(National Emissions Standards for Hazardous Air Pollutants for Portland Cement Plants)
The Clean Air Act requires the Environmental Protection Agency (EPA) to regulate hazardous air pollutants, through the National Emissions Standards for Hazardous Air Pollutants program established in Sec. 112  of the Act. EPA must identify sources of the 188 hazardous air pollutants  (HAPs ) listed in Sec. 112(b), including acid gases, asbestos, dioxin, benzene, chlorine, lead compounds, mercury, phosphorus, various metals and others. Major sources of these pollutants are those that emit 10 tons per year of a single HAP or 25 tons per year or more combined of several HAPs.
EPA promulgates technology-based standards for reducing HAP emissions using maximum achievable control technology  (MACT) for both new and existing sources. Determination of the MACT considers a number of factors, including cost, energy requirements, and non-air quality health and environmental impacts. The Act established certain stringency requirements for MACT for new sources, known as "floor" requirements. Existing sources are also subject to MACT, which may be less stringent than the MACT for new sources, but must not be less stringent than the best-performing 12 percent of existing sources in the same category. EPA has recently established new MACT requirements for Portland cement manufacturing plants.
As with some other Act programs, the Federal government establishes and state air quality programs implement NESHAP programs.
Starting in 1990 and revised every eight years thereafter, EPA determines a list of categories and subcategories of sources of HAPs. The cement manufacturing source category was added in 1999 based on emissions of arsenic, cadmium, beryllium, lead, and polychlorinated biphenyls. Emissions standards issued in 2010 include limits on emissions of mercury, hydrocarbons, particulate matter, and hydrochloric acid. There are 97 cement manufacturing facilities across all regions of the United States. EPA estimates that twenty new facilities may be built in the five years following promulgation of the rule and would, therefore, be subject to the new regulations.
The MACT for cement manufactures was issued in 1999, but it did not include standards for hydrochloric acid, mercury, total hydrocarbons and metal HAPs. This absence became the basis for litigation against EPA, and in 2000, the courts ordered EPA to set standards for those HAPs. Based on this court action, a new rule with standards for those HAPS was promulgated in December 2006 for new and existing cement plants. EPA separately announced at that time that it was reconsidering the emissions standards set for new plants in response to public comment, and that revision was completed as a final rule in September 2010. On February 12, 2013, EPA issued a final MACT and NSPS rule for cement plants that made modifications to the 2010 rule. The new rule extended the compliance period from 2013 to 2015, changed the way particulate matter emissions are monitored, and made other changes.
Read more from EPA  on the Cement MACT.