I asked Nick what caused the dirt on vehicles. Here is his reply:
“First of all, the accumulation of dirt on vehicles can be attributed to sandstorms in China that get picked up and carried over on air streams from the west and then deposited down on to Japan. This is why many vehicles look like they have been driven down a dusty road. Indeed, before coming to work earlier last week, I wondered why there was a dusty sediment on my scooter.. As I have not been driving down any gravel roads. I have been warned that it can be hazardous to your health, and another reason why wearing masks is a part of the norm. Also, do not bother washing vehicles as they will just get coated in the China-yellow-sand soon afterwards.
If the air seems a little smoggy or smokey, it is in fact an invasion of Chinese dust.
Secondly, it is allergy season. Yet there are not any flowers in bloom yet that I have seen. There are pollen-emanating evergreens (that are sometimes brown) that exist all throughout Japan, and this is the reason behind allergy season in Japan.
It turns out Japan is a much more dangerous place than I had originally thought… Especially in spring.”
Narita-san mentioned that the sand is much finer than normal beach sand, which is how it is able to make the journey from China.