Open Data Insight of the Day

Fireworks in Basel, especially during New Year's Eve and on August 1, lead to a noticeable but temporary increase in air pollution due to fine particles. These particles can linger in the air, particularly in cold weather conditions, worsening air quality. The Swiss Federal Office for the Environment is aware of this issue, and Basel has already reduced its New Year's Eve fireworks as a step towards environmental responsibility. Fireworks release a large amount of fine particles, causing high short-term concentrations. Cold temperatures and inversion conditions can trap these pollutants near the ground, increasing exposure. While fireworks contribute to about 1–2% of Switzerland’s annual particulate pollution, this is concentrated over just a few days.

In the last two days, we observed a significant rise in PM2.5 and PM10 levels. Concentrations began to increase in the evening and peaked around midnight, with PM2.5 reaching 128.8 µg/m³ and PM10 reaching 140.1 µg/m³. These values are significantly higher than the historical average levels observed before the fireworks. Figure 1 illustrates the hourly time series of PM10 and PM2.5 concentrations, showing both background levels and the peak caused by the fireworks. After the peak, concentrations declined rapidly.

Air quality limit values exist to protect public health, and PM10 and PM2.5 are regulated differently due to their distinct health effects. The health effects of coarse particulate matter (PM10) and fine particulate matter (PM2.5) differ in part. For this reason, Switzerland introduced a separate annual limit value for PM2.5 in addition to the existing PM10 limits. The annual limit of 10 µg/m³ for PM2.5 is in line with the recommendations of the World Health Organization (WHO).

With the revision of the Swiss Air Pollution Control Ordinance (LRV) of 11 April 2018, the following ambient air quality standards apply:

Swiss air quality standards for particulate matter

Although there is a clear peak around midnight, the pollution caused by fireworks is too short-lived to significantly affect the annual average. Over the past 365 days, the annual average concentrations were 8.8 µg/m³ for PM2.5 and 12.5 µg/m³ for PM10. The 24-hour mean PM10 concentration on the day of the fireworks was 36.6 µg/m³, which did not exceed the legal threshold of 50 µg/m³. Such exceedances are legally permitted on no more than three days per year, and the observed values align with current air quality regulations.

Measurements at the St. Johann air quality monitoring station capture only part of the actual impact on local air quality. The measured concentrations depend strongly on wind direction and atmospheric conditions. If smoke from the official city fireworks is not transported toward the station, the recorded peak may underestimate pollution levels in other parts of the city. In highly polluted cities such as Delhi, India, average PM10 concentrations over a year can reach 190–270 µg/m³, with severe pollution events rising to 400–500 µg/m³ or more. This comparison is provided to illustrate scale and context, not to downplay local impacts. For more information, you can visit Air pollution in Delhi – particulate matter levels.

In summary, fireworks cause clear and measurable short-term air pollution peaks. These effects are brief, strongly weather-dependent, and regulated, and they do not substantially influence long-term average air quality.