Levels of ozone regularly exceeding legal limits

Never mind the excessive heat, continuing drought, prevalence of ticks and spreading ragwort, now a new hazard is in the air, literally, in the form of ozone, and too much of it.

Photographs of smog hanging over Los Angeles with its population of almost four million are not unusual. While Zug with its 30,000 inhabitants is scarcely the size of one suburb of the Californian city, smog is evident here, too.

In Switzerland 120 microgrammes per cubic metre is regarded as the legal immission limit for ozone, and as Melinda Suter, a project leader of the Cantonal Office of Environmental Protection, confirmed, this level has been exceeded for the past two weeks now, and, with the weather forecast to remain hot, the level is expected to remain high, too.

Suter further confirmed that levels of ozone had started to exceed the limit on a few days as early as April, when this period of warm weather began. “And since the beginning of July we have been experiencing unacceptably high levels on a daily basis,” she added, bearing in mind that the limit should not be exceeded on more than ten days in any one year.

High levels of ozone can cause a number of health troubles, such as mucous membrane irritation and other respiratory problems, other symptoms being irritation to the eyes, a burning sensation in the throat, pressure on the chest and pains when breathing deeply. People who suffer from asthma or pregnant women should take particular care and avoid strenuous activity in the afternoons.

Excessive levels of ozone result from pollution from industrial processes, combustion engines, heating systems, use of solvents and is accentuated by hot weather.

For just under 20 years now, the cantons of Lucerne, Nidwalden Obwalden, Schwyz, Uri and Zug have been monitoring the quality of the air in central Switzerland, with the current situation published on their website, www.in-luft.ch, though cutbacks in Zug mean that ozone levels in the city itself have not been published since 2016, with those for Ebikon, in the canton of Lucerne, and Altdorf, in the canton of Uri, used instead.

What has been indicated is that the accepted levels of ozone over the Zugerberg have been exceeded for the past ten days, with as many as 170 microgrammes per cubic metre having been recorded on Thursday 19 July. As of midday on Tuesday, the level had fallen to 120.7 microgrammes, rising to 142 microgrammes later that day. What may be surprising is that the ozone produced in conurbations during the day is broken down during the night, yet lingers over more rural areas where there are fewer noxious substances to use it up, so to speak. However, as there are other air pollutants evident over cities, overall the quality of air is still better in rural areas.