Complex sentence: By 21 June, The Department of Environment, Parks and Recreation of Brunei said the PSI readings were "relatively higher than normal", but air pollution levels are still considered "moderate" as the PSI readings in Brunei are still below 100.
Split into simpler sentences: By 21 June, The Department of Environment, Parks and Recreation of Brunei said the PSI readings were "relatively higher than normal". But air pollution levels are still considered "moderate" as the PSI readings in Brunei still below 100.