Leaching tests for emissions from building products

Building products which come into contact with groundwater or rainwater should not release harmful amounts of pollutants. An environmentally compatible choice of products requires reliable and comparable data on the leaching of substances. UBA has published reference data based on new European leaching tests, which are now available for producers and users.

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Information on leaching behaviour to become standard information on building products

Users of building products seldom find information on the pollutant emissions or content of a given building product. This is about to change. After the EU Member States have agreed on a reporting format, architects and construction firms could see products with CE marking including information like “Leaching of hazardous substances: Class I“. Years of European standardization work are the basis for that simple declaration.


Wanted: validation of new test standards

The European Commission has commissioned the European Committee for Standardization (CEN) since 2005 to harmonise methods for the assessment of hazardous substances released from building products. Work on standardisation in recent years has produced a number of test standards, which require a two-phase validation procedure before they are accorded the status of a harmonised European standard. The purpose of the validated harmonised methods is to provide reliable data for the CE marking of building products.

A German Environment Agency research project (see “Publications”) carried out by the central organisation of the German cement industry (VDZ) and the Institute of Building Materials Research at the RWTH Aachen University conducted validation tests for the new European “Horizontal dynamic surface leaching test (DSLT)” on cements and mortars. In this leaching test pollutants are dissolved of a construction product using water as solvent (eluent) under specified conditions. The eluted substances in the eluates generated in the test can subsequently be analysed with suitable analytical methods. The validation tests demonstrated, how varying test conditions (e.g. test temperature or ratio of eluent volume to surface area of test specimen) affect results. Also constancy of results in multiple analysis was surveyed. The study confirmed that the leaching test is robust. No changes to the European draft standard were required as concerns the admissible range of test conditions.

The figure below illustrates as an example the cumulated amounts of TOC (total organic carbon in mg/m2 over the test duration) leached in all the mortar tests carried out. The very good consistency of the test results under the various test conditions shows that the analysed test methods are appropriate for testing the leaching of organic substances as well as for the release of inorganic substances from construction products. This offers a practical advantage: when developing new product formulations manufacturers can optimise the leaching behaviour by using one test.

Diagramm: TOC release of reinforcement plaster is rising to ca. 5,000 to 6,000 mg /m² after ca. 35 days, according to different test conditions
TOC release of reinforcement plaster under varying test conditions
Source: Umweltbundesamt diagram and legend as PDF file

Reliable information on emissions of hazardous substances now state of the art

The application of the new method, now available as a technical specification (CEN/TS 16637-2), is recommended in a legal context under the EU Regulation laying down harmonised conditions for the marketing of construction products ((EU) No 305/2011) as well as its application for voluntary labelling and environmental product declarations. The new method offers a solid basis to ensure the safety of construction products for soil and water bodies and to implement the environmental protection requirements of the Construction Products Regulation (Article 3 and Annex I).


Testing for the Blue Angel ecolabel

In a research project entitled “Construction products in contact with rain: Development of awarding criteria for the ecolabel Blue Angel using leaching tests“ the Federal Institute for Materials Research and Testing (BAM) performed leaching tests on different construction products on behalf of the German Environment Agency. Materials tested included varnishes for outdoor applications, external thermal insulation composite systems, roof tiles and polymeric roof membranes which are all exposed to precipitation when in use. Leaching tests according to the dynamic surface leaching test (DSLT) as developed by CEN/TC 351 and the immersion test according to EN 16105 were performed using these products. Emission curves were determined for inorganic as well as organic substances in the eluates. The project objective was to further develop the award criteria for the Blue Angel for certain building products in respect of their leaching of pollutants.

The results can be used as first publicly available reference data for a range of building products with low levels of leaching determined with the new European testing procedure. The data gives producers, public authorities and other users a helpful point of reference with which to judge the results of other products. The results confirm that the current Blue Angel criteria for product formulas are well suited to minimise the release of hazardous substances from building products.

It is not yet possible to determine the release of all mobilisable organic substances completely nor do eluate test results from the laboratory enable the derivation of substance concentrations in the environment. Suitable models to apply to laboratory test data are currently under development. UBA sees here a need for further research and action.


Emission and transfer functions

In addition to the material properties of building products themselves, leaching is significantly influenced by the geometry of the component and the weather. To derive concentrations in the environment from laboratory eluates, it is useful to implement model-based simulations with harmonised scenarios. Producers do not know what conditions their products will be exposed to when put into use. The simplest application scenarios possible – established by convention for all producers – would help producers with product labelling and users in making appropriate choices when selecting products.

To enable improved assessment of the environmental risk of substance leaching, HSR University of Applied Sciences Rapperswil, Switzerland, developed the simulation model COMLEAM (COnstruction Material LEAching Model). The model uses emission functions to describe the relation between the substance emission and rainwater runoff. In a project commissioned by UBA entitled Emission and Transfer Functions for the Modelling of Leaching from Construction Products HSR conducted extensive testing of five emission functions with three field data sets with the biocidal substance Terbutryn. The results show that the logarithmic emission function is currently able to provide the best predictions of leaching when using field data. In a next step it should be possible to add standard scenarios into COMLEAM that enable predictions based on laboratory test results. This next step in development should make it possible to take the leaching of substances into account in future building planning, when data on the leaching behaviour of the used products becomes available at the same time.