The natural and biogenic sources are significant, but do not produce much acid deposition worldwide because they are so widely scattered and are therefore diluted. The anthroposgenic SOx sources tend to be concentrated in a few places, especially where electric power is begin generated, and therefore concentrate their effects in a few problem areas.

The pie chart shows the breakdown of the anthropogenic SOx sources. The most significant atmospheric sulfur source is coal combustion (one of the fossil fuels) used to produce electricity.

Transportation is a very minor contributor to sulfuric acid deposition, since most fuels for automobiles and trucks are very low in sulfur (the fuels are derived from oil, which is already low in sulfur, and the refining process removes almost all of this sulfur). However, there may be a local, rather than regional, acid deposition or fog problem from the NOx emissions from these mobile sources, besides the usual photochemical smog vs. health issues.