Stainless steel melting shops of Outokumpu Group are located in Finland,Sweden and England(UK). In all of the countries the European Union legislation is the same,but in practice the plants face different technical,economical and administrative challenges in developing sustainable treatments and use of by-products. Due to availability of good natural construction materials,the use of slag and other industrial by-products has been quite small in Northern Europe.Blast furnace slag has been completely utilized,while slag from stainless steel processes has earlier been regarded as waste.Steering of the metallurgical melt phase,slag cooling,treatment and metal recovery processes are the main technical challenges for increasing the sustainable use of stainless steel slag. Moreover,product properties have to fulfill standards and customer requirements.Dry or water-cooled EAF slag aggregates are typically used in road construction.Outokumpu has developed light mineral slag aggregates which are cooled in rapid water process.During this process,a specific structure and mineralogy is formed in the slag and leaching from the material decreases.In many regulatory discussions,it seems that there is not enough relevant scientific data from harmful compounds.Limit values are based only on laboratory tests and model estimations,not on the material use itself or real nature.A risk-based approach is needed when environmental acceptance is not clear.Limit values based on content are not applicable because environmental or health risks depend on the release or leaching of substances from the material.This is the case especially with metals. Stainless steel melting shops of Outokumpu Group are located in Finland, Sweden and England (UK). In all of the countries the European Union legislation is the same, but in practice the plants face different technical, economical and administrative challenges in developing sustainable treatments and use of by-products. Due to availability of good natural construction materials, the use of slag and other industrial by-products has been quite small in Northern Europe. Blast furnace slag has been completely utilized, while slag from stainless steel processes has earlier been regarded as waste. Steering of the metallurgical melt phase, slag cooling, treatment and metal recovery processes are the main technical challenges for increasing the sustainable use of stainless steel slag. Moreover, product properties have to fulfill standards and customer requirements. Dry or water- cooled EAF slag aggregates are typically used in road construction. Outokumpu has developed light mineral slag aggregates which are cooled in rapid water process. In many regulatory discussions, it seems that there is not enough relevant scientific data from potentially harmful compounds. Limits values ​​are based only on laboratory tests and model estimations, not on the material use itself or real nature. A risk-based approach is needed when environmental acceptance is not because for environmental or health issues depend on the release or leaching of substances from the material.This is the case especially with metals.