The results of an airborne lead contamination study commissioned by Santa Clara County have been published in the online version of the scientific journal the Proceedings of the National Academy of Sciences and could help address the issue in an ongoing U.S. Environmental Protection Agency evaluation of the effects of lead from airports on public health.

The abbreviated version of the 113-page report appeared online in the PNAS Nexus on Jan. 10 for inclusion in the March 2023 issue.

The county-commissioned study found that leaded aviation fuel from airport operations contributed to significantly increased blood lead levels for children living within a half-mile of the airport. The lead levels during peak hours were double the levels seen during the height of the Flint Water Crisis in Michigan, the county noted in a statement released on Jan. 11.

The peer-reviewed study found that children living downwind from the airport had higher blood lead levels, with increases of 0.40 micrograms per deciliter, over children living upwind from the airport. Lead levels detected during the peak of the Flint Water Crisis were between 0.35 and 0.45 micrograms per deciliter over the baseline, the county noted.

The study examined levels during times of maximum exposure to air traffic for children within a half-mile of the airport. It estimated an increase of 0.83 micrograms per deciliter at peak times, significantly higher than the Flint levels.

Children living within a half-mile of the airport had blood lead levels 20% higher than children living between half-mile to 1.5 miles from the airport, the study found. It also correlated blood lead levels with the proximity of a child’s home and school to Reid-Hillview Airport. Children who commute toward Reid-Hillview to attend school had substantially higher blood lead levels than children who commute away from the airport, the study found.

As a result of the study, the county prohibited the sale and distribution of leaded avgas at county airports in January 2022 and petitioned the U.S. Environmental Protection Agency to eliminate lead pollution at the national level.

The county sought to publish the report in a scientific journal to disseminate the findings and to ensure they are considered by the EPA as it undertakes a process for issuing standards for emissions of any air pollutant that might reasonably be anticipated to endanger public health or welfare. Such emissions would include from aircraft fueled with avgas.

Health organizations agree that there is no known safe level of lead in a child’s blood, and exposure to even a small amount of lead has a negative effect on cognitive ability, particularly in developing children who absorb lead more efficiently than older children and adults, the county noted.

"Leaded gas remains in use by more than 170,000 aircraft in the United States, with 4 million people and 600 K-12 schools within 500 meters of an airport used by these planes. In January 2022, the U.S. Environmental Protection Agency launched an evaluation of whether lead emissions from aircraft contribute to pollution that endangers public health," the county noted.

Supervisor Cindy Chavez, who originally requested the study, said publication by the National Academy of Sciences puts the important study on the official scientific record and in the national dialogue regarding the continued use of leaded fuel at airports throughout the nation.

"It’s important to recognize and document the results of this study, which clearly show that lead presents an immediate hazard to all those in the vicinity of these airfields, and particularly children,” she said.

The PNAS study was conducted by Dr. Sammy Zahran, Dr. Christopher Keyes and Dr. Bruce Lanphear. It incorporated three main tests of exposure risk and was controlled for other sources of lead exposure, the county said.