The distribution of Parmotrema tinctorum, known as an excellent bioindicator of air pollution, was examined in Kanagawa Prefecture, Japan, by comparing data from 2005–2007 with that from 2022. Field investigations were conducted in cemeteries and parks at 140 sites in 2005–2007 and at 128 sites in 2022. In 2005–2007, a large gap in the distribution of this species was observed in urban areas with higher concentrations of NO, NO2 and SPM likely due to automobile exhaust emissions. In 2022, the recolonization of P. tinctorum was observed at six sites, and one new growth site was confirmed within the gap area of 2005–2007. The recolonization in the urban area is considered to be related to the significant improvement in air quality, due to the strict regulation of exhaust gas from diesel engines implemented since 2003 in and around Tokyo, including Kanagawa Prefecture. Similar phenomena of recolonization of P. tinctorum have also been reported within Tokyo, supporting this conclusion. Keywords : air pollution, bioindicator, lichen, nitrogen oxide, nitrogen dioxide, urban areas.