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SSBRA (Site Specific Bio-Aerosol Risk Assessment)

A Site Specific Bio-Aerosaol Risk Assessment seek to establish risks from bio-aerosols at a given site. They are normally required where a source of bio-aerosols such as a composting facility is in close proximity to a dwelling or other sensitive receptor.

Sensitivity to Bio-Aerosols

We have mentioned composting as an example source of bio-aerosols, but sewage works and other wet processes involving organic matter can be sources of bio-aerosols. bio-aerosol_risk_assessment

During the shredding, tipping and bagging of the manure / bedding mixtures, there is the potential for release of bio aerosols. The manure / bedding mix is primarily treated via shredding, secondarily there is some aerobic break down of material before the shredded mix is bagged.


Bio-aerosol policy has been developed with respect to Composting. The EA has issued a bioaerosols  policy statements  on potential health effects of bio-aerosols from composting and bio-waste. The policy only covers the risks posed by bio-aerosols on human health.






At the point of receptor there are define acceptable levels for bio-aerosols.

How does Wind Effect Bio-Aerosol Levels  wind_bio-aerosol

Wind is a powerful tool in the control of bio aerosol emissions, whether prevailing winds blow towards or away from sensitive receptors can be a make of break factor in the application process.

Of course if it turns out that an open air activity is giving rise to unacceptable levels of bio-aerosols then the operation can always be put in a building. .  .but this is expensive and normally unnecessary.

Compiling an SSBRA is pretty tricky stuff, even for a professional, and is fairly time consuming if you would like SWEL to compile an SSBRA for your facility then please call or email and we will help out.

Types of Bio-Aerosol


Fungal spores produced during reproduction can vary in size, typically between 2 and 50 µm.  They are often small, light and therefore easily transported by air. Fungi produce secondary products during metabolism, such as mycotoxins (toxic substances produced by fungi during their growth), as well as shedding components, such as glucans.  Glucans are highly-branched polymers of glucose that occur as components of the cell walls of yeasts and other fungi.  


Bacteria are single-celled prokaryotic organisms and are the most important group during the initial stages of the aerobic degradation ( Miller, 1996).  Bacteria are usually between 1 and 5 µm in size, and are divided into Gram-negative bacteria (predominantly of animal origin) and Gram-positive bacteria (predominantly of plant origin).         


These are filamentous Gram-positive bacteria, some of which are thermophilic and thrive in wet compost.  They are of concern since the thermophilic actinomycetes species are recognised respiratory allergens which produce large numbers of very small spores (1-3 µm diameter) capable of deep penetration in the human lung.


This is a term given to fragments of the bacterial cell wall from all Gram- negative bacteria and some blue-green algae.  Endotoxin is present in compost as a consequence of the presence of Gram-negative bacteria as well as being a component of some organic dusts which may contribute to feedstocks. Endotoxin may cause both short-term and long-term illness by inhalation.       


These are non-volatile low molecular weight secondary metabolites produced by fungi.  Most commonly encountered through ingestion, mycotoxins can be carcinogenic, neurotoxic and teratogenic, and may also contribute to occupational lung disease in workers exposed to organic dusts.


These are polymeric species of glucose found in the cell walls of fungi, some bacteria and plants.  (1  → 3)-β -D-glucan is a potent inflammatory agent which has been associated with an increased prevalence of atopy, decrease in lung function and adverse respiratory health effects in the indoor and occupational environment.  There is evidence that (1 → 3)-β - D-glucans may enhance pre-existing inflammation in human subjects.

Health Risks from Bio-Aerosols

As mentioned above bioaerosols can penetrate deep into the lungs; causing respiratory and gastro-intestinal symptoms such as inflammation, coughs, fever and exacerbation of respiratory diseases. Endotoxins cause symptoms from eye irritation and dermatitis or in extreme cases resemble those of influenza, such as shivering, an increase in body temperature, dry cough, and muscle and joint pains.

Relevant to waste management are infections caused by Aspergillus fumigatus. Invasive aspergillosis is a severe infection, which may be fatal and is a concern with 'at risk' and 'immuno-suppressed' patients. Healthy individuals are not usually affected by bioaerosol in the natural environment and there is no published evidence that nearby occupiers have suffered ill health effects from bioaerosol from waste sites. However, it is accepted that, at some point, high concentrations or long exposure could affect a vulnerable individual and in some circumstances bioaerosol or associated toxins could overwhelm the body's natural defences.

Therefore a precautionary principle is adopted for the assessment of potential health risks. A study of health effects from waste management on behalf of Defra reviews bioaerosol from various waste activities. In addition to worker health the report considers public health.

For example, the report refers to studies by the HSE & others measuring bioaerosol from various waste locations that found levels reduced to background within 50 metres of the sites; suggesting that emissions from are not likely to be significant. Review of Environmental and Health Effects of Waste Management: Municipal Solid Waste and Similar Wastes