Just searching the article for "lead" only gets this quote: "The possibility of environmental legislation banning the use of leaded avgas (fuel in spark-ignited internal combustion engine, which usually contains tetraethyllead (TEL), a toxic substance added to prevent engine knocking), and the lack of a replacement fuel with similar performance, has left aircraft designers and pilot's organizations searching for alternative engines for use in small aircraft."

Also a reference to "Planemakers challenged to find unleaded fuel option - The Wichita Eagle" a 2009 article which has a dead link.

Curious to me why you would cite an article that says the opposite of your assertion and then repeat the definitive statement. I must be missing something.