Compost and legionella risks

Hi all,

There’s a lot of attention recently (over here) about Legionella longbeachae (Pontiac fever/legionnaires disease).. there’s a few hundred cases a year, some of which cause deaths.

This is believed to be contracted from compost (presumably store brought) where the bags provide an ideal breeding ground. Precautions are suggested including breathing masks, gloves, washing things down etc.

Is this something that we should be worried about with home made compost? Would appreciate any info from anyone with knowledge on the topic!

Thanks :)

I had done some reading on this and have been unable to find any mention of a risk of Legionella longbeachae in homemade compost. Everything I have read has mentioned risk in regards to store bought soil and compost, but doesn't mention why the store bought compost has a risk of infection. It does seem the risk is more prevalent in Australia and New Zealand, and there have been reported cases in Scotland, but gardeners in North America and Europe should not discount the possible risk of infection.  In the United States, a few cases have occurred among people who used potting soil prior to getting sick and at least some of those soil samples also tested positive for Legionella longbeachae. People with certain underling illnesses, immunosuppression, the elderly, and smokers seem to be of higher risk from the cases that have been studied. Wearing a mask or gloves while using compost does not seem to have a significant protective effect. It is suggested that people should consider minimizing aerosolization of the soil by opening bags away from one’s face and keeping hands away from the face until washing.  

This is a lung infection sickness.

I think the bacteria only grows in temp above 75F, so I can see it happening less in April/May (spring) in Frigid North America/EU then in more normative Aus/NZ.

This sickness mostly happen in USA when folks cultivate the bacteria in water, then turn the water+bacteria into a mist that they then breath in. aka They take a shower(mist/aerosol) in water, that is above 75F where there reproduce but below 145F which kills them.

I wonder what people are doing with their compost to make it airborne? Wearing a mask should help.

S Bengi wrote:I think the bacteria only grows in temp above 75F, so I can see it happening less in April/May (spring) in Frigid North America/EU then in more normative Aus/NZ.

Late spring -> early autumn, day time temps here are usually in the range of 75-86F - compost, potting mix etc is generally sold to the typical gardener in a plastic bag that sits in a pile on a pallet outside, so probably stays quite toasty for most of summer when people are using them.

S Bengi wrote:I wonder what people are doing with their compost to make it airborne? Wearing a mask should help.

Just seems to be by opening the bags and using it - nothing special or unusual is being done. People are wetting it down and letting it settle after opening it before using it to try and minimise the risk, but even then - without a mask it's not enough it seems.

Legionella is, apparently, everywhere here in the water and soil. Which is why I wonder - is it something to be concerned about with home-grown compost and gardening in general as well..
I know there's a lot of talk on here about how being in contact with the soil is generally thought to be good for you - but .. now I wonder if that's still true here.

Would appreciate any resident experts on soil life adding some thoughts! :)

[edit to fix broken quote tag]

As long as you don't make and inhale a aerosol it will be fine. I took baths (not showers) in legionella invested water for YEARS and it never hurt me or anyone that I knew. I digg in the soil and swam in the river. I am sure that not taking showers isvwhat saves my lungs, because the microbes cant do anything to my skin or even my belly if I drink it. It only affects/infects lungs.

My experience with it comes from the industrial use waters , especially from cooling towers. Never had a problem, at least that I know of, from compost.

I am wondering if bagged , wet, compost, setting in warm conditions is a perfect breading ground for the bug?

I am wondering if when folks open the bags and work with the compost they are getting a good dose of the bug as it becomes airborne?

I am wondering if the suppliers need to rethink their packaging strategies, to be sure that the bug cannot grow in the compost to begin with?

Possible make the bag breathable so that the air doesn't get a lethal buildup of bacteria per X volume. But with breathable packaging it would be more aerobic vs anaerobic (out competition). And the microbes concentration would be closer to the background low level that is "non-lethal' due to simple diffusion.

It is also possible they don't have a backflow preventer on their hose and the microbes goes back to the water supply then multiple and next time some spraying or misting or shower happens it is filled with legionella.

This is a microbe that simply needs moist conditions to multiply (it is just about everywhere on the planet like almost all bacteria and just like most other "harmful bacteria" if the conditions are not just right, illness in humans or other organisms doesn't occur.

