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Why did petroleum refiners stop relying on lead additives to make high-octane gasoline?

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Aerial view of an oil refinery complex near New Orleans, Louisiana, with storage tanks, industrial structures, and smoke rising from the facility, surrounded by open land. — petroleum refining Aerial view of an oil refinery near New Orleans.

Petroleum refiners stopped relying on lead additives—specifically tetraethyl lead—primarily because lead interfered with the performance of catalytic converters. These pollution-control devices were introduced in automobiles in the mid-1970s to reduce harmful emissions, and lead deposits quickly rendered them ineffective.123

Additionally, the phase-out was driven by significant public health concerns regarding the toxicity of lead. Research conducted in the 1960s and 1970s highlighted the accumulation of lead in the environment and its detrimental effects on human health, particularly regarding intellectual development in children.14

Following the implementation of environmental regulations, such as those enforced by the Environmental Protection Agency, refiners shifted their processes to achieve high octane ratings without lead. This transition required substantial investment in new refinery infrastructure, including alkylation units and catalytic reformers, to produce high-quality, unleaded gasoline components.125