Detecting biosignatures , such as molecular oxygen in combination with a reducing gas , in the atmospheres of transiting exoplanets has been a major focus in the search for alien life .
We point out that in addition to these generic indicators , anthropogenic pollution could be used as a novel biosignature for intelligent life .
To this end , we identify pollutants in the Earth ’ s atmosphere that have significant absorption features in the spectral range covered by the James Webb Space Telescope ( JWST ) .
We focus on tetrafluoromethane ( \text { CF } _ { 4 } ) and trichlorofluoromethane ( \mathrm { CCl } _ { 3 } \mathrm { F } ) , which are the easiest to detect chlorofluorocarbons ( CFCs ) produced by anthropogenic activity .
We estimate that \sim 1.2 days ( \sim 1.7 days ) of total integration time will be sufficient to detect or constrain the concentration of \mathrm { CCl } _ { 3 } \mathrm { F } ( \mathrm { CF _ { 4 } } ) to \sim 10 times current terrestrial level .