Tetraethyl lead is a toxic chemical compound that was once widely used as a fuel additive in gasoline to improve engine performance. However, due to its harmful effects on human health and the environment, it has been banned in many countries. Synonyms for tetraethyl lead include TEL, lead tetraethyl, ethyl lead, and lead(IV) ethoxide. Other related terms include lead poisoning, lead toxicity, and environmental contamination. Despite its ban, there are still some industries that continue to use TEL, highlighting the need for increased awareness and regulatory measures to prevent its continued use.