Despite the widespread belief that the federal government banned lead from automotive gasoline two decades ago, a little known federal regulation allows unleaded gasoline to contain trace amounts of the toxic metal. Experts say it contributes to environmental contamination and harms children, particularly those living in traffic-congested urban areas.
The regulation doesn’t allow lead to be added intentionally to gasoline, but does permit unleaded gasoline for motor vehicles to contain up to .05 grams of lead per gallon. This is to account for accidental cross-contamination with lead in the gasoline distribution system, which may carry leaded aviation gasoline via the same pipeline, according to a spokeswoman for the Environmental Protection Agency [EPA].
How much lead cross-contamination occurs is unknown, but one demographer who has extensively studied lead emissions said a majority of the existing emissions flow (50 to 60 percent) is attributable to leaded aviation gasoline, while by comparison, the contribution due to the .05 gram allowance is small.
No amount of lead exposure is safe
“While the allowance of .05 grams per gallon accounts for a small fraction of the current flow, it’s worth emphasizing that both the CDC [Centers for Disease Control and Prevention] and EPA have concluded that there is no known safe level of lead exposure,” wrote Sammy Zahran, an associate professor in the department of economics at Colorado State University, in an email to ThinkProgress. “Limiting this allowance is good policy, as health economists have repeatedly established the cost effectiveness of expunging lead from the lived environment of human beings.”
Professor Howard Mielke of Tulane University’s School of Medicine and one of the nation’s leading experts on lead soil contamination said that it would be incorrect to assume that a fraction of a gram is insignificant given the high traffic flow and congestion that occur in urban environments.
“If you’re talking about .05 grams per gallon, that’s one heck of a lot of lead when you pay attention to the number of gallons being consumed,” said Mielke, an urban geochemistry and health expert who teaches in the department of pharmacology at Tulane University’s School of Medicine.
“You have traffic congestion along any major freeway into a city and then you have the congestion within the city… So, if you have any lead in gasoline, you basically end up with an issue.”
The Clean Air Act prohibition on leaded gasoline for highway use took effect Jan. 1, 1996, but the EPA confirmed that the definition for unleaded gasoline allowing the .05 gram per gallon has been in effect since 1974. The definition is outlined in the “Protection of the Environment” section of the Code of Federal Regulations.
Politicizing the science: lead’s long history of exhaust contamination
Tetraethyl lead was originally added to gasoline in the 1920s as an anti-knock agent to keep engines running smoothly, and manufacturers then claimed the additive was safe. Health experts at the time knew better. Yale Physiology Professor Yandell Henderson warned the U.S. government that lead exhaust from cars would cause widespread chronic lead poisoning in urban centers.
In the 1950s, the use of lead additives in gasoline began to increase due to growing automobile sales, the expansion of the U.S. highway system, and the decline of public rail transit systems, according to Mielke.
It was only after the passage of the federal Clean Air Act in 1970 that the automobile industry, compelled to decrease sulfur emissions to reduce smog, introduced a catalytic converter, which required lead-free gasoline, according to the 2013 book “Lead Wars: The Politics of Science and the Fate of America’s Children,” by David Rosner and Gerald Markowitz.
This resulted in a gradual phase-out of lead additives starting in 1975. The EPA also issued the first lead emissions reductions standards in 1973 that called for a gradual wind-down of lead use by 1986. This was followed by the 1996 Clean Air Act ban on lead additives to gasoline sold for highway use.
The federal government, however, allowed certain aircraft, racing cars, farm equipment, and marine engines to continue to use leaded fuel. Most leaded aviation gasoline contains just over 2 grams of lead per gallon of fuel, said Mielke.
The regulatory future of a notorious toxin
Environmental organizations such as Friends of the Earth petitioned the EPA to make an endangerment finding on aviation gasoline and to regulate lead emissions from piston-engine aircraft. Such a finding would have started the regulatory process to determine whether to phase lead out of all fuel, but the EPA ruled against the petition and called for more studies on the risks of leaded aviation gas.
Zahran, who co-authored a recently published study on the effects of leaded aviation gasoline on Michigan children’s blood lead levels, found that the levels increased based on proximity to airports. Particularly for people who live within a kilometer of airports that service piston-engine aircraft, “the continuing flow of lead into the environment remains a potentially serious source of exposure risk,” the study found.
The effects of lead, a neurotoxin, on a child’s developing brain can be devastating and irreversible. Elevated blood lead levels can lead to increased aggression, lack of impulse control, hyperactivity, inability to focus, inattention, and delinquent behaviors. A growing body of evidence has also shown that low blood lead levels are associated with multiple issues such as lowered IQ levels, attention-related behaviors, and poor academic achievement.
Nationally, blood lead concentrations in U.S. children have dropped dramatically over the past four decades, but lead continues to plague communities across the country, particularly in urban centers. There are about half a million young children in the United States with blood lead levels above five micrograms per deciliter, the level at which public health intervention is recommended, according to the Centers for Disease Control and Prevention.
Mielke has spent four decades studying lead soil contamination and its effects on the health and behavior of children throughout the United States, including New Orleans. He found that about 5.4 million metric tons of lead additives were used in U.S. gasoline from 1927 through 1994. And despite the removal of lead from gasoline, the environmental ramifications of the neurotoxicant continue to be felt today because lead does not degrade and remains in the soil.
Children who play in areas with lead-contaminated soil run the risk of ingesting or inhaling the lead particles in the soil, particularly during the summer and fall or during hot, dry weather when dust picks up tiny particles of lead, suspending the substance in the air.
As more research has shown the significant role that inhalation of lead particles plays in blood lead levels, Mielke said that the impact of the EPA allowance of .05 grams of lead per gallon in “unleaded” gasoline becomes clearer.
“It would have a very large impact,” said Mielke, citing studies in Detroit and Flint, Michigan that have examined the role of air lead contamination on blood lead levels.
“The tendency is to talk about ingestion and not inhalation,” said Mielke. “All of the emphasis is put on ingestion as if the only way exposure is taking place is hand to mouth, but if you pay attention to the details you discover that inhalation apparently was much more important in exposure than is being talked about.”