Portland Cement Manufacturing
Air Emissions from the Portland Cement Industry
Portland cement manufacturing is an energy-intensive process that grinds and heats a mixture of raw materials such as limestone, clay, sand and iron ore in a rotary kiln. That product, called clinker, is cooled, ground and then mixed with a small amount of gypsum to produce cement. Cement is mixed with aggregate and water to make concrete.
A variety of pollutants are emitted from the burning of fuels and heating of raw materials used to make cement, including mercury, acid gases, and particulate matter. Emissions also can occur from grinding, cooling and materials-handling steps in the manufacturing process.
Air toxics are known or suspected to cause cancer or other serious health effects. For example, once mercury from the air reaches water, microorganisms can change it into methylmercury, a highly toxic form that builds up in fish. Methylmercury exposure is linked to damage to developing nervous systems of unborn babies and young children.
Particulate matter, also called particle pollution, is associated with a variety of serious health effects, including premature deaths, heart attacks and asthma attacks.