Pollution
noun, verbal noun
A dirty dye that's all throughout the sky and makes things gross when it touches them is pollution. If it's bad enough it really is like a dye, too, making your white clothes brown, yuck.
おせん
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
自国のPM2.5汚染レベルはどうすれば分かるのでしょうか。
How can I find out about PM2.5 contamination levels in my community?