According to the U.S. Bureau of Mines, there are over 180 cement manufacturing plants now in operation in the United States. The growth rate of the cement industry has increased regularly since World War II. Producers are still uncertain about long-range prospects for the industry but generally are optimistic. In a cement plant the initial materials are dust and the end product is a fine dust. Other types of pollution from a cement plant include gaseous emissions from the combustion of fuel in the kiln. Most of the sulfur dioxide formed from the sulfur in the fuel is recovered because it combines with the alkalies and also with the lime when the alkali fume is low.