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Why A Flood Is The Worst Thing That Can Happen To Your Home And What You Can Do About It That Will Also Help Your Mental Health

Did your home get flooded by ex-cyclone Debbie?  Check your home for mould contamination and take action as necessary.


Floods rate high in severity when compared to many other natural disasters. Not only do they cause widespread material damage, but they can impair the physical and mental health of people affected.


Climate change has led to more floods globally and more devastation to homes and businesses. It’s not only the occupants of a flooded property who are affected. First responders and rescue workers entering the flooded properties, are also risking their health. Even more at risk are the building contractors and restorers engaged for months on remedial work.

So what are the health risks associated with flooding? Before we answer this fundamental question, lets review the most recent Australian flood problems caused by wild weather and what this means for your health and wellbeing.

The Australian Flood Water Context due to Cyclone Debbie

The toll from ex-tropical cyclone Debbie that just tore through New South Wales, Queensland and New Zealand will cause flood woes for years to come. In the wake of the PR disaster following the 2011 floods in Queensland where many homeowners discovered they had no flood insurance at all, an all too familiar chorus starts up again. In fact, ABC News confirmed that early figures from the insurance industry suggest there are at least $306 million worth of claims from nearly 30,000 claimants in the first week after the deluge. It is noted that flood insurance is related to the risk of catastrophic flood but it may turn out that many building owners who think they are insured may not be?

Immediate impacts caused by water flooding are made all the worse by unexpected evacuations, loss of electrical power and the need to get help from authorities like the SES and local councils. Some have even had to make application for Immediate Hardship Assistance grants. Add to this, the flow-on effects caused by business interruption and general upheaval, with many analysts also predicting major agricultural losses leading to price hikes and hard to get items at the supermarket.

But what about the aftermath to the water? After the media stories dwindle and the thousands of volunteers are left with no camera crews to document the floodwaters, what about the water that remains? This will surely lead to massive mould problems affecting homes, businesses and industry. What about those volunteers, and unscrupulous cleanup crews that come to prey on victims in the wake of a disaster…do they know how to properly remediate water damaged buildings?

This blog post aims to provide some much needed ‘scientifically factual’ information that should help those affected.

Source removal of water damaged home contents after a flood is often the best and most effective way to reduce indoor mould risks

Why Mould & Bacterial Growth is a Health Hazard

It’s been known for years that wet building materials create the perfect conditions for bacterial, yeast and fungal growth. These same microbes exist benignly outdoors. But when a building becomes water damaged, these microbes start to eat the house, and when they start to grow indoors at high concentrations, they can make people ill in several ways. Inhaling the airborne spores is a major health risk, but also skin contact, and even to a lesser extent ingestion of contaminated foods, can be harmful.

Inhaling mould and fungal spores can also trigger rhinosinusitis and asthma. According to the Institute of Medicine, 20% of current asthma cases in the USA occur because of chronic dampness in homes.

Runny noses, watery eyes, sore throats and coughs are all symptoms produced by breathing in spore-laden indoor air.

Alternaria alternata fungal spores.  Alternaria is a frequent contaminant in water damaged homes. Image courtesy of Biological Health Services.

Get these microbes on your skin, and if you’re allergic you can find yourself with a nasty rash. Fatigue, headaches, muscle and joint aches can all arise after being in contact with the toxic air produced inside a flooded building. Other research shows that once people become sensitized to mould, their immune system will mount an allergic response even to juts the smell of mould!

Remedial Works – The Need For Speed

Remedial works on flooded properties must be carried out as soon as possible. Mould can start to grow within 24-48 hours of flooding. Floodwaters also introduce bacteria and endotoxins into the home (often from sewage). The good news is that if done well, post-flood remedial measures can eventually restore a home’s indoor air quality and background mould levels to normal. The problem is how do you know what normal levels are?

Thankfully there exists several documents that cover how to deal with mould and water damage. These documents in order of relevance are:

1. Australian Mould Guideline (2010)
2. ANSI/IICRC S500 Standard and Reference Guide for Professional Water Damage Restoration, 4th Edition, 2015
3. ANSI/IICRC S520 Standard for Professional Mold Remediation, 3rd Edition, 2015
4. ANSII/IICRC R520 Reference Guide for Professional Mold Remediation, 3rd Edition, 2015

Always make sure that your remediator/restorer or Insurer or trades that they may organise are following the Guideline and Standards and get this undertaking in writing.

