With thanks to a reader who submitted this article.
Aspergillosis – is it a New Occupational Disease caused
Aspergillosis is a general medical term given to a wide variety of disease caused by Aspergillius fumigatus.
What is Aspergillus?
Aspergillus is a group of several hundred fungal mould species with a worldwide distribution.
Aspergillus species produce fungal spores, these are microscopically small particles (typically five microns in size – 1 micron equals 1'000 of a centimetre) that are invisible to the naked eye. They can remain airborne for long periods of time, forming what are known as bio aerosols (an airborne micro-organism). Bio aerosols may also contain other fungal spores and bacteria. These may be viable or non-viable, viable means alive and capable of growth in a laboratory. Viable bio aerosol may contain pathogens, these are micro-organisms that can cause disease through infection. Viable, or non-viable micro-organisms also contain allergens, these are capable of causing an immunological response in the human body – an allergy.
A mould commonly found is Aspergillus fumigatus, this is known to be an opportunistic pathogen with allergenic properties and viable or non-viable or broken down into smaller particles. Aspergillus fumigatus retains it's toxic and allergenic properties.
Aspergillus fumigatus is commonly found in decaying plant and animal matter, this includes: green garden waste, composted garden waste, animal manures, stable bedding, shredded wood-chip and bark, household kitchen waste, also found in soils.
Activities that involve disturbing potentially mouldy materials, such as leaf raking, cutting down Herbaceous plants in Autumn, spreading compost, bark or wood-chip as a mulch or any other activities such as turning compost piles, loading or spreading compost, if the conditions are right will cause Aspergillus spores to become airborne, often in high levels.
Aspergillus, by its ubiquitous nature is found in the everyday air that we breathe, normally at very low concentration but, in the months July through to November, fungal spores can peak to very high levels in the atmosphere. As well as Aspergillius, the following fungal spores are found at this time of year in air samples: Alternaria, Cladosporium, Didymella, and Penicillin & Sporobolomyces. These fungi are also allergens.
One of the concerns with spores from Aspergillus fumigatus is its particle size. Typically about 5 microns in size. Particles above 10 microns the human respiratory system can adequately filter out, through a combination of hair which line the nose and specialized cells in the upper parts of the airways. The smaller particles below 10 microns escape capture from these mechanisms and penetrate deep into the areas of the lungs, particles below 5 microns can enter the alveoli, the smallest structure of the lung, where gasses are exchanged.
Recent research into Aspergillus fumigatus has found it to be made up of some 10,000 proteins, of these 34 proteins are allergens and 3 of these are found to be protease, which means they are capable of breaking down proteins such as proteins found in the lungs.
Aspergillus has other routes into the human body, other than being breathed in, absorption through the mucus membranes, eyes, nose, and throat and by ingestion.
A New Industry
The compost industry is relatively new industry producing levels of composted green waste and food waste in levels that have never been reached before. This is partly due to the EU landfilled directive to meet set targets on recycling and at present in England some 95% of local authorities have some form of green waste recycling.
The result of this is an estimated 25 million tonnes per annum of compost from green waste (the un-composted green waste levels will be two or three times this amount – 50-75 million tonnes). Of this 50% is used by agriculture, the rest between the horticultural industry and land regeneration schemes. A further 500,000 tonnes per annum is estimated to be composted at the home. In 2005/06 the composting industry distribution of sales was estimated to have a turnover of £90 million.
Composting green waste on a commercial scale, although it uses a natural process, could be argued is itself not natural. A close control must be kept at all times on moisture levels, oxygen levels and the correct levels of carbon and nitrogen in the feed stocks. If correct levels are maintained a temperature of 70°C may be produced by the process. This sanitises the compost, killing off a lot of pathogens and weed seeds.
Commercially the processed compost may be ready for use after a 12 week period of composting, though after this short time, the “maturation” stage will not have been completed. The compost may still retain some heat and high levels of Ammonia.
Of course there are many benefits of using correctly composted green waste, such as improving soil structure, providing slow release plant nutrients, some improved plant resistance to pest and disease and directing green waste away from landfill.
The composting industry seems to be very well regulated by the Environment Agency and recently they have changed the permitting regulations for composting green waste, food waste, taking into account environmental factors as well as health and safety of the employees as well as bio aerosol levels in the area surrounding the sites.
Health Implications For Humans
We all react to bio aerosols in different ways; it depends on a variety of factors and can never be predicted. People may have been working with compost for many years without apparently displaying any adverse health effects, but it does not mean there will be no long-term effects on health, we simply do not yet know, and with the increased use of composted materials we may well expect health problems to rise.
Although problems with bio aerosols is not a new phenomenon, for many years occupational diseases associated with mould spores have been known e.g. farmers lung, mushroom workers lung although these have been associated more with the fungus Alternaria than Aspergillus.
There is a particular group to whom Aspergillus may cause serious health problems.
These people are those who may have a compromised immune system such as: cancer patients undergoing chemotherapy treatment, patients with leukaemia, cystic fibrosis, HIV or AIDS, tuberculosis and adults with severe asthma.
They may be particularly vulnerable to Aspergillus infections, such as:
Ø IA – Invasive Aspergillus – Serious or potentially life threatening, rare in normal healthy people
Ø CPA – Chronic Pulmonary Aspergillus – A long term Aspergillus infection of the lungs
Ø Allergic reaction to Aspergillus could affect a far greater number of the population, allergies such as:
Ø ABPA – Allergic Broncho-Pulmonary Aspergillus – Range of lung problems caused by Aspergillus, some mild, some severe
Ø AFS – Allergic Fungal Sinusitis – A disease where fungal debris and mucus build up in the sinuses.
