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Hazardous Substances in Fertilizers Used by Agriculture

Denmark is a small country with a large agricultural sector managing approximately 60 % of the land use. In the past couple of decades, awareness has been growing of the many potential problems in modern agriculture caused by the demanding use of chemicals or soil- or crop improving products containing hazardous substances. Besides pesticides, these include veterinary pharmaceuticals, growth promoting metals like copper and zinc, and contaminants arising from the use of mineral fertilisers, manure and sewage sludge.

For decades, the Section of Soil Fauna and Ecotoxicology has created and compiled fundamental knowledge needed to enable optimal and sustainable use of organic waste on arable land in Denmark.  Recently, for example, a project attempted to evaluate whether selected organic contaminants in sewage sludge could potentially pose a risk to soil ecosystems after soil amendment. The selected groups were perfluorinated chemicals, brominated flame retardants (BFR), synthetic musks, pharmaceuticals and polychlorinated biphenyls (PCB).  Read the report here.

Studies on the potential impact of the use of copper and zinc on piglet production are on-going, and recently a publication compared the input of other heavy metals from various fertilisers in Denmark. The following conclusions were made:

“Mineral fertilisers contain a range of impurities that may be harmful to the environment if loads are too high. In EU, it has been suggested to regulate the content of arsenic (As), cadmium (Cd), chromium (VI) (CrVI), mercury (Hg), nickel (Ni) and lead (Pb) in mineral fertilisers by setting cut-off values for these six metals. There is no indication of short-term risk after one application of the six metals if the proposed cut-off values for fertilisers are used. If fertilisers contain the suggested cut-off concentration, the annual load of the six metals via fertilisers and atmospheric deposition corresponds to less than 0.2 to 1.9% of the average background concentration in Danish agricultural soils. A comparison with critical loads established for agricultural soils in the Netherlands and Denmark indicates that no long-term risk of As and Cd accumulation is anticipated when using the suggested cut-off values for fertilisers. However, a comparison with critical loads established for agricultural soils in the Netherlands indicates that long-term risks of total Cr, Ni and Pb accumulation cannot be ruled out in some of the most sensitive agricultural soils when using the new cut-off value for fertilisers. For Hg, a comparison with critical loads established for agricultural soils has not been possible, as no suitable critical load for Hg has been identified.”


John Jensen

Viceinstitutleder, Seniorforsker,


Jordfaunaøkologi og økotosikologi
Aarhus Universitet
Institut for Bioscience
Vejlsøvej 25
8600 Silkeborg