Can You Get Legionnaires’ Disease From Potting Compost?
This article examines the potential risks of contracting Legionnaires’ disease from potting compost, how this might happen and what can be done to reduce the risk.
What is Legionnaires’ disease?
Legionnaires’ disease is a serious lung infection caused by Legionella bacteria. There are several different types of the bacteria but the one responsible for most cases is called Legionella pneumophilia. Other types include Legionella longbeachae which has been found in compost.
Are there different types of Legionella bacteria?
You may know that Legionella bacteria appear in natural water sources such as lakes and ponds. They can also move into manmade water systems including plumbing pipework, storage tanks and water outlets, increasing the risk of contamination, colonisation and potential illness.
There are several dozen types of Legionella bacteria we know about. Most individuals who have been affected by Legionnaires’ disease are afflicted by Legionella pneumophila. However, there are other variants of the bacterium that can also cause illness. Indeed, more than two dozen species can potentially cause humans to fall ill.
Compost and the risks from Legionella
But is it just the water we should be alert to for risk? One study looked at the incidence of Legionnaires’ disease in Australia and New Zealand and found many cases were linked to Legionella longbeachae. This variant of the species doesn’t cause many issues at all in European countries, but links have been found with the use of compost in Australia and New Zealand.
While the link between compost and Legionella bacteria is proven in those countries, it isn’t clear why it doesn’t appear to be as big an issue in other countries. It’s possible that climate and weather have roles to play, but this hasn’t yet been proven.
That said, Legionella longbeachae has been confirmed present in bags of compost tested in other countries as well. While there are far fewer cases elsewhere, there is still clearly a link between this type of Legionella bacteria and compost, seemingly an innocent and necessary addition to any garden.
Legionnaires’ disease from potting compost
The study followed the actions and health of those taking part, looking for risk factors and compost use to see whether possible links could be drawn between them.
There were some highlighted factors that did suggest how one person might see an increased risk of Legionnaires’ disease while someone else might not. For example, most people who participated in the study did have a garden, whether that was a small indoor area or an outdoor plot. However, in people who developed Legionnaires’ disease, the incidence of indoor gardens or spaces was far higher.
There was also a strong association between potting compost use and those who had fallen ill, affected by Legionella bacteria. It appeared that buying compost, opening the bag, tipping it out or using a trowel to remove it from the bag were all seen as risk factors that increased the chances of someone falling ill. There was a higher incidence of such actions among those with the disease than there was among those without – especially in association with indoor gardening.
Health risk factors and Legionnaires’ disease
We already know that some people are at far greater risk of developing Legionnaires’ disease than others. For example, age is known to be a risk factor, with those aged 45 and over at an increased risk compared to those who are younger.
Similarly, those with certain health conditions are more likely to fall ill if exposed to Legionella bacteria if it is present in the air and inhaled into the lungs. Those who smoke, have pre-existing lung conditions or compromised immune systems are among those at greatest risk in this sense.
The study confirmed this fact, noting that those with chronic obstructive pulmonary disease, otherwise known as COPD, were most likely to be afflicted by Legionnaires’ disease. Smoking also proved to be a key factor.
Is there anything we can do to reduce Legionella risk when using compost?
If we suspect that Legionella longbeachae may potentially be present in any compost bought in any country, is there anything we should do to try and reduce any risk of inhaling the product?
We usually associate Legionella with inhaled water vapour, but it appears that the dust sometimes seen in drier bags of compost might also be inhaled. Therefore, careful handling of any compost is important. Make sure you open any bag to minimise the creation of dust, keep the bag well away from your face, regardless of whether it is a new bag, or you have previously opened and resealed it.
It’s also a good idea to try and remember not to touch your face until you’re finished handling the compost. At that stage, carefully close the bag and head inside to wash your hands and face.
Taking sensible precautions to reduce the risks
While this may seem like overkill, especially if you do not live in Australia or New Zealand, there have been cases of Legionnaires’ disease in other countries that have been linked to the Legionella longbeachae variant. Taking a few additional and sensible steps doesn’t take long in this instance. Furthermore, we should certainly feel that the extra few moments would help reduce any associated risk from Legionella connected to the compost.
Anyone over 45 and those who have long-term health conditions, particularly ones that affect the lungs, should certainly take a few extra steps to prevent inhalation of any particles from compost in the garden. If in an enclosed space, this becomes even more vital, as the study seems to suggest in this case.
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