There are other forms of water contamination, as well. Fertilizers and pesticides, for example, have contaminated aquifers and waterways with nitrogen, phosphorous and highly toxic heavy metals, such as copper and zinc. Another major contributor to water degradation is urbanization. Based on current trends, water pollution, particularly from households in medium and smaller cities, will increase fivefold. This has serious consequences for farming communities downstream, whose surface and ground water may become unsuitable for agriculture.