A recent paper in the journal Clinical Microbiology and Infection by researchers at the University of  Strathclyde in Glasgow, Scotland, posits that Legionella bacteria present in commercial compost and commercially blended topsoils may present a significant public health risk. The authors suggest that the addition of general hygiene warnings to compost package may be beneficial in protecting public health.

The study is based on analysis of twenty-two store-bought composts, one green-waste compost and one homemade compost. Legionella sp. bacteria were found in fifteen of the twenty-four samples.  Public concern has been enhanced by a couple of recent cases of UK gardeners being diagnosed with Legionellosis after working with compost in their gardens and one UK case of a 63 year old female death ascribed by an inquest of Legionellosis.

Experts suggest that gardeners can reduce their exposure to dust from commercial compost by wetting the material before working with it, wearing gloves and a face mask, and washing their hands afterwards. In any case the risk of acquiring Legionellosis from compost remains at an extremely low level. However, even one premature death is one too many. Gallondaily suggests that the further research is urgent because the last thing the compost industry needs, as environmental experts work to increase the amount of organic waste going to compost rather than landfill, is a barrier to markets for finished compost.

The scientists recommend further research to better understand the problem and to determine whether the results from this small scale study transfer to the larger universe of commercial compost.

An abstract and a link to the full article (payment or subscription required) are available at http://onlinelibrary.wiley.com/doi/10.1111/1469-0691.12381/abstract