After decades of regulating the emission of anthropogenic substances into the environment, a retrospective analysis of their effects is informative, as it allows determining the actual costs and benefits related to the regulations. As a first example we have considered the case of gasoline lead in Europe. With the help of a regional climate model, NCEP re-analyses, spatially disaggregated lead emissions from road traffic, and various local data, an attempt was made to reconstruct the airborne pathway and deposition of gasoline lead in Europe since 1958. During the 1960s the emissions of this neurotoxin grew steeply until first regulation was introduced in the early 1970s by the German government and in 1978 by the European Community. In 1985 the European countries began to phase out lead in gasoline and nearly all European countries have agreed to the exclusive usage of unleaded gas by the years 2005 (1998 Aarhus Treatry).

It turned out that the regulations were mostly successful in ecological terms while not having exerted an undue load on the economy. For instance, the emissions in Hamburg (Germany) fell by 90% from the mid 1970s until the mid 1990s. The lead concentrations in plants fell by about two thirds, and the lead concentration in human blood by two thirds and likely more. However, in coastal ecosystems (e.g. mussels) the lead concentrations have remained at a relatively high level, due to accumulated sediments acting as a time-delayed lead source.

During the time of maximum emissions, in the late 1960s and early 10970s, little data on the abundance of lead in the environment exists. Using measured data since the 1980s and the modelled aerial concentrations of lead, we have estimated the lead concentration in human blood in Germany in the early 1970s to be on average 150 micro g/l, which is considered potentially harmful by the German Human-Biomonitoring commission.

A methodological result of the study is that the reconstruction of regional environmental change is doable with dynamical regional environmental models (at least: climate, passive tracers). Past political and economic evolutions may be assessed quantitatively by a retrospective analysis. Scenarios of environmental impact of possible future socio-economic developments can effectively to be constructed. Specifically, regional atmospheric modeling allows for dynamical downscaling consistent with large scale forcing.