site.btaData from Air Quality Measurement Stations Not Trustworthy, Says Sofia Mayor

At a news briefing on Wednesday Sofia Mayor Vasil Terziev said that the data from the municipal network of air quality measurement stations is not trustworthy. That was established after this past summer the City Hall commissioned a report on air quality measurement to be prepared by a leading foreign company. "The results were disappointing," Terziev pointed out, adding that the measuring devices from Airbg.info turn out to be much more reliable in terms of indicators than those in which the Municipality has invested nearly BGN 1 million.

Airbg.info is a platform for monitoring air quality run by enthusiasts and based on voluntary participation of people with home-based air quality sensors across the country. It is part of the worldwide project Luftdaten.info, which started in Stuttgart in 2015.

NGO and Ministry responses

On October 8, the For the Earth non-government organization raised concerns that the national air quality control system is compromised, pointing out that air quality measurement stations are often placed far from areas with high concentrations of fine particulate matter. In response, the Ministry of Environment and Water published a statement asserting that it does not hide data on urban air quality and that Bulgaria reports accurate data to the European Commission.

Necessary elements for improvement

Mayor Terziev emphasized that two key elements are necessary for the air quality system to function effectively. First, the city needs high-precision air quality stations, of which Sofia currently has only five. Second, there should be a network of numerous, less expensive but moderately precise stations distributed across the city for broader coverage. He also mentioned that the municipality does not own the data from the current system and that it is not functioning as intended. Establishing a network of properly functioning sensors will be a priority for the current administration, the Mayor said.

Nadezhda Bobcheva, Sofia Deputy Mayor in charge of the green system, ecology and land use, explained that an analysis had been commissioned due to significant discrepancies observed between the municipal and national reference networks. "We specifically chose an independent US company to conduct the analysis," Bobcheva noted. The results revealed a significant deviation: only a 0.005% correlation between the municipal and national systems, compared to the expected standard of 0.6%, which is a 12-fold variance.

Bobcheva also announced plans to develop a new programme aimed at addressing pollution sources. She pointed out that the municipality does not have access to the system’s code, which prevents them from calibrating the equipment or correcting the inaccurate data. "The funds have already been spent, and ownership of the system has been transferred to a private company," she remarked.

Sofia Inspectorate Director Nikolay Nedyalkov spoke about ongoing efforts to control air quality. He noted that the number of inspections conducted by the inspectorate's staff, focusing on issues such as waste burning and construction site pollution, had increased from January 1 to September 30, 2024, compared to the same period in 2023. The number of fines issued has doubled. Nedyalkov added that street cleaning activities had been ramped up by 10% compared to the previous year.