How does sulphur dioxide cause acid rain?

When sulfur dioxide dissolves in water droplets in clouds, it forms sulfuric acid. This makes the rain more acidic than normal.

Sulphur dioxide is a gas produced in many industrial processes and the burning of fossil fuels. The gas rises up into the atmosphere and dissolves in water droplets in clouds so that when it rains the water contains sulphuric acid. This rain causes lakes, ponds and rivers to have more acidic water in them.