Floods and health

Soon after heavy rains have stopped and waters have drained off the ground surface, sewers will generally return to normal function. It is important to clean up, drain and dry out the house as quickly as possible.

• Take photos of the damage before starting the clean-up.
• Take out everything that is wet and that can be moved, for example, floor coverings, furniture, bedding, clothing, and put them outside to dry when the weather is fine.
• Get rid of mattresses and other large items that have been soaked with floodwater. Foam rubber mattress or pillows may be able to be washed, disinfected and dried in the open air.
• Get rid of contaminated clothing, carpets, upholstered furniture, toys and bedding unless they can be cleaned and disinfected.
• Check for trapped water and mud in wall cavities, as well as under shower trays, baths, benches and bottom shelves. You may have to chisel out some bricks at the bottom of brick veneer walls.
• Remove skirting, if necessary, and cut out softened plaster board in damaged areas. Consult an expert such as an insurance assessor or builder.
• Use heaters, for example, hot air blowers for under-floor space, but open all doors and windows.
• Replace things such as wall linings and floor coverings only after things have dried out.
• Leave redecorating for at least 3 months after finishing the repairs to prevent risk of mould, blistering and peeling.
• Do not light fires in brick fireplaces for at least 2 weeks, and then use only small fires until the firebricks have dried out.
• Consult an engineer if there are signs that the house has moved on its foundations, for example, buckled floors, new cracks in walls, out of shape door frames.

• Cover any cuts or wounds before you start cleaning up to help protect you from bugs.
• Dust, silt, mud and soil in the air can harm your health is by getting into your lungs and airways. This can damage your lungs. Coughing, lots of mucus and shortness of breath are all signs to watch out for.
• Properly fitting masks are the best protection, like P2 and N95 masks. However, even surgical masks will still help. Make sure masks fit correctly. Straps should go above and below the ears.
• Be aware that muddy floodwaters/sludge can contain sharp objects like nails and broke glass. Wear closed toe, sturdy footwear to prevent injuries. If you are injured, treat cuts and puncture wounds immediately to help prevent infection. Wash cuts and puncture wounds with clean water then apply a clean bandage. If your wound becomes infected or if you are not up-to-date with your tetanus vaccinations call your GP or Healthline on 0800 611 116.
• Anyone coming into contact with silt should wash and dry their hands or use hand sanitiser.
• If possible, wear cleaning gloves, sturdy shoes and protective clothing.
• Clean up, drain, and dry inside as quickly as possible.
• Use ordinary cleaning products and follow standard instructions. Do not mix products.
• If you are drying your property naturally, keep doors and windows open as much as possible. If using dehumidifiers, close external doors and windows. 

Hard surfaces (floors, walls, tables and benches)

Scrub first with clean water and dishwashing liquid to remove all visible dirt. Then wipe down with a household disinfectant, for example 2 cups of bleach to 10 litres of water.

Kitchen utensils

Discard wooden items such as chopping boards and spoons, plastic utensils, and baby bottle teats and dummies, if they have come into contact with floodwater. There is no way to safely clean them.

Wash cooking, eating, and any other kitchen utensils in clean hot soapy water.  

Rinse thoroughly then disinfect by immersing for 1 minute in a solution of 500 ml (about two cups) of plain, unperfumed household bleach in 10 litres of water.  

Rinse again in safe water. Alternatively, boil all utensils for one minute and let cool.

Soft furnishings, clothing, blankets and curtains 

Take out everything that is wet and that can be moved – floor coverings, furniture, bedding, clothing and so on. Thoroughly wash and disinfect all items and dry in the sunshine.

Get rid of items that cannot be cleaned and disinfected. Large items, such as mattresses that have been soaked in flood waters, should be discarded.

Remember: you could also contact local dry cleaners and carpet cleaners to assist.

Appliances (fridges, freezers and electrical goods)

Do not use electrical products if they have been soaked in water. If unsure, throw them out.

Garden produce

Do not eat garden produce if the soil has been flooded.

Clean-up any debris and sprinkle with garden lime to stop smells and flies. Lime can be purchased from your local garden shop.

Outside areas

The best way to make your outside areas safer is to rely on natural processes such as sunlight, drying and wind. Let garden surfaces and lawns dry naturally in the air and sunlight. Use a fork to make drainage holes for better airflow.

Remove solid materials (sanitary products, toilet paper and faecal matter) and place in sealed bags.

A garden hose is useful for washing down the outside of the property to remove silt, salt deposits and fine debris but do not use high-pressure hoses as they can blast contaminated matter into the air.

