Generation of bioaerosols during manual mail unpacking and sorting

Abstract

Aims: The dynamics of bioaerosol generation in specific occupational environments where mail is manually unpacked and sorted was investigated. Methods and Results: Total number of airborne particles was determined in four different size classes (0AE3-0AE5, 0AE5-1, 1-5 and >5 lm) by laser particle counting. Time dependent formation of bioaerosols was monitored by culturing methods and by specific staining followed by flow cytometry. Besides handling of regular mail, specially prepared letters (Ôspiked lettersÕ) were added to the mailbags to deliberately release powdered materials from letters and to simulate high impact loads. These letters contained various dry powdered biological and nonbiological materials such as milk powder, mushrooms, herbs and cat litter. Regarding the four size classes, particulate aerosol composition before mail handling was determined as 83AE2 ± 1AE0, 15AE2 ± 0AE7, 1AE7 ± 0AE4 and 0AE04 ± 0AE02%, respectively, whereas the composition changed during sorting to 66AE8 ± 7AE9, 22AE3 ± 3AE6, 10AE4 ± 4AE0 and 0AE57 ± 0AE27%, respectively. Mail processing resulted in an increase in culturable airborne bacteria and fungi. Maximum concentrations of bacteria reached 450 CFU m )3 , whereas 270 CFU of fungi were detected.Conclusions: Indoor particle concentrations steadily increased during mail handling mostly associated with particles of diameters >1 lm. However, it was not possible to distinguish spiked letters from nonspiked by simple particle counting and CFU determinations. Significance and Impact of Study: The dynamics of bioaerosol generation have to be addressed when monitoring specific occupational environments (such as mail sorting facilities) regarding the occurrence of biological particles.

Short-term dynamic patterns of bioaerosol generation and displacement in an indoor environment

“…The relative concentration of very small particles (size range 0.3-0.5 lm) concurrently decreased. Variations in composition (as a percentage contribution of different size ranges) have previously been observed on other occasions when temporal fluctuations of indoor airborne particle concentrations have been triggered by anthropogenic activity such as unpacking of mail, unloading of agricultural products in industrial environments, and smoking, cooking, and cleaning in residential locations (Brandl et al 2005;Branis et al 2005;Morawska et al 2003;Stetzenbach et al 2004). Diurnal variations have been observed; these were correlated with human activity (Morawska et al 2003;Abt et al 2000).…”

“…At that time it had already been observed that bioaerosols in indoor environments were heterogeneously distributed in the air and occurred in ''bacterial clouds'' (Tyndall 1876). Microbial concentrations may fluctuate in time periods of minutes by several orders of magnitude (Brandl et al 2005;Lighthart and Shaffer 1995). Indoor bioaerosol concentrations are related to climatic factors (e.g.…”

“…It has been estimated that at some locations and times of the year particles of biological origin can contribute up to 50% of total airborne particle numbers (Jaenicke 2005). Airborne microorganisms might pose an environmental hazard when present in high concentrations in indoor environments, resulting in health problems (Stetzenbach et al 2004), especially in industrial or agricultural environments (Brandl et al 2005;Dutkiewicz et al 2000;Zollinger et al 2006;Zormann and Jeršek 2008).…”

Bioaerosols in Indoor Environment - A Review with Special Reference to Residential and Occupational Locations

“…MAS-100eco single stage impaction samplers are used for the collection of bioaerosols by some authors [11,33]. An amount of 50 to 500 l of air (or less depending on the sampling location) can be collected in time intervals of 3 to 5 minutes.…”

“…Generally it is necessary to perform replicate sampling using different culture media or to divide samples for inoculation on to multiple types of nutrient media. Several broad spectrum media have been evaluated for culturable airborne fungi such as malt extract agar, Rose Bengal agar and DG-18 agar [33,[67][68][69]. For the cultivation of bacteria, several broad spectrum media such as tryptic soy agar or nutrient agar are commonly used [27,56].…”