be alarmed about the chance that mold contamination could make you or your family ill.  Once you know what the threat it, it's possible to take steps to avert it.  The biggest risk is in not knowing, and in failing to do all you can to prevent it from occurring.  Be alert to the harm that molds indoors can cause – and prevent it before it occurs.