Metal flows in the Netherlands Cu and Zn

In the Netherlands, two mathematical models, "FLUX" and "Dynabox", were used to evaluate options for overall Dutch metals management and the results were published in a book (by Kluwer Acad. Publ.) receiving wide international attention. The first step of this work was to make inventories of flows and stocks of Cd, Cu, Pb and Zn in the Dutch economy. The second step consisted of an analysis of the ultimate health and environmental consequences of the present metal management regime, while the third step was a comparison (expressed in terms of "sustainability indicators") with some possible alternative regimes.

It was found that emissions of all the investigated metals had decreased considerably and are today small compared to the flows through the economy. Although the metal accumulation in the Dutch economy does not cause risk levels to be transgressed at present, the authors claim that with the present management regime, emissions will rise again in the future, causing transgression of human and ecosystem health standards, especially for Cu and Zn (but - surprisingly enough - not for Cd and Pb).

A critical review of the Dutch modelling work and of the conclusions reached, however, results in a great number of questions: Just as one example, there is an obvious contradiction between the statement that the metal emissions to the Dutch environment are low and the figures given to substantiate this. According to data in the book, the emissions of Cu to the Dutch environment would be about 3,500 times higher than those in Sweden and the Zn emissions about 1,600 times higher. Many of the other exercises with numbers shown in the book clearly indicate that the conclusions based thereupon have a low credibility.

3.2.1 Models used

As a part of an interdisciplinary research programme, "The Metals Programme", financed by the Dutch National Science Foundation, two mathematical models have been used to evaluate options for overall Dutch metals management: "FLUX" and "Dynabox". Both are essentially

"substance flow analysis" (SFA) models (van der Voet et al., 2000). "FLUX" was used:

• to make an inventory of flows and stocks of cadmium, copper, lead and zinc in, out and through the economy for the base year 1990;

• to calculate steady-state societal flows and stocks, the 'ultimate consequence of the present metal management regime';

• to compare alternative regimes with the present regime on a steady-state basis.

The outcomes of "FLUX" were then translated into sustainability indicators regarding the metal's metabolism. These indicators included some describing the fate of the metals, such as total emissions, total landfill, accumulation in the economy, pollution export, while others were used for evaluation of the present management regime, for example, environmental concentration (Predicted Environmental Concentration divided by Predicted No-Effect Concentration, or PEC/PNEC), human intake (Predicted Daily Intake divided by Tolerable Daily Intake, or PDI/TDI) or environmental accumulation, and a few indicators, finally, for designing a future sustainable management regime, like technical efficiency and recycling rate.

It was recognized that the concept "indicator" is not strictly defined, and in practice many widely differing things may serve as indicators. The indicator concept developed during the Dutch research programme was designed to provide information with regard to:

• the existence and causes of environmental problems related to metals;

• the management of metal chains or cycles in society;

• an early recognition of future problems;

• the influence of policy measures, including both their effectiveness and various types of problem-shifting.

These demands imply the need for defining reference values which indicate a desired or sustainable level for the individual indicators. However, for several of the indicators, it was considered difficult or even impossible to define a reference value, which may have some repercussions on the evaluation of the results in terms of future metal flows.

The second model, "Dynabox", was used to calculate substance flows and stocks related to environmental compartments based on physico-chemical substance characteristics. It also contained a risk assessment module translating the flows and stocks into environmental concentrations and human intake. It also compared these to policy standards or no-effect levels.

The "Dynabox" model was used for the following purposes:

• to calculate steady-state environmental flows and stocks, 'the ultimate consequence of the present metal management regime';

• to calculate the ecosystem and human health risk ratios occurring in the steady state;

• to compare alternative management regimes with the present one on a steady-state basis.

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