Saharan dust results in poor air quality

The current weather conditions may worsen symptoms for people with asthma and pollen allergies. The environmental authorities in Central Switzerland are thereby advising residents to limit outdoor activities due to a surge in airborne dust from the Sahara.
 

People with asthma or pollen allergies are currently being urged to take extra care. Last Friday, Umwelt Zentralschweiz - a partnership of the Central Swiss cantons responsible for monitoring regional air quality—said that levels of fine particulate pollution have been rising steadily since Thursday afternoon.

Air quality measurements carried out by the environmental authorities in Lucerne, Zug, Uri, Schwyz, Obwalden and Nidwalden show that pollution levels currently exceed the legal daily average limit of 50 micrograms per cubic metre. According to the authorities, this threshold has already been surpassed at monitoring stations in Altdorf and Kaiserstuhl.

Under current regulations, this limit may be exceeded no more than three times a year. Officials have explained that the elevated readings are the result of a Saharan dust event combined with dry weather conditions. Saharan dust—one of the world’s largest sources of mineral dust—is regularly carried to Switzerland by high-altitude winds from the Sahara Desert. Because conditions are currently dry, the particles remain suspended in the air for longer, which can aggravate respiratory problems, particularly for asthma sufferers and people with pollen allergies.

The dust has also created striking atmospheric effects across the region. Along the shores of Lake Lucerne near Buochs, the air appeared hazy and the sky took on a deep orange tint usually associated with sunrise or sunset. Similar scenes were reported in Küssnacht am Rigi, Chaiserstock and Sörenberg, where the sunlight appeared muted beneath a milky sky.

Evening atmosphere with Saharan dust already visible on Wednesday. Since then, the concentration of dust in the air has steadily increased.                  
Milky sky and hazy sunshine on Friday morning in Küssnacht am Rigi.        Reader photos: Rashmi Seshadri.
Saharan dust was also clearly visible at higher altitudes on Thursday at Brienzer Rothorn (Sörenberg)         Reader photo: Andrea Lipp-Hemmi
 

The sources of fine particulates
Fine particulate matter (Feinstaub) is made up of extremely small airborne particles. Natural sources include Saharan dust, pollen, and ash from volcanic eruptions. Most of the particulate pollution in the atmosphere is caused by human activity, however —particularly emissions and tyre and brake wear from road traffic, as well as aviation and industrial processes.

Improvements in exhaust filtration technology have reduced particulate pollution over the past decade. Nevertheless, Umwelt Zentralschweiz notes that pollution levels in many areas still remain close to the legal limits.

Saharan dust is generally considered less harmful than the fine particulates generated by traffic or industry, because the particles are larger and therefore more easily filtered by the lungs when inhaled. Even so, people with asthma or pollen allergies may experience more severe symptoms.

Anyone currently suffering increased discomfort is advised to avoid strenuous outdoor activities and to keep windows closed. For healthy individuals, however, spending time outdoors—including physical exercise—remains safe.

Other Effects of Saharan Dust
Saharan dust events in Switzerland occur most often in spring and autumn. They are typically visible through a yellow-reddish sky, thicker cloud cover and deposits of fine dust on cars and windows.

Dust settling on solar panels, together with reduced sunlight, can temporarily lower solar power production, and high concentrations of mineral dust can also affect aircraft engines and may pose challenges for aviation safety.

On the positive side, the dust can benefit plant life, as the minerals it contains act as a natural fertiliser, delivering important nutrients to soils.

Note:
Up-to-date air quality data and daily analyses are available on the *Umwelt Zentralschweiz* website: www.in-luft.chand http://www.in-luft.ch.