To understand the problem posed by diesel, it is necessary to understand the new information that has emerged over the last decade about its ill-effects. The first big finding come with air pollution experts discovering that diesel exhaust consists of 10-100 times more particles than petrol. More than that, experts soon began to realise that it is not the total quantity of particles that matters so much for public health as the size of the particles in vehicular exhaust. This monograph busted the myth that diesel is the fuel of the future and shows how harmful it is for the health.