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Acceptable daily intake

Cadmium Copper Lead

Zinc

Figure 30.2 Human toxicity risk ratios for cadmium, copper, lead and zinc in the Netherlands, 1990, and steady state

Figures 30.3 and 30.4 show the risk ratios for aquatic and terrestrial ecotoxicity. The Dutch maximum permissible concentration (MPC) standard has been applied in calculating the risk ratios for aquatic and terrestrial ecotoxicity. The MPC is defined as the sum of the maximum permissible addition (MPA) and the existing background concentration in the Netherlands, with the MPA defined as the amount of a metal originating from anthropogenic sources that is allowed on top of the natural background concentration. The MPC is an ecotoxicological value (Crommentuijn et al. 1997). For aquatic and terrestrial ecotoxicity it appears that copper gives the highest risk ratios, then lead and zinc, and then cadmium. These results mean that the current metabolism of these metals is generally not sustainable.

The transition periods for the various metals are shown in Table 30.2. In calculating the transition periods, current background levels in the various environmental media have been taken into due account. The transition periods vary from 0 years for cadmium in water to reach the reference and the limit value, to 1000 years for lead in water to reach

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