EU Water Law

Nutrients, such as nitrates and phosphates contained in farm fertilisers and household detergents can over-fertilise the water, causing the growth of large mats of algae, some of which can be toxic. In severe cases of eutrophication, planktonic algae spreads. As dead algae decompose, the oxygen in the water is used up, bottom-dwelling animals die and fish either die or leave the affected area. Increased nutrient concentrations can also lead to changes in the aquatic vegetation. Nutrients are discharged into the aquatic environment by the operation of many human activities, e.g. through wastewater from households and industry or by loss of nutrients from agriculture and fish farming. Agriculture is the main source of nitrogen loading and a major source of phosphorus loading, although much phosphorus also comes from point sources and sparsely built-up areas.

Pesticides and veterinary medicines from farmland and chemical contaminants, including heavy metals and some industrial chemicals, can threaten wildlife and human health. Some of these damage the hormonal systems of fish, causing feminisation. Waste-water contains many hazardous substances derived from detergents and other substances, and many substances are used in industrial production and in the transport sector. Pesticides and other substances leach from contaminated sites. Pesticides also occur in watercourses.