A plastic bag full of compost, left in the sun, will sweat the water out of the compost, that gives the legionella bacterium perfect breeding conditions inside the bag, when the bag is opened there will be aerosol action caused by the outside air moving into the bag.
When most people open a bag of this type, their faces are generally in close proximity to the new aerosols that will be forced out just from the actions of opening the plastic bag.
I suspect this is the mechanism that is causing such infections.

Redhawk

I'm so glad permies are talking about this already - thanks for starting the thread Nathan and for all of the reasonable replies.

I think this is one article that has gone a bit viral about Legionnaire's disease in potting soil:  https://theplantguide.net/2019/01/03/dangers-of-potting-mix-highlighted-after-death-of-christchurch-gardener/ (Christchurch, New Zealand).

What's interesting to me is that the infected man contracted pneumonia from the potting soil, went to the hospital, and was being cured, then contracted pneumonia from the hospital that did him in! Some of Paul's research had indicated that most hospital pneumonia is also caused by legionella and might be due to water heaters not keeping the water hot enough. Gosh.


(picture from article above)

We've had other discussions on permies about legionella in solar hot water systems:
alternative hot water and legionnaires' disease
Legionella and solar water heating.

These might explain more about the optimal breeding temperature for legionella, and how it is the water vapor that is inhaled to infect folks.

One more reason for us to be less centralized and more home-scale.
The potting mix now have pharmaceuticals (human bio-solids) and pneumonia (Legionnaire)

This really makes me mad, because here is the skinny, at least here in Maine...

Our soil is acidic, VERY acidic and a few years ago the only lime plant in New England stopped selling Agricultural Lime to farmers. We can import it from New Brunswick, Canada, but the price is $120 a ton! That is too high. So we found out that we could get ash from the local biomass boilers for free! Like any ash, it acts like lime, sweeting our soil so we can grow crops. We liked it, and the boiler guys liked giving it away instead of paying for landfills to take it.

But water treatment plants had a problem. They can treat 99% of human waste, but what about the 1% of solid human waste they cannot? They tried to give it to farmers, but we did not want that crap...literally.

So the government stepped in and said the human waste from the treatment plants (called sludge) has to be mixed with ash. Most of the dairy farmers around here, already tight on money, just accepted that they had to take both if they wanted a cheap way to get the PH in the soil up. I refused, and still do. But now sludge is EVERYWHERE. They mix it with a little sand when the Maine Dept of Transportation does their projects where they need "loam", and it is in many concoctions labeled as "compost". Its sludge...human waste and is so bad, that back in the 1990's, the farms that spread straight sludge on their land, cannot be used for homes for 100 years due to the contamination. That is saying nothing about the fields litered with condoms and other "trash" that was in it.

I told the town back in 1990..."South Portland is not here because this stuff is great, they are here in rural Maine (2 hours away) because no one else wants this crap." Now years later the government has figured out a way to get rid of the sludge no one wants. Need a little loam anyone? It is only "compost".

But when you open a bag of "compost"...if its store bought, your most likely getting human manure. No wonder Legionaires Disease is prevalent.

Thanks everyone for the robust discussion on this!

Jocelyn Campbell wrote:I think this is one article that has gone a bit viral about Legionnaire's disease in potting soil

I'm not sure how much noise it's made overseas - enough, I guess :) - but we live in the Christchurch 'region' (it's our nearest main center). (I'm not sure about the about hospital side of his case either, but that sucks if it's the case!)

The other recent one that made a lot of noise in the local media - and perhaps for the sake of my original question here, perhaps more relevant - was a driver who delivered compost and garden "soil" in bulk. This wasn't the bagged stuff, so the conditions the bag introduces as a breeding ground seem less relevant.
( https://www.stuff.co.nz/national/health/107654679/legionnaires-survivor-worked-for-compost-company-wants-to-warn-others-of-danger )

(Side note - as far as I am currently aware, I don't believe waste sludge from the treatment plants is recycled into compost. A small portion is used in land-application on forestry, but the vast majority goes to landfill here I believe.)

Bryant RedHawk wrote:This is a microbe that simply needs moist conditions to multiply [....] will sweat the water out of the compost

Thanks for the input Dr R - are you saying that it's more likely to be growing not in the compost as such, but in the water that sweats out of the compost and gathers in the folds and creases? (Because aren't we meant to keep compost lightly moist for the bacteria to do it's job in breaking things down?)
Microscope-wise, do you think I would be able to identify legionella with the types of scopes you've recommended in your soil thread? (Most local options only go up to 1000x - I'd have to get one from a specialist company that imports them to get the 2500x)