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 noticeable increase in particulate matter levels due to fireworks. Concentrations of PM2.5 and PM10 began to rise in the evening and peaked around midnight, as shown in Figure 1. This figure illustrates the hourly time series of PM10 and PM2.5 concentrations, highlighting both the background levels and the firework-related peak. The peak PM2.5 concentration reached 34.4 µg/m³, with an associated PM10 peak of 40.4 µg/m³. These values were significantly higher than the historical average levels observed before the fireworks, which were much lower. However, the concentrations declined quickly after the peak, returning to typical levels by the next morning.

Air quality limit values exist to protect public health, as different particulate matter sizes have varying health impacts. PM10 and PM2.5 are regulated separately in Switzerland, with PM2.5 having a stricter annual limit of 10 µg/m³, in line with WHO recommendations. The annual average concentrations over the past 365 days were 9.7 µg/m³ for PM2.5 and 13.6 µg/m³ for PM10, both below their respective limits. Although there was a clear peak around midnight, the pollution from fireworks is too short-lived to significantly affect the annual average. The 24-hour mean PM10 concentration on the day of the fireworks was 13.4 µg/m³, which does not exceed the legal threshold of 50 µg/m³. Such exceedances are legally permitted on no more than three days per year, ensuring compliance with air quality regulations.

Measurements at the St. Johann air quality monitoring station capture only part of the actual impact on local air quality. The concentrations measured 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 provides scale and context, not to downplay local impacts. More information can be found at 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. They do not substantially influence long-term average air quality.