Sulphur dioxide (SO2) and nitrogen oxides (NOx) are two of the most common air pollutants, and they are both primarily produced by human activities.

Sources of sulphur dioxide:

- Power plants that burn fossil fuels, such as coal and oil, are the largest sources of sulphur dioxide.

- Industrial facilities, such as refineries and smelters, also release sulphur dioxide into the air.

- Transportation vehicles, such as cars and trucks, also contribute to sulphur dioxide emissions.

Sources of nitrogen oxides:

- Power plants that burn fossil fuels are also the largest sources of nitrogen oxides.

- Industrial facilities, such as chemical plants and fertilizer manufacturers, also release nitrogen oxides into the air.

- Transportation vehicles, such as cars and trucks, are also major contributors to nitrogen oxide emissions.