Astronomy, a field for which few have claimed relevance, is now becoming relevant to a pressing problem, atmospheric pollution. It turns out that those pesky atmospheric contaminants that have been annoying astronomers looking at the sun and other stars, have been leaving tell‐tale lines on spectra, which can be measured to infer their presence and strength. Serendipitously, for decades observatories throughout the world have been collecting plates from which such pollution data can be inferred, which can now be used to establish trends, either regionally or globally.