Ozone in Summer: How Dangerous Is the Gas?
In the stratosphere, ozone acts as a protective layer, preventing dangerous ultraviolet radiation from the sun from reaching us. Down on Earth, mixed in with the air we breathe, ozone is harmful instead. Ozone levels at ground level rise especially in summer. We explore the causes and explain why the gas is so dangerous.
Ozone (O₃): causes & formation
Ozone (O₃) is a colorless to slightly bluish gas with a pungent, sharp to chlorine-like smell. Under intense sunlight, it forms near the ground through the reaction of oxygen, nitrogen oxides, and volatile organic compounds. At an altitude of 20 to 30 kilometers, it forms the protective ozone layer.
The gas's precursor pollutants are mainly human-caused, e.g. combustion plants, over-fertilized soils, solvents (including paints, varnishes, adhesives), fuel combustion, or electrical devices like printers.
Why does the ozone level rise in summer?
In summer, ozone exposure rises. On sunny, windless days, summer smog is especially high. Meteorological conditions of summer high-pressure weather patterns, like high temperatures and strong sunlight, promote the formation of the gas near the ground. In the afternoon hours, when the sun is strongest, ozone levels are therefore also highest.
Ozone isn't released directly. Rather, intense sunlight triggers complex photochemical processes in precursor pollutants. Nitrogen oxides and volatile organic compounds are formed. Ozone is therefore considered more of a secondary pollutant.
To characterize ozone exposure, the O₃ value is measured over an eight-hour period, the average is calculated, and given as a comparison value of 120 micrograms per cubic meter (µg/m³). Due to climate change, summer temperatures are rising, heat summers are becoming more frequent, and readings are therefore increasingly exceeding the recommended limit value. The alert value (1-hour average) from the Federal Environment Agency is 240 µg/m³.
How do you notice high ozone levels, and what health consequences does the gas have?
Ozone is toxic to humans. Even at slightly elevated concentrations, it causes strong irritation of the mucous membranes and airways. The gas also promotes combustion and can form ignitable and explosive mixtures. O₃ is absorbed via breathing as well as through the eyes and can cause lasting damage to them.
Symptoms of high ozone exposure are:
- Hoarseness
- Coughing & bronchitis
- Headaches & nausea
- Irritated, itchy, and/or watery eyes
- Nosebleeds
- Poor concentration, decreased performance & fatigue
At high O₃ concentrations, pulmonary edema — fluid accumulation in the lungs — can even threaten.
What helps against excessive ozone levels?
Protect yourself from summer ozone exposure. With our tips, you can get through summer smog more calmly:
- Schedule sports and other physically strenuous activities for the evening or early morning hours where possible. Avoid sports and physical exertion outdoors.
- It's best to ventilate your home in the morning and evening. Keep windows closed during the day when there's strong sunlight.
- Drink significantly more than usual: ideally unsweetened drinks like water and tea. Avoid sweetened and alcoholic drinks, though.
- Avoid products that emit ozone.
- Measure the O₃ level in your rooms and ventilate as needed, meaning when the concentration exceeds the recommended limit value
It's best to check room air with an air quality monitor like the air-Q.
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