A fundamental component of the Standard is adequate microbiological and air quality sampling and testing inside properties suspected of having a mould or water damage problem. This is to guide remediation efforts using suitable baseline lab data. After remediation you should insist on appropriate post remediation verification. This is another round of sampling to check that mould and spore levels have actually been effectively reduced and have brought back air and surface levels to normal. Again, you may need to insist on this in writing from your trades or Insurer.

You can use any of our DIY test kits to perform your own ‘before’ and ‘after’ testing, and this then gives you some solid foundation on which to make any claims in the event that you are not happy with the results after work has been performed. Alternatively, you may need to engage a suitably qualified microbiologist, mycologist or other environmental health or occupational hygienist to do the sampling.

Mould damage after floodwaters caused by ex-cyclone Debbie must be dealt with professionally as soon as the water subsides in order to minimize the risks from mould spores and mycotoxins.

What the Research Shows

A study carried out soon after the Colorado Front Range floods in September 2013 looked at water damage caused to flooded properties. Air samples taken from affected homes contained 3 times the normal levels of fungal contamination. Samples were collected 2 – 3 months after the flooding from both affected and non-affected homes. By this time many of the 36 flooded homes sampled had had remedial works completed and were showing no visible signs of flood damage. And yet they still contained high levels of fungal contamination.

The most effective way to restore a flooded property is SOURCE REMOVAL followed by clean up of all remaining affected areas with soap and water, and then HEPA vacuum up the residual mould and spores throughout. Avoid biocides as the harm these chemicals can do to the occupants may outweigh any restorative benefits. Beware of any claims for 'mould fogging' since in the main this approach is without scientific merit. If you are offered the option to fog your home, definitely insist on the operator providing you with a valid MSDS for the chemical composition of the product as well as an approval certificate from the Australian Government - Department of Health, Therapeutic Goods Administration showing it to be an effective fungicide when used in the vapour phase. If this information is not forthcoming, then you should not take any claims seriously and don’t waste your money or risk your safety. Dodgy operators should be reported to Consumer Affairs in each State and Territory.

Often damaged plasterboard and flooring needs to be completely stripped out/demolished. Wet furnishings and possessions, if unsalvageable, should be discarded too. All these can harbour harmful mould and bacteria that can attack the airways and mucous membranes of anyone living inside. Documents may need to be remediated by a specialist.

Once all the water has been pumped out, the house must then be thoroughly dried to prevent further mould growth. This is done using any combination of the central heating system, fans, heaters and dehumidifiers usually in combination with industrial-grade HEPA air scrubbers. For a severely flooded home, the drying process may take several weeks, even months. Structural drying must only occur provided there is suitable barrier containment in place to minimise aerosolising mould cells, fragments and spores throughout the house. Again, beware of Companies who install dryers without barrier containment, since they are not following the Standard and Guideline.

As stated earlier, it’s important to complete remedial works as quickly as possible. A study carried out soon after the 2008 Cedar River flooding looked at levels of bacteria and endotoxins in flooded homes. They found microbe levels to be 1.5 to 5.1 times higher in homes undergoing restoration than in those where restoration was complete.

It's vital that those carrying out remedial work wear personal protective equipment (PPE) to protect the lungs and skin. Suitable eye, skin and respiratory protection should always be worn. At the very least a P2/P3 particulate mask is required, although many experts would agree that a full-face or powered respirator is safer. See for example the Sundström P2/P3 Filter or similar that can be attached to either a half-face or full-face mask. Gloves and goggles and disposable coveralls will protect the skin and eyes from airborne microbes, and help stave off an unwanted allergic reaction.

Even after the floodwater has gone, chronic dampness in the walls can still facilitate mould growth. It can take months for the property to become ‘dry’ again. All the while, anybody working or living inside the house is risking their health. And as it happens, we’re not just talking about physical health, but mental health too.

Flood devastation after ex-cyclone Debbie wrecks havoc in Australia and then comes the mould.

Mental Health Impact on Flood Victims

There have been many studies in recent years to examine the long term mental health effects of flooding. One carried out recently in Spain, looked at the link between flood disasters and Post-Traumatic Stress Disorder (PTSD). In September 2012 the province was hit by an intense storm, which lasted 45 minutes. 4300 properties were flooded. 70 people who had been directly affected by the flooding filled in trauma questionnaires. These were compared with 91 questionnaires from people living in neighbouring, unaffected areas.

Results showed a significant increase in PTSD cases among those affected by the flooding. Many of these disaster victims were still suffering long after the event, despite support from friends and family. The financial implications of remedial works was a common stress factor, and many lived in fear of further flooding events. Further, certain stimuli can trigger dream flashbacks of the trauma for many months after the actual event.

