Government regulations now restrict the amount of sulfur dioxide (SO2) that can be released into the atmosphere from coal-burning furnaces. Most of the S is now removed from natural gas used in home heating and in industry. Also, catalytic converters in new automobiles remove most of the S that was previously returned to the atmosphere when S-containing gasoline was burned in automobiles. In addition, S-free compounds have replaced many of the insecticides and fungicides formerly applied to control insects and diseases in crops. As a result of these government restrictions, less S returns to the soil in rainfall.