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 rise in PM₂.₅ and PM₁₀ levels starting in the evening and peaking around midnight, as shown in Figure 1. The peak PM₂.₅ concentration reached 71.9 µg/m³, and PM₁₀ reached 83.8 µg/m³. These levels are much higher than the historical averages observed before the fireworks, where PM₂.₅ averaged 10.9 µg/m³ and PM₁₀ averaged 15.8 µg/m³ over the past year. Figure 1 illustrates the hourly time series of PM₁₀ and PM₂.₅ concentrations, highlighting the background levels and the sharp increase due to fireworks.

Air quality limit values exist to protect public health, with PM10 and PM2.5 regulated differently due to their distinct health effects. 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 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 10.9 µg/m³ and 15.8 µg/m³, respectively. The 24-hour mean PM10 concentration on the day of the fireworks was 28.9 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, placing the observed values in the context of current air quality regulations.

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 illustrates scale and context, not to downplay local impacts. More information can be found here: 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.