Sulfur dioxide (SO₂) concentrations in Istanbul, Turkey, decreased by approximately 24% between 2016 and 2025, according to a study by Istanbul Technical University (ITU) researchers.
The study, titled 'Temporal Variation of SO₂ Concentrations in Istanbul (2016-2025)', was published in the Journal of Research in Atmospheric Science. The research was conducted by Prof. Dr. Hüseyin Toros, Dr. Özkan Çapraz, and Dr. Nisa Özge Önal Tuğrul from Istanbul Technical University.
Average SO₂ concentration in Istanbul in 2025
The average SO₂ concentration in the city fell from approximately 5.4 micrograms/m³ in 2016 to approximately 4.1 micrograms/m³ in 2025. Seasonal variations were also noted, with average SO₂ levels reaching approximately 4.9 micrograms/m³ during winter and approximately 3.8 micrograms/m³ during summer.
Regulatory and Industrial Factors
Prof. Dr. Hüseyin Toros noted that the International Maritime Organization (IMO) implemented a low-sulfur fuel regulation in 2020, contributing to air quality improvements in Istanbul.
Sulfur dioxide values dropped from over 200 to about 5 micrograms today.
Toros stated that the daily limit value for sulfur dioxide set by the World Health Organization (WHO), Turkey, and Europe is 40 micrograms per cubic meter. The study further determined that only the Kandilli station showed a statistically significant decrease in SO₂ levels after multiple comparison corrections.
