Alastair Hay, now Emeritus Professor of Environmental Toxicology at the University of Leeds, is a chemist who’s had a dual career as an academic researcher and an outspoken activist and campaigner. The common theme has been the application of his knowledge to how chemicals affect our lives, in the workplace and during conflicts. Alastair Hay is best known for his work to rid the world of chemical weapons, a concern about this horrific form of warfare that goes back to the use of Agent Orange in the Vietnam War. His work culminated in the Chemical Weapons Convention, which came into force in 1997, outlawing their production, stockpiling and use.He spent his childhood in Zimbabwe and returned to the UK when he won a scholarship from Shell to study chemistry in London in the late 1960s. After a spell working on the biochemistry of animals, including a stint at London Zoo where one of his more difficult jobs was taking blood from penguins, he moved on to studying the effects of chemicals on humans. Jim al-Khalili talks to Alastair Hay about his love of chemistry and his shock to see that chemical weapons are still being used over twenty years after the signing of the Convention.