Potting mix warning and guidelines – Legionella infection (legionellosis)

Media Release

Nursery & Garden Industry Association supports Ministry of Health gardening guidelines

Following recent cases of Legionnella infection (legionellosis) in Christchurch, the Nursery and Garden Industry Association (NGIA) endorses Ministry of Health guidelines on safe gardening.

“Gardening is a popular pastime enjoyed by thousands of New Zealanders,  helping people relax and escape the stresses of life. It provides enjoyment and exercise. The huge growth of interest in home-grown vegetables and fruit in recent years has added to people’s culinary enjoyment, and help stretched their budgets further” said Dr John Liddle of the Nursery and Garden Industry Association.

“Soil is rich with living organisms beneficial to plants which generally cause no harm to animals or people.  Soil does, however, also contain some organisms that are not beneficial.   A type of Legionella bacteria, which is commonly found in the environment, is one of these. It has been shown to cause Legionnaire’s disease in a few people.”

Dr Liddle said it could, on rare occasions, be inhaled in water vapour and in the dust associated with soil and potting mix.

“Not all those who come into contact with the bacteria become sick and symptoms will vary from person to person.  If people become infected with Legionella, they may get flu-like symptoms that can range from mild to severe.  It can, however, be life-threatening to people who have health factors that increase their susceptibility. Those most at risk include smokers, the elderly and those with existing respiratory illnesses and weakened immune systems.”

“NGIA endorses the Ministry of Health safe gardening guidelines provided to help reduce the risks when gardening,” said Dr Liddle.

The guidelines advise gardeners to:

  • Minimise the amount of dust when working in the garden.
  • Water gardens and indoor plants using a gentle spray.
  • Read the warning label on bagged composts or potting mix.
  • Wear gloves.
  • Wear a dust mask so that any dust is filtered out before you can breathe it in.
  • Dampen potting mixes before use.
  • Open bags of soil products slowly, away from the face.
  • Make sure the working area (glasshouse, potting shed) is well ventilated.
  • See a doctor if you develop a flu-like illness which is worsening.
  • Wash hands thoroughly after gardening or handling soil products.

These are simple, easy and natural steps that all gardeners can take to reduce risk while continuing to enjoy their garden.  The Ministry of Health guidelines also provide advice on garden chemicals, poisonous plants, insect stings and bites, garden machinery, injuries and sunsmart.


Safer and Healthier Gardening – Ministry of Health – HE4605, 2008 August

Legionellosis – What You Should Know If You Work With Soils, Compost And Potting Mix – OSH and


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