2. Leaded Gasoline
In the 1920s, tetraethyllead was introduced as an antiknock agent to enhance engine performance by reducing knocking in internal combustion engines. This addition significantly improved vehicle efficiency and power. However, the widespread use of leaded gasoline led to substantial environmental contamination, as lead particles were emitted into the atmosphere through vehicle exhaust. This pollution resulted in elevated blood lead levels among children, causing developmental delays, learning difficulties, and other health issues. The persistence of lead in the environment also led to soil and water contamination, affecting ecosystems and human health. Recognizing these severe health risks, many countries began phasing out leaded gasoline in the late 20th century. The United States, for instance, banned the sale of leaded fuel for on-road vehicles in 1996. Despite these efforts, the legacy of leaded gasoline continues to pose challenges, particularly in regions where its use persists.