DSS
Federal Office for the Environment FOEN
Lead contamination of soil is mainly linked to atmospheric deposition from industrial and transport-related emissions. Depending on the concentration, lead is toxic to animals, humans and, under certain circumstances, plants. Contamination occurs primarily through inhalation and oral ingestion of soil particles. Contaminated playgrounds pose a particularly high risk to children due to their body weight and behaviour while at play. The health consequences of excessive lead exposure can be serious and, especially in children, may include irreversible neurological disorders (lead poisoning). In contrast, lead is only stored in plants to a limited extent and therefore rarely enters the food chain.
good
positive
The average lead content in the top 20cm of soil was significantly below the guidance value according to Annex 1 SoilPO (50mg/kg DM) throughout the entire measurement period. The situation can therefore be considered good.
Lead levels remained relatively stable between the first (1985–89) and third (1995–99) sampling cycles and fell considerably thereafter. This reduction can be linked with the improvement in air quality. The reduction in the lead content of motor fuel from the 1970s and its complete elimination from 2000 contributed, among other things, to a reduction in atmospheric inputs. On the other hand, lead is only soluble in highly acidic soils and is rarely introduced by leachate or absorbed by vegetation. As long as lead pollution persists, this element will continue to accumulate in the topsoil and remain stored there indefinitely.
The results of the seventh survey cycle (2015–19) show a slight increase in lead concentrations in topsoil. Future surveys will show whether these slightly higher values are attributable to increased lead input and whether they will continue. The increase in concentration is low, which suggests that lead concentrations have remained stable thanks to effective measures taken in the past (e.g. the ban on leaded petrol). The development is therefore still considered positive at this point in time.
More detailed information can be found in the publication 'Results of the National Soil Observation 1985–2019' (available in german and french).
Since 1985, composite samples have been taken every five years from the top 20cm of soil at all 114 permanent plots of the Swiss Soil Monitoring Network (NABO).
Lead content testing is carried out on the topsoil as this is where the lead contamination from atmospheric pollution accumulates.
The lead content is analysed using the method specified in the Soil Protection Ordinance (SoilPO) (solvent: 2M nitric acid (HNO3)). The results (in mg·kg-1 of dry soil) are presented in the form of average content per survey cycle. All non-forestry plots with continuous time series are taken into account when calculating the average value.
| Targeted trend | Initial value | Final value | Variation in % | Observed trend | Assessment |
|---|---|---|---|---|---|
| Decrease | Average 1985/89-1995/99 | Average 2005/09-2015/19 | -3.33% | Decrease | positive |