Measured Sulfur dioxide concentrations in outdoor air.

Crude accidental hourly values of sulphur dioxide (SO2) at ground level in the outdoor air measured in the National Air Quality Monitoring Network (LML). Sulfur dioxide is a colourless gas. It is mainly formed the use of sulfur-containing fuels. Important sources include coal-fired power plants, refineries and traffic (in recent years, mainly international shipping has been important). Sulphur dioxide concentrations have fallen sharply in the Netherlands due to measures on the main sources. Since the 1990s, there have been no norms. At high concentrations, sulphur dioxide has negative effects on human health and contributes to the acidification of ecosystems. Sulphur dioxide is partially converted into sulphate particles in the air, contributing to fine dust.