Leonardo Dicaprio has defended using his position as an A-list actor to campaign for the environment, asking the public to just treat him like a "concerned citizen". The Departed star was in Cannes, France this month (May07) to promote global warming documentary The 11th Hour, which he co-produced, co-wrote and narrated. DiCaprio tells American magazine Us, "I am completely aware of the fact that my mere attachment - being someone from Hollywood - will garner a certain amount of skepticism and criticism. Why should we listen to this person? "I want to pose myself as a concerned citizen, not an expert."