EPA Lead (Pb) Research: Air
Reducing lead air pollution is one of the nation’s earliest and most enduring environmental success stories. That story began to unfold when the Agency and its federal partners initiated a phase out of lead in gasoline in the 1980s. It continued as they took actions that dramatically reduced lead emissions from industrial air pollution. As a result, levels of lead air pollution decreased 99% between 1980 and 2018 (source: Lead Trends).
But because there is no safe level of lead exposure, the Agency’s clean air research program continues to advance environmental monitoring technologies and assess lead contamination in the air. Much of that work is conducted to directly support the Agency’s Office of Air and Radiation and the enforcement of the Clean Air Act.
Examples of how EPA researchers are working to support efforts to combat lead air pollution are highlighted below.
Recent Highlights
Understanding Lead Dust for Healthier Homes
Agency scientists used both chemical fingerprinting and bioavailability assessments to investigate the sources and toxicity of lead in dust samples collected as part of the American Healthy Homes Survey—a collaborative effort between the Department of Housing and Urban Development (HUD) and EPA.
The study showed that when lead contamination was found in house dust, it was in large part from highly toxic, lead-based paint. The results offer insights for understanding lead exposure risks in households and provide important information for future studies and remediation strategies as EPA and its partners from HUD and elsewhere work to reduce lead exposure.
Publication: Sowers, T. D., Nelson, C. M., Diamond, G. L., Blackmon, M. D., Jerden, M. L., Kirby, A. M., ... & Bradham, K. D. (2020). High lead bioavailability of indoor dust contaminated with paint lead species. Environmental Science & Technology, 55(1), 402-411.
Exploring Contaminated Soils as a Source of Lead Air pollution
Lead found in the soil of contaminated areas began as dust or particulate matter released into the air during mining and smelting operations before settling onto and into the land. To determine if soil in these areas can become a pollution source due to resuspended lead in the air, EPA researchers and collaborators analyzed soil samples at two different areas in China, one in the vicinity of an abandoned lead smelter and one near an active smelter.
The study showed that contamination at both sites was mainly from the soil, and not directly from the active smelter. Atmospheric deposition at both an operating and an abandoned lead smelter site were likely due to resuspended particles from the ground or soil surface, with those resuspended particles enriched with heavy metal(loid)s from lead smelting activities. Results show that taking actions to reduce contaminated soil from blowing into the air, such as maintaining healthy ground cover, can help mitigate public health risks.
Publications: Xing, W., Yang, H., Ippolito, J. A., Zhao, Q., Zhang, Y., Scheckel, K. G., & Li, L. (2020). Atmospheric deposition of arsenic, cadmium, copper, lead, and zinc near an operating and an abandoned lead smelter (Vol. 49, No. 6, pp. 1667-1678).
- Advancing the Science of Lead Inhalation
Agency researcher Albert Juhasz and partners analyzed soil impacted by mining and smelting activities in Australia to determine the types of lead that existed, and then used simulated lung fluids to assess the inhalation bioaccessibility—a measure of toxicity—of the types found. The study adds important insight into how lead dust and particulate matter can pose inhalation risks, a lead exposure pathway that is not as well studied as ingestion.
Source: Kastury, F., Karna, R. R., Scheckel, K. G., & Juhasz, A. L. (2020). Correlation between lead speciation and inhalation bioaccessibility using two different simulated lung fluids. Environmental Pollution, 263, 114609.
See the EPA Science Inventory summary to Correlation between lead speciation and inhalation bioaccessibility using two different simulated lung fluids
EPA researchers monitoring the air quality impacts of wildfires in California have observed that while many fire days are not associated with increased lead concentrations, some large spikes were associated with the fires burning the most infrastructure (e.g., houses, vehicles). The results of the research have implications for both the people and ecosystems near these fires and suggest that wildfire will become an increasing contributor to lead air quality concentrations as fire seasons become longer and more intense. Understanding why particular fires contribute more lead than others will be critical for anticipating and potentially mitigating impacts.
Source: Boaggio, K., S. Leduc, R. Rice, P. Duffney, K. Foley, A. Holder, S. McDow, AND Christopher Weaver. Beyond Particulate Matter Mass: Heightened Levels of Lead and Other Pollutants Associated with Destructive Fire Events in California. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 56:14272–14283, (2022).
See the Science Inventory summary to Beyond Particulate Matter Mass: Heightened Levels of Lead and Other Pollutants Associated with Destructive Fire Events in California.
Featured Research
Lead Integrated Science Assessment
EPA research provides the scientific foundation for National Ambient Air Quality Standards (NAAQS) for lead, designated as one of six criteria air pollutants. The Clean Air Act requires Agency scientists to periodically review these standards through the comprehensive Lead Integrated Science Assessment (ISA). The assessment is a synthesis evaluation of the “most policy relevant science that forms the scientific foundation for the primary (health-based) and secondary (welfare-based) national ambient air quality standards for Lead (Pb).”
The Agency recently announced the availability of the 2023 External Review Draft of the Lead (Pb) Integrated Science Assessment (ISA). It outlines key policy-relevant conclusions, including those on the populations at increased risk of lead-related effects, the lead exposure concentrations at which such effects occur, and the overall strength of the evidence supporting relationships between lead exposures and health or welfare effects. The Clean Air Scientific Advisory Committee reviewed the draft assessment, providing comments that will strengthen the final version. Agency researchers are currently revising the document and plan to release the Final Lead (Pb) ISA in 2024.
References: U.S. EPA. Integrated Science Assessment for Lead (External Review Draft for Public Comment). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-10/075F.
U.S. EPA. Integrated Science Assessment for Lead (Final Report, Jul 2013). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-10/075F, 23. Download at: https://cfpub.epa.gov/ncea/isa/recordisplay.cfm?deid=255721.
Risk and Technology Review of Emission Standards for Lead from Industries
Consistent with Clean Air Act requirements, EPA periodically reviews and revises, as necessary, emission standards for air toxics (including lead) from industries. In late 2011, EPA completed residual risk and technology reviews of the National Emission Standards for Hazardous Air Pollutants (NESHAP) for the Primary Lead Processing and Secondary Lead Smelting categories. As a part of these reviews, EPA evaluated developments in practices, processes, and control technologies for these industries since the original emission standards were published. Read more on the risk and technology reviews for these and other categories.