Legal limits for fine dust in the air are based on the mass and size of the particles. Jing Wang, ETH Zurich, Switzerland, Maosheng Yao, Peking University, Beijing, China, and colleagues have collected ambient particulate matter (PM) in 13 different size ranges (10 nm to 18 μm) in two regions (Zürich, Switzerland, and Beijing, China) and have investigated the particles’ mass, metal content, endotoxin distributions, and related oxidative potential. They found remarkably different PM distribution patterns: As expected, the air quality of the Beijing region was worse than the samples from Switzerland indicated. However, looking at the oxidative potential of PM, for example, the effect of some Swiss samples with comparable particle quantities was more severe.
The oxidative potential is a measure of the damaging effect of fine dust, as aggressive substances trigger oxidative stress and reactions of the body’s immune system. Oxidative stress can be caused by metals such as cadmium and arsenic or soot particles. In China, large quantities of ultrafine arsenic particles indicated an increased health risk. Samples from the Zurich suburb of Dübendorf, in contrast, contained significantly more iron particles in the 10 µm range. They originate from the abrasion of the nearby railway line. Together with copper and manganese, the iron dust in the Dübendorf air contributed to the oxidative potential of the air samples.
In addition, an air sample from a Swiss farm fared worse than that from a busy road in the middle of Beijing concerning the contamination with certain bacterial products. It is known that such endotoxins are abundant in the air in the surroundings of cows and other animals. Especially for people with a weakened immune system, particles contaminated with bacterial endotoxins can pose a serious health risk.
The researchers conclude that the effects of fine particles on air quality and health cannot be solely based on their amount. Only if the composition of particulate matter is known, can a regionally adapted health protection plan be implemented. The researchers are now developing standards for more precise analyses of PM to identify dangerous components more easily and to prevent health risks with optimized strategies.
- Size-Resolved Endotoxin and Oxidative Potential of Ambient Particles in Beijing and Zürich,
Y. Yue, H. Chen, A. Setyan, M. Elser, M. Dietrich, J. Li, T Zhang, X. Zhang, Y. Zheng, J. Wang, M. Yao,
Environm. Sci. Technol. 2018.