Depression and anxiety is also more prevalent among those who have suffered flood trauma. After the UK floods of 2013/2014, a study revealed an increased incidence of depression and anxiety of over 20% among flood victims. It also showed the traumatic effects of flooding are not only prolonged but affect people outside the flooding radius.

Mental health impacts after flooding are a likely consequence for people dealing with unexpected business loss and interruption and allied effects on personal choice.

Flood victims, even those only indirectly affected, are 2 to 5 times more likely to suffer anxiety or depression 3 to 6 months after the event. Psychological disorders are 6 to 7 times more prevalent for those whose homes were flooded. They are 1.5 to 2 times more prevalent for those who merely suffer disruption of a utility. And those flooded and evacuated were found to be 8 times more likely to suffer PTSD.

Without doubt, it is important to consider both the adverse physical and mental effects on the health of people affected by floods. These detrimental effects to health can take a long time to reverse, often enduring for several months or more after the flood event.

Dr. Cameron Jones, PhD.
CEO Biological Health Services


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Hsu, N-Y., Chen, P-Y., Chang, H-W. and Su, H-J. (2011). Changes in profiles of airborne fungi in flooded homes in southerm Taiwan after Typhoon Morakot. Science of the Total Environment. 409: 1677-1682. DOI:10.1016/j.scitotenv.2011.01.042

Hoppe, K.A., Metwali, N., Perry, S.S., Hart, T., Kostle, P.A. and Thorne, P.S. (2012). Assessment of airborne exposures and health in flooded homes undergoing renovation. Indoor Air. 22(6): 446-456. DOI:10.1111/j.1600-0668.2012.00785.x

Solomon, G.M., Hjelmroos-Koski, M., Rotkin-Ellman, M. and Hammond, S.K. (2006). Airborne mold and endotoxin concentrations in New Orleans, Louisiana, after flooding, October through November 2005. Environmental Health Perspectives. 114(9): 1381-1386. DOI:10.1289/ehp.9198

Waite, T.D., Chaintarli, K., Beck, C.R., Bone, A., Amlot, R., Kovats, S., Reacher, M., Armstrong, B., Leonardi, G., Rubin, G.J and Oliver, I. (2017). The English national cohort study of flooding and health: cross-sectional analysis of mental health outcomes at year one. BMC Public Health. 17: 129. DOI 10.1186/s12889-016-4000-2

Fontalba-Navas, A., Lucas-Borja, M.E., Gil-Aguilar, V., Arrebola, J.P., Pena-Andreu, J.M. and Perez, J. (2017). Incidence and risk factors for post-traumatic stress disorder in a population affected by a severe flood. Public Health. 144: 96-102. DOI:

Emerson, J.B., Keady, P.B., Brewer, T.E., Clements, N., Morgan, E.E., Awerbuch, J., Miller, S.L. and Fierer, N. (2015). Impacts of flood damage on airborne bacteria and fungi in homes after the 2013 Colorado flood range flood. American Chemical Society. 49(5): 2675-2684. DOI: 10.1021/es503845j

Johanning, E., Auger, P., Morey, P.R., Yang, C.S. and Olmsted, E. (2014). Review of health hazards and prevention measures for response and recovery workers and volunteers after natural disasters, flooding, and water damage: mold and dampness. Environmental Health and Preventative Medicine. 19(2): 93-99. DOI: 10.1007/s12199-013-0368-0

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One Day Mold Removal "Mold Fogging SCAM" Beware of companies that offer "fogging" as a mold remediation/ removal solution.

Eleanor Hall and Tom Joyner, NSW floods: Insurance industry defends high premiums, calls for more disaster mitigation. ABC News, Tuesday 4th April, 2017.

Cyclone Debbie: The overall cost. SBS News. Friday 7th April 2017.

In the wake of cyclone Debbie: pictures. Crinkling News.

Flood psychological preparedness and recovery: Resources for practitioners.

Beyond Blue Support Services.

Australian Government, Department of Health, Therapeutic Goods Administration. Disinfectants and Sterilants.

Kemp, P. and Neumeister-Kemp, H. (2010). Australian Mould Guideline. 2nd Ed.

ANSI/IICRC S500 Standard and Reference Guide for Professional Water Damage Restoration, 4th Edition, 2015.

ANSI/IICRC S520 Standard for Professional Mold Remediation, 3rd Edition, 2015.

ANSII/IICRC R520 Reference Guide for Professional Mold Remediation, 3rd Edition, 2015.

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