Bioaerosol monitoring – a practical evaluation of methodology

Hall, S.1,2, Gibson, H.1, Lambert, A.M.2 and Hill, D.J.2, University of Wolverhampton, 2Crestwood Environmental Limited, UK



Bioaerosols are airborne particulate constituents that include microorganisms, cell components (e.g. endotoxins) and other inhalable particles (e.g. pollen). Whilst ubiquitous in ambient air, industrialised processes can increase bioaerosol levels which raises concerns for people working within the industry as well as local residents and businesses. Particular processes have been associated with specific bioaerosol constituents (e.g. Aspergillus fumigatus with composting and Legionella with waste water). Health concerns associated with inhalation/ingestion of particular bioaerosol components justify the need to evaluate risk to human health through monitoring of bioaerosol levels. Biomonitoring methods commonly use impingement, impaction and filtration methods. This study evaluated these different methods by direct comparison of bioaerosol sampling undertaken at different industrial process sites. Data from these case studies is presented and critically evaluated. The impingement method used was significantly more frequently effective in yielding higher counts than the filter method. It is concluded that the effectiveness of the method used is likely to be influenced by the nature of the environment of the industrial process being analysed.

Key words:

Bioaerosol, monitoring, impingement, filter, air sampling, respiratory health, Aspergillus, gram-negatives,


Naturally present in the environment, suspended particulates of biological origin such as bacteria, fungi, viruses or protozoa and their constituents such as toxins, spores, allergens, pollen, mycotoxins and β(1→3)-glucans are referred to as bioaerosols (Taha et al., 2005). They can be suspended in the air as clumps, aggregates, single cells or cell fragments and due to their small size (typically less than 10µm in diameter), they are easily transported via wind. Their small size means that they can easily penetrate the lungs as they are not filtered out by hairs or specialised cells that line the inside of the nose (Taha et al., 2006).

Many respiratory illnesses have been attributed to be caused or worsened by bioaerosols to include aspergillosis and asthma. Endotoxins, which are fragments of lipopolysaccharide from gram negative bacterial cell walls, can produce airway inflammation when inhaled as they are potent proinflammatory agents (Deacon et al., 2009). Whilst some bioaerosol related illnesses can be acute, the main groups of people most likely to be affected are the very young, elderly, immuno-compromised, those exposed to high levels on a regular basis or people already suffering from some form of respiratory illness.

There are many sources of heightened outdoor bioaerosol levels associated with activities including wastewater treatment plants (Grisoli et al., 2009) livestock breeding and farming (Herr et al., 2003) and composting (Sanchez-Mondedero and Stentiford, 2003). Due to their variety in size when clumped together or attached to organic dust particles, plumes of bioaerosols can occur when levels are high whereby levels are super-concentrated in a particular timeframe. The source of bioaerosols will determine the key microorganisms present i.e. green waste composting and Aspergillus fumigatus, food waste composting and coliforms such as Escherichia coli and the wastewater industry, coliforms and potentially Legionella pneumophila.

Whilst most recent publicity has been concentrated on how current waste-based processes have an effect on the general public, more attention is now focused on people who regularly work at very close proximity to sources of bioaerosols such as compost facility operators (especially at in-vessel composting sites). Whilst there are Health & Safety concerns for the people working in industries associated with heightened bioaerosol concentrations, there are no dose-response levels in place to date making it difficult to assess the immediate risk to the health of the worker. However, with research on-going in trying to get closer to realistic threshold limits for bioaerosols, this paper looks at the effectiveness of different monitoring units to assess the levels exposed to. The most commonly used methods are impaction, filtration and impingement.

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