The more humans use water, the more they also influence water quality: Nutrients from fertiliser and from sanitation systems are carried directly into aquatic ecosystems (see nutrient cycle), and also pesticides, industrial pollutants, or medical substances eventually end up in water. As all these substances can be soluble, they also become part of the water cycle (WWAP 2003). Hence, freshwater resources are further reduced by pollution. Some 2 million tons of waste per day are disposed of within receiving waters, including industrial wastes and chemicals, human waste and agricultural wastes (fertilisers, pesticides and pesticide residues) (UNEP & UN HABITAT 2010) (see also soil degradation).