Open Data Insight of the Day

Fireworks in Basel, especially on New Year’s Eve and on 1 August, cause a significant but short-term increase in fine particulate pollution. In cold conditions and during temperature inversions, the particles can remain in the air for a long time and severely worsen air quality. The Swiss Federal Office for the Environment (FOEN) acknowledges this issue, and Basel has already reduced its New Year’s Eve fireworks as a sign of environmental responsibility. Fireworks release large amounts of fine particles, leading to very high short-term concentrations. Cold temperatures and inversion conditions trap pollutants near the ground, increasing exposure in Basel. Fireworks account for about 1–2% of Switzerland’s annual particulate pollution, concentrated over just a few days.

In the last two days, we observed a significant increase in fine particulate matter, PM2.5 and PM10, due to fireworks. Concentrations began to rise in the evening and peaked around midnight on January 1st, with PM2.5 reaching 115.6 µg/m³ and PM10 reaching 128.8 µg/m³. These peaks were significant, with PM2.5 levels being over ten times the background concentration. Fortunately, concentrations declined quickly after the peak. It's worth noting that Basel-Stadt has stopped the official city fireworks, which has already led to a clear decrease in the peak compared to years when the official fireworks were still in practice.

Air quality limit values exist to protect public health. PM10 and PM2.5 are regulated differently because their health effects differ. 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, pollution caused by the city's official fireworks is too short-lived to significantly affect the annual average. The annual average concentrations of PM2.5 and PM10 over the past 365 days were 10.0 µg/m³ and 15.0 µg/m³, respectively. PM10 concentrations may temporarily exceed the 24-hour average limit of 50 µg/m³. However, the 24-hour mean PM10 concentration on the day of the fireworks was 39.1 µg/m³, which did not exceed the legal threshold.

Measurements at the St. Johann air quality monitoring station capture only part of the actual impact on local air quality. 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 used 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, but these effects are brief, strongly weather-dependent, and regulated, and they do not substantially influence long-term average air quality.