The Growing Media Association will discuss standard legionella warnings on compost bags when the HTA-run body meets in November, HTA policy manager Gary Scroby has said.
This follows a University of Strathclyde paper on the issue and an ongoing Health Protection Scotland (HPS) investigation into a recent outbreak among gardeners.
The study found 15 out of 22 bagged composts contained the pathogen, which is harmful to human health. It suggests that peat compost has fewer legionella issues.
Another HPS investigation made recommendations including "a label containing generic advice on good hygiene in relation to gardening, covering wearing gloves, wearing a mask if dusty especially indoors and washing hands immediately after use".
Scroby said the HTA used an independent microbiologist. "Legionella is out there. It's on your toilet seat, in the kitchen and in the garden. It would be disproportionate to do anything other than advise sensible precautions given the extremely low incidence rate. But we will consider labels like they have in Australia and New Zealand at our November meeting."
The Strathclyde study, Legionella spp. in UK Composts: A Potential Public Health Issue, published in Clinical Microbiology & Infection, states: "Over the past five years, a number of cases of legionellosis in Scotland have been associated with compost use. However, studies investigating sources of infection other than water systems remain limited."
Compost study - Public-health risk assessed
Of 22 store-bought composts, one green-waste compost and one homemade compost tested for legionella, 15 tested positive for Legionella spp., "a higher level of contamination than previously seen in Europe".
Authors Sandra Currie, Tara Beattie, Charles Knapp and Diane Lindsay concluded: "The occurrence of legionella in more than half of the samples tested indicates compost could pose a public-health risk. The addition of general hygiene warnings to compost packaging may be beneficial in protecting public health." See http://onlinelibrary.wiley.com/doi/10.1111/1469-0691.12381/abstract.