A protester with  a sign reading Diesel-Abgase Toeten! (Diesel Emissions Kill) at  the ministry of transport in Berlin. Reports of  experiments with diesel pollutants on animals and people  have caused horror in German political circles. Photograph: Clemens Bilan/EPA

Dieselgate has revved back into life with revelations that German car manufacturers carried out medical tests on humans using exhaust fumes. After re(...)