Common sense? If some quantity of emissions n causes a number of illnesses resulting in death D(n), then n + x will result in D(n + x) illnesses/deaths. So, if

Common sense? If some quantity of emissions n causes a number of illnesses resulting in death D(n), then n + x will result in D(n + x) illnesses/deaths. So, if 'dieselgate' resulted in some sizeable quantity of pollution increase, then it also resulted in increased illness/death. The author seems to be asserting that, indeed, that x was positive and therefore people died as a result of dieselgate.