Background Aggregate is the common term for crushed bedrock and mineral soils used for construction purposes like infrastructure works and concrete production. Aggregate production is one of the largest industry sectors in Finland. In the Tampere region in southern Finland, extracted rock aggregates may contain high concentrations of arsenopyrite (FeAsS) and high arsenic concentrations have also been detected, particularly in deeper layers of glacial till. The presence of arsenic sulphides in aggregate rock leads to a deterioration in the quality of construction material and it can also become a source of contamination. Arsenic is a carcinogenic substance and people can be exposed to this via drinking water, crop and dust. No unified guidelines or instructions existed in Finland, nor in other countries, on how to handle the arsenic issue. Extraction and construction works usually require permits or environmental impact assessments. However, no consistent approach was applied by the competent authorities (in Finland or elsewhere) to control such potential contaminants in groundwater. Valid data and information was scarce (for Finland as well as other countries) about arsenic and its behaviour in soils and bedrocks. Objectives The main objective of the ASROCKS project was to provide guidelines for the exploitation of natural aggregate resources (crushed bedrock, sand and gravel) in an area with elevated arsenic concentrations in bedrock and soil. Guidelines were also to be developed for the re-use of aggregates in construction sites in areas with a high natural occurrence of arsenic. The demonstration area was the Tampere-Häme region in southern Finland, where natural arsenic in bedrock and soil is known to be a problem. Specific objectives related to: Identifying the current aggregate production areas and planned large construction sites with potential for arsenic hazards; Identifying the environmental impacts at demonstration sites. Potential pathways to surface and groundwater were to be investigated in sites that show elevated concentration of arsenic. Worst-case scenarios would be defined for the selected sites; Developing a risk assessment and risk management procedure at the demonstration sites. The main aim of this was to develop a decision support model for the aggregate production and application in construction sites in areas with a high natural occurrence of arsenic.Results ASROCKS project outcomes included an extensive survey of 20 soil and bedrock extractions sites that were expected to be sources of arsenic emissions and leaks. Out of the 20 sites surveyed, four were selected for detailed analyses including leaching tests and emission to the air as results of the extraction and soil and bedrock processing works. The air quality survey was not included in the original plan but was deemed to provide added value. Findings from the survey work informed the design of new guidelines for sustainable aggregate production and construction in arsenic-rich areas. Guidelines focused on introducing a consistent method for landowners and authorities regarding sampling the rock and soil. This unified approach extended to advice on handling extraction permits, including the use of obligatory environmental impact assessment procedures for larger extraction proposals (over 20 000 tonnes). ASROCKS was the first project in the world to investigate and develop risk management tools for arsenic in crushed rock aggregate and construction industry. The guidelines, which are already in use by project stakeholders, can be modified by introducing respective local parameters for other countries with high arsenic levels in soil and bedrock. Such new knowhow that was developed by the project was able to increase awareness about the toxicity and other adverse impacts of aggregate content. Information was presented in a way that was understandable for non-experts and this helped to demystify uncertainties as well as clarify concerns. Innovative methods were used to develop the guidelines involving close cooperation, workshops and continued discussions between various stakeholders, companies, authorities and researchers, i.e. involving also non-experts and businesses in the development work. Research institutes, universities, regional and national authorities, companies and other stakeholders participated in the project activities from the kick off meeting to the final seminar and close cooperation was planned during the After LIFE phase. Results can be used in the further development of the EU soil thematic strategy and in water management plans (regarding the protection of ground and surface waters) based on the Water Framework Directive. Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).