A critical look at the impact assessment modelling of metals in Life Cycle Impact Assessment and improvement options.
|Looptijd||2003 - 2004|
|Financiering||International Council on Metals and Mining|
|Dutch Duurzaam BouwMetaal Foundation|
Life Cycle Assessment is a much-used instrument to assess the environmental impact of products and functions, including materials. Its setup has been standardised in the ISO 14040-series, which distinguishes four phases: goal and scope definition, inventory analysis, impact assessment, and interpretation.
The impact assessment, or LCIA, consists with a number of steps, amongst others related to the conversion of emitted substances into contributions to environmental impact categories. Thus, quantified emissions of benzene, cadmium, dioxins and pesticides are converted into quantified contributions to ecotoxicity and human toxicity. The numerical details for this conversion are provided by characterisation factors, which are derived from characterisation models.
Problems encountered with LCIA-characterisation modelling of metals are the following:
- The validity of the fate models: it is as yet not clear to which extent the emission of heavy metals has lead to such a concentration increase in the deep soil, in sediments and in the ocean, that any damage is to be expected in these media, because at concentrations close to the background concentration no negative effects are to be expected;
- The inclusion of essentiality is effect models: some metals like zinc and copper, are essential elements for life functions, implying that below a given threshold background level emissions are to be regarded as environmentally beneficial instead of toxic;
- The no-effect level in effect models: for most elements the crustal concentration can act as one of the possible thresholds. Taking this point into account would require spatial differentiation of LCAI modelling;
- The inclusion of homeostasis in effect models: in addition to the point of metals possibly being nutrients, the uptake of metals by organisms may be regulated through homeostasis, which affects the dose-response curve for the metal;
- The inclusion of speciation and bioavailability in effect models: metals may be present in different speciation, with highly differing biological availability and/or toxicity characteristics.
The project’s main purpose was to organise a workshop on the inclusion of state of the art expertise and current expert knowledge on risk assessment of non-ferro metals in LCIA. Basis for the workshop were the preliminary results of a concise study, which addresses the scientific issues and practical dilemmas that are encountered when developing or using characterisation factors in Life Cycle Impact Assessment, and which identifies a number of directions for improvement.This report can be downloaded below.
The workshop was held in Apeldoorn (Location TNO) on 19 March 2004 with around 20 invited experts in the fields of LCA, RA and ecotoxicology, and an affiliation in academia, research institutes and metals industry.
The participants of the workshop recognised that current ecotoxicity LCIA methods often produce a probably incorrect emphasis on the impact of metals. The so-called "Apeldoorn declaration" shortly describes the short comings of the current LCIA methods for metals and warns LCA practioners to use the methods cautiously. It has been published in SETAC globe and the fourth issue of UNEP/SETAC's Life Cycle Initiative's Newsletter. The "Apeldoorn declaration" can be downloaded below.
A second result of this project is an outline of the actions that need to be taken in the short- and long-term to arrive at a more scientifically defendeable assessment of the metals in LCIA, see the report for more details.