Not only pollen (that causes hay fever) and Asian Dust, the PM2.5 density increases in this season.
In this page, we can see if the PM2.5 high density alert is announced or not.
「現在、PM2.5高濃度予報等はありません」:Now there is NOT PM2.5 high density alert etc.
*Sorry, we don't know what sentence is used when it's on alert since we haven't seen it yet.
When the alert is on,
1) we should avoid going outside without inevitable reasons
2) we should not do any sports outside for a long time
3) try to minimize the ventilation of the house/room
4) pay attention to those who suffer respiratory diseases, young children and elderly people
The alert will be announced at around 8 o'clock according to the measurement of 5, 6 and 7 o'clock in the morning.