Monitoring outdoor concentrations of airborne asbestos in urban and residential areas in the four major cities of Denmark: Copenhagen, Odense, Aarhus and Aalborg

Background and aim:
In Denmark, 1.3 million buildings are currently registered as having asbestos-containing roofing. Studies have demonstrated that natural weathering of asbestos-containing materials can lead to the presence of airborne asbestos in the environment. The objective of this study was to measure the outdoor concentrations of airborne asbestos fibers in urban and residential areas of Denmark.
Methods:
We collected 192 outdoor air samples during June to September 2024 and March to May 2025 across four major cities: Copenhagen, Odense, Aarhus, and Aalborg. In each city, we conducted measurements at four sites in urban and residential areas, respectively. Additionally, we collected samples at four sites within each of two natural areas and four sites within each of two residential neighborhoods consisting exclusively of houses with asbestos-containing roofs. All samples were analyzed using phase-contrast optical microscopy (PCM) and scanning electron microscopy combined with energy-dispersive X-ray analysis (SEM-EDX).
Results:
Asbestos-like fibers were detected in 108 (58 %) samples analyzed by PCM; however, the concentrations exceeded the limit of detection (LOD) of 300 f/m3 in only nine samples. The majority of these samples were collected in urban areas with concentration ranging 300–500 f/m3. Asbestos fibers were detected in 10 (5 %) samples analyzed [...]