Allergy is the most common response to Aspergillus in humans. Allergy is an immunological response that results in the body becoming “sensitised” following exposure, the next time the body encounters exposure it “over reacts”, even if the allergic substance is present in extremely low concentrations.
Apart from ABPA and AFS, an allergic response to Aspergillus may cause headaches, tiredness, and mucous membrane problems, skin problems, asthma and also Alveotis, producing flu-like symptoms. It’s worth bearing in mind that many allergies require taking lifelong medication on a daily basis, and seriously affect an individual’s quality of life.
In 2009 Dr. Alison Searle – Director of analytical services at the Institute of Occupational Medicine, warned waste workers about the potential impact of bio aerosols on their own health. She claimed that the problem was like a time-bomb of major respiratory health problems in the future.
In Germany in 2008 Harold Moor, a leading neurologist who is also chairman of the German Lung Foundation said studies showed that airborne mould spores from organic waste could lead to allergic reactions, asthma attacks, hay fever-like symptoms and itchy skin lesions, “Even just opening the lid of a bin containing organic waste can cause mould spores to be stirred up which if breathed in can damage the lungs”. As a consequence of this report German households are now being warned to empty their organic bins more regularly and to wear face-masks or hold their breath and keep a distance while dealing with the rotting material.
An extreme reaction to Aspergillus has caused two fatalities that have been reported in the press in the past few years. The first highlights the need for care when handling garden green waste. In 2008 in Buckinghamshire a man died from complications related to Aspergillosis. From what this partner described “he has been surrounded by a cloud of dust when he opened several bags of compost that he had prepared for use in his garden”.
David Waghorn, a doctor at Wycombe hospital in Buckinghamshire and a microbiologist, said the man had been unlucky: “He’d been opening bags of compost and mulch which had been left to rot. The fungus spores had grown in perfect conditions. He was extremely unlucky – there must have been a very large number of spores which he inhaled”, people with weak immune systems are particularly vulnerable. “What we don’t know is how strong his defences were. He was a smoker and a welder by trade and his lungs may have been damaged. It’s a very unusual thing to happen but if people are dealing with big bags of mulch, there is a potential danger” said Waghorn.
The man, who had previously been healthy, became ill 24 hours later, but was not admitted to hospital until a week later, when he complained of chest pains and breathing difficulties. Despite being given oxygen by medical staff, tests showed his tissue was starved of oxygen and that he was suffering from “overwhelming sepsis”, a life threatening condition caused by an over-active immune system. Symptoms include a fast heart rate, low blood pressure and kidney problems. Doctors initially thought he had developed pneumonia from a bacterial infection but treatment with antibiotics was not successful.
Once aspergillosis was confirmed, doctors gave intravenous antifungal drugs, but the treatment came too late.
Dr Waghorn said “I don’t know if he could have been saved had we known about the spores, but we could have given the antifungal drugs sooner.”
The authors of the article said that while acute aspergillosis after contact with decayed plant matter is rare, “it may be considered a hazard for gardeners.”
The second case was reported in The Scotsman in 2009. Stephanie Smith, aged 21, a trainee teacher who had suffered from mild asthma for most of her life, died after an asthma attack. She was diagnosed as “suffering from aspergillus, an infection contracted by inhaling the spores of a fungus that grows on soil, plant debris and rotting vegetation.”
The Need For Improved Education and Information
These two cases, though rare, highlight the need for a better informed and educated public as to the potential harm caused by Aspergillus, both the general public who buy small bags for home use and those who may well come into contact with large levels of composted material in their professional life; gardeners, agricultural workers, forestry workers, market gardeners and nursery workers.
With 50% of produced composted green waste going to agriculture, I wonder how many agricultural workers have even heard of Aspergillus, let alone the possible health concerns? Suppose 200 tonnes of composted green waste has been delivered to a farm.
The most probable way this would be put onto the land would be by using a slurry spreader, which would be very effective, if conditions were right, i.e. a dry, windless, sunny day, with low moisture levels in the compost, for creating high levels of a transient area of dust and spores, which may not be seen with the naked eye – bioaerosol. If the field where the compost is spread has a public footpath in the vicinity, or is nearby housing or roads, or if the tractor operators do not have adequate protection, such as a sealed cab fitted with hepa filters, how many people could be subjected to high unnecessary exposure levels of bio aerosols, with potential for harm.
Composted green waste is also used in peat reduced compost for potting and garden use (also composted manure, stable bedding is bagged and sold for garden use.) Sold to the general public, usually on a “Buy one get one free” basis, at many garden centres and DIY stores across the country. Suppose two bags of compost are bought, one bag of compost gets used, the second bag gets opened but not all used and is stored in a garage or shed for use next year. In storage perfect conditions may occur for the development of Aspergillus to proliferate. Next year the bag, when opened, may produce a “surrounding cloud of dust” with potentially harmful consequences.
More than one scientist has remarked the “Aspergillus may be the new Asbestos”, some, however, claim that it is as harmful as a walk in the autumnal woods, this may indeed subject us to higher than normal levels of airborne moulds and fungi spores, but in the main our bodies cope with these natural low exposure levels.
The middle ground between these two extremes must dictate that if there is a risk to human health, then this risk needs to be well managed, exposed, and not hidden behind green objectives or financial profit.
We are facing an ever increasing rise in the number of people suffering from allergy in this country. A recent report by Allergy UK reveals that allergy to dust mites is the biggest problem followed by pet allergy and mould allergy, and it seems levels of people suffering from allergies of all types are rising annually.
Perhaps once the next decade has passed the scientists may come up with the answer to some of these questions, regarding Aspergillus. Some of us however may have already found out, at our own personal cost to our health.