Production and characterization of particle atmospheres in the ExpoLab for human inhalation studies and characterization of further particles.

Status:

completed 12/2023

Aims:

Results from animal experiments are still used to derive limit values and protective measures at the workplace, but they contain great uncertainties and risks regarding transferability to humans. In the exposure laboratory (ExpoLab) of the Institute for Prevention and Occupational Medicine (IPA), experimental human studies have therefore been carried out on volunteers for ten years to derive limit values. In various projects, among other things, the inflammatory reactions in the respiratory tract of healthy volunteers are determined, which are triggered by particles dispersed in the respiratory air of the volunteers. Basically, two different aerosol generator systems are used to generate particle atmospheres in the ExpoLab of the IPA. The aim of the investigations at the Institute for Occupational Safety and Health (IFA) was to characterize the particles generated in this way. The chemical composition of the aerosols, the particle size and shape, as well as the dispersion and agglomeration should be determined. The investigations should help to ensure that the particles brought to the exposure correspond to the type, size and distribution in the breathing air intended for the experiments.

Activities/Methods:

To obtain the best overview of the processes and results of the generation of particle aerosols from the aerosol generator systems, different types of samples are analyzed. In addition to material samples of the source and generated substances, air samples taken by means of air sampling in the breathing air of the exposure chamber are also analyzed. A wide range of methods is used for the qualified description of the samples. Depending on the task, phase contrast microscopic, infrared spectroscopic (IR), X-ray diffraction and scanning electron microscopic (in combination with energy dispersive X-ray microanalysis (EDX)) evaluations are performed.

Results:

Scanning electron microscopy proved to be primarily suitable for characterizing the particles used for the inhalation studies. The particle size and shape, as well as the dispersion or agglomeration could be determined. The degree of dispersion could be determined by comparing the analysis of the starting material (material sample) and the particles collected from air samples. EDX analysis was used to verify the chemical composition of the aerosols. For further qualitative analysis (type of phase, purity and possible contamination of the materials), X-ray diffraction, IR spectroscopy and phase contrast microscopy were used. The successful generation of suitable test atmospheres was verified on nano- and micro-zinc oxide, micro-barium sulfate and two different nano-titanium dioxides.

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