Pollutants in the atmosphere fall with the rain, but it is not certain what they are. For example, there is "coal slurry rain" near the coal chemical plant, and "mud" will fall in the dusty place.

Generally, the washing powder (or other detergent) is dissolved in warm water, and the clothes are soaked for about 15 minutes, and can be washed off after washing. If there is oil stain, it can be cleaned with thinner.