Large stocks of metals have accumulated in the urban technosphere (i.e., the physical environment altered by human activity). To minimize health and environmental risks, attempts were begun in the 1980s to phase out the use of cadmium (Cd), lead (Pb), and mercury (Hg). To study the effect of this attempt, we conducted substance flow analyses (SFAs) in Stockholm, Sweden, in 1995 and in 2002–2003, which allow a comparison of the results over time.
The SFAs showed a reduction in the stocks of Cd and Hg by approximately 25% to 30% between 1995 and 2002–2003. For Pb, the stock development was more uncertain. Cd and Hg inflow was substantially reduced during this period, but Pb inflow increased. Amounts of Cd and Pb in waste were still large, whereas Hg flows in waste were decreasing. Furthermore, although emissions of Pb decreased, Cd and Hg emissions were in the same range as in 1995.
The application of SFAs has provided unique data on the accumulation of metals in the Stockholm technosphere, thus serving as a valuable indicator of how the phasing out progresses. The changes can be related to regulations, initiatives by industries and organizations, and the proactive attitude of the local environmental authorities and of the water company.