Air toxics are those pollutants known or suspected of causing cancer or other serious health effects. Industrial process cooling towers remove heat from chemical and industrial processes. Specifically, water treatment chemicals, such as chromium, are added to cooling tower waters to protect equipment and piping from corrosion, and to control algae growth in the tower. Chromium emissions are released into the atmosphere from the cooling tower during the cooling process. The final rule will reduce emissions of chromium by approximately 25 tons annually, representing a 100 percent reduction from current levels.
Hexavalent chromium is a potent human carcinogen and is known to cause lung cancer.
Under the Clean Air Act Amendments of 1990, EPA is required to regulate emissions of 189 listed toxic air pollutants. Major industry sources, such as petroleum refineries, chemical manufacturing plants, and primary metal producers, that operate industrial process cooling towers, using chromium-based water treatment chemicals, will be affected by EPA's regulation. There are approximately 800 industrial process cooling towers located at about 400 major sources nationwide that will be affected by the regulation. Industrial process cooling towers that are used exclusively for cooling, heating, ventilation, and air conditioning systems, which are referred to as comfort cooling towers, are not covered by this rule. A regulation that prohibited the distribution and commercial use of chromium-based water treatment chemicals in comfort cooling towers was promulgated under the Toxic Substances Control Act in January 1990.