Evidence shows that early automotive engineers and gasoline inventors knew tetraethyl lead was a potent neurotoxin as early as the 1920s [1].

This discovery suggests that the public health risks associated with leaded gasoline were recognized long before the fuel was phased out. The delay between the identification of the poison and the implementation of safety regulations highlights a significant gap in industrial accountability.

Tetraethyl lead was added to gasoline to reduce engine knocking and improve overall performance [1]. While the additive achieved these technical goals, it did so without a full understanding of the toxic effects on the human body. The additive was used most widely in the U.S. [1].

"The lead was known to be a poison," said David Cleland, an environmental historian at the University of Maryland [1]. This sentiment was echoed by researcher James K. Simmons in a 1923 paper, where he said that the lead was known to be a poison [1].

Despite these early warnings, the industry continued the use of the additive for decades. The knowledge of the substance's toxicity existed in the 1920s [1], but the full scale of the environmental and biological impact remained obscured from the general public. This disconnect allowed leaded fuel to remain a standard in the automotive industry for a significant portion of the 20th century.

It took several more decades for the scientific community to reach a consensus on the total impact of the chemical. "It wasn’t until the late 1970s that scientists fully understood the extent of the damage," said Robert Weller, a former EPA official [1].

“"The lead was known to be a poison,"”

The gap between the initial discovery of lead's toxicity in the 1920s and the full scientific understanding in the late 1970s illustrates the tension between industrial performance and public health. By prioritizing engine efficiency over known neurotoxins, the early automotive industry created a long-term environmental health crisis that required decades of regulatory action to mitigate.