Hewson became involved in anti-nuclear activism in the 1990s. She narrated Black Wind, White Land, a 1993 Irish documentary about the lasting effects of the Chernobyl disaster, and has worked closely with activist Adi Roche. She has been a patron of Chernobyl Children's Project International since 1994 and has participated in a number of aid missions to the high-radiation exclusion zones of Belarus. She has also campaigned against Sellafield, the northern English nuclear facility. In 2002 she helped lead an effort which sent more than a million postcards, urging the site be closed, to Prime Minister Tony Blair and others. Hewson has repeatedly been discussed by tabloid newspapers as a possible candidate for political offices, including President of Ireland; none of these suggestions have come to fruition.