Hard surfaces, such as driveways, can be cleaned and disinfected with 1 litre of household chlorine bleach in 10 litres of cold water (a household bucket). Leave the disinfectant on for 30 minutes, then rinse with clean water.

Garden lime can be used to help disinfect the area.

Wet furniture and surfaces get mouldy after a couple of days, making the air in your whare unhealthy. Mould may make some people with asthma, allergies, or other breathing problems sick.

If mould has developed on surfaces, take extra care when cleaning.

When dealing with large areas of mould, seek advice from a professional mould removal specialist.

Small amounts of mould can be removed using commercial mould cleaner or hypochlorite bleach.

• Mix 1½ cups of household bleach in 4 litres of water, apply to the affected area and leave for 10 minutes before rinsing and drying. Detergent may be added to the diluted bleach, so it penetrates surfaces.
• Some organisations recommend sanitisers other than bleach, but there is no evidence they are any more effective than diluted bleach. These other sanitisers include organic acids (white vinegar) and alcohols (methylate spirits or isopropyl alcohol).
• Do not mix bleach with ammonia, acids or other cleaners – this can release hazardous chlorine or chloramine fumes. Read product labels before use. 
• Avoid spreading the mould through areas that are not contaminated. Rinse cleaning cloths often and dispose of cloths after use in a sealed plastic bag.  
• Avoid using water blasters as this can cause mould to become airborne.
• After treating the area, vacuum the room using a high efficiency particulate air (HEPA) filtered vacuum cleaner. 
• Regularly take breaks and make sure you wash your hands and face with soap before eating, drinking, smoking or vaping (hand sanitiser may not work). 
• If you cut yourself or break the skin, stop work and apply first aid including cleaning the wound. Seek medical attention if you think the cut is deep or there is sign of infection.

When you are finished

• Remove your mask and disposable gloves and seal them in a bag for disposal.
• Immediately wash your hands, arms and face with warm soapy water or shower with soap to remove any remaining mould.
• Wash all clothing used separately from regular laundry. Consider wearing a mask and gloves when handling these clothes, especially if they are muddy or dusty.

More information on household mould

Information on preventing and dealing with household mould from Consumer New Zealand and the Institute of Environmental Science and Research (ESR) and the Australian Department of Health and Aged Care:

• Avoiding mould – Consumer New Zealand
• Dealing with mould – Consumer New Zealand
• Report on the decontamination of mould-affected environments – ESR
• Mould in the environment – Australian Department of Health and Aged Care
• Mould related illness – Australian Department of Health and Aged Care

Flood waters can deposit large quantities of silt. When the silt dries the surface layer can become airborne when disturbed by wind, vehicles or clean-up activities.

Dust generated from airborne silt can affects people's health. It can cause eye irritations, a cough, exacerbate asthma or lead to other respiratory problems. Silt may also contain other toxic substances.

If dust levels are high and you can see, smell or taste dust in the air, or visibility is reduced, it is a good idea to take precautions:

• If possible, keep the surface of the silt wet, or cover it to prevent it drying and blowing around. Alternatively, use barriers to protect the silt from the wind.
• If possible, stay indoors and close windows and doors when dust levels are high.
• Avoid exercising outside.
• Air conditioners are safe to use but make sure filters (HEPA filters are recommended) are kept clean.
• Clean indoors regularly using mops and damp cloths to remove dust.
• Avoid sweeping and dusting as it kicks dust into the air, and only use a vacuum cleaner with a HEPA filter.
• If dust exposure can’t be avoided wear a properly fitted P2 or N95 mask; these are your best protection. Otherwise, a surgical mask.
• Drive slowly within silt impacted areas – slower is better and will result in less dust. Aim for under 10km/h.

Removing silt

Not all silt needs to be removed. Generally, in open areas where silt is less than 15mm deep you won't need to remove it. The silt will gradually disappear in the weeks following the floods, assisted by the effects of sun, wind and rain.

Follow advice and instructions about removing silt from your local council and local Civil Defence Emergency Management Group.

Always work safely when cleaning up silt:

• Protect yourself by wearing a properly fitted P2 or N95 mask, safety glasses or goggles, gloves, clothes that cover your arms and legs, and gumboots or work shoes.
• Cover any open cuts, scratches, grazes and wounds with waterproof plasters or dressings.
• Always wash your hands thoroughly after each clean-up session and before handling food.

Avoid digging deep trenches with high sides when cleaning up silt. Silt and debris can collapse easily without warning. Collapsing trenches can injure or kill people.

• If silt is deeper than one metre, create stepped trenches rather than digging straight down, to reduce the risk of collapse.

Working with silt or contaminated soil after a natural event or emergency – Worksafe