On-Line BioAerosol Sensing
The objectives of the OLBAS study are:
- To provide a comprehensive literature review of sources, removal pathways and concentrations of airborne Primary Biological Aerosol Particle (PBAP) releases with an emphasis on waste-management sites.
- To perform two bioaerosol/metereological measurement campaigns at two contrasting green waste/composting sites in Ireland, in order to develop the concept of “bioaerosol site profiles”.
- To provide a scientific foundation for assessing the environmental/occupational advantages of on-line (real-time) instrumental approaches to the detection of airborne microbes that promote adverse health effects, like Aspergillus fumigatus.
- To assess the possibility of developing a national pollen monitoring service in Ireland at the Met Eireann Valentia Observatory site.
To provide a “proof of principle” for compiling PBAP “early warning” systems to the general public, particularly those with “at risk” respiratory health issues.
The need to measure the occurrence and transformation of aerosols in our atmosphere has increased dramatically in recent years. The necessity is based on the undesirable effects that they can have on our health and the role they play in climate change. The atmospheric aerosol does not, of course, consist of abiotic chemical components alone. Field measurements have shown that Primary Biological Atmospheric Particles (PBAPs) are also present and comprised of materials such as viruses, bacteria, fungal spores, pollen, and plant fragments. The diameters of these materials range between nanometres and hundreds of microns with a wide variety of morphologies.
Waste management processes that involve strategies to reduce waste to landfill typically involve the composting of organic materials. Despite the obvious benefits of such activities, it is also known that exposure to composting-released PBAP (e.g. Aspergillus fumigatus) can be detrimental to human health. Concerns then arise because bioaerosols released from composting sites (including home composting activities) can remain airborne for some time and travel off-site. Due to the small diameters of certain PBAP, they are able to penetrate deep toward the inner lining of the lungs into the alveoli and lead to health problems. Many respiratory illnesses and infections such as Farmers’ lung, hypersensitivity pneumonitis, aspergillosis and chronic obstructive pulmonary disease (COPD) have all been linked with agricultural/composting work.
In the past, detection techniques for fungal spore types and also pollen have been generally confined to methods such as impaction of air samples onto adhesive sample substrates before analysis using optical microscopy. This undertaking relies on the intrinsic skill of the identifier and is also very labour intensive because careful preparation of the substrate is required for accurate analysis. Other, more modern, methods for determining fungal spore concentrations and species identification include: (i) the IOM (inhalable dust) filtration sampler, which can be deployed close to the source of the bioaerosol emissions; (ii) the Andersen sampler, an impaction device that is prone to overloading and cannot be used reliably in highly contaminated environments. While both of these culture-based techniques are more exact in their determination of differing species, which cannot be attained on all occasions using optical microscopy, they also require considerable time for the sampled fungal spore to grow on a suitable agar. One experimental aspect in common between the culture and non-culture based methods is that only “snapshot” results are obtainable. In other words data are generally collected just once or twice over periods of minutes at sites downwind and upwind (as a control) rather than being obtained continually over periods of days. Therefore detailed long-term profiles of green-waste site bioaerosol emissions cannot be constructed as a function of important variables such as site location, weather conditions or agitation activities such as turning and loading.
The use of light induced fluorescence (LIF) and laser scattering to the qualitative and quantitative determination of PBAP represents a relatively new, on-line approach to provide for their counting and discrimination. For this purpose instrumentation such as the Waveband Integrated Bioaerosol Sensor (WIBS) series has been developed. Its LIF methodology depends upon the fact that many structural components and secondary metabolites of PBAP such as tryptophan, tyrosine and NAD(P)H fluoresce. Hence the use of UV flash lamps tuned to 280 nm and 370 nm for appropriate biofluorophore excitation gives rise to emission profiles that separate them from non-fluorescent chemical particles. Such a non-destructive and rapid process, in theory, could be used to determine and characterise individual PBAP number counts with much greater time-resolution and rapidity than any other techniques that are currently available.
No previously published study has employed the on-line WIBS technique for the monitoring of bioaerosol emissions from a composting/green waste site. We intend to produce the equivalent of “videos” of bioaerosol release as a function of time, site activity and weather.
Currently Ireland’s pollen counts depend upon the collection and characterization of data generated by the University of Worcester, UK. The measurements are made by the traditional impaction/eyeball analysis described above. We will set WIBS up at the Valentia Observatory in Kerry to try to characterize and count (in real-time) birch pollen specifically because of its allergenic effects.