Steel slag
Staalslak (steel slag) is a stone-like material that remains after steel production. This steel slag is then processed and used as a building material under certain conditions. Steel slag is marketed in the Netherlands with an milieuverklaring bodemkwaliteit (environmental declaration of soil quality) that demonstrates that the steel slag meets the quality requirements for building materials. The Human Environment and Transport Inspectorate (ILT) oversees this.
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In recent years, steel slag has been used on a large scale at various locations, for example in earth and noise barriers. Steel slag has also been used in foundations under pavements, as well as in footpaths and cycle paths.
Oversight
The ILT ensures that steel slag complies with the legislation and regulations in the Besluit bodemkwaliteit (Soil Quality Decree, in Dutch) and the Regeling bodemkwaliteit 2022 (Soil Quality Regulation, in Dutch). These stipulate, among other things, that before steel slag can be used in the Netherlands, its quality must be demonstrated by means of a soil quality environmental declaration. Together with omgevingsdiensten (environmental services), the ILT is also responsible in the case of nationally operating contractors for checking for overseeing whether steel slag is being used in accordance with the rules laid down in the legislation and regulations.
Risks and points for attention
In recent years, the ILT has conducted research (in Dutch) in response to reports of environmental pollution caused by the use of steel slag. The ILT has concluded that the current legislation and regulations are insufficient to prevent environmental damage. The ILT has therefore issued 2 warnings to the staatssecretaris van het ministerie van Infrastructuur en Waterstaat (State Secretary for Infrastructure and Water Management). In its reports, the ILT indicated that, in any case, there are risks to the environment and human health at locations where large quantities of steel slag have been applied in thick layers.
Temporary ban
Partly in response to the ILT's warnings, on 23 July 2025 the State Secretary imposed a partial ban and a permit requirement for the use of steel slag. Exemptions may be granted.