Although you should not flush a used condom down a toilet, if a person did, this type of wastewater pollutant would represent

This type would be debris and grit pollutants. Sewage treatment plants separate this type of pollutants from the water and clean the water making it available for further use. It is basically recycling of water, so you should not drop it into the toilet, but if you do it will be cleaned eventually and removed from the water.

Its decreasing because of illnesses