(The Hill) — Children who live near airports may be unknowingly exposed to dangerous concentrations of lead, a new study finds.

The decade-long investigation, published Tuesday in PNAS Nexus, determined that kids who lived adjacent to the Reid-Hillview Airport in Santa Clara County, Calif., had elevated lead levels in their blood.

The closer that a child lived to the airport, the greater the probability that their blood lead level exceeded California’s state-defined threshold of 4.5 micrograms per deciliter, according to the study.

Following the passage of the Clean Air Act of 1970, the phase-out of tetraethyl lead from automotive gasoline had dramatic impacts on the blood-lead levels of children in the United States, the authors acknowledged.

Nonetheless, leaded gasoline remains a standard part of aviation, as the fuel is used by about 170,000 piston-engine aircraft nationwide, they explained.

Such aircraft have one or more piston-powered engine — a type of reciprocating internal combustion engine — connected to a propeller to provide the vehicle with thrust, according to the National Business Aviation Association.

Piston-engine aircraft typically use “low-leaded” fuel and fly relatively short missions at altitudes below 15,000 feet, per the Washington, D.C.-based trade organization.

While such planes may be low-leaded, the use of lead-formulated aviation gasoline is responsible for up to two-thirds of lead emissions in the U.S. today, according to the PNAS Nexus study.

And those emissions are affecting children who live in the vicinity of these airports, the researchers stressed.

“Across an ensemble of tests, we find consistent evidence that the blood lead levels of children residing near the airport are pushed upward by the deposition of leaded aviation gasoline,” lead author Sammy Zahran, a professor of economics at Colorado State University, said in a statement.

“This indicates we should support policy efforts to limit aviation lead emissions to safeguard the welfare of at-risk children,” Zahran added.

To draw their conclusions, Zahran and his colleagues analyzed 14,000 blood samples children under six years of age from 2011 through 2020.

For children living a mile or more away from the airport, the authors found that the probability of a blood sample that exceeded the threshold was 21.4 percent lower than for children living within a half-mile of the airport.

Meanwhile, they observed that children who lived east — downwind — of the airport were 2.18 times more likely to present a blood lead level above this limit. 

Child blood levels also increased along with piston-engine aircraft traffic and with the quantities of leaded aviation gasoline being sold at the airport, according to the study.

About 4 million Americans reside within half a mile of an airport that services piston-engine planes, the authors noted, citing data from the Environmental Protection Agency.

About 600 elementary schools are also located near such facilities, the researchers added.

Citing the National Academies of Sciences, Engineering and Medicine, the authors stressed that “lead does not appear to exhibit a minimum concentration in blood below which there are no health effects.”

As such, they emphasized a “compelling need” to reduce lead emissions in aviation and improve the wellbeing and “life chances of at-risk children.”