Guide To Bioaerosol MonitoringCompost producers are increasingly being asked to perform bioaerosol monitoring at existing facilities or when submitting planning applications for new sites. Data has been published on the subject of bioaerosols but due to the lack of clear legislation in terms of emissions or occupational exposure, confusion exists about why bioaerosol monitoring is necessary. There are presently no UK or European standard methods (2006) relevant to sampling at waste facilities but the Composting Association has produced a standardised protocol for the enumeration of bioaerosols that contains useful information and provides the basic model for monitoring. The Environment Agency Technical Guidance Document M17 references the Composting Association Protocol and contains additional information on air quality. These two documents are essential reading for anyone concerned with any aspect of environmental air quality legislation and the following information may be useful to both existing compost producers and to the planners of new composting sites. Bioaerosol is a term used to describe micro-organisms (bacteria, actinomycetes, fungi/moulds, or viruses) or their products (enzymes, endotoxins, mycotoxins, and glucans) that are suspended in air i.e. airborne. Composting by its nature involves biological activity and operations such as shredding, screening, and turning of open windrows, can release organisms that can form bioaerosols. A single bioaerosol particle is so small that it is not visible to the naked eye and some particles may travel up to 1 kilometre from the point of emission. In-vessel composting systems can also produce bioaerosols as decomposing material awaiting processing can give rise to bacterial and fungal spores. Harvesting material from in-vessel systems can also release fungal spores and thermophilic bacteria that survive processing. Localised concentrations of bioaerosols may travel a considerable distance from the source of an emission depending on environmental and weather conditions. Bioaerosols are very small (less than 10 microns in diameter) and may come from a number of different sources. There are concerns that they may pollute the environment so monitoring is carried out to ensure environmental compliance. Some bioaerosols can produce toxins that may affect human health in the form of skin allergies, sickness, or respiratory diseases therefore monitoring may be carried out to check levels and types of bioaerosols that composing site workers may be exposed to (occupational exposure levels). Generally no. Bioaerosol monitoring is extremely specialised and should be carried out by competent people who are familiar with how to devise site-appropriate sampling plans and sampling procedures. They will be familiar with handling sterile or sensitive equipment without causing contamination. Contamination can lead to results that are difficult to analyse or interpret. There are currently no legal occupational or environmental exposure limits in the UK . The Environment Agency and other regulators in the countries of the UK favour a risk-based approach to evaluating bioaerosol emissions. Consequently, where there is a dwelling or work place within 250 metres of a composting facility, the regulator will seek scientific evidence that demonstrates an appropriately low level of bioaerosols. There are a number of techniques that may be used for measuring and estimating bioaerosols but the Environment Agency Document M17 advocates the following methods:
Agar plates containing specific growth media are incubated in a laboratory where microbiologists will examine the plates to identify which micro-organisms are present and at what levels. Airborne micro-organisms can be calculated to estimate their intensity and they will be expressed as the number of colony forming units detected per cubic metre of air sampled (i.e. cfu per cubic metre). You should consider what the final results will be used for and you should choose the most appropriate test method for your needs. A service provider will be able to advise on the most suitable test method for a particular application and generally a compost producer will not be concerned with the particular analytical method used. Some methods will examine ‘viable’ micro-organisms (those that can reproduce or replicate), whilst other methods will examine ‘total micro-organisms’ (viable micro-organisms plus dormant, dying, or dead micro-organisms). Yes, the Environment Agency (or Scottish Environment Protection Agency and Heritage Service) are primarily concerned with bacteria and fungi, and their bi-products such as toxins. Due to the lack of current legislation and European standard methods, the Composting Association Standardised Protocol for the Sampling and Enumeration of Airborne Micro-organisms at Composting Facilities is used as the basic model when monitoring of mesophilic bacteria (bacteria that can grow and survive in temperatures between 20-45 ° C), and fungal spores (including Aspergillus species). In addition Gram-negative bacteria may also be monitored as some Gram negative bacteria can cause harmful effects to humans. Again, a specialist service provider will be able to advise on an appropriate monitoring programme. Additional information about bioaerosols and bioaerosol monitoring can be found as follows: The Composting Association’s publication ‘The Standardised Protocol for the Sampling and Enumeration of Airborne Micro-organisms at Composting Facilities’ Environment Agency Technical Guidance Document M17 ‘Monitoring of Particulate Matter in ambient air around waste facilities’ http://www.environment-agency.gov.uk/commondata/acrobat/m17mon_partic_matter_758466.pdf Health and Safety Executive Research Report 130 ‘Occupational and Environmental Exposure to Bioaerosols from Composts, and Potential Health Effects’ http://www.hse.gov.uk/research/rrpdf/rr130.pdf Environment Agency Guidance on Assessment of Risks for Landfill Sites, May 2004
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