This polygon shapefile depicts nonattainment and maintenance areas for the United States and its Territories for the enforcement of the lead (Pb) 3 month average NAAQS, which is 0.15 micrograms per cubed meter. Exposure to lead can occur through multiple pathways, including inhalation of air and ingestion of lead in food, water, soil or dust. Excessive lead exposure can cause seizures, mental retardation and/or behavioral disorders. A recent National Health and Nutrition Examination Survey reported a 78% decrease in blood lead levels from 12.8 to 2.8 ug/dL between 1976 and 1980 and from 1988 to 1991. This dramatic decline can be attributed to the reduction of leaded gasoline and to the removal of lead from soldered cans. Although this study shows great progress, infants and young children are especially susceptible to low doses of lead, and this age group still shows the highest levels. Low doses of lead can lead to central nervous system damage. Recent studies have also shown that lead may be a factor in high blood pressure and in subsequent heart disease in middle-aged males. Lead gasoline additives, non-ferrous smelters, and battery plants are the most significant contributors to atmospheric lead emissions. In 1993 transportation sources contributed 33% of the annual emissions, down substantially from 81% in 1985. Total Pb emissions from all sources dropped from 20,100 tons in 1985 to 4,900 tons in 1993. The decrease in lead emissions from highway vehicles accounts for essentially all of this decline. The reasons for the decrease are noted below. Two air pollution control programs implemented by EPA before promulgation of the lead standard in October 1978 have resulted in lower ambient lead levels. First, regulations issued in the early 1970's required gradual reduction of the lead content of all gasoline over a period of many years. The lead content of the leaded gasoline pool was reduced from an average of 12.0 gram/gallon, to 0.5 gram/gallon on July 1, 1985, and still further to 0.1 gram/gallon on January 1, 1986. Second, as part of the EPA's overall automotive emission control program, unleaded gasoline was introduced in 1975 for automobiles equipped with catalytic control devices. These devices reduce emissions of CO, VOCs and NOx. In 1993, unleaded gasoline sales accounted for 99% of the total gasoline market. In contrast, the unleaded share of the gasoline market in 1984 was approximately 60%. These programs have essentially eliminated violations of the lead standard in urban areas except those areas with Pb point sources. Programs are also in place to control lead emissions from stationary point sources. Lead emissions from stationary sources have been substantially reduced by control programs oriented toward attainment of the PM-10 and lead ambient standards. However, significant and ambient problems still remain around some lead point sources, which are now the focus of new monitoring initiatives. Lead emissions in 1993 from industrial sources, e.g., primary and secondary lead smelters, dropped by about 91% from levels reported in 1970. Emissions of lead from solid waste disposal are down about 76% since 1970. In 1993, emissions from solid waste disposal, industrial processes and transportation were: 500, 2,300 and 1,600 short tons, respectively. The overall effect of the control programs for these three categories has been a major reduction in the amount of lead in the ambient air. Additional reduction in lead are anticipated as a result of the Agency's Multimedia Lead Strategy issued in February 1991. The goal of the Lead Strategy is to reduce lead exposures to the fullest extent practicable. Title 40, Part 50 of the Code of the Federal Regulations lists the ambient air quality standard for lead. This layer is part of the 2014 National Transportation Atlas Database. The National Transportation Atlas Databases 2014 (NTAD2014) is a set of nationwide geographic datasets of transportation facilities, transportation networks, associated infrastructure and other political and administrative entities. These datasets include spatial information for transportation modal networks and intermodal terminals, as well as the re¬lated attribute information for these features. This data supports research, analysis, and decision-making across all transportation modes. It is most useful at the national level, but has major applications at regional, state and local scales throughout the transportation community. The data used to compile NTAD2014 was provided by our partners within the United States Department of Transportation (USDOT) and by other agencies throughout the United States Federal Government. These contributors are the actual data stewards and are ultimately responsible for the maintenance and accuracy of their data. In United States environmental law, a nonattainment area is an area considered to have air quality worse than the National Ambient Air Quality Standards (NAAQS) as defined in the Clean Air Act Amendments of 1970 (P.L. 91-604, Sec. 109). Nonattainment areas must have and implement a plan to meet the standard or risk losing some forms of federal financial assistance or other consequences, such as industrial facilities being required to install pollution control equipment, enforce limits on their production and otherwise offset their emissions. An area may be a nonattainment area for one pollutant and an attainment area for others. This dataset establishes the spatial boundaries of each nonattainment and maintenance area.
