Detection of airborne biological agents under difficult analytical conditions - background measurement and exclusion of inhibitory substances

Project number: F 2383 Institution: Federal Institute for Occupational Safety and Health (BAuA) Status: Completed Project

Description:

The interest in airborne microorganisms gains in significance since their metabolic products or components are discussed as causatives of health impairments for employees who handle microbially colonised material, e.g. in composting and animal husbandry facilities. The same holds true for residents of such facilities. Therefore, the risks resulting from the exposure to airborne microorganisms need to be assessed and evaluated.

In this context, the risk assessment of bioaerosols in comparison with "unaffected" outdoor air as a background reference is necessary. However, the investigation of outdoor air can be challenging due to the small amounts of microbial material.

Therefore, this project aimed at improving background investigations of bioaerosols. It also aimed at identifying parameters that influence the microbial concentration and composition of outdoor air. For this purpose, i) the extraction of DNA, ii) its quantification iii) the use of digital PCR and iv) metagenomics analysis were successfully established. Subsequently, daily background bioaerosol analyses in combination with the monitoring of various meteorological and air quality parameters were conducted at three different rural sites for a year.

A clear seasonal decrease in bacterial concentrations in rural outdoor air was observed in winter and spring. At the same time, however, the proportion of bacterial DNA in the total DNA in the air increased in winter and spring. A significant negative correlation was observed between bacterial concentration and humidity at all sampling sites and in all seasons. The results also showed that the bacteria in the studied rural outdoor air were mainly of animal origin. However, the concentrations were markedly lower than those found in agricultural workplaces or in the exhaust stacks of industrial livestock facilities.

The results of this project help to identify the sources of airborne bacteria and the factors influencing microorganisms in outdoor air, and thus to better classify the risk to bioaerosol exposures at the workplace.