Endotoxins in urban air in Stockholm, Sweden
2011
Nilsson, S. | Merritt, A.S. | Bellander, T.
Endotoxins, i.e. components originating from the outer membrane in the cell wall of Gram-negative bacteria, activate the human immune system, which may result in airway symptoms such as shortness of breath and airway inflammation. Endotoxins are present in the environment, both outdoors and indoors, and stay airborne for a long time. In order to investigate the levels of endotoxins in urban air and the influence of traffic and meteorological factors, particles (PM₁₀ and PM₂.₅) were collected at five sites in Stockholm, Sweden on four occasions per site between May and September 2009. Endotoxins were extracted from the filters and analysis was conducted with the Limulus Amebocyte Lysate (LAL)-assay. Endotoxins were present in urban air in Stockholm, albeit in low levels, and were similar to levels found in urban areas outside Sweden. To our knowledge, this is the northernmost location where endotoxins have been measured. The endotoxin levels found in PM₁₀ ranged from 0.020 to 0.107EUm⁻³ with a geometric mean of 0.050EUm⁻³ and the levels found in PM₂.₅ ranged from 0.005 to 0.064EUm⁻³ with a geometric mean of 0.015EUm⁻³. No obvious effects of traffic or meteorological factors on endotoxin levels were observed, although a moderate correlation could be seen with soot. The small number of sampling sites is however a shortcoming of the present study. In future studies, more sites and sampling during all seasons would be preferable in order to get a better picture of the influence of different sources on endotoxin levels.
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