Sahara sand clouds Swiss visibility after Canadian smoke

Sahara sand clouds visibility after smoke from Canada Keystone-SDA

Sahara dust has further clouded visibility in Swiss skies, adding to smoke particles that drifted over from forest fires in Canada.

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As a result, the atmosphere is cloudy and visibility is reduced, MeteoSwiss wrote on X.

The Federal Office of Meteorology and Climatology (MeteoSwiss) published images of the cloudy visibility on this short news platform on Friday.

When Saharan dust is in the air, it reflects and scatters some of the sunlight. The sky takes on a yellowish colour and the sunrises and sunsets are more spectacular. The dust also leads to an increased concentration of particulate matter in the air.

However, the air quality was better than in the middle of the week, when the smoke from Canada polluted the air.

In Zurich, the concentration of so-called PM2.5 particles was 29 micrograms on Friday morning, according to the website of the Swiss environmental company IQAir. This is particulate matter with a diameter of less than 2.5 micrometres. The legal daily average limit is 50 micrograms per cubic metre of air.

According to the weather service, Saharan dust events contribute significantly to aerosol pollution in spring and autumn. Mineral dust is an important component of atmospheric aerosol. It originates mainly from deserts, but is also produced by soil erosion and agriculture.

The Sahara is the largest source of mineral dust, releasing between 60 and 200 million tonnes of dust per year. While the larger particles quickly fall to the ground again, the smaller ones can be carried thousands of kilometres and reach the whole of Europe.

Poor air quality

The smoke from Canada caused poor air quality this week. Some measuring stations recorded values on Wednesday that are considered unhealthy.

The legal limits were exceeded in many places. According to IQAir, particulate matter levels were particularly high. The concentration of PM2.5 particles at the Bern-Bollwerk measuring station on Wednesday afternoon was more than ten times the World Health Organisation’s (WHO) annual guideline value.

The concentration at numerous other measuring stations throughout Switzerland was also more than five times the annual guideline value. These fine dust particles are a health risk primarily due to their small size. The fine particles can penetrate deep into the respiratory tract and even into the blood.

Translated from German by DeepL/mga

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