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Ambient Concentrations of Lead

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  • Learn more about how to use this interactive exhibit
  • Save the complete indicator as a printer-friendly PDF
  • Download this image
  • Download data for this exhibit

Hover your mouse over the display to reveal data.

  • Introduction
    • Lead is a naturally occurring metal found in small amounts in rock and soil. Despite steep decreases in emissions since 1970 (the Lead Emissions indicator), lead remains an important environmental health issue because low lead exposure can have adverse effects on the nervous systems of fetuses and young children (the Blood Lead indicator) (U.S. EPA, 2013). People can be exposed to lead by inhaling airborne particles that contain lead, drinking contaminated water, eating contaminated food items, or ingesting non-food items that contain lead, such as leaded paint chips and dust (U.S. EPA, 2013).

      Lead has been used industrially in the production of gasoline, ceramic products, paints, metal alloys, batteries, and solder. Emissions to ambient air and associated air lead concentrations have declined substantially over the past several decades (U.S. EPA, 2013). The most dramatic reductions in lead emissions occurred prior to 1990 in the transportation sector due to the removal of lead from gasoline used in on-road vehicles (the Lead Emissions indicator). The majority of lead emissions nationally is associated with combustion of leaded aviation gasoline by piston-driven aircraft. The largest sources on a local scale and the areas of highest concentrations in outdoor air are generally associated with metals industries (U.S. EPA, 2014).

      This indicator presents ambient lead concentrations in micrograms per cubic meter (μg/m3) from 1980 to 2016. Trends for this indicator are based on measurements made at seven monitoring stations in seven counties nationwide. These trend sites were selected because they are part of the State and Local Air Monitoring Stations network or are special purpose monitors and they have consistently measured ambient air concentrations of lead over the entire period of interest. Reported values are annual maximum 3-month averages. This indicator’s exhibits display the 2008 lead National Ambient Air Quality Standard (NAAQS) as a point of reference, but the fact that the average national lead concentrations fall below the standard does not mean that all monitoring sites also are below the standard.

  • What the Data Show
    • Between 1980 and 2016, average lead concentrations decreased 99 percent nationally (Exhibit 1). This decrease, which occurred mostly during the 1980s and early 1990s, is largely attributed to reduced lead content in gasoline used in on-road vehicles (U.S. EPA, 2003), with later decreases also attributed to reductions from stationary industrial sources (U.S. EPA, 2013). In addition, of the seven sites used to determine this trend (out of 155 total monitoring sites that were operating in 2016), the number reporting annual maximum 3-month average lead concentrations above the level of the 2008 NAAQS (0.15 µg/m3) declined from seven to zero between 1980 and 2016 (Exhibit 2).

      Also shown in Exhibit 1 are the 90th and 10th percentiles based on the distribution of annual statistics at the monitoring sites. This provides additional graphical representation of the distribution of measured concentrations across the monitoring sites for a given year. Thus, the exhibit displays the concentration range where 80 percent of measured values occurred for each year.

  • Limitations
      • The nationwide trends might not accurately reflect conditions outside the immediate areas of the trend monitoring sites. In addition, the seven trend sites in this indicator are not dispersed uniformly across all states in the EPA Regions. The seven trend sites are located in five states. In the remaining 45 states, there currently are insufficient long-term data from the existing monitoring sites to include in this indicator.
      • To ensure that long-term trends are based on a consistent set of monitoring sites, selection criteria were applied to identify the subset of lead monitoring sites with sufficient data to assess trends since 1980. Monitoring sites without sufficient data are not included in the trend analysis. Some excluded monitoring sites reported lead concentrations above the level of the lead standard over the time frame covered by this indicator. In 2016, for example, five monitoring sites measured 3-month average lead concentrations above the level of the 2008 NAAQS: none of these sites are shown in Exhibit 2 because they did not have sufficient long-term data to be considered trend sites for this indicator.
  • Data Sources
    • Summary data in this indicator were provided by EPA’s Office of Air Quality Planning and Standards, based on lead ambient air monitoring data in EPA’s Air Quality System (U.S. EPA, 2017a) ( National trends in this indicator are based on the subset of lead monitoring stations that have sufficient data to assess trends since 1980.

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