Ensuring Air Quality through Lead Measurement Methods

Lead in the Air – An Unseen Threat

Combustion of fossil fuel products like gasoline and coal produces exhaust fumes that contain particulate matter (PM), which contains several toxic materials, both carbon-based and metallic. One of the most widely-known contaminants in PM is lead, a potent neurotoxin that can produce severe cognitive effects, especially in children. The United States Environmental Protection Agency has established regulations to monitor and control lead in the air in the National Ambient Air Quality Standards (NAAQS). In 1979, the NAAQS standard for lead in air was established based on lead measurement levels that could be reasonably achieved using the technology available at the time and reliably detected by laboratories for monitoring.

Due to the gradual phase-out of lead additives in automotive gasoline and its eventual ban in 1996, levels of lead in air in the United States drastically decreased. At the same time, new developments in the instruments used for lead measurement allowed laboratories to detect even lower concentrations. Because of these changes, in 2008, the NAAQS standard for lead in air was decreased by an order of magnitude, from 1.5 µg/m3 to 0.15 µg/m3. Although the existing published method for lead measurement in suspended particulates could detect lead at such low concentrations, it was concluded that the reference method should be updated to reflect modern instrumental capabilities that would allow laboratories to produce high-quality data at substantially lower concentrations. Several acceptable alternative methods were already in use that would meet those objectives, so EPA initiated a collaboration with RTI to support a study comparing the existing reference method with the proposed new reference method.

Gathering Scientific Expertise for Method Assessment

Establishing federal regulations requires widespread input from several sectors so that policies to protect human health are based on both sound science and practical considerations. Data is needed from different types of labs to demonstrate that the proposed new method performs comparably to the original method. Drawing on our expertise in lead measurement and the measurement of other critical air pollutants and our long track record of laboratory proficiency testing program and interlaboratory study administration, RTI’s Center for Analytical Science initiated an interlaboratory study designed to test the methods. By asking several laboratories to analyze the same sample with the same lead measurement method, it’s possible to gauge the reliability of the method and how similar the results are between laboratories. Statistical analysis of the results from all of the participating laboratories showed that the equivalent methods produced comparable results, and using the newer instruments would provide limits of detection low enough to exceed the needs of most areas. EPA used the results to support their decision to implement the new lead measurement method, currently included in the Code of Federal Regulations (CFR) Part 40, Appendix G.

Take a Breath of Fresh Air

RTI remains a leader in laboratory analysis of air quality for many state governments, using the experience gained from this collaboration. Although leaded fuel has been phased out in automobiles, there are other sources still in use, including aviation fuel, metal processing operations, and mining. This lead measurement testing is critical to maintaining public health and allowing children to grow up healthy.