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Compost Safety (Hint: Compost Can Cause Legionnaires’ Disease)

Posted in Food Safety,Legionella,Legionnaire's disease,Our Blog on April 3, 2019

Compost is called black gold for a reason. A mainstay of organic gardening, compost is considered a valuable soil conditioner, one that makes soil more hospitable to plants. Made of decomposed organic material, compost encourages healthy populations of earthworms and other beneficial insects. Compost increases moisture retention and reduces the incident of damping off in plants. Compost promotes the aeration of soil and makes it more friable, allowing plants to more productively take root. All this from a mix of carbon rich “browns” (such as leaves, newspaper and dryer lint) and nitrogen dense “greens” (like kitchen scraps). But let’s talk compost safety for a minute. Did you know that compost can cause Legionnaires’ Disease?

However, as noted by the International Associations of Certified Home Inspectors, “The benefits of the practice are generally well-known, but few people are actually aware of the potential hazards and dangers composting can pose.”[1]

While it’s true that organic material will break down without human help, some intervention and responsible use is needed to make sure compost remains healthy for humans and plants. For all its beneficial gardening properties, compost piles can also be a breeding ground for pathogens. Rotting plant matter can incubate fungus and bacteria. Animal waste and pesticide can contaminate compost bins not properly guarded. Composting is an effective organic gardening practice as long it is done with care.

One of the most common pathogens present in composting is aspergillus. This fungus can cause a range of respiratory ailments. Infections or allergic or asthmatic reactions are possible when exposed to aspergillus. Plant Nature Resource Center explains that aspergillus “is ubiquitous not only in compost heaps but in the atmosphere. Aspergillosis usually attacks people whose health is already compromised. Especially at risk are people who have asthma, those whose lungs are pitted or scarred by previous diseases such as tuberculosis, and those who have seriously compromised immune systems such as AIDS patients.”[2]

Another pathogen possible in compost bins is legionella. This bacteria causes the atypical pneumonia, Legionnaires’ disease. As reported in Medical News Today, “ First isolated in 1980 from a patient in Long Beach, CA, L. longbeachae is found in compost and potting soil. Studies have suggested that inhalation and ingestion of these products may cause Legionnaires’ disease.” [3]Smokers and those with chronic pulmonary diseases are at greater risk of infection.

In addition to inhaled pathogens, it is possible to contract infection via the skin. Even a small cut can allow tetanus into the bloodstream. Paronychia, a nail and skin infection caused by staph bacteria, can be caused by contact with compost and garden soil. As with any other infection, those with reduced immune efficiency are at greater risk.

Another item that should be of concern is pathogen infection via animal waste. As the International Association for Certified Home Inspectors note, “histoplasmosis is caused by fungus that grows in guano and bird droppings” which can be especially problematic is touched or bacteria is inhaled by the immunocompromised. Environmental contamination from cat and dog feces is more common an issue that is widely known. A number of different types of contaminations are possible, including staph, giardia and campylobacter.

Finally, the presence of pesticide or pesticide residue is also an item for concern for compost users. As Mother Jones explains: “Pesticide-laced compost has presented a quandary for the USDA’s National Organic Program ever since California regulators traced residues of dichlorophenyl-dichloroethylene, a breakdown product of DDT, and bifenthrin, an ant killer, to compost in pots of organic wheatgrass in Northern California  grocery stores (the levels were not high enough to make anyone sick). DDT was banned for most uses in the early ’70s and bifenthrin is classified as a possible human carcinogen and is highly toxic to fish. The NOP initially proposed setting a strict upper limit for bifenthrin levels in compost but abandoned the idea when wider tests revealed that many brands of commercial compost wouldn’t pass. Regulators ultimately decided to allow any level of contamination in compost so long as “residual pesticide levels do not contribute to the contamination of crops, soil, or water.”[4] It is impossible for consumers to get a clear sense of where compost might be derived from if they are purchasing it in a store but home composters can avoid pesticides by choosing to use organic matter in their own bins.

Though these risks associated with composting are real, the remedy to the problems are often easy. Create your own compost with organic ingredients. Make sure to critter proof your compost bin or heap so that pets or wild animals access it and contaminate it. Wear a mask when turning compost, especially if you are immunocompromised. Wear gloves when handling compost and gardening and wash your hands well with soap and water when you are done.

By: Kate Delany, Contributing Writer (Non-Lawyer)