Hazardous Substances

Hazardous substances can harm ecosystems and human health. Due to their intrinsic properties, they can accumulate in the food web up to levels that are toxic to organisms, especially higher predators. Hazardous substances can remain in the environment for a very long time.

What are Hazardous Substances?

Hazardous substances are substances that are toxic, persistent and liable to bioaccumulate, or otherwise give reason for concern - by influencing the hormone or immune systems of animals, for example.

Although monitoring indicates that the loads of some hazardous substances have been reduced considerably in recent years, many problems still persist. There is still relatively little comprehensive information about the overall impact of most chemicals available on the market, particularly concerning the effects of combinations of chemicals on human health and the environment. The increasing number of man-made substances present in the environment is a matter of great concern, and calls for the application of the precautionary principle.

The list of priority substances comprises heavy metals and organic substances.

Heavy Metals

The first Joint Danube Survey in 2001 revealed serious contamination of the Danube and several of its tributaries by heavy metals, including copper and nickel.

The tributaries with the highest excess heavy metal concentrations included the Rusenski Lom, the Iskar and the Timok.

Concentrations of lead, copper and cadmium in the Danube itself are fairly high. About half of all water samples exhibit concentrations exceeding the German target limits. Increased cadmium concentrations were observed in the lower part of the river Danube. In the Danube’s tributaries the situation is slightly better.

Eight heavy metals are regularly analysed within the TransNational Monitoring Network (TNMN). These are arsenic, copper, chromium, zinc, cadmium, lead, mercury and nickel, which are priority substances for the Danube River Basin. Cadmium, lead, mercury and nickel are also included in the list of Priority Substances in Annex X of the EU Water Framework Directive.

Organic Hazardous Substances

Pollution loads of hazardous substances are significant although the full extent cannot be evaluated to date. Currently, there are only few data available for hazardous substances such as pesticides.

p,p’-DDT is a substance of special concern in the lower Danube. Here the very low TNMN target values are often exceeded in the order of two magnitudes. This means that despite a high analytical uncertainty the level of p,p’-DDT is significant and gives a strong indication of potential risk of failure to reach the good status as defined by the EU Water Framework Directive.

For Lindane the results of the TNMN classification are not so alarming. It is however, foreseen that the environmental quality standard that will be set by the EU may be substantially lower than the TNMN target value. In this case, the risk of failure to reach the good status will be much higher and the situation will be similar to that for p,p’-DDT. Some tributaries (Sió, Sajó and Sava) show random occurrence of high concentrations of Atrazine.

During the first Joint Danube Survey significant concentrations of the EU WFD priority substances 4-iso-nonylphenol and di[2-ethyl-hexyl]phthalate were found in the bottom sediments as well as in suspended solids. The values ranged from a few µg/kg up to more than 100 mg/kg, indicating the relevance of these compounds as an indicator of industrial pollution in the Danube River. 



  • » Joint Danube Survey 1
    The Joint Danube Survey 2001 was carried out by the ICPDR and is the most homogenous analysis of the water quality and the ecological status of the Danube River. Over 140 chemical and biological parameters were analysed and over 40.000 laboratory results were generated.
  • » TNMN - TransNational Monitoring Network
    The TransNational Monitoring Network is an important tool under the DRPC, whose Contracting Parties are committed to co-operate in the field of monitoring and assessment. Formally launched in 1996, it aims to provide a well-balanced overall view of pollution and long-term trends in water quality and pollution loads in the major rivers in the Danube River Basin.