The nutrients in urine can cause overgrowth of aquatic plants in lakes, rivers, and streams. When they die and decompose, they use up oxygen in the water, which suffocates other aquatic, life such as fish. This is called hypoxia

When it gets into drinking water supplies, nitrogen can result in such diseases as methemoglobinemia or blue baby syndrome. To protect public health, The Safe Drinking Water Act now requires reducing the nitrogen through tertiary treatment, often involving expensive denitrification equipment.